Some guides to REW and acoustic measurement

skid00

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Mar 20, 2020
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2 x Adcom GFA 555
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Carver Amazing Platinum Mark IV
I've done several dozens of measurements. I've tried hand-held, hand-held with a 3' heavy tripod leg, on a heavy tripod, on a heavy tripod with 3" of fiberglass on the front side of the legs and mount, and on the tripod with a 9" square by 2" soft foam baffle 3" behind the tip of the microphone.

The foam baffle produced the 'cleanest' impulse responses (with lower dB ripples/echoes).

I've done measurements at 1' intervals from the speaker. (Note I'm measuring Carver Amazings which have a 5' long, vertical dipole diaphragm, so comb-filtering is a thing). I see reflections from the couch becoming an issue with the mic closer than 3 feet from the couch back.

Due to the age of the speakers (almost 30 years old), and the 'acoustics' of my 18' x 32' with 12' cathedral ceiling and no treatment, I'm EQing the whole 20-16,000 Hz range. I've tried blending close-up scans for high frequencies with various bass scans.

I *really* wish I had access to an anechoic room!
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
I've got a umik1 mic and I played with it in rew a few weeks ago on my denon x3500h. I had no problem testing the sub only. I tried to do the same thing today to test a few other listening positions and I can't figure out why the low frequencies go to the sub and the front speaker(s) in the same time. I turned off audyssey. The front speakers are set to small. The cross over is 250hz for the fronts. I play stereo sound. The driver is set to java in preferences. Even when I use the generator in rew with the sub cal option, I get sound through the front speakers.

What am I'm missing?

Another interesting thing is that when I play with the crossover, the overall spl changes, but shouldn't the fronts be silent if I set the crossover to 250hz and the test sound in rew is below that?
 

dcibel

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The front speakers are set to small. The cross over is 250hz for the fronts. I play stereo sound.
When speakers are set to small, 2.1 configuration is assumes so subwoofer plays low freq when there is no dedicated LFE channel. This allows subwoofer to be in use when only playing stereo audio.

If you want to measure your speaker with the high pass filter in place from your AVR, easiest thing to do is just turn off or unplug your sub, or disable it through your AVR settings.

250Hz crossover is quite high, typical use for a subwoofer would be more like 120Hz.
 
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acconstantinescu

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Main Amp
Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
I've got a umik1 mic and I played with it in rew a few weeks ago. I had no problem testing the sub only. I tried to do the same thing today to test a few listening positions and I can't figure out why the low frequencies go to the sub and the front speaker(s) in the same time. I turned off audyssey. The front speakers are set to small. The cross over is 250hz for the fronts. I play stereo sound. The driver is set to java in preferences. Even when I use the generator in rew with the sub cal option, I get sound through the front speaker.

What am I'm missing?

Another interesting thing is that when I play with the crossover, the overall spl changes, but shouldn't the fronts be silent if I set the crossover to 250hz and the test sound in rew is below that?
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
When speakers are set to small, 2.1 configuration is assumes so subwoofer plays low freq when there is no dedicated LFE channel. This allows subwoofer to be in use when only playing stereo audio.

If you want to measure your speaker with the high pass filter in place from your AVR, easiest thing to do is just turn off or unplug your sub, or disable it through your AVR settings.

250Hz crossover is quite high, typical use for a subwoofer would be more like 120Hz.
Maybe I wasn't clear. I don't want to test the speakers. I want to test the sub only. That's why I set the speakers to small. I set the crossover to 250 hz to make sure the fronts don't play anything, just for testing. Normally I use 100hz for crossover on the front speakers.
 

John Mulcahy

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A sub cal signal is nominally 30 to 80 Hz, but with random noise the filters (per Dolby specs) are fairly shallow so there is content to much higher frequencies. You can choose to use periodic noise for level shecks in the REW soundcard preferences.

Spectrum of a sub cal signal with random pink noise:

1686394609725.png


Spectrum of a sub cal signal with periodic pink noise:

1686394678334.png
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
I remember the first time I did it only the sub was playing the random pink noise, not the fronts. Also, when I used the measurement option in rew between 10hz and 200hz only the sub was playing the test sound. Nothing was coming out of the fronts. Now it does. Clearly I'm not setting the avr correctly but I can't figure what is that I'm doing wrong.
One would think that setting the fronts to small and setting the crossover for them to 250hz is enough to avoid any sound below the crossover being played on the fronts.
Before I started playing with rew I watched some YouTube videos of "home theater gamer". In one video where he shows how to set the level of the front and the sub to 75db, he uses the random pink noise for that. Between setting the level of the front and the level of the sub, the only change he makes is going from speaker cal to sub cal. Nothing else. I was able to match what that video shows first time, but I can't do it anymore.
One thing that I didn't check is to see if the sub plays any sound when I do the speaker cal. If it does maybe is not the avr but a rew setting that I'm missing.
 

John Mulcahy

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A typical processor 250 Hz crossover would be down about 24 dB at 62.5 Hz.
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
A sub cal signal is nominally 30 to 80 Hz, but with random noise the filters (per Dolby specs) are fairly shallow so there is content to much higher frequencies. You can choose to use periodic noise for level shecks in the REW soundcard preferences.

Spectrum of a sub cal signal with random pink noise:

View attachment 62312

Spectrum of a sub cal signal with periodic pink noise:

View attachment 62313
OK, I did some more testing. When I do the sub cal and speaker cal with the period pink noise I get only one of them at a time to play sound.
The denon app allows me to see what kind of audio signal the avr receive. It says pcm stereo. Is that what's supposed to be?
 
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acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
A sub cal signal is nominally 30 to 80 Hz, but with random noise the filters (per Dolby specs) are fairly shallow so there is content to much higher frequencies. You can choose to use periodic noise for level shecks in the REW soundcard preferences.

Spectrum of a sub

I've been playing only with the sub and main speakers so far in REW, so I only used the Java driver. I'd like to measure the center too. I installed the ASIO driver. When I choose it in Preferences, I can set the Umik1 mic, but it tells me that no output is connected. Please tell me what I'm doing wrong. Here is a screen shot.

20230620_195555.jpg
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
You can use the EXCL device entries for multichannel with the Java drivers. If you use ASIO you need to select the device entry corresponding to your HDMI output.
I thought the Java driver for Windows doesn't support multi channel ...
When I choose the Java driver, I can see my Denon AVR in the list of outputs. When I choose ASIO, I don’t see it. All I see is not connected 1 and 2.
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
You can use the EXCL device entries for multichannel with the Java drivers.
I figured out what I was doing wrong when using the Java driver: I had the stereo option checked. Once I unchecked that I could see all the channels. However, when I try to play the periodic noise on either the fronts or the center, I don't hear any sound. The out channel in the preferences window shows some activity but nothing comes out of the speakers. I tried to set my avr on multi channel stereo and Dolby surround. Neither settings helped. Do I need to adjust something else on my avr?


20230622_173830.jpg
 

acconstantinescu

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Denon x3500h
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Yamaha ns c444
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Svs sb 3000
If you're connecting to a front panel port on the AVR, try a rear panel port instead. Are you using an actual HDMI output port on the PC, or a USB to HDMI adapter?
I am conecting the laptop through an hdmi cable to the denon avr. No usb adapter. There is no hdmi front port. I tried 2 different hdmi ports and the result is the same.

The interesting thing is that when I don't use the EXCL output, I get sound through the speakers.
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
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Yamaha ns c444
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Svs sb 3000
Try following the instructions in that post to get a debug log file, and attach it to a
I tried the pink noise first and a sweep after that. It keeps logging PB INNER: Missing event. No idea what that is.

I tried to attach the log file, like I attached the screen shots earlier. For some reason it doesn't want to attach it.

This is a sample of it.

16:31:35.5202412 INFO [src\lib.rs:123] Initialized from thread: AWT-EventQueue-0

16:31:35.5209169 INFO [src\lib.rs:144] Lib initialized

16:32:01.8499375 WARN [src\wasapi_impl.rs:911] PB INNER: received chunk in stopped device, starting automatically!

16:32:01.9222454 WARN [src\wasapi_impl.rs:977] PB INNER: Missing event! Resetting stream. Interval 0.058625 s, expected 0.029333333333333333 s

16:32:02.0108817 WARN [src\wasapi_impl.rs:977] PB INNER: Missing event! Resetting stream. Interval 0.0580625 s, expected 0.029333333333333333 s

16:32:02.0959231 WARN [src\wasapi_impl.rs:977] PB INNER: Missing event! Resetting stream. Interval 0.0580625 s, expected 0.029333333333333333 s

16:32:02.1832304 WARN [src\wasapi_impl.rs:977] PB INNER: Missing event! Resetting stream. Interval 0.058520833333333334 s, expected 0.029333333333333333 s

16:32:02.2692299 WARN [src\wasapi_impl.rs:977] PB INNER: Missing event! Resetting stream. Interval 0.058395833333333334 s, expected 0.029333333333333333 s
 
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thothsong

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I tried to attach the log file, like I attached the screen shots earlier. For some reason it doesn't want to attach it.
We need to see the entire file. Either rename it to be a .txt file, or put it into a .zip file, either of those should be attachable to a post.
 

acconstantinescu

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Denon x3500h
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Yamaha ns 555
Center Channel Speaker
Yamaha ns c444
Subwoofers
Svs sb 3000
We need to see the entire file. Either rename it to be a .txt file, or put it into a .zip file, either of those should be attachable to a post.
 

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thothsong

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It seems there was some problem in your setting up the proper debug log level, as the log file is missing all of the relevant debug output. Did you accidentally create a file named roomeqwizard.vmoptions.txt instead of just roomeqwizard.vmoptions, perhaps?
 

acconstantinescu

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Denon x3500h
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Yamaha ns c444
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Svs sb 3000
It seems there was some problem in your setting up the proper debug log level, as the log file is missing all of the relevant debug output. Did you accidentally create a file named roomeqwizard.vmoptions.txt instead of just roomeqwizard
This is the modified file. I didn't change the file extension. I just edited the file using office libre. When I list it in Windows Explorer, it says it's a vmoptions file, not a txt file.

# Enter one VM parameter per line
# For example, to adjust the maximum memory usage to 512 MB, uncomment the following line:
# -Xmx512m
# To include another file, uncomment the following line:
# -include-options [path to other .vmoption file]
-Xmx1024m
-Dsun.java2d.d3d=False
-DcsjsoundLibLogLevel=debug
 
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