# Penngray's HT room project



## penngray (Feb 21, 2007)

Im going to use this thread to get all my questions answered and to post updates of doing full room analysis of my new HT room.

The room is ready for acoustical treatment but I want to run initial charts just so I know what Im starting with. Its a 13x25 room but the sound is on the 25 foot wall, I have run my theater sideways actually for many different reasons, I know already its not optimal and I need to really absorb reflections on the "back" wall because I have one row and it is 2 feet of the back wall. I will post pics and graphs as I go along.

Anyways, here is the Equipment....

Nady CM-100 condensing mic, I assuming its identical to the Behringer brand so I will use the same cal. file
Xenyx 1002Fx pre-amp
HP Notebook with Vista
soundblaster live! 24bit external USB 

Note: IF I can get his all done in 7 days I can return all the equipment


----------



## penngray (Feb 21, 2007)

I have connected all equipment according to the pics and posts on here.

I have added the Behringer cal. file to calibrate the mic, should I have c Weighted SPL meter checked for this mic?

and now Im trying to calibrate REW but Im stuck. I have read many threads, help files and they all talk about changing the REW input volume.

Those options are greyed out. I can not change them...what can I do? I selected the proper soundblaster USB options in my My input and output device selections but what else?


----------



## penngray (Feb 21, 2007)

Here is the Mic/meter tab...











here is the soundcard tab










So far Im stumped on how to calibrate...I have the left main speaker out connect to the left line in to do the loop testing (although I can not tell left and right when looking at the 1/8" plug y-splitter that splits into 2 RCA connections.

Here is what I get when I start measuring....










Here is what I get when I start the sound card calibration, I can not get even close to a 3 dB differential?????










Its all very confusing but it doesnt seem that Im doing this correctly. I do get a signal on the left channel, not shown in the last pic, its gets up too -14 which is green but the message still says my DB is too low...is it thinking I need the right channel?










Maybe its a Right and left thing ? I did switch input channel to Left and clicked "OFF" the use Left channel. I get a better headroom of 19dB but there is still a message talking about 10 dB.


I guess my questions are....

What did I do wrong?


----------



## penngray (Feb 21, 2007)

EDITED:

There is a phones/control room nob that I had set to zero......hang on.....I see dB levels now....

btw, 75 dB is pretty low to hear...should it be?

Well, I still dont have a clue so I will wait for some help. Its hard to know if Im doing anything right, the numbers are all over the place it seems to me. Its kind of a **** shoot if you have never done this before. 

Note: this isnt a very active site is it? I hang on AVSForum and there is a tons of activity, help, opinion. I will be patience


----------



## JohnM (Apr 11, 2006)

The SB Live! 24-bit external seems very problematic under Vista, I don't think anyone has had good results with it. To check the volume settings, when you have REW running right click the volume control icon in the taskbar, select Open Volume Mixer and set the level for REW to the maximum. Close the volume mixer, right click the icon again and select recording devices. Double-click the Soundblaster Live Line In/Mic-In entry on the Recording tab that appears, select the Levels tab and put the Line In level to max. On the advanced tab set the sample rate and bit depth for shared mode to 2 channel, 16 bit, 48000 Hz (DVD Quality).


----------



## brucek (Apr 11, 2006)

Uncheck the _Use Left Channel Calibration reference_, since you're not using it.

This is explained in the REW HELP FILES under Calibrating the soundcard and under Soundcard connections

You are using the soundcard cal file method of calibration, so you will use the looped cabled during calibration to create your soundcard file and then store it and load it into REW.

Then you'll remove the looped cable and your ready to go and hook up your cables.

With an ECM8000 type cal file, the C-Weight check box doesn't have any effect.

There are some reported problems with that soundcard and VISTA...

brucek


----------



## penngray (Feb 21, 2007)

thanks, Im going to move the sound card to my desktop which is running XP. I will do a test there and see if I can get better results.

I seem to be getting the Mic calibrated but I can never get it to match my RS SPL....

Example, I set my receiver volume so that my RS SPL shows 75 dB then I press calibrate on the mic, it comes up with a value I should enter on the screen the default is 75 dB so I assume I just press enter to calibrate. 

Then after that I look at the SPL meter and its reading about 10 to 15 dB higher then my RS meter still  I guess this could be still a Vista issue so I will test with my XP box first.


----------



## penngray (Feb 21, 2007)

> This is explained in the REW HELP FILES under Calibrating the soundcard and under Soundcard connections


its explained but Its about as clear as mud to me....the first problem is that those 1/8" plugs with two RCA connections (Y plugs) dont tell me which is right or left so I have no idea how Im suspose to connect right out to left in for the looping. Im just not clueing in on how that is achieved.


----------



## penngray (Feb 21, 2007)

Okay, I think Im getting somewhere on XP.

Current Mic and sound card calibrations.










To get no distortion I had to disconnect my RCA connection from my mic pre-amp...otherwise I was getting a huge distorted line for my soundcard calibration. I never read that in any the help docs I was just experimenting to try and get a decent plot. I might have missed that I had to disconnect it when doing my loop connection.

so Im going to assume Im calibrated and Im going to play around with it now.


----------



## penngray (Feb 21, 2007)

Okay, so this is my first full 0 to 10K Hz measurement....











comments? This is a test in my office so I know its going to be a crazy bad plot. I just want to know that Im ready to move the equipment in the room.

Im not confident that its running full sweeps (mains and sub) I assume it is but those big distorted part on the right side seems like its screwed up and not set right, it simply looks like its all sub... how can I make sure it runs a full sweep with all main speakers together?


----------



## brucek (Apr 11, 2006)

Use a vertical graph axis of 45dB-105dB and a horizontal graph axis starting at 15Hz for all graphs. This is set by clicking the Graph Limits icon on the REW screen. 

When displaying graphs higher than 200Hz, you may turn on the smoothing feature (1/3 octave). This removes the normal comb filtering you're experiencing in your graph.

Your receiver must be in stereo mode so that only the mains and sub are on. These are the only channels you can test since REW is a mono signal.

Try the sub alone first (by disconnectingthe mains wires) and measure to 200Hz and use a graph horizontal axis of 15Hz-200Hz. Then when you get a smooth response by moving the sub around, add the mains and adjust the level (it's obviously low right now).

brucek


----------



## salvasol (Oct 31, 2006)

penngray said:


> ....the first problem is that those 1/8" plugs with two RCA connections (Y plugs) dont tell me which is right or left so I have no idea how Im suspose to connect right out to left in for the looping. Im just not clueing in on how that is achieved.


Aha ... I'm not the only one who had this problem (I was trying to figure it out the same thing) :bigsmile:

I checked my receiver AUX input, and the red side is what you need to use :bigsmile:


----------



## penngray (Feb 21, 2007)

> add the mains and adjust the level (it's obviously low right now).


I can not figure out how to add the mains in REW...I only get the subs evertime I test. I change teh "Target Defaults, speaker" option to "full range" and then I run a measurement and only my subs have sound still.


----------



## brucek (Apr 11, 2006)

> I can not figure out how to add the mains in REW...I only get the subs evertime I test. I change teh "Target Defaults, speaker" option to "full range" and then I run a measurement and only my subs have sound still.


REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.

If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........

brucek


----------



## penngray (Feb 21, 2007)

> REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.
> 
> If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........
> 
> brucek


Hmmm...that is what I figured, I will double check the receiver.


----------



## Jerm357 (May 23, 2006)

brucek said:


> REW only generates a single mono signal that you are feeding to the AUX or CD input of your receiver.
> 
> If your receiver is in stereo mode and the mains are set to small, there will be a signal coming from the sub and the mains.........
> 
> brucek


 The signal only comes out of one of the front main speakers and the sub right? Not both the mains at the same time?


----------



## brucek (Apr 11, 2006)

> The signal only comes out of one of the front main speakers and the sub right? Not both the mains at the same time?


It will come from both mains if a splitter is used at the receivers input to direct it to both right and left channel (as shown and explained in the Connections post).

I do try and get everyone to read this thread before they buy any equipment and attempt to hook up REW. It explains all the equipment required, where to get it, how much it costs, and how to hook it up. Combine that with the REW Help files and that's all anyone needs to be an expert.

brucek


----------



## Jerm357 (May 23, 2006)

Ok I see what you mean but if hooked up like this pic with out the optional loop back connections it should only come out of one right?


----------



## brucek (Apr 11, 2006)

Yep, unless you had a mono button on your receiver............

brucek


----------



## penngray (Feb 21, 2007)

I started my HT room measurements tonight (the room has no treatments yet) I had everything calibrated friday but now I get the below message...











"impulse peak not were it should be" ??? I double checked all calibrations and things seem to be fine so I dont know.

here is the filter adjusted plot....










Here is the measurement plot.....










and here is the waterfall plot.....










The real measurement plot looks better then the filterd plot, is this always true?

Also, I can not get the waterfall to show anything past 90 Hz....besides that the waterfall for the low end looks pretty good so far, doesnt it? Of course now Im nervous because if its good then I have to believe I did something wrong!


----------



## JohnM (Apr 11, 2006)

To fix the problem with the waterfall display set the frequency axis to logarithmic by clicking the Freq Axis button in the toolbar when you are looking at the waterfall. Those are almost certainly not valid measurements, however. If you post screenshots of the Scope page and the Impulse page that may give some clues what is going wrong. You can save a jpeg of any graph by clicking the disc icon in the bottom left corner of the graph, at the ends of the scroll bars.


----------



## penngray (Feb 21, 2007)

Ok, so Im trying to get my soundcard calibrated again!! Is it really this hard all the time, I mean it laid out step by step but it never ******** works and that is really annoying!!!


Sound card calibration

1 kHz test tone...










That is good correct? 

The loop back is connect Right RCA cable out connected back into the line in adapter, of course I dont know which is left or right on this adapter?? Does it matter?










Sooooo....all should be good to run the sweep? correct?










Nope, this time its a straight line. Man this stuff is really, really fussy and things dont work easily my fustration level is extremely high now. **** I have 20 years of software and hardward experience in the IT world and it shouldnt be this hard. 

Been through the help too many times now so something is missing. 

Please help, I need to get this stuff working because I have to get the room done this week


----------



## brucek (Apr 11, 2006)

> Is it really this hard all the time,


Nope, should be simple.



> That is good correct?


Why do you have a signal at both right and left input showing in your picture?
You only loop the line-out right to the line-in right for soundcard calibration. Leave the left channel open.



> of course I dont know which is left or right on this adapter?? Does it matter?


Sure it matters. You need to use _right_ on the line-out adapter and _right_ on the line-in adapter.
Use a multimeter to identify the left and right on both adapters and mark them if needed. The tip is left and the ring is right and the sleeve is ground. You can use right or left, just be sure to use the same on line-in and line-out.

brucek


----------



## salvasol (Oct 31, 2006)

> ...Ok, so Im trying to get my soundcard calibrated again!! Is it really this hard all the time, I mean it laid out step by step but it never ******** works and that is really annoying!!! ...


I think most of us struggled when doing this calibration :yes: ... you need to do it just one time.



> ... The loop back is connect Right RCA cable out connected back into the line in adapter, of course I dont know which is left or right on this adapter?? Does it matter? ...


Yes, I think it matters (that was the problem I have when calibrating my soundcard, I was using a 1/8" cable without the splitter) :duh:

What I noticed is that you have marked to use left input channel (it has to be right), also, the input/output device need to be your soundcard not default ... if the adapter doesn't have a mark to see which side is R or L, try one side and if doesn't work switch sides.

The soundcard calibration will look similar to this 









Relax ... you'll make it work :T


----------



## penngray (Feb 21, 2007)

Ok, started from scratch...


1. Rebooted notebook, my memory was all used up and REW was pretty slow so that might have cause problems.

2. rechecked all line levels on my sound card....made sure everything was muted except Volume/Wave...on problem here could have the fact that CD wasnt muted and probably was screwing things up...

3. started REW, selected mic calibration and added the correct file.

4. selected the sound card calibration and made sure I connected Right line out back into Right line in. This time I didnt get errors and I did get a plot similar to plots shown above and in the help files so I think Im getting further again.

5. Did a measurement from 10 Hz to 200 Hz and here is the plot, it definitely looks real this time!










One thing that still bothers me is that when running these test my subs are going to be so much louder then my main speakers so doesnt that skew the results for the 100 -200 Hz?


----------



## brucek (Apr 11, 2006)

> One thing that still bothers me is that when running these test my subs are going to be so much louder then my main speakers so doesnt that skew the results for the 100 -200 Hz?


I'm not fully sure I understand you, but I'll give the answer to the question I think you're asking.

Normally, we first test with the sub only playing and find the best position (and equalize if need be).

Then we add the mains along with the sub and retest over the same range to 200Hz. This time we're checking to see how the mains and sub mix together around the crossover region, and it's also a good time to observe and tweak the mains vs sub level. If the mains and sub crossover looks poor, the phase control of the sub is adjusted to get the smoothest transition.

brucek


----------



## penngray (Feb 21, 2007)

I will unplug my mains to test just the sub but in my intial tested I was interested in seeing if the crossover worked.

You answered it now I have to figure out if my AVR (Yahama V663) still applies the crossover while in direct mode for when I run my sub and mains together.


----------



## brucek (Apr 11, 2006)

> You answered it now I have to figure out if my AVR (Yahama V663) still applies the crossover while in direct mode for when I run my sub and mains together


Why are you using direct mode?

brucek


----------



## penngray (Feb 21, 2007)

> Why are you using direct mode?


Thats a good question, I figured it was an analog mono signal in then I should just run direct out. 

What mode do you suggestion?


----------



## brucek (Apr 11, 2006)

Stereo, so that the mains and sub are active with their crossovers and the rest of the speakers are off.

brucek


----------



## penngray (Feb 21, 2007)

Ok set to 2 channel stereo and Im running more measurements for simply sanity checks because I just dont have confidence in anything I have done so far.... 

My current focus is on why my measurement drops off at around 80 Hz even though I have set everything I know to 150 Hz...










My crossover on my Yamaha reciever is set at 150 now, my sub amp crossover is set at 150 also and I set the target settings to 150 Cutoff so why doesnt the measurement show that?


----------



## brucek (Apr 11, 2006)

You can observe the desired target if you would change the speaker type from Bass Limited (for mains only) to SUBWOOFER. You'll observe that the crossover isn't a brick wall, but starts quite a bit before 150Hz.



> My crossover on my Yamaha reciever is set at 150 now, my sub amp crossover is set at 150


The subwoofer crossover is interfering with the receivers crossover. When you assign the bass management to the receiver and set it to 150Hz, you want to eliminate the subwoofers own internal crossover as it will interfere. If you don't have a bypass or defeat switch on the subwoofer to accomplish this, you simply dial the crossover filter to maximum clockwise position.

Why are you using a 150Hz crossover and not an 80Hz crossover?

brucek


----------



## penngray (Feb 21, 2007)

I will change the target to subwoofer, I actually didnt look at that...I do know its a rolloff but it should be down 20dB at 100 Hz.

As for the discussion on the crossover configuration, I just changed things to see if I could get a measurement change. I changed it to all ranges and nothing changed in the measurements and that is why I posted the questions wondering why.

In the end I have a pretty complex sub setup (Low and mid bass) and my mains are smaller bookshelves that handle only above 120 Hz so 80 Hz crossover is unacceptable for me. 

My receiver will have a 120Hz crossover, my low end large subs have a crossover of 80 and my mid bass subs have a high pass filter at around 70 or 80. 

Of course that is all later on once I get room treatments in place. My primary goal right now is to just get general measurements and then install all my acoustical treatments (bass traps and reflection points).


----------



## penngray (Feb 21, 2007)

btw, Bruce, I want to thank you and John for all your free time and advice helping us NEWBIES out!!! I spent years doing moderating and online support in other hobbies. I know what passion it takes to continuously answer even the silly questions


----------



## penngray (Feb 21, 2007)

Okay, changing from Bass limited to Subwoofer did nothing, I ran the measurements again and I still get that drop off @ around 80 Hz which looks like a crossover? Its the same plot as above.

REW cutoff is set too 150 Hz, My sub crossover is set to 150Hz and My receiver crossover is also at 150Hz.

All Im trying to do is get decent measurements of my subs from 80Hz to 120 Hz or so but that isnt happening. My sub amp has zero filters on it so I dont know what to do....can we do 80Hz to 120 Hz measurement on Subs?


----------



## brucek (Apr 11, 2006)

> Okay, changing from Bass limited to Subwoofer did nothing, I ran the measurements again and I still get that drop off


It wasn't suppose to do anything. It simply allows you insight into what the desired target looks like, so you'll be better equipped to evaluate the response versus the target.



> REW cutoff is set too 150 Hz, My sub crossover is set to 150Hz and My receiver crossover is also at 150Hz.


Again, REW target is there so you can evaluate. 

Why do you have the subwoofer at 150Hz, when it should be defeated, so that the receiver can handle the bass management?



> All Im trying to do is get decent measurements of my subs from 80Hz to 120 Hz or so but that isnt happening.


Can you explain this statement. I don't understand. You appear to have a perfectly valid measurement of your sub from 10hz to 200Hz in the picture above. REW has done its job. What's the problem?



> My sub amp has zero filters on it


Yet you said, _"my sub amp crossover is set at 150 "_. I admit to being confused.

brucek


----------



## penngray (Feb 21, 2007)

> Yet you said, "my sub amp crossover is set at 150 ". I admit to being confused.


Sorry, I have two DIY subs, one is powered by a QSC 1850 amp and it has no filtering/crossover capabilities. The other sub is power currently by a Velodyne SC-1250 amp that has crossover settings and I set it all the way up to 150Hz so it would not interfer with testing.



> Can you explain this statement. I don't understand. You appear to have a perfectly valid measurement of your sub from 10hz to 200Hz in the picture above. REW has done its job. What's the problem?


I guess it doesnt look like a good measurement to me in terms of getting more out of the higher frequencies. Im trying to get my subs to be flatter up to 120 Hz but the plot above shows a huge drop off at 80Hz (looks like a crossover at 80Hz) and I just dont understand why.

I have nothing set at or around that frequence to have such a drop so Im just confused. Atleast Im not aware that I have anything set that would cause my frequence roll off to happen way before 150Hz.

I just want to see a flatter line closer to 150, even a rolloff at 120 would be nice but I can not get that to happen. Ie... 70 dB at 100 Hz and not something like 60dB.


----------



## brucek (Apr 11, 2006)

> I just want to see a flatter line closer to 150, even a rolloff at 120 would be nice but I can not get that to happen.


OK, but that has nothing to do with REW. The measurement you showed above looks quite valid to me. Continue to measure from 0-200Hz.

You need to determine what is causing your problem.

Measure one sub at a time, with the sub dragged out to the middle of the room and do a near-field measurement of it (mic within two feet of the business end). This will help to eliminate the room influence on the subs response and give a more true measure of the actual sub itself.

Do that, and you may reveal the problem.

brucek


----------



## penngray (Feb 21, 2007)

ok, thanks!

Btw, dragging these subs anywhere is almost impossible, they are over 150 lbs each!! 

Also, one more question. Is that a dip around 20Hz or an actually NULL? I didnt think I could get a null that low so I just assume its a dip.


----------



## brucek (Apr 11, 2006)

> Is that a dip around 20Hz or an actually NULL? I didnt think I could get a null that low so I just assume its a dip.


Impossible to tell. You need to move it around and see if it goes away. You may also need to move the listening position. 

brucek


----------



## penngray (Feb 21, 2007)

> Impossible to tell. You need to move it around and see if it goes away. You may also need to move the listening position.


Ran some more tests to continue to learn this...did I say Im a complete noob yet?

I didnt move the speakers but I moved the mic around an its amazing what three feet right, three feet left does!!!!!

I did turn smoothing on for the plot but the Blue is when the mic is the normal position it was in yesterday, the purple is the new position (three feet right) today. Im amazed at the smoothness of that second measurement, 3 feet makes that much difference??? No dip at 22 or 80 Hz any more. Strange.










Note, My subs are fixed position in the HTRoom so I dont have the ability to move them, they are built into a wall actually.

Here is a pic of one of the subs


----------



## brucek (Apr 11, 2006)

> 3 feet makes that much difference???


Not too unusual. Some people get lucky and find a nice response that remains constant over their seating positions, but not many.

A BFD would equalize that response quite nicely.............

brucek


----------



## penngray (Feb 21, 2007)

Yeah, I have the DSP1124 waiting to be configured just want to make sure I can work and understand REW first then do the room acoustics (bass traps in corners, 2" on reflection points and rear wall), then I will start to set all the filters needed.

Its been a great learning experience and you guys have been extremely patience and helpful with me!!


----------



## brucek (Apr 11, 2006)

> just want to make sure I can work and understand REW first then do the room acoustics (bass traps in corners, 2" on reflection points and rear wall), then I will start to set all the filters needed.


Smart.............

brucek


----------



## penngray (Feb 21, 2007)

Okay, so today Im tring to run full waterfall measurements for 100 Hz too 3000 Hz (or so) so I can start my room treatement.

My results look like huge distortion, bad measurements and it measures way below the 75 dB target so my questions are .....

Can I get REW to give me acurate measurements for 100 Hz too 300Hz?

Should I be recalibrating with just my main speakers to get a better dB level?

The 1/3 octave smoothing doesnt work on higher frequences, so what should I do to remove those seriously out of wack lines?

I also think I just be using RT60 above a certain frequency instead of Waterfalls but what frequency is that?

As always, thank you for helping us helpless individuals


----------



## penngray (Feb 21, 2007)

Here are some pics to help with my questions....

settings is this.....










I just changed to the crossover from 24db/Octave to 12db/octave too see any differences and I guess I should first ask...what is that?

I also just changed from subwoofer to full Range because I want to measure full range


10 Hz to 1000 Hz measurements......










What is the reason Im down below 56 dB for 150 to 1000 Hz, is it because my subs are just so over powering during the 75 dB calibration that my mains are not loud enough during the measurement?


----------



## brucek (Apr 11, 2006)

> Can I get REW to give me acurate measurements for 100 Hz too 300Hz?


Sure....



> My results look like huge distortion, bad measurements and it measures way below the 75 dB target so my questions are


I don't really understand. If you use the same vertical and horizontal axis with the waterfall plots as you do with the the response plots and you have them both set to LOG graphs, then the 1st slice (one of thirty) of the waterfall is identical to the response plot. What distortion are you talking about...



> Should I be recalibrating with just my main speakers to get a better dB level?


I don't understand. You certainly want the sub and mains playing together to meaure up to 300Hz. Just measure from 0-300 and use the graph axis to select the range you want.



> The 1/3 octave smoothing doesnt work on higher frequences,


The smoothing works on all frequencies...



> I just changed to the crossover from 24db/Octave to 12db/octave too see any differences and I guess I should first ask...what is that?


It modifies the slope on the REW target line.



> What is the reason Im down below 56 dB for 150 to 1000 Hz


Your sub versus mains levels are not the same. Use the simple receiver test tone routine to set your levels if you're having trouble setting them with REW.

brucek


----------



## penngray (Feb 21, 2007)

here is my waterfall that should show for 10 Hz too 1000 Hz....










I can not get it to show past 500 Hz, what did I miss?


----------



## JohnM (Apr 11, 2006)

Set the frequency axis to logarithmic using the button in the menu bar.


----------



## penngray (Feb 21, 2007)

> Set the frequency axis to logarithmic using the button in the menu bar.


Well that was dumb of me, I did it for the measurement tab and I thought it did it across all tabs....Yeah, mucho better.....


----------



## brucek (Apr 11, 2006)

Above modal resonance bandwidth, waterfall is not really recommended since you really don't get much meaningful information from it.

So for frequencies below ~200Hz, use waterfall and decay plots. Above that you would rely on RT60 plots (be sure to use a mains speaker for this).


brucek


----------

