Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 718 - AVS Forum | Home Theater Discussions And Reviews
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post #21511 of 29331 Old 02-11-2017, 04:22 PM
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Originally Posted by turboman123 View Post
Actually, I struggle with the same problem. I have a Cambridge Audio 551R AVR. Also without subwoofer distance adjustment.
I wonder how speaker delay is set. E.g. does it make a difference (relative to the subwoofer) if all speakers are set at 1meter, or all speakers set at 2meters.
I have to try to measure it with a timing reference.
Delays are relative to the listening position, not between mains and subs. Each speaker and sub needs to have a delay based on its distance from the MLP. I can't imagine an AVR that has no delay setting for the sub channel.
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post #21512 of 29331 Old 02-11-2017, 04:48 PM
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Really, it doesn't. It doesn't control the sub at all (besides level).
https://www.avsforum.com/forum/91-aud...l#post50661113
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post #21513 of 29331 Old 02-11-2017, 11:38 PM
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Originally Posted by AustinJerry View Post
OK, I am guilty--I forgot to add a winkie emoji.
No need for an emoji. The device does work. Only little tactile input is necessary to make one feel bass.

Markus

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post #21514 of 29331 Old 02-11-2017, 11:55 PM
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Quote:
Originally Posted by turboman123 View Post
Actually, I struggle with the same problem. I have a Cambridge Audio 551R AVR. Also without subwoofer distance adjustment.
I wonder how speaker delay is set. E.g. does it make a difference (relative to the subwoofer) if all speakers are set at 1meter, or all speakers set at 2meters.
I have to try to measure it with a timing reference.
Yes, measure with an acoustic timing reference:
1. Set timing reference to L
2. Measure LFE
3. Measure R
4. Increase speaker distance of L and R by the same amount
5. Measure LFE
6. Measure R

If the measurements show always the same delay between sub and R then you're out of luck and you need to buy a new AVR with proper bass management.

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole

Last edited by markus767; 02-12-2017 at 02:30 AM.
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post #21515 of 29331 Old 02-12-2017, 07:34 AM
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Originally Posted by markus767 View Post
then you're out of luck and you need to buy a new AVR with proper bass management.
"Need," of course, only relative to you're being allowed back into this thread.
Michael
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post #21516 of 29331 Old 02-12-2017, 08:55 AM
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Quote:
Originally Posted by Sittler27 View Post
Ok, I managed to borrow an Audyssey mic from my friend who has a Denon receiver but I confirmed that it is interchangeable with mine.
As soon as I started to do the Aud. calibration and it allowed my subs at lower gains to proceed I knew it was the issue and that my original mic was pooched. It was further confirmed on how my Fronts, Center and Top Middles were set to Full Band/Large once completed (which of course I then set to small).

So I carried on and below are some response curves of LF/RF/C of what Audyssey set (only change I made after Aud. before I took these measures was to set fronts & center to small).
Audyssey also set the speaker levels very differently than with the old mic.

However, as you can see the sub's volume was very low, so I raised it 6dB using the sub trim on the AVR (note: I did the 75dB test and determined after Aud, with the good mic, the result was now the opposite with all speakers around 78dB and the subs at about 72dB) I then started playing around with raising the individual speaker crossovers from the 40Hz it set it took once I set the speakers to small from large after Audyssey.
After trial and error, I determined that the following crossovers produced the best response (again, only by raising the crossovers)
Front 60Hz (up from 40Hz)
Center 80Hz (up from 40Hz)
Surround 60Hz (up from 40Hz)
Surr. Back 110Hz (untouched from Aud.) - likely higher because mounted lower on my ceiling causing some affect, not sure
Top Middle 60Hz (up from 40Hz) - didn't test, but just set to match surrounds

Finally, I started to tackle with my subs' PEQs that big crater around 30Hz, by setting both PEQs as follows:
31Hz, +3dB, Q:5.7

I posted here as well the comparisons between the first three (after aud calibration in red) compared to the end result after these adjustments.

I know I still have issues, and some may be resolved by moving the subs around, but my room is very challenging so not sure if I've improved to a point where I can leave that for another day - my SVS PB12-Pluses are really heavy

Feedback very welcome!
Anyone care to comment on this? Last time I'm bumping it, sorry.
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post #21517 of 29331 Old 02-12-2017, 09:48 AM
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Quote:
Originally Posted by Sittler27 View Post
Anyone care to comment on this? Last time I'm bumping it, sorry.
Nothing that a small dose of Borje Salming, Ian Turnbull, and Mike Palmateer can't fix

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post #21518 of 29331 Old 02-12-2017, 10:06 AM
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Originally Posted by stsand View Post
Nothing that a small dose of Borje Salming, Ian Turnbull, and Mike Palmateer can't fix

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Yes!
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post #21519 of 29331 Old 02-12-2017, 10:15 AM
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Quote:
Originally Posted by Sittler27 View Post
Anyone care to comment on this? Last time I'm bumping it, sorry.
I'll say it again--I have no idea why Audyssey would kill the low frequency output as it is shown on the measurements. The issue seems to have been somewhat mitigated by the PEQ, but the fact that the Audyssey calibration seems to be flawed leaves me without further recommendations.
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post #21520 of 29331 Old 02-12-2017, 11:54 AM
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Quote:
Originally Posted by AustinJerry View Post
Delays are relative to the listening position, not between mains and subs. Each speaker and sub needs to have a delay based on its distance from the MLP. I can't imagine an AVR that has no delay setting for the sub channel.
Quote:
Originally Posted by markus767 View Post
Yes, measure with an acoustic timing reference:
If the measurements show always the same delay between sub and R then you're out of luck and you need to buy a new AVR with proper bass management.
hallo Jerry, Markus,
Not good news. For me. Buying a new AVR would be expensive. I wondered how much disadvantage I have with the present setup. So I wanted to understand more, did some measurements, and as a result of that, I have some more questions for you. I hope you can help.

With my standard setup, and impulse response measurements with the center channel as reference, the proper speaker distance is as follows (I live in meter-land):
FrontLeft 2.6m, FrontRight 2.6m, FrontCenter 2.6m, SurroundLeft 1.7m, SurroundRight 2.3m. With this setup, the subwoofer has a 5ms delay (based on the first negative peak in the impulse response).

I wondered if I could change these settings in order to change the time delay relative to the subwoofer. This is related to how the AVR sets the time delay based on these distances.

One possibility is that a time delay is made by the AVR relative to the max possible distance that is possible in the AVR, which is 10meter. Changing the distance of front left/right/center however to 10m however did not change the delay between center and subwoofer.

The other possibility is that the AVR calculates a delay for a speaker based on the difference between that speaker, and the speaker which has the max distance. In order to test that, I changed the surroundright speaker distance. As long as the distance is below the max distance (2.6m) there is no difference in the delay center-subwoofer (blue curve) . When I increase the distance above 2.6m, the delay between center-subwoofer is reduced. When I set the surroundright at 4.4m, center and subwoofer have no delay (green curve).

Now my questions.

For the evaluation, is it correct to use the first small negative peak of the subwoofer as evaluation point?

What would be more important: get the delay of the subwoofer relative to front left/right/center correct, or get the delay surround - front correct?

Should I use the subwoofer max peak level (of the first negative peak), or the start of the peak? For better evaluation, should I run all speakers with narrow frequency band measurement sweep around crossover frequency, in order to avoid the evaluation problem of mixing narrow and wide peaks?
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post #21521 of 29331 Old 02-12-2017, 12:08 PM
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@turboman123 Did you do the measurements outlined in post 21514?

Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole
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post #21522 of 29331 Old 02-12-2017, 12:08 PM
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Quote:
Originally Posted by AustinJerry View Post
I'll say it again--I have no idea why Audyssey would kill the low frequency output as it is shown on the measurements. The issue seems to have been somewhat mitigated by the PEQ, but the fact that the Audyssey calibration seems to be flawed leaves me without further recommendations.
Hmmm. That's unfortunate.

It's funny, since I swapped out the mic (which definitely had an issue) for what I presume to be a fully working mic and yet it still set the low frequency output incorrectly.

So is correcting it the way I did acceptable in regards to the response curve now (presuming the fact that the low frequency issue with Audyssey isn't messing something else up we can't see/don't know about)?
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post #21523 of 29331 Old 02-12-2017, 12:35 PM
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Originally Posted by Sittler27 View Post
Hmmm. That's unfortunate.

It's funny, since I swapped out the mic (which definitely had an issue) for what I presume to be a fully working mic and yet it still set the low frequency output incorrectly.

So is correcting it the way I did acceptable in regards to the response curve now (presuming the fact that the low frequency issue with Audyssey isn't messing something else up we can't see/don't know about)?
If you are pleased with the sound with PEQ correction, there is nothing wrong with that. I think you have made a good effort to overcome what is still a strange result of the Audyssey calibration.
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post #21524 of 29331 Old 02-12-2017, 01:54 PM
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Originally Posted by markus767 View Post
@turboman123 Did you do the measurements outlined in post 21514?
Yes, more or less. That is what I described in my post as the first possibility. Since that did not change the time delay between the front speakers (left/right/center) and subwoofer, I tried the second possibility.

Jerry, Markus: how do you judge the results of the second possibility, and questions?
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post #21525 of 29331 Old 02-12-2017, 02:19 PM
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@markus767 :

A learning moment for me WRT using the impulse graph overlay with acoustic timing reference. What does the attached measurement tell us about the alignment between my center channel and my subs? I.e. please help me interpret how to analyze alignment using the impulse graph.

Edit: I think I am getting closer to understanding. See second measurement with the pop-up message when I hover the cursor over the legend. It says the sub has a delay of 13ms (15ft) relative to the front right channel. Please help me interpret exactly what this means and what do do to fix it if it is indeed showing something is not properly aligned.

Thanks in advance for your explanation!
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post #21526 of 29331 Old 02-12-2017, 02:20 PM
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Originally Posted by turboman123 View Post
Yes, more or less. That is what I described in my post as the first possibility. Since that did not change the time delay between the front speakers (left/right/center) and subwoofer, I tried the second possibility.

Jerry, Markus: how do you judge the results of the second possibility, and questions?
I think @markus767 is in the better position to provide you with feedback.
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post #21527 of 29331 Old 02-12-2017, 03:55 PM
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If you are pleased with the sound with PEQ correction, there is nothing wrong with that. I think you have made a good effort to overcome what is still a strange result of the Audyssey calibration.
Thanks, was looking for that affirmation. Yes, I am happy.

If I get an afternoon of free time soon I will play around with sub placement further. This stuff soaks up so much time though.
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post #21528 of 29331 Old 02-12-2017, 04:22 PM
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Originally Posted by LastButNotLeast View Post


Note to Jerry: might want to make this more clear in the Guide.
Michael
Note received. I have updated the guide with the following note (page 60):

The assumption is that you are using a boom mic stand to support the REW mic. Using a tripod and placing it on top of seat cushions is not recommended, and could result in flawed measurements. Additionally, the boom mic stand should not touch anything other than the stand feet touching the ground—avoid contact between the stand shaft or the boom itself with pieces of furniture, etc. And finally, ensure that the mic is placed in such a manner as to provide an unobstructed path from all speakers to the tip of the mic. Placing the tip of the mic below the top of a seat back is not recommended, and will negatively affect measurement results.
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post #21529 of 29331 Old 02-12-2017, 04:23 PM
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Originally Posted by Sittler27 View Post
Thanks, was looking for that affirmation. Yes, I am happy.

If I get an afternoon of free time soon I will play around with sub placement further. This stuff soaks up so much time though.
Thanks for being a good sport, and keep us advised if you make significant progress.
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post #21530 of 29331 Old 02-12-2017, 04:35 PM
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Originally Posted by AustinJerry View Post
Note received. I have updated the guide with the following note (page 60):



The assumption is that you are using a boom mic stand to support the REW mic. Using a tripod and placing it on top of seat cushions is not recommended, and could result in flawed measurements. Additionally, the boom mic stand should not touch anything other than the stand feet touching the ground—avoid contact between the stand shaft or the boom itself with pieces of furniture, etc. And finally, ensure that the mic is placed in such a manner as to provide an unobstructed path from all speakers to the tip of the mic. Placing the tip of the mic below the top of a seat back is not recommended, and will negatively affect measurement results.

Sweet! Happy my mistake might help others going forward.
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post #21531 of 29331 Old 02-12-2017, 05:00 PM
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Originally Posted by AustinJerry View Post
Placing the tip of the mic below the top of a seat back is not recommended, and will negatively affect measurement results.
Didn't you do some stuff in another thread with a board in front of the mic? Dirac?
What if your ears are below the back of the seats?
Thanks for taking my suggestion.
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post #21532 of 29331 Old 02-12-2017, 05:51 PM
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Originally Posted by LastButNotLeast View Post
Didn't you do some stuff in another thread with a board in front of the mic? Dirac?
What if your ears are below the back of the seats?
Thanks for taking my suggestion.
Michael


Also curious for an answer to this. I always wondered about it. I read long ago not to place the top of the mic under the back of the couch, but my ears sit about an inch or so from the top of the back of the couch down. So I always place mic where my ears are.

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post #21533 of 29331 Old 02-12-2017, 06:14 PM
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Originally Posted by LastButNotLeast View Post
Didn't you do some stuff in another thread with a board in front of the mic? Dirac?
What if your ears are below the back of the seats?
Thanks for taking my suggestion.
Michael
Don't recall what you are referring to.

If your ears are below the seatback, you have the wrong seat. How can you hear the rear surrounds? If you indeed have a high seat back, and if the back reclines, then at least recline it out of the way for the calibration/measurements. The important point is to have an unobstructed line of sight to all speakers. JMO.
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post #21534 of 29331 Old 02-12-2017, 07:36 PM
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Originally Posted by LastButNotLeast View Post
Didn't you do some stuff in another thread with a board in front of the mic? Dirac?
Only reason I know of to obstruct the mic in this manner is to try to determine the path of unwanted reflections. Say, if you think a reflection is coming from a certain direction.
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post #21535 of 29331 Old 02-12-2017, 07:48 PM
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Only reason I know of to obstruct the mic in this manner is to try to determine the path of unwanted reflections. Say, if you think a reflection is coming from a certain direction.
Yes, that is the "Blocking Techique" used with the ETC measurement. I don't know how this would pertain to the previous topic, which was best practices for mic placement when taking REW measurements. Completely unrelated.
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Follow-up question for @markus767 :

Two impulse overlays below show two different sub configurations. It would seem that the difference between the two is polarity. By looking at the two impulse overlays, can you tell which shows correct polarity WRT the center channel? Does this question make sense?
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post #21537 of 29331 Old 02-12-2017, 10:23 PM
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Quote:
Originally Posted by turboman123 View Post
Yes, more or less. That is what I described in my post as the first possibility. Since that did not change the time delay between the front speakers (left/right/center) and subwoofer, I tried the second possibility.

Jerry, Markus: how do you judge the results of the second possibility, and questions?
Do the measurements I've outlined in 21514 and we will know.

Markus

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post #21538 of 29331 Old 02-12-2017, 10:30 PM
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Originally Posted by AustinJerry View Post
@markus767 :

A learning moment for me WRT using the impulse graph overlay with acoustic timing reference. What does the attached measurement tell us about the alignment between my center channel and my subs? I.e. please help me interpret how to analyze alignment using the impulse graph.

Edit: I think I am getting closer to understanding. See second measurement with the pop-up message when I hover the cursor over the legend. It says the sub has a delay of 13ms (15ft) relative to the front right channel. Please help me interpret exactly what this means and what do do to fix it if it is indeed showing something is not properly aligned.

Thanks in advance for your explanation!
REW searches for the max. peak and defines that as the start of the response, i.e. "0". This can be used to align sources that extend to higher frequencies. For subs the alignment point is where the impulse response starts. Just like in your graph.

Markus

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Last edited by markus767; 02-12-2017 at 11:41 PM.
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post #21539 of 29331 Old 02-12-2017, 10:36 PM
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Originally Posted by AustinJerry View Post
Follow-up question for @markus767 :

Two impulse overlays below show two different sub configurations. It would seem that the difference between the two is polarity. By looking at the two impulse overlays, can you tell which shows correct polarity WRT the center channel? Does this question make sense?
Well, the first one "seems" to be correct. But, at low frequencies it makes more sense to look at the combined frequency response of sub and sats. Sometimes the response is better with the sub inverted.

Here's the IR of a "perfect" Linkwitz-Riley low pass – note how long the IR is:

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Markus

"In science, contrary evidence causes one to question a theory. In religion, contrary evidence causes one to question the evidence." - Floyd Toole

Last edited by markus767; 02-12-2017 at 10:42 PM.
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post #21540 of 29331 Old 02-12-2017, 11:38 PM
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Hey guys,

Silly question of the day: What is this "PEQ" you are talking about?

I see I need to buy a microphone stand. Also that there is not much point in doing measurements/treatments before I'm done with the "dedicated" HT-room. Right now it's awaiting funds for projector and screen (got a TV there now), which means I'll move pretty much all the speakers and create a baffle-wall. Guess I'm just gonna wait for that before returning here
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