# not getting far with this!



## mdfire (Aug 11, 2008)

I am trying rew for the first time but not getting very far. I am using a creative soundblaster mp3+ external usb sound card. When I go into settings and measure the levels I am only getting a reading of about -32dbfs and getting the error message of very low signal level. I have all the levels in the sound card up full and running windows &:help:


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## brucek (Apr 11, 2006)

Is your loopback connected on the right channel with the right channel selected when you run the soundcard calibration file?

Do you see the output and input VU meters responding when you run the soundcard calibration file?

What version of Windows? XP or Vista?

brucek


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## glaufman (Nov 25, 2007)

Sorry you're having trouble. Which Windows are you using?
It seems like your trying to run a Check Levels routine... Is this the one prior to running a soundcard calibration?
I sometimes find there's an extra control panel somewhere that I forget to make sure is setup properly for the volume controls. Have you tried adjusting the levels in the REW screen?


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## mdfire (Aug 11, 2008)

brucek said:


> Is your loopback connected on the right channel with the right channel selected when you run the soundcard calibration file?
> 
> Do you see the output and input VU meters responding when you run the soundcard calibration file?
> 
> ...


First off, thanks for the reply. Im running windows 7, just got the laptop yesterday. The input and output meters do go up and down when I click on measure. They just dont go up very far.

I have the cable connect to the line in and line out (right (red)) and right is selected in REW


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## brucek (Apr 11, 2006)

I suspect Windows 7 is much the same as Vista, in that it doesn't offer REW much access to control the levels. So you have to control the levels using the Windows Device Mixer (that's what they call it in Vista anyway). 

brucek


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## mdfire (Aug 11, 2008)

brucek said:


> I suspect Windows 7 is much the same as Vista, in that it doesn't offer REW much access to control the levels. So you have to control the levels using the Windows Device Mixer (that's what they call it in Vista anyway).
> 
> brucek


I did try that. I set all the levels in the windows control panel to max. Then set rew to the default input/ouput.

Initially the readings were about 60, then when I downloaded and installed a windows 7 (beta) driver for the sound card it went up to -32. I am suspecting that its a driver problem. Any suggestions on alternative usb sound cards.


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## brucek (Apr 11, 2006)

> Any suggestions on alternative usb sound cards.


Not many have reported results with Windows 7, so I don't have any concrete suggestions.

I wonder if a card that doesn't use drivers, such as the Behringer UCA202.

brucek


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## glaufman (Nov 25, 2007)

mdfire said:


> I did try that. I set all the levels in the windows control panel to max. Then set rew to the default input/ouput.
> 
> Initially the readings were about 60, then when I downloaded and installed a windows 7 (beta) driver for the sound card it went up to -32. I am suspecting that its a driver problem. Any suggestions on alternative usb sound cards.


I'm using Vista, and a different soundcard, BUT, IIRC the soundcard driver has it's own set of level controls that I had to play with to get my levels right the first time... is it possible your driver has the same and they got "reset" when you downloaded the update?


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## mdfire (Aug 11, 2008)

I have two of the soundcards and getting the same problem in each..so its not a hardware issue. 

I connected up to a desktop running windows vista and updated the driver and still the same problem. So it is obviously something I am doing!


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## mdfire (Aug 11, 2008)

One thing I have just noticed is that is that even if I select the Creative soundblaster speaker for the output device, the output dropdown menu below it is greyed out. Subsequently the control output mixer is also greyed out and the output volume is 0.


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## mdfire (Aug 11, 2008)

Enclosed are my sound card settings


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## vaidas (Nov 9, 2009)

Hi, i can see that in "line in properties/advance" window sampling rate is set 44.1khz, and in rew it set on 48khz. What is why your input and output fields are grey, rew cannot see any supported sound card with 48khz sample rate. Set your sound card input and output to 48khz. Good luck


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## brucek (Apr 11, 2006)

You have a monitor loopback turned on.

You have to mute the line-in in Playback (as shown) or it feeds the output to input internally.

You only want the line-in enabled in Record, not Playback.









brucek


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## mdfire (Aug 11, 2008)

vaidas said:


> Hi, i can see that in "line in properties/advance" window sampling rate is set 44.1khz, and in rew it set on 48khz. What is why your input and output fields are grey, rew cannot see any supported sound card with 48khz sample rate. Set your sound card input and output to 48khz. Good luck


Thanks I had noticed that one - no luck unfortunately


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## mdfire (Aug 11, 2008)

brucek said:


> You have a monitor loopback turned on.
> 
> You have to mute the line-in in Playback (as shown) or it feeds the output to input internally.
> 
> ...


Thanks brucek, will try that when I get home from work tonight


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## JohnM (Apr 11, 2006)

I guess Windows 7 is similar to Vista in that each application has its own local volume control applied, so you will need to make sure the volume setting for REW is at max. To see those settings (in Vista at least), right click on the volume control icon and select Open Volume Mixer, or click on the "Mixer" link at the bottom of the volume slider that appears when you left click the volume control icon.


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## mdfire (Aug 11, 2008)

brucek said:


> You have a monitor loopback turned on.
> 
> You have to mute the line-in in Playback (as shown) or it feeds the output to input internally.
> 
> ...


Great! that sorted it. Thanks to everyone who posted/helped.

Took my first measurement of my subwoofer










Looks like I have some work to do on it!!!!


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## mdfire (Aug 11, 2008)

Simply moving the sub along the wall and out of the corner achieved this









I will play around with sub position over the next few nights. I was having definitely boomy sound particularly with music. The room is fairly square (4.1m x 4.0m) and has an attic roof so I knew I would have problems. One question I would have, is it possible to input filters generated by REW manually into my AVR? (Pioneer SC-LX81) Edit Apparently not for the sub!


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## brucek (Apr 11, 2006)

> is it possible to input filters generated by REW manually into my AVR?


REW filters are Equalizer model specific. Each type of equalizer defines bandwidth differently. This math is programmed into REW when the type is selected. The filters are variable center frequency, bandwidth and gain. That's what a parametric EQ does - an AVR isn't up to the task I'm afraid.

Note: The floppy icon in the lower left hand portion of an REW graph saves a jpg of the graph of 800 bits wide suitable for posting - you don't need to post the entire page.

Also note that for subwoofer plots, always use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - 200Hz) using the Graph Limits button in the top right corner of REW. Use a measurement start frequency of 0Hz and an end frequency of 200Hz. Use the appropriate target line that matches your crossover.

For full range plots, use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - upper limits) you desire, i.e. 15KHz -20KHz. Use a full range target line.

For full range only, enable smoothing (1/3 octave) to eliminate the comb filtering.

brucek


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## mdfire (Aug 11, 2008)

brucek said:


> REW filters are Equalizer model specific. Each type of equalizer defines bandwidth differently. This math is programmed into REW when the type is selected. The filters are variable center frequency, bandwidth and gain. That's what a parametric EQ does - an AVR isn't up to the task I'm afraid.


Thanks, 

so without an equalizer such as BFD, the best I can achieve it seeking a resonably flat response by moving the sub around the room?


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## brucek (Apr 11, 2006)

> so without an equalizer such as BFD, the best I can achieve it seeking a resonably flat response by moving the sub around the room?


Yep......

brucek


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## mdfire (Aug 11, 2008)

Thanks, just one final question (for now), is the fact that the response line between 20 and 45Hz is well below the target line signficant? or is the name of the game getting a flat response? Also what is an "acceptable" peak or dip in terms of +-dB?

Three questions I think:sneeky:


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## glaufman (Nov 25, 2007)

mdfire said:


> Thanks, just one final question (for now), is the fact that the response line between 20 and 45Hz is well below the target line signficant?


Yes, sort of. What sub are you using? All subs roll off at some point, so that area may not be one to "fix" so much as one to indicate you may want a different sub. 


> or is the name of the game getting a flat response?


Yes, sort of. A flat response can be considered ideal for the room's acoustics. Then again, some like shelving filters on the low end. Peaks and Dips are the enemy. Sometimes they can be minimized by sub/listener positioning, sometimes by trapping, sometimes phasing, and of course EQing... BUT... you don't want to achieve a perfectly flat line by introducing hundreds of filters. As you alluded to, some variation is inevitable, expected, and not to be worried about.


> Also what is an "acceptable" peak or dip in terms of +-dB?


I suppose people have different opinions on this, and to some extent it might depend on just what you have to do to get rid of it. I persoanlly think +/-3dB is acceptable. But that doesn't mean 4 isn't.


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## brucek (Apr 11, 2006)

> Took my first measurement of my subwoofer


You haven't loaded the mic/meter calibration file. The graphs are not that meaningful at low frequencies until you load that file. What mic/meter are you using - we have cal files on our download page.

brucek


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## mdfire (Aug 11, 2008)

ooops...just spent the last hour moving my sub around the room and taking measurements:crying:

I have a radioshack sound meter (digital)


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## mdfire (Aug 11, 2008)

OK, calibration file for mic/meter loaded. This is what I got after all the moving round the room.

















How am I doing


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## mdfire (Aug 11, 2008)

glaufman said:


> Yes, sort of. What sub are you using?


B&W PV1


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## glaufman (Nov 25, 2007)

brucek said:


> You haven't loaded the mic/meter calibration file. The graphs are not that meaningful at low frequencies until you load that file. What mic/meter are you using - we have cal files on our download page.
> 
> brucek


:scratch:
I thought that at first, as the pic looks like the show mic cal file optoin is grayed out, but...
It looks like it's doing "something" with a mic cal, which it thinks is -0.1dB where the cursor is...:huh:


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## mdfire (Aug 11, 2008)

glaufman said:


> :scratch:
> I thought that at first, as the pic looks like the show mic cal file optoin is grayed out, but...
> It looks like it's doing "something" with a mic cal, which it thinks is -0.5dB where the cursor is...:huh:


At this stage I have lost track of what I did last night. Anyway the last graphs posted where definitely with the mic cal file loaded.


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## glaufman (Nov 25, 2007)

mdfire said:


> OK, calibration file for mic/meter loaded. This is what I got after all the moving round the room.
> 
> How am I doing


Well, I'm afraid the next step is to figure out why your waterfall stops at 80Hz...


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## glaufman (Nov 25, 2007)

mdfire said:


> At this stage I have lost track of what I did last night. Anyway the last graphs posted where definitely with the mic cal file loaded.


Answered myself on this one... you must've had "c-weight mic" checked in the setting page (which would be correct if you're using the RS in C weighted mode)... that's the -0.1dB at 1.16k being used as a mic cal even though you dind't have the specific file loaded.:doh:


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## mdfire (Aug 11, 2008)

glaufman said:


> Well, I'm afraid the next step is to figure out why your waterfall stops at 80Hz...


:rofl: nearly choked laughing there glaufman!









I changed the zoom in zoom out scale


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## glaufman (Nov 25, 2007)

mdfire said:


> :rofl: nearly choked laughing there glaufman!


Glad to be of service!


> View attachment 17152
> 
> 
> I changed the zoom in zoom out scale


That's easier to read, but best bet is to use the same scale as the FR plot, so we can compare them directly.


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## mdfire (Aug 11, 2008)

glaufman said:


> Glad to be of service!
> That's easier to read, but best bet is to use the same scale as the FR plot, so we can compare them directly.


When I use the same scale as FR, the waterfall stops at 80Hz as before


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## mdfire (Aug 11, 2008)

glaufman said:


> Glad to be of service!
> That's easier to read, but best bet is to use the same scale as the FR plot, so we can compare them directly.


Waterfall graph was on linear as opposed to log


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## mdfire (Aug 11, 2008)

And this was the original position I had the sub when I set the room up


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## glaufman (Nov 25, 2007)

mdfire said:


> Waterfall graph was on linear as opposed to log


Getting better all the time!

I'm still learning the art of reading these graphs, but it seems to me you've got a mode ringing there just above 40Hz, and it's second harmonic at just over 80Hz. I think the suggeston there will be EQ. There's something going on at 50Hz too, but since your in Ireland, the stuff that's still there at 300ms is probably noise from your AC...

Here's a link to the results of some testing done on that sub...
http://www.hometheatershack.com/forums/subwoofer-tests-archived/5749-b-w-pv1.html

I'm still unsure why you seem to hit a high noise floor down low... Can you generate an impulse response chart?


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## glaufman (Nov 25, 2007)

mdfire said:


> And this was the original position I had the sub when I set the room up


I sure like the other one better.


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## mdfire (Aug 11, 2008)

glaufman said:


> Getting better all the time!
> but since your in Ireland, the stuff that's still there at 300ms is probably noise from your AC...


I assume you are having a laugh there..any residual noise is probably the rain hitting of the window!!!

I have no idea what this graph means but this is the impulse response for the original sub position


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## brucek (Apr 11, 2006)

> Well, I'm afraid the next step is to figure out why your waterfall stops at 80Hz...


Known bug in the program. Waterfall must be used with LOG, not LIN mode.

brucek


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## mdfire (Aug 11, 2008)

This is actually the impulse response after I moved the sub..my new preferred position.


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## glaufman (Nov 25, 2007)

mdfire said:


> I assume you are having a laugh there..any residual noise is probably the rain hitting of the window!!!
> 
> I have no idea what this graph means but this is the impulse response for the original sub position
> 
> View attachment 17161


Actually not having a laugh here, but I meant to mention I was talking specifically about the 50Hz stuff that doesn't seem to go away... sorry for the confusion...:innocent:


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## mdfire (Aug 11, 2008)

glaufman said:


> Actually not having a laugh here, but I meant to mention I was talking specifically about the 50Hz stuff that doesn't seem to go away... sorry for the confusion...:innocent:



No worries mate.

In terms of the sub I am pretty happy with it. Its goes low enough for me. With movies it was really good. Just some music was very boomy. Moving it has helped a lot. Thanks for the comments. I guess thats as good I will get it without an EQ?


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## glaufman (Nov 25, 2007)

Hmmm...
Brucek- Is does this window look alright, or should he push out the right gate?


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## glaufman (Nov 25, 2007)

mdfire said:


> No worries mate.
> 
> In terms of the sub I am pretty happy with it. Its goes low enough for me. With movies it was really good. Just some music was very boomy. Moving it has helped a lot. Thanks for the comments. I guess thats as good I will get it without an EQ?


Where exactly do you have it now, and where was it before?
Also, you might want to take a scan of the mains (just the same frequency range) and then the mains+sub to see how they're combining.


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## mdfire (Aug 11, 2008)

It was at the front of the room just to the left of the left main speaker, 2ft out from the front wall but against the side wall. Running sweeps for positions all along the left wall gave really bad peaks/dips. Moving to the opposite wall gave much better readings. Its now against the right hand wall in the middle. The sub is firing against the front and rear walls.

Yes I was going to try the mains, and then the mains and sub. Just home too late tonight and too tired.


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## mdfire (Aug 11, 2008)

This might be easier to visualise. This was the original position









and this is were it is now


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## Audioguy (Jun 25, 2008)

brucek said:


> REW filters are Equalizer model specific. Each type of equalizer defines bandwidth differently. This math is programmed into REW when the type is selected. The filters are variable center frequency, bandwidth and gain.
> 
> brucek


I will be using a QSC DSP 30 which has parametric EQ capability. Can I not use the Q, Center Frequency and Amplitude that I obtain in REW and manually use it in my QSC product. I assume that the definition of those is generic and does not apply to a specific parametric EQ --- or not?


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## glaufman (Nov 25, 2007)

mdfire said:


> This might be easier to visualise. This was the original position


Getting a sub out of a corner often gives you a smoother response, at the expense of some gain...
Interesting though... your room looks symmetrical (maybe I'm missing something) so I would expect similar performance on either wall...

Nice looking room, BTW...:T

Where in Ireland are you? My wife grew up outside of Dublin.


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## glaufman (Nov 25, 2007)

mdfire said:


> Yes I was going to try the mains, and then the mains and sub. Just home too late tonight and too tired.


Oh believe me, I understand THAT!


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## mdfire (Aug 11, 2008)

glaufman said:


> Getting a sub out of a corner often gives you a smoother response, at the expense of some gain...
> Interesting though... your room looks symmetrical (maybe I'm missing something) so I would expect similar performance on either wall...
> 
> Nice looking room, BTW...:T
> ...


Yes the room is almost square - 4.1 x 4.0m. When I was getting it done I would have liked to have moved the rear wall back a few metres but there were technical reasons for not being able to do so.

Thanks for the compliment!

I work in Dublin, but live on the Cooley Peninsula just south of the border with Northern Ireland (near newry)


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## mdfire (Aug 11, 2008)

glaufman said:


> Getting a sub out of a corner often gives you a smoother response, at the expense of some gain...
> Interesting though... your room looks symmetrical (maybe I'm missing something) so I would expect similar performance on either wall...


There is a velux window in the ceiling on the side of the room with poor performance when I think about it.

You can see it here 

http://www.avforums.com/forums/members-home-cinema-gallery/1095874-attic-cinema-room.html


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## mdfire (Aug 11, 2008)

OK, another run tonight. This time i did the professional eq setup on the pioneer, and discovered that there is a standing wave adjustment for the sub, which allows you to tweak. This is what I got for the sub alone.

















Then the sub with the main speakers


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## glaufman (Nov 25, 2007)

mdfire said:


> There is a velux window in the ceiling on the side of the room with poor performance when I think about it.
> 
> You can see it here
> 
> http://www.avforums.com/forums/members-home-cinema-gallery/1095874-attic-cinema-room.html


Maybe that window, maybe the off-center door is leaky and reflecting less back...
On your new sub only scan there are the two huge dips that weren't there before... I guess they're pretty narrow, but it was the EQ that did that?


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## mdfire (Aug 11, 2008)

yes that was the eq on the avr. sub never moved. There was an option to address standing waves with three positions. The normal MCACC equalisation only considers one. I then played about with the filters at 81hz and 96hz. Those (plus one at 180hz) were the only ones it offers.

Played some music tonight (Jack Johnson Broken which is very bass heavy) and the system really sounds so much better.


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## glaufman (Nov 25, 2007)

I'm certainly glad it sounds better. The graphs certainly show you're making progress. I just don't understand where the sharp dips at 40something and 100 came from. 
So you've got "standing wave" filters at 81 ,96 and 180... any chanc eyou took graphs with just the 81Hz filter? I'm concerned you may be over-filtering... I'd like to see it each step of the way... I don't think you mentioned yet which Pio AVR you have... how much adjustment does it allow to those filters in terms of Fc, Gain, and BW(Q)?
Did you ask REW to recommend filter parameters?


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## laser188139 (Sep 19, 2009)

The dips could be from reflections generating complementary waves. 

The 45Hz dip would correspond to a 1/4 wave distance of about 6'3". From the sub, this could as easily be a reflection off the ceiling as off one of the walls. 

The 78Hz dip which appears from the mains would correspond to a 1/4 wave distance of about 3'8". From the pictures, I'm guessing this could be a reflection off a side wall, as the fronts appear much closer than this to the front wall. I don't know what the distance is to the back wall. 

It's harder to guess what is happening just above 100Hz. There is a dip in the sub, that could be a 1/4 wave reflection off a wall at 2'9". That could be the effective distance of the sub from the side wall. But as the dip moves when the main is added, it is not clear if the main is trying to fill in the sub's dip and does so only partially, or whether it fills in the sub's dip completely but has its own dip around 110Hz. You would know a little more with a graph of the mains alone without the sub. 

These are all just hypotheses for what reflections might be causing the dips. You could try to verify each separately by moving one speaker at a time in one or two dimensions and seeing what the effect is. That could tell you where you might add damping, or at least you would be reassured as to what the cause was. 

RealTraps offers a freq-distance calculator that is helpful in estimating what distances could be causing complementary reflections at a particular frequency. 

Have fun,
Bill


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## mdfire (Aug 11, 2008)

Thanks guys, apart from those two dips though, everything else looking ok?

Will work on them next week.


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## glaufman (Nov 25, 2007)

laser188139 said:


> The dips could be from reflections generating complementary waves.


Normally I'd agree, except assuming he's now using the mid right side position, those dips weren't there (or at least not as severe) before engaging the EQ.


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## glaufman (Nov 25, 2007)

Have you tried the sub on the front wall on either side of the table?


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## mdfire (Aug 11, 2008)

glaufman said:


> Have you tried the sub on the front wall on either side of the table?


I moved the sub around the walls 1ft at a time, including at the front between the speakers and the cabinet. The best position was were it is now.

In terms of reflections, the sub fires from both sides which are both directed at the front and rear walls. Im going to turn it slightly and see how that works.


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## mdfire (Aug 11, 2008)

I turned the sub approx 30 degrees and add some filtering at 63 and 71 Hz. It has lifted those dips a bit.

The first graphs below are from the very first sweep before any filtering or moving the sub.

















These graphs are where I am at now.


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## glaufman (Nov 25, 2007)

So, how does it sound now?


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## mdfire (Aug 11, 2008)

Not boomy:T

Question is, am I likely to see/hear significant improvements to the graphs/sound by buying a dedicated EQ unit such as BFD?


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## brucek (Apr 11, 2006)

The peak at 40Hz would tend to overwhelm the lower signals, so if it was reduced with an EQ, those lower level signal would be heard at your listening position.

brucek


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