# I'm back but confused, again!



## angryht

It's been quite a while since I played around with REW. I have gone through the help file and installed version 5.0. I am looking for some simple examples of threads. I've got an Onkyo 606, which has audyssey 2EQ. It also has manual EQ with certain frequencies to adjust. Can someone point me to some simple examples to get me started again? I've gone down this road before but after countless measurements, I never seemed to get resolution. My room is tiny. It's 12.5' by 9'. I've got some drawings so I'll post those soon. Actually, I've posted here before but it's been a few years. Just need to jump back into it again, I guess. Thanks in advance.



*Edit on 4/19/2012:* FYI ~ It may be more beneficial to skip ahead to this post here. In that post, I have summarized a lot of what was done in the first 14+ pages (146 posts). Otherwise there is a lot of me figuring out how to use REW.


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## EarlK

angryht said:


> It's been quite a while since I played around with REW. I have gone through the help file and installed version 5.0. I am looking for some simple examples of threads.


> Threads that offer examples to accomplish what, precisely ?

> Moving on, I think it's worth your while to * review your own thread from 2007 .* 
> Lots of good interactive info was ladled out to you by BruceK & Wayne . 
> An observation , it seems to me that you had a good handle on how to do things almost 5 years back, so what's changed ?
> Hopefully a review of the process you engaged back then, will nudge your memory in the right direction .



angryht said:


> I've got an Onkyo 606, which has audyssey 2EQ. It also has manual EQ with certain frequencies to adjust. Can someone point me to some simple examples to get me started again?


> If the big "change" here is that you now have Audyssey ( within a new AVR ), then I know I've seen threads about using REW & Audyssey together .



angryht said:


> I've gone down this road before but after countless measurements, I never seemed to get resolution.


> According to my first linked-to-thread ( started by you ) you achieved quite good success ( from a Frequency Response perspective ) . 
> Therefore I don't really understand your observation about  *"resolution"*  ( note the different meanings of the word ) .
> If you meant "finality" ( to the process of tweaking ), then I would argue that the process itself is a Pandoras Box. Once opened / it never closes ( thus, there is no "resolution" to the never-ending process of tweaking ) .
> If you want to improve the sonic resolution of your listening experience, then that is an entirely different kettle of fish ( requiring much much more than REW & a BFD ). The simple way to that experience is to listen to some good headphones . lddude:

> From your second thread of note  *Did moving my couch make a difference? *  ;



angryht said:


> I will continue to move things around. I was wondering if I was correct in my interpretation above.
> 
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> 
> Wayne said:
> 
> 
> 
> Don’t know what the “change in the center” is but otherwise I’d agree with your assessment.
Click to expand...

> As a review, you do realize that moving things ( as well as changing the listening position ) changes the spectral balance within the normal listening room .

> That was an important realization to gain .


:sn:


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## robbo266317

Welcome back.

As EarlK asked, what particular aspects are you confused about?

Cheers,
Bill.


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## angryht

EarlK said:


> > Threads that offer examples to accomplish what, precisely ?
> 
> > Moving on, I think it's worth your while to * review your own thread from 2007 .*
> > Lots of good interactive info was ladled out to you by BruceK & Wayne .
> > An observation , it seems to me that you had a good handle on how to do things almost 5 years back, so what's changed ?
> > Hopefully a review of the process you engaged back then, will nudge your memory in the right direction .
> 
> 
> > If the big "change" here is that you now have Audyssey ( within a new AVR ), then I know I've seen threads about using REW & Audyssey together .
> 
> 
> 
> > According to my first linked-to-thread ( started by you ) you achieved quite good success ( from a Frequency Response perspective ) .
> > Therefore I don't really understand your observation about  *"resolution"*  ( note the different meanings of the word ) .
> > If you meant "finality" ( to the process of tweaking ), then I would argue that the process itself is a Pandoras Box. Once opened / it never closes ( thus, there is no "resolution" to the never-ending process of tweaking ) .
> > If you want to improve the sonic resolution of your listening experience, then that is an entirely different kettle of fish ( requiring much much more than REW & a BFD ). The simple way to that experience is to listen to some good headphones . lddude:
> 
> > From your second thread of note  *Did moving my couch make a difference? *  ;
> 
> 
> 
> > As a review, you do realize that moving things ( as well as changing the listening position ) changes the spectral balance within the normal listening room .
> 
> > That was an important realization to gain .
> 
> 
> :sn:


Excellent! I had some trouble getting to those old posts (my own) because it's been so long since I logged on. I had to update my profile and email blah blah blah. . . anyway, thanks for finding those. I've been going through that stuff too and you are right, just need to nudge myself into relearning some of the stuff. I'm trying to get my sub and mains equalized better. I'm also curious if the Audyssey will make a difference in my case. My room is so small, it just seems so boomy. Sometimes I need a longer learning curve on these things.

Correct, I want to, oh how did you put it, improve the sonic resolution of my listening experience (that's good stuff). Alright, I'll get back to getting some new graphs posted.


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## angryht

robbo266317 said:


> Welcome back.
> 
> As EarlK asked, what particular aspects are you confused about?
> 
> Cheers,
> Bill.


Just trying to dive back into measuring, moving, adjusting, , , , . 

I'd like to take advantage of the EQ in my receiver and I also have a 2nd sub that I'd like to add, if it helps. The primary sub (in the room now) is a Def Tech Super Cube II but the 2nd is an old Yamaha. 

I'm also not sure the crossover in my receiver is working properly. When I set it to 80 Hz (front speakers) there is still a lot of bass coming out of the speakers when I play the subwoofer tone in Avia. So, I have some questions but I do need to take some new measurements. I did some last night but they didn't seem right.


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## angryht

Here is my crossover problem. Green is the mains with the sub turned off and blue is the sub with the mains turned off. The crossover is set to 80 Hz but look at how the mains have so much bass at the lower end. Is that illustrating a 1st order rolloff? Which I think is supposed to be approximately 6 dB reduction between 80Hz and 40 Hz. FYI I set my levels at 65 dB to begin with.


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## angryht

Here is both combined.


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## angryht

Here is the waterfall of sub and mains combined.


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## angryht

Does the combined graph show that my sub level is too low?


And.. . how do I know what is reference. I set up the levels so that 65 dB was the reference in the preferences menu. I set it using the main speaker check/set levels. Again, I am trying to balance my sub with the mains.


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## robbo266317

Hi Greg, 
On the Def Tech Super Cube II you have the high pass set to minimum, ie 40 Hz, and the low pass set to 80 Hz I assume.
Can you turn Audyssey off, manually set the crossover in the amp to 80 Hz and run the sweeps again.


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## angryht

robbo266317 said:


> Hi Greg,
> On the Def Tech Super Cube II you have the high pass set to minimum, ie 40 Hz, and the low pass set to 80 Hz I assume.
> Can you turn Audyssey off, manually set the crossover in the amp to 80 Hz and run the sweeps again.


Audyssey is off and the crossover for the mains (the speakers I'm testing) are set to 80 Hz in the receiver. The subwoofer has a low level line in and the low pass and high pass on the sub are set to their highest value, which should mean the crossover in the receiver is doing the work. The high pass in the sub only works if the speaker outputs are connected. Since I've got the sub low pass (which could be used if I wanted to turn it down) set to the highest value, it's not doing anything. That means the receiver is doing the bass management.


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## robbo266317

That is confusing.

The two graphs suggest they are crossed over at ~40 Hz. :scratch:
What happens if you set them to cross at a higher frequency. 120 or 150 Hz?


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## angryht

robbo266317 said:


> That is confusing.
> 
> The two graphs suggest they are crossed over at ~40 Hz. :scratch:
> What happens if you set them to cross at a higher frequency. 120 or 150 Hz?


I agree it's a head scratcher. The crossovers seem to be half of the value shown in the receiver's menu. :huh: I think I've found part of my problem.

Here is the crossover set to 150. It looks like it's set at about 65. This is crazy:


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## angryht

The big hump between 30 and 40 Hz can be tamed a bit if I change the phase setting on my sub from 0 to 180 degrees. The green trace is set to 0 and the purple is 180. But the big dip at about 110 gets worse. I don't understand the phase graphs yet. The graph below is the combined sub and mains.


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## angryht

Well, here is my last measurement for the night. I was trying to match the sub to the mains but it looks like I may not have enough gain in the sub. Is there any way to get rid of the null at 110 Hz? I am guessing something would need to move.

Ooops! Looks like I changed the graph to linear instead of log. I'll have to change that.

I'm really curious about my crossover especially in the previous post showing the sub and mains separate traces when the crossover was set to 150 (2 posts back). This seems to be confirming what I was having trouble with and hearing so much bass in the speakers when I had it set to 80 Hz (which was more like 40 Hz).

Just not sure which frequency range to match to the sub, the 180 to 200 or the 130 to 160, or kind of an average.


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## angryht

Not sure if it helps or not but here is an updated drawing of my room. The marks along the bottom and the left side (with the Hz) are the room modes determined from the room mode calculator.


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## angryht

Or perhaps I should start over and just focus on the sub first. Anyone?


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## EarlK

Greg,

> You clearly know how to run REW to make meaningful measurements ( that's a good thing :T ).

> Here are some observations ( just my 2 cents before I go back to observing ) ;

*> I think you need to ;*

*(i)* Identify & eliminate the source causing your 130hz cancellation ( at some point ) .

*(ii)* Find a way to obtain steeper roll-offs for both the HiPass & LowPass sections of your system .
- It does seem ( with the LF "room-gain" in play here ) that your AVR is only giving you 6 db slopes . 
- Personally, I would want much steeper slopes than 6db an octave .
- This may mean taking away HiPassing & Bass-Management duties from your Onkyo ( which is clearly failing in both capacities , IMO ) .
- I read the specs for your sub ( slope of the HiPass & LowPass controls ) and it offers 12db & 24db ( for one or the other / I forget which ) 

*(iii)* You should get a handle on the problem with the non-linear output from that sub ( as pointed out by Waldo some 5 years back ) . 
- The bandwidth ( & linearity ) of your sub, looks to drastically change with the application of different input levels. ( Fwiw, this is quite bizarre , unless it's supposed to be a feature specific to this line of subs ) .

*(iv)* When one adds both points (ii) & (iii) together , it's no wonder you have problems with your systems low-end response .

*(v)* To effectively address either one or both points [ (ii) & (iii) ] , may require a forum jump ( thread relocation ) // ie; contact a forum moderator or administrator for an opinion about relocating . 

:sn:


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## angryht

Thanks so much for responding, EarlK.



EarlK said:


> Greg,
> 
> > You clearly know how to run REW to make meaningful measurements ( that's a good thing :T ).


Thanks, EarlK. It took a few days to get back into the swing but I'm getting there.



EarlK said:


> > Here are some observations ( just my 2 cents before I go back to observing ) ;
> 
> *> I think you need to ;*
> 
> *(i)* Identify & eliminate the source causing your 130hz cancellation ( at some point ) .


Yes, but probably more on that later. For now I'm really trying to figure out my crossovers. I upgraded my receiver since my previous testing a few years ago but the results are really screwy. I thought that since I got a receiver with Audyssey (Onkyo 606) that I didn't need to worry about measuring any more. I was wrong, especially since it appears that the crossover is completely different from the settings, e.g. setting to 150 Hz gives me a roll-off at about 75 Hz???



EarlK said:


> *(ii)* Find a way to obtain steeper roll-offs for both the HiPass & LowPass sections of your system .
> - It does seem ( with the LF "room-gain" in play here ) that your AVR is only giving you 6 db slopes .
> - Personally, I would want much steeper slopes than 6db an octave .
> - This may mean taking away HiPassing & Bass-Management duties from your Onkyo ( which is clearly failing in both capacities , IMO ) .
> - I read the specs for your sub ( slope of the HiPass & LowPass controls ) and it offers 12db & 24db ( for one or the other / I forget which )


Great points. Here are the specs for my sub (Def Tech, Super Cube II:http://www.definitivetech.com/documents/manuals/SuperCube%20I/SuperCubes_Manual_12909_read.pdf ):

SuperCube®II
Dimensions: 12"W x 12"D x 121/4"H
Frequency Response: 14 Hz – 200 Hz
Driver Complement: One 8" long-throw SuperCube Technology subwoofer coupled to two 8" infrasonic radiators
Ampliﬁer: 1250 Watts Digitally-Coupled Class D ampliﬁer
Low-Level: High-Pass Filter 12 dB/octave continuously variable (40 – 150 Hz)
Speaker Level High-Pass Filter: 6 dB/octave (80 Hz)
Low-Level Low-Pass Filter: 24 dB/octave continuously variable (40 – 150 Hz) plus unﬁltered LFE direct coupled input
Phase Control: 0 – 180 degrees continuously variable​
I can adjust the low pass filter if I connect to the low level input (not the LFE input). That would allow me to get a steeper drop from the sub but the speaker (high pass) would be the same.




EarlK said:


> *(iii)* You should get a handle on the problem with the non-linear output from that sub ( as pointed out by Waldo some 5 years back ) .
> - The bandwidth ( & linearity ) of your sub, looks to drastically change with the application of different input levels. ( Fwiw, this is quite bizarre , unless it's supposed to be a feature specific to this line of subs ) .
> 
> *(iv)* When one adds both points (ii) & (iii) together , it's no wonder you have problems with your systems low-end response .


That's why I got so frustrated that last time and quite measuring. But this time I'm gonna win! Do you mean Otto from my previous posts?



EarlK said:


> *(v)* To effectively address either one or both points [ (ii) & (iii) ] , may require a forum jump ( thread relocation ) // ie; contact a forum moderator or administrator for an opinion about relocating .
> 
> :sn:


I may have to do that. Thanks again.


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## EarlK

Yes, ( sorry ) , I meant to say Otto ( not Waldo ) . :rofl2: 

I guess I'm showing my age .

:dontknow:


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## angryht

Any more thoughts on the crossovers???

I'm thinking I should do some near field measurements.


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## angryht

Here is the near field measurements with the crossover set to 80Hz. I think this shows that I'm getting a lot of room effects in the previous measurements. I do have ports in the backs of my speakers. Would that cause problems too?









And below is with the Center channel added just to be complete.


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## robbo266317

From the near field it looks like your room interactions are indeed causing you grief.
The only options are to move the sub and/or mains to try and remove some of the problems.
The other thing that may be quicker is to do the sub crawl. Put the sub at the listening position then go around the areas you can place the sub with the mic while playing REW's white noise and look for the flattest response. 
Also check your layout compared to here http://www.realtraps.com/art_room-setup.htm


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## angryht

I'll try the crawl. I'm surprised at how different my readings are, near compared to seating position. I have 1"' Linacoustic on most of the walls and some cut triangular 'bass traps', so I thought that would help a bit more. It's still location, location location though. Thanks for the link, it's been a while since I poked around Mr. Winer's site. Fantastic resources.


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## angryht

What about the speaker ports? Could that be causing some of this?


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## EarlK

Hi Greg,

> The nearfields look good ( what's your measuring distance here ? )

> Are we to assume that the Onkyo is providing both subs & mains with this 80hz crossover point ?

> The nearfields show that the HP & LP slopes ( from the Onkyo I guess ) are quite steep / meaning the subs builtin filters won't do any better .

> Close off the ports belonging to the main speakers ( stuff them with either foam or fabric ) and remeasure ( nearfield & farfield ) to see how much LF content ( the sealing ) removes .

:sn:


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## angryht

EarlK said:


> The nearfields look good ( what's your measuring distance here ? )


The Radio Shack mic is about 1.5 inches away from the sub and speakers when measuring the near field. I am also wondering about the 2 passive woofers in the Super Cube II. Could that have some adverse effect.



> Are we to assume that the Onkyo is providing both subs & mains with this 80hz crossover point ?


That's correct. The sub is connected to the Onkyo and the Onkyo is set to 80 Hz crossover for the speakers.



> The nearfields show that the HP & LP slopes ( from the Onkyo I guess ) are quite steep / meaning the subs builtin filters won't do any better .


Good. That should help keep things simple, I hope.



> Close off the ports belonging to the main speakers ( stuff them with either foam or fabric ) and remeasure ( nearfield & farfield ) to see how much LF content ( the sealing ) removes .


I have a choice of a couple of insulation materials. I have some batting and a bunch of left over Linacoustic. I've seen somewhere (can't remember where at the moment) where the rolled up Linacoustic to seal the ports. Is there a recommended material for best results?


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## EarlK

> Is there a recommended material for best results?


Whatever material stops air-flow / / socks, rags, small pillows, can all work just fine, when jammed into a cabinets port .

:sn:


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## angryht

EarlK said:


> Whatever material stops air-flow / / socks, rags, small pillows, can all work just fine, when jammed into a cabinets port .
> 
> :sn:


Got it! Thanks. It sure looks like that the extended bass in the mains is a serious problem. I bet the fact that I need to put them (the mains) in the corner doesn't help much either. Although I don't have much of a choice based on how small my room is. 

Here are both graphs again, for review.


Here is from the seating position:








. . .and here is near field (just sub and mains this time) :


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## angryht

It's interesting how both near and seating position measurements for the mains have that hump between about 35 and 45 Hz, even when it's further down the curve at near field.


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## angryht

EarlK said:


> Close off the ports belonging to the main speakers ( stuff them with either foam or fabric ) and remeasure ( nearfield & farfield ) to see how much LF content ( the sealing ) removes .
> 
> :sn:


 I was doing some searches for sealed ports, before and after measurements, but I couldn't find any. If anyone has some examples, I'd love to see them.


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## angryht

Here is a comparison with sealed and open ports @ crossover = 80 Hz:
Near field sealed ports = Blue (lowest @ 50Hz)
Normal Speaker position with open ports = Green (highest @ 50 Hz)
Normal Speaker position with sealed ports = Blue (middle @ 50 Hz)

It looks like sealing the ports helped, yes?


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## robbo266317

That certainly looks more like the result you are after. I was going to suggest setting the mains to "small"but sealing the ports seems to have done the trick. :T


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## angryht

robbo266317 said:


> That certainly looks more like the result you are after. I was going to suggest setting the mains to "small"but sealing the ports seems to have done the trick. :T


They are set to 80 Hz crossover. Isn't that the same thing? Now I think I need to do some more work moving my sub around.


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## EarlK

Good Pic ! Thanks ! ( also, thank-you very much for labeling your different files in a meaningful way )

*Some Observations ( & To-Do's ) ;*

(i) Your space has an enormous amount of cabin ( room ) gain causing you LF problems . ( I thought I would repeat the obvious ) .

(ii) Running your mains with sealed ports here, is the way to go here ( since doing so partially offsets the "over the top" room gain ) .

(iii) ( If possible on your AVR ) , I would now apply a 40 or 50 hz PEQ cut filter ( to your front speakers only ) .
- For Now ; Set it to cut by 10 db // make the filter 1/2 octave wide . ( BTW, PEQ = Parametric EQ )

(iv) Repeat your measurements ( at the listening position ) with ( & without ) the EQ filter applied ( from now on, keep the main speakers sealed ) .

:sn:


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## angryht

*sealed and open ports compared*

Here's comparing open ports with crossover set to 150Hz to sealed ports with crossover set to 80Hz. Looks like it also helped the dip a little.

For clarity:
Purple = the crossover set to 150Hz with the ports open
Green = the crossover set to 80Hz with sealed ports


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## angryht

^ . . . but maybe got a little deeper dip in the 170 Hz to 200 Hz range. 

Oh wait, EarlK, I just noticed you replied. I better read that.


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## angryht

> *Some Observations ( & To-Do's ) ;*
> 
> (i) Your space has an enormous amount of cabin ( room ) gain causing you LF problems . ( I thought I would repeat the obvious ) .


Yep, that seems to be a problem. I have a feeling that having the mains basically in the corners of the front of the room is causing a lot of that. I did do a quick measure with the speakers pulled out about a foot but it had very little affect.



> (ii) Running your mains with sealed ports here, is the way to go here ( since doing so partially offsets the "over the top" room gain ) .


I'm on board with that. So glad I did that and thanks for suggesting it! I also sealed the center channel but I haven't done the measuring on that from the seating position.



> (iii) ( If possible on your AVR ) , I would now apply a 40 or 50 hz PEQ cut filter ( to your front speakers only ) .
> - For Now ; Set it to cut by 10 db // make the filter 1/2 octave wide . ( BTW, PEQ = Parametric EQ )


Hmmm. . .would that require a BFD? At this point, that's not an option (probably). That requires preamp outputs, correct? I knew these answers before, I just need to relearn. Are there any other options? My receiver has a manual EQ, but I've read that it won't do much. I'll check out the set up guide for the BFD again.



> (iv) Repeat your measurements ( at the listening position ) with ( & without ) the EQ filter applied ( from now on, keep the main speakers sealed ) .


I figured it was time to see if I can get the sub dialed in at this point. Does that make sense?

Thanks again for the help!


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## angryht

onder:Wait! There may be hope for a BFD after all. Does it just connect between the receiver and the sub? Sorry if I'm a little slow.


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## robbo266317

I would run Audyssey again after you get the response as flat as you can by moving the speakers. 
Then see how your graphs look. (You may also be able to set filters manually, My Onkyo has this available)


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## angryht

Thanks. I see that there are settings for different frequencies in my Onkyo 606. Have you had good success with your Onkyo? Which model do you have?


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## robbo266317

I have been happy with TX-SR607 except I think it needs a factory reset and reprogramming.
The OSD for the setup no longer appears after I replaced my PVR. The old unit was composite and the new HDMI.
For me I found the best location for the sub was slightly off centre and 2m (~6') behind the couch.


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## angryht

robbo266317 said:


> I have been happy with TX-SR607 except I think it needs a factory reset and reprogramming.
> The OSD for the setup no longer appears after I replaced my PVR. The old unit was composite and the new HDMI.
> For me I found the best location for the sub was slightly off centre and 2m (~6') behind the couch.


Are you using any of the manual EQ or Audyssey? Or maybe you have a BFD?

Regarding the OSD, have you seen the many problems associated with the capacitors and the HDMI going out. Lots of problems with the 606. I had to have mine serviced for that same reason. On the 606 the OSD going out is the first sign of the problem with the capacitors. The next problem (with the 606 at least) is no video from that HDMI input.


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## robbo266317

angryht said:


> Are you using any of the manual EQ or Audyssey? Or maybe you have a BFD?
> 
> Regarding the OSD, have you seen the many problems associated with the capacitors and the HDMI going out. Lots of problems with the 606. I had to have mine serviced for that same reason. On the 606 the OSD going out is the first sign of the problem with the capacitors. The next problem (with the 606 at least) is no video from that HDMI input.


I'm using Audyssey, it seems to do a reasonable job for me. I am still considering getting a BFD, for the extra versatility, as they are quite reasonably priced. 
I was going to rerun some sweeps this week but couldn't get in to adjust anything.

OK, I did the reset, power on while holding vcr/dvr, and I have the setup display again. :sweat:

I will keep an eye out for the other issues, thanks for the heads up.


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## EarlK

*To Review ( your goals ) ;*

I believe you'll enjoy the sound of your system ( at the listening position ) if you can achieve system responses closer to the following nearfield captures .










As opposed to what has previously existed ;










Some progress has been made ( sealing the ports of the main speakers ) giving the middle trace in the following capture ;










I would encourage you to use the onboard EQ of the Onkyo to see if you can do better at matching the nearfield response by pulling down 65hz a few db in your AVR ( too bad 40hz is offered as a choice / that would be really helpful here ) . Anyways, you know the drill ; Make some change, remeasure & compare .

Regarding the sub ;

> It's time to move it out from where it is and start measuring the response in various locations .
> Essentially, (IMO) you are after a new location that offers a response that is closest to the ideal ( the response as measured in the nearfield / see the first pic ) .









:sn:


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## angryht

> Regarding the sub ;
> 
> > It's time to move it out from where it is and start measuring the response in various locations .
> > Essentially, (IMO) you are after a new location that offers a response that is closest to the ideal ( the response as measured in the nearfield / see the first pic ) .


Excellent! And that is exactly what I did last night. Here are some comparisons with the sub in different location and the near field measurements:

Here is the old location compared to the near field measurement. Actually, the rest of the graphs below will have the near measurement for reference:

Below is the old location:
Dark Red (without the hump @ ~ 30 Hz) = near field (the goal)
Greenish = Old/current sub location (just to the right of the left front spkr)









Below is position 4:
Dark Red = near field
Purple = position 4 (against the left wall)









Below is position 3:
Dark Red = near field
Green = position 3 (again, against the left wall but as close to the front)









Below is position 2:
Dark Red = near field
Yellow = position 2 (against the right wall, about 4' back from the front)









Below is position 1:
Dark Red = near field
Green = position 1 (against the right wall in the nook by the door)









I think I may have found my winner!

Edit: Here's the drawing to show the test locations:


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## ALMFamily

Wow, no doubt - position one is almost spot on. Thanks much for posting all the details throughout this thread - great learning experience for those of us with this task in front of us. Cheers!


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## angryht

Thanks, ALM.

One note on the previously my posted graphs (on the first page of this thread here and then re-posted by EarlK right before my last measurements)

The reason it's different than the 'old location' is that the phase was set at 180 deg previously and then 0 for the more recent posts. More on that coming up! Maybe there is more to that like the ports in the mains (before they were sealed) contributed somewhat. I'm not sure.


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## angryht

Now, how do I determine what the phase reading is telling me?

Here is my near field measurement with phase showing:










Here is my old position with the phase showing:









Here is my position 1 with the phase showing:










I tried to go through the help file but I didn't understand what to look for. What would be the target, to get close to the near field measurements?? I'd like a simplified clarification if possible.


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## angryht

I did find this thread that seems to give a pretty straight forward discussion about phase: http://www.hometheatershack.com/forums/rew-forum/54146-guidelines-phase-graphs-valutation.html I'll have to take a closer look.


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## angryht

robbo266317 said:


> OK, I did the reset, power on while holding vcr/dvr, and I have the setup display again. :sweat:


I'm glad to hear that!


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## EarlK

Glad you found a better location . :clap:

Now the challenge you have is to integrate that subs new position with the fronts ( ie ; add some delay to it's AVR out ) .












> Green = position 1 (against the right wall in the nook by the door)


> Cool spot , I don't think I saw that coming ( I'll admit though , that I gave it little to no thought ) .onder:


> To get into the ballpark ( for sub delay ) simply measure the distance in feet x .8 ( & add a couple of milliseconds to account for the slowness of the woofer / slowness = group delay ) . Add that number into the delay settings within the AVR ( sub out ) . Looks like 5 to 7 ms to these eyes ( ms = milliseconds )

> Then do a sweep to see how they combine ( Main L & R ) with the sub .

> Forget "Phase" ( for now ) as seen in those new sub pics / it's simply telling you ( quite obtusely , via all the rotations displayed as phase "wraps" past 360° many times ), that you should add some delay to the sub / which I think you knew anyways lddude: .

There are other methods for dialing in the sub delay more accurately, which we'll get to .

:sn:


----------



## angryht

EarlK said:


> Glad you found a better location . :clap:
> 
> Now the challenge you have is to integrate that subs new position with the fronts ( ie ; add some delay to it's AVR out ) .
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> > Cool spot , I don't think I saw that coming ( I'll admit though , that I gave it little to no thought ) .onder:


Thanks for posting my layout, that helps. I never would have thought that it would be a good spot (nook behind the main door). Last time I measured (back in 2007 & 2008) I didn't even try it.




> > To get into the ballpark ( for sub delay ) simply measure the distance in feet x .8 ( & add a couple of milliseconds to account for the slowness of the woofer / slowness = group delay ) . Add that number into the delay settings within the AVR ( sub out ) . Looks like 5 to 7 ms to these eyes ( ms = milliseconds )


I wonder if I should try to get things fairly close then run Audyssey? It provided a delay by increasing the distance to the sub. It should be noted that all the readings have been with audyssey turned off. Although the distances are still the same as the setup gave me from audyssey. I'll check the manual.



> > Then do a sweep to see how they combine ( Main L & R ) with the sub .
> 
> > Forget "Phase" ( for now ) as seen in those new sub pics / it's simply telling you ( quite obtusely , via all the rotations displayed as phase goes past 360° many times, that you should add some delay to the sub / which I bet you knew anyways lddude: ) .


Consider it forgotten - for now. :dontknow: 



> There are other methods for dialing in the sub delay more accurately, which we'll get to .
> 
> :sn:


Very interested in this but I'm not sure if audyssey would help or not. I'll leave it off for now.

Still a lot to do but we're making progress! :T


----------



## EarlK

> Set the delay via the method I just mentioned / then capture a sweep of Main Fronts with sub /

> Then run Oddysey / then capture a sweep of Main Fronts with sub 

> Compare the sweeps ( of both methods ) & choose what looks & sounds best to you .

:sn:


----------



## angryht

Got it! Homework assignment received.


----------



## angryht

> > To get into the ballpark ( for sub delay ) simply measure the distance in feet x .8 ( & add a couple of milliseconds to account for the slowness of the woofer / slowness = group delay ) . Add that number into the delay settings within the AVR ( sub out ) . Looks like 5 to 7 ms to these eyes ( ms = milliseconds )


I double checked the manual and the delay is determined by the distance setting. So, based on what you said above, I'll measure it and add 2.5 FT to start with to account for slowness. 

That's based on:
Distance in feet x 0.8 = milliseconds delay

So, to get the Distance (to add to the actual distance) and get 2 (a couple) more milliseconds I get:
2milliseconds/0.8 = 2.5 FT added to the actual distance. That makes a lot of sense since when I did it with Audyssey, it gave me a distance that was actually 2 FT greater than the actual, which is to account for that as well. I'm guessing that is based on the speed of sound @ 1130 Feet per second, right? 1 FT / 1130 FPS = 0.0009 sec? which is about 0.8 msec.


----------



## EarlK

> So, to get the Distance (to add to the actual distance) and get 2 (a couple) more milliseconds I get:
> 2milliseconds/0.8 = 2.5 FT added to the actual distance. That makes a lot of sense since when I did it with Audyssey, it gave me a distance that was actually 2 FT greater than the actual, which is to account for that as well.


> What delay time did Audyssey come up with ?
> Using my rough formula, what delay time does it give you ?




> I'm guessing that is based on the speed of sound @ 1130 Feet per second, right? 1 FT / 1130 FPS = 0.0009 sec? which is about 0.8 msec.


> More or less correct . The speed of sound actually varies somwhat based on a few other atmospheric factors .

:sn:


----------



## angryht

EarlK said:


> > What delay time did Audyssey come up with ?
> > Using my rough formula, what delay time does it give you ?


For my previous setup, I think it gave a few more feet than actual. I think the actual was 10 FT and it gave 12 (although it may have been 14). Either way it was more than actual, which, based on the Audyssey FAQ's, is typical.

I'll measure and add a couple of feet. I haven't updated it yet based on the new location yet. Do you think that will change the graph? You were right about your guess, the new location is about 5 FT away + or -.




> > More or less correct . The speed of sound actually varies somwhat based on a few other atmospheric factors .


Good. Just wanted to make sure I was getting the idea.


----------



## EarlK

> I'll measure and add a couple of feet. I haven't updated it yet based on the new location yet. Do you think that will change the graph? You were right about your guess, the new location is about 5 FT away + or -.


Yes, 2ft either way ( unless one hits dead-center of the sweet spot ) will change the FR of the overlap ( transition zone ) between the sub & the mains .

:sn:


----------



## angryht

Another quick question about smoothing the curves. Should I add a smoothing to them or just leave them alone for now?


----------



## angryht

EarlK said:


> Yes, 2ft either way ( unless one hits dead-center of the sweet spot ) will change the FR of the overlap ( transition zone ) between the sub & the mains .


Overlap. . . it should not affect the sub alone, right?


----------



## EarlK

> Another quick question about smoothing the curves. Should I add a smoothing to them or just leave them alone for now?


1/6 OR 1/3 SMOOTHING for full range sweeps is fine .



> Overlap. . . it should not affect the sub alone, right?


A timing difference between the Main & Subs is only relevant when both are playing-back the same content .




:sn:


----------



## angryht

Got it.


----------



## angryht

FYI, or maybe it's mostly for me to keep track of. Here is my drawing to show the locations of the subs when I did the testing. I also edited the original post with the test data in it: HERE


----------



## angryht

EarlK said:


> > Set the delay via the method I just mentioned / then capture a sweep of Main Fronts with sub /
> 
> > Then run Oddysey / then capture a sweep of Main Fronts with sub
> 
> > Compare the sweeps ( of both methods ) & choose what looks & sounds best to you .
> 
> :sn:


Okay, here they are the comparison with and without audyssey:

Blue = with no audyssey
Green = with audyssey

I know which one looks better to me. What say you?

Audyssey set my distance to 8 FT and I had it set to 7 FT in the 'without audyssey' measurement. Also, audyssey set my sub to - (neg) 4 and I had it at 0 for my measurement. And a reminder that I only have 2EQ which I believe is the lowest version of Audyssey.


----------



## angryht

Should I start maybe adjusting the phase on the sub? It was set to 0 for these measurements.


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## robbo266317

Does it improve if you go in and manually set it back to 7 feet like you had?


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## angryht

Here are several comparisons to the 'no audyssey' measurement. In all of them the no audyssey (as seen in the legend) is red. Note that when I set up the levels, it was to 65 dB for all.


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## angryht

5 FT looks pretty close but the hump at 30 Hz is still better in the no audyssey. Or maybe I'm missing a big picture thing.


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## EarlK

Yes, the manual entry approach ( using a distance of 7ft ) seems to be the one to keep for now . I would try playing with the phase knob ( in 45° increments ) to see if you can fill in the response hole somewhat ( at 130 hz ) .

> Honestly, I'm having a hard time reconciling the fact that the manually entered 7ft distance doesn't equal Audysseys 7 ft .
- The only reason I can come up with is maybe the mere act of engaging Audyssey adds 2 ms of default delay ( & then it only needs to add 5 ms more, to = 7 ) . 
- Which leaves me thinking "Great , yet another consumer display that one can't trust " / why not tell us about this 2ms default . Oy vay !










> Anyways , about the 15db deep suck-out at @ 130hz . You can't fix that with EQ . I would say that is a classic case of  *SBIR Speaker Boundary Interference Response* 
- The relatively high frequency of that huge null is quite consistent with the closeness of your speakers to the rear & side walls ( a consequence of the overall "coziness" of this room ).
- You'll need to research some effective mitigation techniques here ( this area is really not my thing ) . 
- FWIW, that high a frequency ( 130hz ) will require less depth ( of bass trapping super-chunks ) than if the hole was an octave lower ( so count yourself lucky , I suppose) .

:sn:

PS 1 ; BTW , how does this all sound , now ? Afterall that's what this is all about, isn't it ? :huh:

PS 2 ; Can you please post an .mdat file of *only the following 2 Full Range sweeps that include the main L,R speakers with sub *; ( the original sub position with the 80hz crossover + your new sub position with the manually entered 7ms delay on the sub ) I don't want the rest . ( The original sub position file can be a file where the main speakers were sealed ) Thanks !


----------



## angryht

EarlK said:


> Yes, the manual entry approach ( using a distance of 7ft ) seems to be the one to keep for now . I would try playing with the phase knob ( in 45° increments ) to see if you can fill in the response hole somewhat ( at 130 hz ) .


Got it! I'll be able to do that this weekend, or even tonight.



> > Honestly, I'm having a hard time reconciling the fact that the manually entered 7ft distance doesn't equal Audysseys 7 ft .
> - The only reason I can come up with is maybe the mere act of engaging Audyssey adds 2 ms of default delay ( & then it only needs to add 5 ms more, to = 7 ) .
> - Which leaves me thinking "Great , yet another consumer display that one can't trust " / why not tell us about this 2ms default . Oy vay !


Yeah, and I never would have thought that the distance (delay) would affect the measurements so much.



> > Anyways , about the 15db deep suck-out at @ 130hz . You can't fix that with EQ . I would say that is a classic case of  *SBIR Speaker Boundary Interference Response*
> - The relatively high frequency of that huge null is quite consistent with the closeness of your speakers to the rear & side walls ( a consequence of the overall "coziness" of this room ).


I'll check out the link to the GIK article.

Question about your post: Is there supposed to be a link in this sentence below or is the reference the same as the link to the GIK article above?


> - You'll need to research some effective mitigation techniques here ( this area is really not my thing ) .





> - FWIW, that high a frequency ( 130hz ) will require less depth ( of bass trapping super-chunks ) than if the hole was an octave lower ( so count yourself lucky , I suppose) .


Oh, I do.



> PS 1 ; BTW , how does this all sound , now ? Afterall that's what this is all about, isn't it ? :huh:


I haven't really listened to the system critically yet. I'll report back on that. Good point!



> PS 2 ; Can you please post an .mdat file of *only the following 2 Full Range sweeps that include the main L,R speakers with sub *; ( the original sub position with the 80hz crossover + your new sub position with the manually entered 7ms delay on the sub ) I don't want the rest . ( The original sub position file can be a file where the main speakers were sealed ) Thanks !


I'm not sure I understand your request. You want the 7 FT distance reading (sub + mains) with the sub in the new position (with no audyssey and the 7FT distance set for the sub). You also want the sweep with the old sub position (sub + mains). The best I can do for now (before I get home this afternoon) is to post the .mdat file that has all the readings shown on the graph. Is that right? I apologize that it is not what you requested and you are welcome to disregard it and wait until I can get some of the other reading removed from the .mdat file.


----------



## angryht

> PS 2 ; Can you please post an .mdat file of only the following 2 Full Range sweeps that include the main L,R speakers with sub ; ( the original sub position with the 80hz crossover + your new sub position with the manually entered 7ms delay on the sub ) I don't want the rest . ( The original sub position file can be a file where the main speakers were sealed ) Thanks !


Okay. Here you go. Here is the .mdat file with the original position (combined) and the new position with the 7 ms (7FT) delay on the sub in the new position. 

By the way, I watched a movie tonight and it sounded much better with the sealed ports!!


----------



## EarlK

Thanks ! I downloaded both files .

I'll get back to you later .


----------



## angryht

This seems odd. I moved the mic a bit closer to the back wall and reran audyssey. I did sweep but left the crossover set to full band. It looks like I get a better response in the low end. What the ?????


----------



## robbo266317

As the Real Estate guys will tell you, Location, Location, Location!


----------



## angryht

robbo266317 said:


> As the Real Estate guys will tell you, Location, Location, Location!


Right, but here is the reading from the same seating location but with the sub on and the crossover set to 80 Hz. Why am I getting such a better response with not sub? Is the sub canceling out the mains in the lowest frequency range and amplifying things around 30 to 40Hz? :dontknow: Is this a phase issue?


----------



## angryht

EarlK said:


> Yes, the manual entry approach ( using a distance of 7ft ) seems to be the one to keep for now . I would try playing with the phase knob ( in 45° increments ) to see if you can fill in the response hole somewhat ( at 130 hz ) .


Here are the measurements with varying settings for the phase of the sub. In all, the sub set to phase = 0 is green:









































It sure looks like I should go with phase set to 180.


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## EarlK

> Which one sounds the best ? 
> Anyways , yes, the reason ( you see less bass below 26hz ) is phase cancellation ( caused by the sub inverting it's output below the boxes tuning frequency ) .











> That's a winning looking graph . :T
- Remember this setting ( & sub position ) as your "return to default" ( the new normal ) . lddude:

(A) Now, another matter .

(i) We ( sort of know ) that Audyssey can't be trusted ( in your particular circumstances ) to choose the delay settings .
- There's always a reason for such paradoxes . I believe it's because it's simply getting confused by room acoustics . I looked at the ETC for your main speakers , and it's apparent that the side walls ( & likely the soffit ) are giving off such strong delayed reflections ( equal in amplitude to the main speakers impulse ) that Audyssey "thinks" the speakers are actually further away than they physically are . ( That's my best guess for now ) .
- Once you clear up the room acoustics ( in that end of the room ), I bet that Audyssey will give more accurate delay times .

(ii) Having said all that , I had a *"serious derailment" in my "train in logic*" when arriving at the delay time ( for the sub ) via the old standby, mental calculation method. :huh:
- The derailment was ; since the sub is already delayed somewhat ( by it's own mechanics & weight ) that inherent delay should be _*"subtracted"*_ from the delay calculated by the physical measurement method ( *& not added* , as I first instructed ) .
- This means, the current 5 real ft measured difference should have been 5ft ( *less* whatever the subs guesstimated figure would be for overcoming its' own inertia ). 
- Meaning, 3 to 4ft should have been the starting area of figures ( from the guesstimating perspective ) .
- Coincidentally, this new ( smaller ) figure is somewaht supported by REWs method of using any differentials observed between the 2 speakers "Excess Group Delay " figures, ( to arrive at a delay time ) . 
- The way I interpret REWs method ( of using these ExGD figures ) would suggest a more accurate delay time ( for the sub ) would be 3.5 ms ( or 4.375 ft ) at around 70hz . This is why I wanted your .mdat files .
- Anyway, do you feel like trying a new delay time ? :wave: If so, set the phase back to 0 deg. on the sub ( then remeasure ).
- If not, it's no biggy, because as you have discovered, sometimes one can fudge a lot of this by simply adjusting the phase knob .


:sn:


----------



## angryht

EarlK said:


> > Anyways , yes, the reason ( you see less bass below 26hz ) is phase cancellation ( caused by the sub inverting it's output below the boxes tuning frequency ) .


Is that normal? And should I start a thread of who wants to buy my sub? Does this have anything to do with having the super cube configuration of 2 passive woofers and 1 active? Maybe my room is too small for this type of sub.




> > That's a winning looking graph . :T
> - Remember this setting ( & sub position ) as your "return to default" ( the new normal ) . lddude:


Will do. But I'm still a little confused about the mains giving a better measurement down to a lower frequency.



> (A) Now, another matter .
> 
> (i) We ( sort of know ) that Audyssey can't be trusted ( in your particular circumstances ) to choose the delay settings .
> - There's always a reason for such paradoxes . I believe it's because it's simply getting confused by room acoustics . I looked at the ETC for your main speakers , and it's apparent that the side walls ( & likely the soffit ) are giving off such strong delayed reflections ( equal in amplitude to the main speakers impulse ) that Audyssey "thinks" the speakers are actually further away than they physically are . ( That's my best guess for now ) .
> - Once you clear up the room acoustics ( in that end of the room ), I bet that Audyssey will give more accurate delay times .


I have Linacoustic on the front and sides and the bottom of the soffit. Is there more I can do?



> (ii) Having said all that , I had a *"serious derailment" in my "train in logic*" when arriving at the delay time ( for the sub ) via the old standby, mental calculation method. :huh:
> - The derailment was ; since the sub is already delayed somewhat ( by it's own mechanics & weight ) that inherent delay should be _*"subtracted"*_ from the delay calculated by the physical measurement method ( *& not added* , as I first instructed ) .
> - This means, the current 5 real ft measured difference should have been 5ft ( *less* whatever the subs guesstimated figure would be for overcoming its' own inertia ).
> - Meaning, 3 to 4ft should have been the starting area of figures ( from the guesstimating perspective ) .
> - Coincidentally, this new ( smaller ) figure is somewaht supported by REWs method of using any differentials observed between the 2 speakers "Excess Group Delay " figures, ( to arrive at a delay time ) .


I'll need a little time to digest all of that. :dontknow:




> - The way I interpret REWs method ( of using these ExGD figures ) would suggest a more accurate delay time ( for the sub ) would be 3.5 ms ( or 4.375 ft ) at around 70hz . This is why I wanted your .mdat files .
> - Anyway, do you feel like trying a new delay time ? :wave: If so, set the phase back to 0 deg. on the sub ( then remeasure ).


I'm in! I really appreciate you taking the time.




> - If not, it's no biggy, because as you have discovered, sometimes one can fudge a lot of this by simply adjusting the phase knob .


I've seen a lot of variation when I adjust the phase so I'll keep measuring.


----------



## angryht

> - The way I interpret REWs method ( of using these ExGD figures ) would suggest a more accurate delay time ( for the sub ) would be 3.5 ms ( or 4.375 ft ) at around 70hz . This is why I wanted your .mdat files .


I don't think I understand the ExGD figures. I have a limit in that my receiver only allows the distance on the sub to be + or - 5 from the distance of the mains.


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## EarlK

> I don't think I understand the ExGD figures. I have a limit in that my receiver only allows the distance on the sub to be + or - 5 from the distance of the mains.


> If your AVR's delay section only does increments in whole numbers ( no decimals ) then then try either 3 & 4 ft .












> Is that normal? And should I start a thread of who wants to buy my sub? Does this have anything to do with having the super cube configuration of 2 passive woofers and 1 active? Maybe my room is too small for this type of sub.



> It's normal for a sub that is either ported or has passive woofers ( like yours ) to flip its' acoustic phase below the subs tuning frequency ( which must be 30hz for your cube ) .
> If you wanted a sub that went to 20hz you should have purchased one with a 20hz tuning ( if it was a ported or passive type ) .

> If you want LF extension down to 20hz ( to better combine with your mains LF below 30hz ) you would do better with a sealed sub ( under these circumstances ) / even if it has a 30hz tuning .

> Having said that, you could play with the phase knob on the sub ( to see if you can get better LF addition below 30hz between your Mains & the Sub) . just be aware that success down lower will be at the expense of the "good signal combining" you are accomplishing from 30hz upwards . 

:sn:


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## jtalden

EarlK said:


> (ii) ...
> The derailment was ; since the sub is already delayed somewhat ( by it's own mechanics & weight ) that inherent delay should be _*"subtracted"*_ from the delay calculated by the physical measurement method ( *& not added* , as I first instructed ) .
> - This means, the current 5 real ft measured difference should have been 5ft ( *less* whatever


Earl, I think you were correct the first time. increasing "distance" in an AVR for the sub is the same as reducing the time delay for the sub signal. It has the same effect as moving the sub closer to the LP. The more delay there is in sub the greater the distance setting needs to be. Normally the physical distances are acceptably close to a resonable setting, but it is not unusual to get a better handoff with the sub distance set a little larger than the physical distance. [This all assumes that the main speakers are set at the proper physical distances.]


----------



## angryht

> > It's normal for a sub that is either ported or has passive woofers ( like yours ) to flip its' acoustic phase below the subs tuning frequency ( which must be 30hz for your cube ) .
> > If you wanted a sub that went to 20hz you should have purchased one with a 20hz tuning ( if it was a ported or passive type ) .


I think I understand but it seems unusual that the specs for the super cube say:


> Frequency Response: 14 Hz – 200 Hz


 I wasn't aware of getting a sub with a 20Hz tuning. Learn something everyday.


----------



## EarlK

> You're going to need to redo your acoustic treatment ( @, in the first 6' of your room ) at the end where the main speakers are located .

> Here's some reading for you to do ;

 * Listen to the Music, Not the Room !* 

 * Issues that Room Correction Can't Correct !*  

 *What is SBIR ?* 

 *Red Spade Audio Blog ( SBIR )* 

 *SBIR !* 

 *Google " Speaker Boundary Interference Response "* 

> Once you understand the cause of your 120 hz notch / you can then start to apply proper room treatment to mitigate it .

>  *Linacoustic*  looks to me to be much too rigid to offer the LF trapping that you need .

> I've included a zipped pdf of a document put together by 2 acousticians that lays out some guidelines towards getting better sound in small rooms .

> I've also included an ETC of just your one speaker ( no sub ) in your room .
> It shows ( to those who know how to look at this stuff ) the severity of the problems within your room .

> You should start a new thread ( for help taming your rooms problems ) in the  *HTS Acoustics Forum*  ( after you've done some reading on SBIR ) .


:sn:


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## angryht

^This is great stuff, Earlk. Thanks again for your help and knowledge. Now, back to studying!


----------



## EarlK

jthalden said:


> Earl, I think you were correct the first time. increasing "distance" in an AVR for the sub is the same as reducing the time delay for the sub signal. It has the same effect as moving the sub closer to the LP. The more delay there is in sub the greater the distance setting needs to be. Normally the physical distances are acceptably close to a resonable setting, but it is not unusual to get a better handoff with the sub distance set a little larger than the physical distance. [This all assumes that the main speakers are set at the proper physical distances.]


Hi John, 

> That all seems pretty counter-intuitive to me / not saying that's not how the AVR actually works/ just that it seems to be "Orwellian Doublespeak" to a guy from the Sound Reinforcement side of things .

> Anyways, it's really a simple matter to include the AVR within a ( time-referenced ) REW loopback ( made with the soundcard) to "see" what adjusting the AVRs knobs actually do accomplish .

> Anyhow, I presently stand by my observation that the sub is delayed by a bit too much .
> Comparing the Excess Group Delay plots for both the main speaker & the sub, seems to show ( the pic is a mess ) that the sub has more delay in the area of crossover ( & this fits nicely with my newly "revised logic" ) .

> I also agree there's a fair amount of wiggle room when syncing subs to mains / due to the wavelengths involved being so long .

:sn:


----------



## angryht

It does look like moving the mic a bit back from my previous measurements reduced the dip at 120 Hz but it has shifted to the 200 Hz.


----------



## robbo266317

angryht said:


> It does look like moving the mic a bit back from my previous measurements reduced the dip at 120 Hz but it has shifted to the 200 Hz.


That is what I would expect from your (and almost any) room. As EarlK suggests, it may be time to start a room treatment thread as that impulse response looks quite bad.


----------



## angryht

EarlK said:


> I've also included an ETC of just your one speaker ( no sub ) in your room .
> > It shows ( to those who know how to look at this stuff ) the severity of the problems within your room .


Let's explore this a little. I am just trying to learn the interpretation but based on the graph you provided what exactly does it show? From what I've read so far, are the two peaks separated by the 9.9 FT the actual sound and the rest are the reflections? That's pretty cool!


----------



## EarlK

Greg said:


> Let's explore this a little. ,,,,,


> As I mentioned, you should explore this ( interpretation of ETC ) within the  *HTS Acoustics Forum .*  

> Alternately , SAC ( from within this forum ) loves to talk about ETC .

> My participation in this thread in now winding down / it's time to hand your education off to someone else ) .


:sn:


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## angryht

Thanks again. I appreciate your time and efforts!


----------



## angryht

EarlK said:


> > I've also included an ETC of just your one speaker ( no sub ) in your room .
> > It shows ( to those who know how to look at this stuff ) the severity of the problems within your room .
> 
> > You should start a new thread ( for help taming your rooms problems ) in the  *HTS Acoustics Forum*  ( after you've done some reading on SBIR ) .


OK, I've done some reading on SBIR but not enough remeasuring to post in the acoustics forum. I will soon, but I wanted to understand what was done with my .mdat file to show the distance of the reflection. I understand that Earl has mentioned that his participation in this thread was winding down so if anyone else could help me, that would be greatly appreciated. As a slight aside, I double checked my connections from my previous measurements and determined I had things connected incorrectly. I actually had both the right and left outputs from the soundcard connected directly into the left and right of the receiver. :doh: I have since only connected the right channel output to a splitter and then to the receiver. I also did the loop back by connecting the left output to the left input (of the soundcard). So, I think I have everything connected correctly. Oh yeah, and I attached a piece of allthread to my tripod so I could get the mic (SPL meter) off of the couch:R​So, back to the ETC measurement provided below:









In order to get that type of information from the impulse response, I should zoom into the first high reflection point and, while holding down the control button, use the right mouse button and drag from the incident (direct) to the reflection point. Is that correct? I did some measurements last night and I could not get it to work but I was using the left mouse button first then the control button then the right mouse button. I'm Just trying to understand these great tools that REW has to offer.

And the conclusion that:


> > You're going to need to redo your acoustic treatment ( @, in the first 6' of your room ) at the end where the main speakers are located .


is based on the fact that the reflected path is very close to the actual distance to the mic, right. Plus the fact that my mains are located so close to the side walls. and the math behind it is just 1125 FPS multiplied by the time (0.0088) = 9.9 FT. Again, just trying to understand these things one step at a time.


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## fotto

Your measurement procedure is correct (CTL + R mouse button), but you really need to take new measurements with your loopback properly connected. Once you run a sweep and display the ETC, you'll get something more like below pic, where your direct signal is at x ms from 0, and your reflections will be at something longer. Once you have this displayed, you only have to put your curser on the peak of the reflection to read actual distance that particular reflection traveled.


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## angryht

fotto said:


> Your measurement procedure is correct (CTL + R mouse button), but you really need to take new measurements with your loopback properly connected. Once you run a sweep and display the ETC, you'll get something more like below pic, where your direct signal is at x ms from 0, and your reflections will be at something longer. Once you have this displayed, you only have to put your curser on the peak of the reflection to read actual distance that particular reflection traveled.


Got it! Thank you. 

What are the settings in the 'Preferences' that need to be checked for the loopback to work correctly?


----------



## angryht

I'm guessing I need to do this (from the help):



> *Impulse Response Calculation*
> The Use Loopback as Timing Reference selection controls whether REW uses a loopback on the soundcard as a timing reference for the channel being captured, to eliminate propagation delays within the computer and soundcard. The reference channel signal must be looped back from output to input for this option to work. If this is not checked REW will set the IR zero time according to the setting of Set t=0 at IR Peak.
> 
> If using a loopback as a reference REW can calculate the delay through the system being measured and show it in the measurement Info panel as "System Delay" in milliseconds, with the equivalent distance in feet and metres shown in brackets. Note that delay values are not accurate for subwoofer measurements due to the limited bandwidth of the subwoofer response, the delay estimate is based on the location of the peak of the impulse response and subwoofers have a broad peak and a delayed response.


Should I just make sure that the "Use Loopback as Timing Reference" is clicked. I thought I read that I should not click the set t=0 because that will not give me a graph showing the time/distance to the speaker being measured (like the example you provided).


----------



## angryht

^I think I found my own answer from a different thread:



localhost127 said:


> you need to be utilizing the hardware loopback - and UNCHECK T=0.
> 
> you cannot simply subtract the spike on the ETC from the direct signal when you have the direct signal set to T=0.
> 
> once you change this and identify the total time of flight of the reflection, then you can work backwards.
> 
> SAC's string test and the blocking method are a good start:
> http://www.gearslutz.com/board/6133764-post8.html
> 
> and do not band-limit your ETCs.


----------



## angryht

Are these the correct settings?









I'm getting really high numbers like 47 FT for my distance from 0 to the first but my speakers are about 9 FT away from the listening position???:dontknow:


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## angryht

I must have something not set right??? HELP


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## angryht

What should I set as the limits for the axis? It looks like -1.0 ms to 40 ms and 5 to -30 dB?


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## fotto

Odds are that you have some "processing" enabled in your AVR. You need to put it in "direct" or "pure" mode (what AVR do you have?). I had similar issue until I put my Onkyo in Direct mode.

Scale your graph from just under 0 to around 40ms in x axis so you can see the peaks better.


----------



## angryht

> Odds are that you have some "processing" enabled in your AVR. You need to put it in "direct" or "pure" mode (what AVR do you have?). I had similar issue until I put my Onkyo in Direct mode.


I had it in stereo mode, which I thought was correct based on the posts I've read. Must not be for the Onkyos. Mine is an Onkyo TX-SR606. I'll change it to Direct and try again tonight.



> Scale your graph from just under 0 to around 40ms in x axis so you can see the peaks better.


 Thanks so much for your help. What about the Y axis? Should that be 0 to -30 dB. That looks like what your had - I'm guessing that may be dependent on the readings.


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## angryht

Here are my waterfalls from last night. Again, I'll do some more measuring tonight when things are set to Direct Mode for the Onkyo. I just wanted to post these to see if there was anything about them that looked wrong due to the stereo mode.


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## angryht

To me it seems like my decay time is actually pretty good, but I'm just learning. That is based on the performance targets provided by Hifizine here: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/ Fantastic read by the way.



> *Spectral decay:* Decay rate of 20 dB in the first 150 ms from 40 – 300 Hz. (Note: The time window setting for any waterfall or decay plot used to determine this must be set to 300 ms.)


----------



## angryht

And here are the SPL graphs from the measurements used to get the waterfalls above.

























I am still reading about SBIR which is what Earl mentioned might be at least one of my issues. I also tried out the RTA function to try to get out of any nulls in the room (at least the seating position for now since I don't have much flexibility with the speaker placement - some, but not much and I'll explore that once I understand the proper way to measure). It is interesting how I get a dip in the right speaker around 100 Hz but not in the left speaker. I'm wondering if that is from SBIR. Doing the math with 100 Hz, I get a distance of . . . 1125/(2*100) = 5.6 FT. That would be the difference in the reflected path and the direct path, right? That's one of the reasons I'm trying to understand the ETC measurements.


----------



## jtalden

angryht,
It's not clear to me what you are trying to accomplish in this thread; bass EQ, ETC for acoustic treatments, other objectives? It's very confusing for me. However, if I follow the recent concern correctly, it seems that you are confused on the ETC charts you made as to why they look different from other charts that are posted. I may be able to help with that. 

If your intent isn't focused on tracking down reflections and installing acoustic treatments to mitigate mid and high frequency reflections, then there is no need to even worry about ETC.

If that is your intent, then I suggest you turn off the sub and run a full range measurement on a single main speaker. You must set the measurement sweep to extend all the way to 20 kHz. [It appears the sweep is stopping a low frequency and it’s not possible to chart high frequencies if you don’t measure them.]

This suggestion is focused why your charts looks different from others (you have no HF content) It is not meant to suggest how to interpret the chart or perform the treatments. While I think I understand the basics of the approach, I have no practical experience in that area.

I hope this helps a little.


----------



## fotto

angryht said:


> Thanks so much for your help. What about the Y axis? Should that be 0 to -30 dB. That looks like what your had - I'm guessing that may be dependent on the readings.


SAC recommends viewing the data with 10 to 40ms on X-axis, and 2 to -30 on Y-axis for what he considers optimal view of the ETC. The goal is to get a good view of it, so whatever you like around those ranges should be just fine. Your underlying data isn't changing, just how it's displayed.

As jtalden said, if your intent is for using ETC for treatment of reflections, you need to take full range sweeps of individual speakers only. You'll then identify the surfaces where the reflections are coming off off, then treat and remeasure to ensure you have them tamed.

Here's my thread where I went through this process as it may help you out with the ETC portion. Note that I did this particular effort not using loopback, but subsequently did more work afterwards using it.
http://www.hometheatershack.com/forums/rew-forum/52211-help-etc-interpretion.html


----------



## angryht

jtalden said:


> angryht,
> It's not clear to me what you are trying to accomplish in this thread; bass EQ, ETC for acoustic treatments, other objectives? It's very confusing for me. However, if I follow the recent concern correctly, it seems that you are confused on the ETC charts you made as to why they look different from other charts that are posted. I may be able to help with that.


Sorry about that. I realize I'm kind of all over the place. My intent in this thread is to try to understand how to run REW correctly and how to interpret some of the results. That's why I'm posting here in the REW forum. I have struggled with the help files/threads and just wanted to use some actual graphs. I'm a bit of a visual learner. 



> If your intent isn't focused on tracking down reflections and installing acoustic treatments to mitigate mid and high frequency reflections, then there is no need to even worry about ETC.


That will be my intent eventually, and that's why I posted my graphs here. Again, I'm probably muddling things up a bit in this thread but I want to learn how to use this fantastic tool. Point taken.



> If that is your intent, then I suggest you turn off the sub and run a full range measurement on a single main speaker. You must set the measurement sweep to extend all the way to 20 kHz. [It appears the sweep is stopping a low frequency and it’s not possible to chart high frequencies if you don’t measure them.]


 True, my sweeps stopped at 200 and 400 Hz so when I do the sweeps I'll take it to full range, turn off the sub and send the full range to the speaker I'm measuring. On the Response graph that I posted I did set the signal to full band to the speaker but I only did the sweep to 200 Hz. Oh yeah, and switch to Direct Mode, suggested by fotto.



> This suggestion is focused why your charts looks different from others (you have no HF content) It is not meant to suggest how to interpret the chart or perform the treatments. While I think I understand the basics of the approach, I have no practical experience in that area.


 Right now, while I'm learning, I'm trying to keep things simplified (maybe overly simplified). A lot of what I'm doing is to try and make sure I have a good start and a fairly competent set of base line measurements. 



> I hope this helps a little.


Absolutely, and I appreciate it.


----------



## angryht

fotto said:


> SAC recommends viewing the data with 10 to 40ms on X-axis, and 2 to -30 on Y-axis for what he considers optimal view of the ETC. The goal is to get a good view of it, so whatever you like around those ranges should be just fine. Your underlying data isn't changing, just how it's displayed.
> 
> As jtalden said, if your intent is for using ETC for treatment of reflections, you need to take full range sweeps of individual speakers only. You'll then identify the surfaces where the reflections are coming off off, then treat and remeasure to ensure you have them tamed.
> 
> Here's my thread where I went through this process as it may help you out with the ETC portion. Note that I did this particular effort not using loopback, but subsequently did more work afterwards using it.
> http://www.hometheatershack.com/forums/rew-forum/52211-help-etc-interpretion.html


Fantastic! Exactly what I was looking for. I'm assuming that my settings in the Preferences were ok in this post
http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-10.html#post515434 I wasn't sure about the sub-sample timing adjustment checkbox.


----------



## angryht

fotto said:


> SAC recommends viewing the data with 10 to 40ms on X-axis, and 2 to -30 on Y-axis for what he considers optimal view of the ETC. The goal is to get a good view of it, so whatever you like around those ranges should be just fine. Your underlying data isn't changing, just how it's displayed.


Just curious about the 10 ms (minimum x-value). Shouldn't that be less than 0 to be able to verify the distance to the speaker (direct sound)?


----------



## fotto

Yeah, if you want to measure the distance, use something like -2ms for left limit so your 0 point will show allowing you to drag for distance from.


----------



## angryht

Okay, that makes sense.


----------



## angryht

fotto said:


> Odds are that you have some "processing" enabled in your AVR. You need to put it in "direct" or "pure" mode (what AVR do you have?). I had similar issue until I put my Onkyo in Direct mode.
> 
> Scale your graph from just under 0 to around 40ms in x axis so you can see the peaks better.


Here's just a test to see if it's working like it is supposed to in terms of the ETC. Onkyo is set to Direct mode and full band sweep to just the speaker with no sub from 0 to 20k Hz. I think I'm getting the hang of it. It was the Stereo mode!! Thanks so much for your help.


----------



## SAC

Is this a display of two sources played simultaneously?

I hope so! Otherwise you have some real issues with a VERY early indirect signal exhibiting higher gain than the direct signal!!

And if it is two sources, you need to measure ONE source at a time. 
As solving for a in a x b=17 is a bit more complex than most folks here are ready...

And so much of this is caused by the recent craze imagining that moving a test signal input from one channel to another is just so much more difficult than trying to selectively route signals through a receiver that was never designed to individually isolate and solo individual channels/signals - all the while ignoring the hardware propagation delay imposed on the time vales of the measured signal skewing (corrupting) the measured time values.


----------



## angryht

SAC said:


> Is this a display of two sources played simultaneously?
> 
> I hope so! Otherwise you have some real issues with a VERY early indirect signal exhibiting higher gain than the direct signal!!
> 
> And if it is two sources, you need to measure ONE source at a time.
> As solving for a in a x b=17 is a bit more complex than most folks here are ready...
> 
> And so much of this is caused by the recent craze imagining that moving a test signal input from one channel to another is just so much more difficult than trying to selectively route signals through a receiver that was never designed to individually isolate and solo individual channels/signals - all the while ignoring the hardware propagation delay imposed on the time vales of the measured signal skewing (corrupting) the measured time values.


Once again I am frustrated and confused. I am not trying to feed 2 sources. I am not trying route signals anywhere other that the left and right channel. I am trying to learn how to do the most basic measurements and frankly it's getting the best of me. That Impulse response seemed to give me the correct distance to the speaker, but it certainly looks like something weird is going on. As I said in my post with that graph, the receiver was set to Direct mode which is supposed to be no processing. I also noticed that when my receiver is in Direct Mode and it is sent a signal from the left and right channels, it appears that it defeats the bass management. :huh: I seem to get reasonable SPL and waterfall plots with the receiver set to stereo mode, but when I look at the Impulse graphs they look like that. :hissyfit: 

When I measure each channel separately, I disconnect the other speaker. And, when I did the full range sweep, I disconnected the subwoofer. I guess I'll have to try it again and make sure that is the case. So, you are saying that my graph looks like there are 2 sources. I just don't get it? :huh:


----------



## SAC

angryht said:


> I seem to get reasonable SPL and waterfall plots with the receiver set to_ stereo_ mode, but when I look at the Impulse graphs they look like that.
> When I measure each channel separately, I disconnect the other speaker. And, when I did the full range sweep, I disconnected the subwoofer. I guess I'll have to try it again and make sure that is the case. So, you are saying that my graph looks like there are 2 sources. I just don't get it? :huh:


Would not the stereo mode send the signal to BOTH front left and right speakers, thus feeding two sources?
Is the other speaker disconnected?

Again, my preferred method is to simply manually input the test source into the individual channel to be tested and not to use the internal switching which adds still more delay propagation to the system under test.

Assuming all is right with the measurement procedure, then you are faced with addressing what the measurement 'says'.

Thus you need to determine the source of the indirect signal arriving ~1ms after the direct signal that is of greater amplitude than the direct signal. The only way that occurs is if two reflections arrive and sum.

As the graph indicates that the total time of flight travel distance for the 2nd significant arrival is ~10.5 feet, you can use the string method to attempt to locate the (apparently) 2 paths the exactly meet that criteria. ( would also perform a quick sanity check to verify the agreement of the direct signal arrival with both the values determined by direct measure and as determined/displayed by REW.

The alternative method would be to use the blocking method and to identify one vector path and note if the amplitude is reduced slightly by a few dB, indicating the presence of another indirect path arriving at the same instance.


----------



## fotto

Try this and see what you get:
1) Turn off sub
2) Put AVR is direct mode
3) Select DVD for source on AVR
4) Connect your signal from the sound card/pre-pro (forgot what you're using) to the rear analog multichannel input for DVD to whichever speaker you're trying to measure (LF or RF).
5) Take a 20-20Khz sweep with RCA jack connected from sound card to rear LF multichannel input only.
6) Repeat step 5 for the RF input.
7) Post ETC's of those two measurements.

Suggesting this approach to try to ensure correct set-up.


----------



## fotto

SAC said:


> Would not the stereo mode send the signal to BOTH front left and right speakers, thus feeding two sources?


If he's in direct listening mode and feeding only one of the front panel aux inputs (either L or R) one would think that it would only output on channel being fed.

Suggested method in my previous post to help rule that possibility.


----------



## angryht

SAC said:


> Would not the stereo mode send the signal to BOTH front left and right speakers, thus feeding two sources?
> Is the other speaker disconnected?


Yes, the other speaker was disconnected. I still have a feeling that either my connections are not correct or the receiver is doing something that I don't understand.



> Again, my preferred method is to simply manually input the test source into the individual channel to be tested and not to use the internal switching which adds still more delay propagation to the system under test.


I agree with simplifying things. I need to triple check my connections. Right now I have the output from the soundcard (right channel) to a splitter then feeding both the left and right channels at the same time, per the connections in the help file for REW. When I measure one speaker at a time, I disconnect the other. But since I'm feeding the signal through a stereo input, I think something is getting processed.



> Assuming all is right with the measurement procedure, then you are faced with addressing what the measurement 'says'.


 I think the inputs may be giving me problems so I'll need to do more checking.



> Thus you need to determine the source of the indirect signal arriving ~1ms after the direct signal that is of greater amplitude than the direct signal. The only way that occurs is if two reflections arrive and sum.
> 
> As the graph indicates that the total time of flight travel distance for the 2nd significant arrival is ~10.5 feet, you can use the string method to attempt to locate the (apparently) 2 paths the exactly meet that criteria. ( would also perform a quick sanity check to verify the agreement of the direct signal arrival with both the values determined by direct measure and as determined/displayed by REW.
> 
> The alternative method would be to use the blocking method and to identify one vector path and note if the amplitude is reduced slightly by a few dB, indicating the presence of another indirect path arriving at the same instance.


I think I'm following, but I'll need to check some things before I get to that. 

Thanks, SAC, I will keep verifying things and see what I find.


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## angryht

fotto said:


> 4) Connect your signal from the sound card/pre-pro (forgot what you're using) to the rear analog multichannel input for DVD to whichever speaker you're trying to measure (LF or RF).


I had it connected to the CD input, which just has left and right channel input. I completely forgot about multichannel input for DVD on this receiver. Great idea, that way I shouldn't need to disconnect the actual speaker leads, just change the input to the channel I'm measuring. I'll remove the splitter from the equation too. Then I'll set it to Direct mode again and see what happens. Thanks.


----------



## angryht

fotto said:


> Try this and see what you get:
> 1) Turn off sub
> 2) Put AVR is direct mode
> 3) Select DVD for source on AVR
> 4) Connect your signal from the sound card/pre-pro (forgot what you're using) to the rear analog multichannel input for DVD to whichever speaker you're trying to measure (LF or RF).
> 5) Take a 20-20Khz sweep with RCA jack connected from sound card to rear LF multichannel input only.
> 6) Repeat step 5 for the RF input.
> 7) Post ETC's of those two measurements.
> 
> Suggesting this approach to try to ensure correct set-up.


Homework done, and here it is. I also included the center channel as well as the .mdat file with the data. Any help would be appreciated:
























Here's a look at the left speaker zoomed out:


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## fotto

Cool, looks "normal" to me. Now you can track down those bigger reflections and address them.
One thing I noticed, is your right speaker about 1/2' closer to your listening position than the left one?


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## angryht

fotto said:


> Cool, looks "normal" to me. Now you can track down those bigger reflections and address them.
> One thing I noticed, is your right speaker about 1/2' closer to your listening position than the left one?


I'm glad to hear that it looks normal. I'm not sure I understand what all the noise before zero represents.

Correct about the listening position. It's a bit off center.


----------



## JohnM

angryht said:


> I'm not sure I understand what all the noise before zero represents.


Those scaled down copies of the main response that appear before it are distortion harmonics, and they look very high. That can be caused by driving the system too hard, or by clipping somewhere in the signal chain.


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## angryht

JohnM said:


> Those scaled down copies of the main response that appear before it are distortion harmonics, and they look very high. That can be caused by driving the system too hard, or by clipping somewhere in the signal chain.


That seems odd. I don't think I'm driving the system too hard. I am actually taking my measurements at 65 dB. I set my levels in the Preferences tab to 65 dB because that's the level I usually listen. Clipping in the signal chain? Could this be showing some type of interference with the computer or something?


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## angryht

Should the *sub sample timing adjustment* and the *decimate IR* in the *Analysis* tab of the *Preferences* be unchecked? It looks like fotto did that in his thread: http://www.hometheatershack.com/forums/rew-forum/52211-help-etc-interpretion.html#post475222 

Could having those checked cause a problem? I'll go try that now.


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## JohnM

Clipping happens when a signal would be larger than a part of the signal path can accommodate and gets limited to the amplitude that fits. If you are using a radio shack SPL meter as your mic, clipping could occur if the RS range was set very low so that, even at 65dB, the meter is being overloaded (on the analog meter clipping starts to occur when the needle reaches the end stop). Clipping can also occur at the soundcard input, but REW warns you if that occurs (the headroom figure shown during measurement turns red). It is also possible to have clipping in the signal output path, for example generating a signal at a high level that clips at the input of a receiver.

One way to check for clipping is to look at the scope graph after taking a measurement and see if there are flat topped areas on the captured trace.


----------



## JohnM

angryht said:


> Could having those checked cause a problem?


No


----------



## angryht

Here is my scope graph. I don't see any flat topped areas.


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## angryht

I did have the SPL meter set to 60 while I was measuring 65 dB. So that may be my problem. Although the graph above was done when I set the meter (radio shack) to 70 dB to measure 65. I could not get the scope measurements to come up for my earlier readings?


----------



## angryht

zoomed out:


----------



## JohnM

The scope plot is only available for the latest measurement, it is not stored as part of the measurement (takes up a lot of storage). How do the impulse response plots look with the 70dB range used, have the distortion harmonic parts become smaller?


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## angryht

Actually, that scope is for the meter set to 70 dB.


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## angryht

I did another for the scope when set to 60 dB and the peaks don't look flat there either.


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## JohnM

Look at the zoomed out *impulse* response to see if this is having an effect on the distortion levels. What other adjustments are you making when you change the meter range? If the range was the only change the captured levels would have been about 3 times higher than on the 70dB range.


----------



## angryht

JohnM said:


> Look at the zoomed out *impulse* response to see if this is having an effect on the distortion levels. What other adjustments are you making when you change the meter range? If the range was the only change the captured levels would have been about 3 times higher than on the 70dB range.


I had to readjust the levels after I set the meter to 70 dB (from 60 dB). I usually shoot for -18 or -19 dB on the Check Levels. I had to increase the volume for the receiver. If I leave the receiver level (volume) set at the same level as the 60 dB reading for the 70 dB measurement, it tells me the levels are too low.

Here are the Impulse readings zoomed out for 60 and 70 dB settings. It looks like the bottom of the graphs dropped a bit but the peaks before the 0 ms are still about the same.


----------



## JohnM

Two things to try: turn down the receiver volume to get -28dB on check levels rather than -18 and see what effect that has on the impulse plot, then put the receiver volume back where it was but turn down the replay volume on the computer until you again get about -28dB on check levels, and see what the effect is.

P.S. In both cases using the 70dB meter setting.


----------



## angryht

When I set the volume in the receiver to -28 dB, in Check Levels, I get a Level is Low when I do a Check Levels right before I measure.

Here is a screen shot of my Preferences. What is the replay volume? Is that the input volume? Do my settings look correct?


----------



## JohnM

Ignore the 'Level is low' message.

Replay volume is the output volume, the normal control you have on the computer for the level of the sounds it generates.


----------



## angryht

Do I need to recalibrate my spl meter in REW? I just checked it and when I set the dial on the meter to 70 dB the reading is off by 10 dB. It shows 55 on the REW SPL Meter and it should say 65 (on the actual dial of the analog meter).


----------



## angryht

Here is with the volume set to -28. The output volume is grayed out. I can't adjust it.


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## angryht

Should I go into the sound card options and adjust there?


----------



## angryht

Okay, I turned up the sound card volume to get the -28 dB on the check levels. Here is that measurement. It looks exactly the same to me.


----------



## JohnM

angryht said:


> Do I need to recalibrate my spl meter in REW? I just checked it and when I set the dial on the meter to 70 dB the reading is off by 10 dB. It shows 55 on the REW SPL Meter and it should say 65 (on the actual dial of the analog meter).


It doesn't matter for the purposes of this test, but in general any change to the meter range or the input volume will mean the REW SPL meter needs to be recalibrated.



angryht said:


> Here is with the volume set to -28. The output volume is grayed out. I can't adjust it.
> View attachment 35891


The level of the harmonics has dropped by about the amount the overall level was reduced, which suggests the distortion is not happening at the receiver input, so the second test isn't needed. Looking at the spectrum of the distortion, it is heavily concentrated at high frequencies, rising rapidly above approx 4kHz. That, and the fact the distortion levels are very similar across left, right and centre speakers in your earlier measurement suggest the distortion is being added in the meter. Stick with the 70dB range, make sure the meter needle does not reach the end stop during the measurement (if it does, measure at a lower level or use the 80dB range), and don't pay much attention to results above a few kHz as the RS meter is not much use above that range (the peak around 5kHz in your measurements and the rapid roll-off beyond that are characteristics of the meter).


----------



## angryht

> It doesn't matter for the purposes of this test, but in general any change to the meter range or the input volume will mean the REW SPL meter needs to be recalibrated.


Okay.



> The level of the harmonics has dropped by about the amount the overall level was reduced, which suggests the distortion is not happening at the receiver input, so the second test isn't needed. Looking at the spectrum of the distortion, it is heavily concentrated at high frequencies, rising rapidly above approx 4kHz. That, and the fact the distortion levels are very similar across left, right and centre speakers in your earlier measurement suggest the distortion is being added in the meter. Stick with the 70dB range, make sure the meter needle does not reach the end stop during the measurement (if it does, measure at a lower level or use the 80dB range), and don't pay much attention to results above a few kHz as the RS meter is not much use above that range (the peak around 5kHz in your measurements and the rapid roll-off beyond that are characteristics of the meter).


I didn't quite follow all of that. I will make sure the meter is not 'redlined' during measurements and make sure I only use the lower frequency data from the RS SPL meter. So, the data before the 0 ms on the Impulse graphs is . . . . . in the meter? Are these measurements normal for someone with a RS meter? I just want to make sure the settings are correct before I proceed. Thank you for all your help, by the way.


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## JohnM

Most probably distortion in the meter, don't often see full range measurements from the RS meter so hasn't really come up before. All looks OK besides that.


----------



## angryht

Great! Yeah, I just want to be able to get reflection distances. I realize that the RS meter has a limit on it's ability to read higher frquecies acurately, just want to make sure I'm doing things correctly. Thanks again for all the help and the tip about the meter setting (set to 70) and no redlining.


----------



## angryht

I will revisit ETC and reflections in a bit. I think I've got the measurement process figured out, so please forgive the previous tangential discussions.

To date I've done the following. The links that follow the items in the list are to the specific posts that show the results:

Sealed the ports on my front speakers (L,R and Center): http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-4.html#post511884
Moved my sub (used the crawl method initially then measuring): http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-5.html#post512221
Adjusted the delay on my sub (7 FT, distance in the receiver menu): http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-7.html#post512443 
Adjusted and verified the best phase setting of the sub (180 degrees): http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-8.html#post513007
All of the above were done to try and match the 'near field' measurements done on the sub and front speakers, and with audyssey turned off (unless I was comparing things, then I turned it on)

Now I'd like to explore the front speaker responses and see if there is anything I can do to make things better. I realize that some of the improvements may be to reduce the effects of SBIR in my very small room (approx. 12.5 x 9' x 7') and I will get to that. Thanks so much to Fotto (Floyd) for the link to his work with the string method - I'll get back to that soon. And, of course thanks to all the others (Earl, John, robbo . . . and others) who have helped me thus far. I think I'm getting much better results than I did a few years ago. 

Up next I'll post the latest waterfall plots. I'd like to focus on the items listed in the Hifizine article here: http://www.hifizine.com/2011/06/bass-integration-guide-part-1/ 

Specifically, these items (quoting from the article, hope that's okay):



> This guide will show you how to meet certain performance targets. I have developed these targets after many years of experimentation, measurement and evaluation.
> 
> 
> *Bass extension:* Adequate low-frequency extension for your typical source material (this could range from 14 to 40 Hz).
> *Headroom:* At least 3 dB headroom at your maximum desired output level at all frequencies. This means cone excursion should not exceed 70% of the driver Xmax.
> *Target curve:* The combined system bass response including all subwoofers and the mains should match the target curve shown in Figure 1 below. The curve is determined by three variables that need to be chosen based on user preferences. The curve shown is just one possibility, but there are many variations where each variable is adjusted within the ranges shown. The midrange level rises at F1 until it reaches F2, below which the curve is flat until the low frequency roll off point. The boost amplitude and both knee points (F1 and F2) are to be chosen from the ranges shown in Figure 1.
> *Frequency response:* Flat response in every significant seat +/- 3 dB relative to the chosen target curve with third octave smoothing applied.
> *Spectral decay:* Decay rate of 20 dB in the first 150 ms from 40 – 300 Hz. (Note: The time window setting for any waterfall or decay plot used to determine this must be set to 300 ms.)
> 
> 
> 
> 
> 
> 
> 
> 
> *Figure 1. Target curve where the bass response is shelved up by 6 dB*


So, up next I'll post my waterfall graphs and determination if there is anything that I can do to improve things without a BFD.


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## angryht

Here is the waterfall graph of the left and right (combined with the sub). I have also attached the .mdat file.


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## angryht

Here is the graph and data (.mdat file) for the center channel (also combined with the sub).










To me, it looks like the decay time is pretty good above 40 Hz. Would bass traps help the 25 to 30 Hz range?


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## fotto

Yeah, I think the decay times look quite nice except for that nasty ringing around 37Hz for the mains/sub graph. Here's another view using spectrogram...that sucker goes on quite long:










Given the size of your room, it might be problematic to get appropriate amount of bass trapping in there to tame these lower frequencies. As an experiment, you could always by a roll of pink fluffy and put in the corners, remeasure and see how that affects it. Would be lower impact on your wallet instead of buying something more expensive and finding it doesn't help out.


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## angryht

Thanks for providing that graph, Floyd. I just took a look at the help file to get a quick understanding of the spectrogram graph. This REW continues to amaze me! I like the description in the help about the spectro being a view of the waterfall from above. I would have never thought that the ringing at ~ 37 would go for so much longer than the one just below it at ~ 27. And from what I understand, the small ringing showing up at the 60 Hz is likely the hum of the computer (my source for that info: http://redspade-audio.blogspot.com/2011/05/rew-understanding-decay-and-waterfall.html). 

I do have some left over insulation, I'll have to try that experiment.


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## Wayne A. Pflughaupt

angryht said:


> Here is the graph and data (.mdat file) for the center channel (also combined with the sub).
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> To me, it looks like the decay time is pretty good above 40 Hz.


Hey angry,

Waterfalls are most useful when the signal is about 50 dB above the noise floor. Your signal is below 70 dB and the graph floor is set high at 45 dB, which only gives us a >25 dB range to look at. I’d suggest getting the signal up to at least 80 dB and lowering the graph floor to 30-35 dB, which is closer to ambient room noise.

Regards, 
Wayne


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## jtalden

The "ringing" at 37 Hz is either constant noise in the room from a low freq source or noise in the measuring system, or less likely, noise from the SW amp. 

I say this because the noise is present from the start of the time period (a full 300 ms before the signal even starts to to rise and remains to the end of the recorded time period. It appears to be about the same level for the entire 1300 ms. You can just ignore this artifact if there isn't a constant LF room noise that is audible. 

[If you like, you can experiment by measuring the noise floor. That is, just take a measurement with the signal reduced to zero and also one with the SW amp turned completely off to try to determine the noise source. If you still have it then it must be either in the room from another outside source or possibly noise from the mic preamp.]


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## angryht

Wayne A. Pflughaupt said:


> Waterfalls are most useful when the signal is about 50 dB above the noise floor.


Good to know, Wayne. I have been keeping the level at about 65 dB for testing, which is my typical listening range. I'm guessing you would you still recommend increasing the output to around 80. Just wondering if I could just lower the bottom or the graph to around 15 to get the 50 dB range. But I guess that's what you meant by the ambient room noise reference in you post. Okay, I'll need to remeasure at a higher level.


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## angryht

jtalden said:


> The "ringing" at 37 Hz is either constant noise in the room from a low freq source or noise in the measuring system, or less likely, noise from the SW amp.
> 
> I say this because *the noise is present from the start of the time period (a full 300 ms before the signal even starts to to rise and remains to the end of the recorded time period.* It appears to be about the same level for the entire 1300 ms. You can just ignore this artifact if there isn't a constant LF room noise that is audible.
> 
> [If you like, you can experiment by measuring the noise floor. That is, just take a measurement with the signal reduced to zero and also one with the SW amp turned completely off to try to determine the noise source. If you still have it then it must be either in the room from another outside source or possibly noise from the mic preamp.]


Well, that makes a lot of sense. The information regarding the 300 ms before the signal is from the spectro graph, right? Yep, that even looks more constant than the what I guessed to be the computer hum at about 60 Hz. Excellent ideas for the experiments - I'll check it out.


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## robbo266317

You can also look at the noise floor using RTA in REW with no signal present.
You can see here http://www.hometheatershack.com/gallery/index.php?n=1487 that the coal loader near where I live is producing a lot of 14.7 Hz noise.


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## Wayne A. Pflughaupt

angryht said:


> Just wondering if I could just lower the bottom or the graph to around 15 to get the 50 dB range.


If your room’s noise floor is 15 dB, it’s quieter than most recording studios! 

Regards, 
Wayne


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## angryht

robbo266317 said:


> You can also look at the noise floor using RTA in REW with no signal present.
> You can see here http://www.hometheatershack.com/gallery/index.php?n=1487 that the coal loader near where I live is producing a lot of 14.7 Hz noise.


I assume I would just disconnect the output and do a measurement. Is that the way to do that? I have a feeling it may be the fan from the central air/furnace. Is there a thread associated with the pictures in your link?

I wonder if that has anything to do with the responses I was getting when I was doing the ETC measurements: http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-15.html#post516242


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## angryht

Wayne A. Pflughaupt said:


> If your room’s noise floor is 15 dB, it’s quieter than most recording studios!


That would be nice. . . . but it certainly isn't that quiet, probably not even close


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## robbo266317

angryht said:


> I assume I would just disconnect the output and do a measurement. Is that the way to do that? I have a feeling it may be the fan from the central air/furnace. Is there a thread associated with the pictures in your link?
> View attachment 35934


37 Hz could easily be due to the furnace and pipework associated with it. 
Yes, just disconnect or turn off the amp and run a sweep so all you get is background noise and generate a waterfall or look at the response graph..


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## angryht

Got it. Thanks, again!


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## angryht

Well, I think I found it (I think we have a BINGO!). Here are the graphs (both shown are with central fan on), waterfall and spectro as well as the .mdat files with the central fan on and off.


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## angryht

And, here is one with the fan on and water running. Basements are loud!!!


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## robbo266317

So if you run your sweeps louder it will overcome some of the Central noise and give a better idea of what it is really like.


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## angryht

Got it!


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## robbo266317

:bigsmile: :T


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## angryht

Dang! And I just realized I haven't done a check of the projector fan yet either. Bet that's loud too Oh well, I better get back to measuring.


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## robbo266317

So where are the new measurements? :whistling:


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## angryht

They're coming shortly.


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## angryht

robbo266317 said:


> So where are the new measurements? :whistling:





Wayne A. Pflughaupt said:


> Hey angry,
> 
> Waterfalls are most useful when the signal is about 50 dB above the noise floor. Your signal is below 70 dB and the graph floor is set high at 45 dB, which only gives us a >25 dB range to look at. I’d suggest getting the signal up to at least 80 dB and lowering the graph floor to 30-35 dB, which is closer to ambient room noise.
> 
> Regards,
> Wayne



Okay, here are the new measurements with the levels turned up to between 75 and 80 dB, to get further away from the room noise levels. Oh yeah, and I've attached the .mdat files.

I have not yet done any experimenting with additional bass trapping with my insulation.


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## angryht

In terms of spectral decay, the way I am interpreting this target value, that I referenced this post:



> *Spectral decay:* Decay rate of 20 dB in the first 150 ms from 40 – 300 Hz. (Note: The time window setting for any waterfall or decay plot used to determine this must be set to 300 ms.)


My guess is that I can extrapolate that target range to be 40 dB in the first 300 ms from 40 - 300 Hz. I only included the plots out to 200 Hz this time, so I'll have to take a look later today on the 300 to 400 Hz range. But looking at the spectro graph, it looks pretty good in that regard. The obvious issue is below 40 Hz, right? Just making sure I understand the targets.


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## fotto

Your extrapolation is pretty accurate based on this paper: http://blog.acousticfrontiers.com/storage/AMS for Stereo List. Rms.pdf 

Note additional advice for sub 35Hz:

o Resonances from 35Hz300Hz
should not extend beyond 350ms before decaying
into the noise floor or reaching a level of 40dB.
o Below 35Hz this standard is relaxed to 450ms


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## angryht

Oh, that gives me an extra 50 ms to get down to -40dB. I'm feeling pretty good about my measurements, in terms of decay, anyway. Looks like I'm just outside of the target for the less than 35 Hz.

Thanks for the reference. I believe that's also the one that Earl provided for me earlier, http://www.hometheatershack.com/forums/rew-forum/56427-im-back-but-confused-again-9.html#post513221 and it helps me to identify the targets.

Also, I noticed that the hdacoustics paper you cited shows a sloping line (dashed being the ideal) between the values.


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## angryht

Here's the figure:


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## angryht

So, at this point anyway, there's not much more I can do about decay time. Currently, I have several triangular pieces of 1-inch Linacoustic RC (leftover from covering most of the walls) placed at the corners where the wall meets the floor. I think that has helped me to get the decay time reduced. It's probably not as effective as other types of traps, but it's something.

Here are some pictures to show what I mean.

































Up next I hope to address some of the dips (nulls) in the SPL responses.


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## ccclapp

Hi Angry and his consultants ;-)

Just letting you know this is a VERY helpful thread for others to follow along on. Looks like Angry is dealing with most of the possible issues/solutions (software, equipment and room) and reporting well, so the rest of us can get up to speed faster.

Thanks for being the Guinea Pig!


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## angryht

^No problem, Caleb, and I am thrilled to hear if anyone has gained any knowledge through my experience. To me, that's the point of this forum. I intend to continue my quest to, as Earl so eloquently wrote earlier, improve the sonic resolution of my listening experience. . . .from earlier:


EarlK said:


> > If you want to improve the sonic resolution of your listening experience, then that is an entirely different kettle of fish ( requiring much much more than REW & a BFD ). The simple way to that experience is to listen to some good headphones . lddude:
> :sn:


He was playing with the words in my earlier posts (resolution having different meanings) but I gotta say, that's audio forum gold! Of course the headphones idea is always a good one, I'm sure my wife would agree to that!

I should be able to post more in the next day or so. I did some more measuring at different listening positions which helped some of the dips in the SPL responses. More on that a bit later.


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## ccclapp

Thanks

..not sure I understand Earl's reply and your reference to Audio forum gold...seems if the goal is to "improve the sonic resolution of your listening experience" that's just what REW can help do...if you want that it in more than a single pin-point location, THAT would be the "entirely different kettle of fish". Maybe his reference was more metaphisical than my literal interpretation :innocent:

Anyway, yes, I look forward to hearing your next chapters. I am preparing to write up my own guide/walk-through/help request based on REW with JRiver Media Center convolution relating to my 2.2 system in a bad room. After the REW/JRMC baseline, I hope to delve into correction solutions, including: REW / Audiolense / Acourate / DRC comparisons, pros, cons. Time will tell if I can cover all of that. I will certainly reference this/your thread for anyone wanting another great walk-through. We all struggle with the same issues, but have different environments/set-ups, goals and solution-paths. Thanks again for yours and to those who helped you (all of us) learn more.


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## angryht

ccclapp said:


> ..not sure I understand Earl's reply and your reference to Audio forum gold...seems if the goal is to "improve the sonic resolution of your listening experience" that's just what REW can help do...if you want that it in more than a single pin-point location, THAT would be the "entirely different kettle of fish". Maybe his reference was more metaphisical than my literal interpretation :innocent:


I just liked that way he took my use of resolution and flipped it to the audio resolution. I appreciated that.



> Anyway, yes, I look forward to hearing your next chapters. I am preparing to write up my own guide/walk-through/help request based on REW with JRiver Media Center convolution relating to my 2.2 system in a bad room. After the REW/JRMC baseline, I hope to delve into correction solutions, including: REW / Audiolense / Acourate / DRC comparisons, pros, cons. Time will tell if I can cover all of that. I will certainly reference this/your thread for anyone wanting another great walk-through. We all struggle with the same issues, but have different environments/set-ups, goals and solution-paths. Thanks again for yours and to those who helped you (all of us) learn more.


Sounds like fun. I'm not familiar with JRiver so I'll keep an eye out! Thanks again for touching base!


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## angryht

Here are some measurements done to determine if I should move my seating related to the SPL graphs (Frequency Response from this earlier post). Position #1 is my current seating location and position #2 is moved forward about 1.5 FT. 

This first graph is showing the comparison between the left and right speakers (together), position 1 and 2. Blue is position 2 (about 1.5' forward).








This second graph shows the comparison with the center speaker. Purple is position 2.








To me it looks like I'm getting a better response (smoother) through the 100+ to ~250 Hz range. The center speaker response merely shifted the dip to around 330 Hz. There are a couple of questions that I have related to these:

Would it be worth moving the seating position?
Should I apply a smoothing to the graphs? If so, which smoothing? I've seen a few posts that indicate 1/24 smoothing and the reference posted (to hifizine.com article discusses 1/3 smoothing).


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## angryht

Oops, forgot the .mdat file from the previous post. It's attached to this. 

Never mind, I'll have to split it up because it was too large to upload.


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## angryht

Here are the same graphs with 1/24 smoothing. Is that supposed to be what my ears are hearing?:


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## robbo266317

angryht said:


> Here are the same graphs with 1/24 smoothing. Is that supposed to be what my ears are hearing?:


That should be what you are hearing, However if you measure at your right ear and your left ear position you will normally find there are variations as well. It is all about compromises and listening to see if the results are worth moving the seat.

I personally would put the seating where the Blue graph was taken.


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## angryht

Okay, that makes sense, the blue looks pretty good to me too. It's pretty impressive how much things change based on small movements! But I've learned that before.


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## ccclapp

"Position #1 is my current seating location and position #2 is moved forward about 1.5 FT. 

This second graph shows the comparison with the center speaker. 

To me it looks like I'm getting a better response (smoother) through the 100+ to ~250 Hz range. The center speaker response merely shifted the dip to around 330 Hz. There are a couple of questions that I have related to these:

Would it be worth moving the seating position?
Should I apply a smoothing to the graphs? If so, which smoothing? I've seen a few posts that indicate 1/24 smoothing and the reference posted (to hifizine.com article discusses 1/3 smoothing). "



...clearly for FR L&R new position is superior (and looks quite good). In low frequencies smoothing is less important, but 1/48 is fine if desired. Don't over smooth, nor worry about every zig/zag if unsmoothed.

As to centers, are you able to try moving speaker, or are you fixed. It should have likely smoothed w new position w others. If it's fixed, I'd give greater weight to mains over center, meaning new position. Also as you say, center dip moved but didn't get much worse. It also narrowed, higher "Q", which is less bad than wide dip. Again moving center may help.

As you know, in addition to FR, please post waterfalls or spectro to see ringing. Both FR and time matter.

Now that your getting your position good for SP and listening pos, will you move into corrections/EQ ? Looks like you're ready to move to that step...


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## angryht

ccclapp said:


> ...clearly for FR L&R new position is superior (and looks quite good). In low frequencies smoothing is less important, but 1/48 is fine if desired. Don't over smooth, nor worry about every zig/zag if unsmoothed.


Thanks again for the great feedback, Caleb (and robbo - previous post), always appreciated.


> As to centers, are you able to try moving speaker, or are you fixed. It should have likely smoothed w new position w others. If it's fixed, I'd give greater weight to mains over center, meaning new position. Also as you say, center dip moved but didn't get much worse. It also narrowed, higher "Q", which is less bad than wide dip. Again moving center may help.


I do have some flexibility. I moved it slightly and didn't get much of a difference but I'd be up for trying some more tweaking. On a side note, I had done a little bit more adjusting/aiming of the center speaker prior to the last measurements. I used a laser level to aim it right at the ear level. I used this little guy:







It's sort of a duh-kind-of-thing but it really helped. I had done it previously but it needed another tweak. You can see from my photos (this post) that I have my center speaker turned vertical to help prevent any lobing based mostly on this article from audioholics: http://www.audioholics.com/education/loudspeaker-basics/vertical-vs-horizontal-speaker-designs 


> As you know, in addition to FR, please post waterfalls or spectro to see ringing. Both FR and time matter.


Yep, I'll need to do that as well as post the .mdat files, like I promised previously.


> Now that your getting your position good for SP and listening pos, will you move into corrections/EQ ? Looks like you're ready to move to that step...


I think the next thing I will check is to see if there is anything I can do further on reflections. My approach is to try and get the system as good as I can without adding any EQ. Then, evaluate if it would be beneficial enough to actually do.


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## angryht

Well, looks like it may be time to pick up where I left off .


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## angryht

As an update, I removed all of the wedges of linacoustic (the walls are still lined up to 47" high) that I had lining the sides and front and installed some 4" thick bass traps in the 4 corners of the room.


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