RS SPL meter useless for In-room subwoofer response? - AVS Forum
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post #1 of 154 Old 07-07-2009, 09:07 AM - Thread Starter
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Quote:
Originally Posted by pepar View Post

Yes, just read that myself. And it further explains the reason that using the Radio Shack meter to measure the frequency response of A SUB is a not a good idea. The only debate is with those who occasionally read what they want to read and ignore the qualifiers.

I know many use the RS SPL meter for subwoofer measurements so I want to understand the truth.

Its it not a good idea to use the RS meter or can people use it even though its accuracy might be in question (even with calibration files)?


I have both it and I have a ECM8000 mic (with professional calibration). I have run REW with both and the differences are just nitpicking stuff.

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post #2 of 154 Old 07-07-2009, 10:25 AM
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not sure quite where you are coming from with your post penn. can you clarify a bit?

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post #3 of 154 Old 07-07-2009, 10:34 AM
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Quote:
Originally Posted by penngray View Post

I know many use the RS SPL meter for subwoofer measurements so I want to understand the truth.

Its it not a good idea to use the RS meter or can people use it even though its accuracy might be in question (even with calibration files)?


I have both it and I have a ECM8000 mic (with professional calibration). I have run REW with both and the differences are just nitpicking stuff.

IMHO, the issue with the RS meter is not its accuracy (which can be ameliorated with calibration) nor with its repeatability (which is fine for A/B comparisons) but with its general use with pink/white noise broadband signals. The combination cannot distinguish between direct/reflected sound nor between early/late signals. It also is averaging across the signal spectrum. Combine it with REW (and its swept tones) and it becomes a useful device but, of course, there is better.

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post #4 of 154 Old 07-07-2009, 10:38 AM
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I use the Digital RS SPL meter audio output jack for most of my routine readings. You just have to make sure that you apply the SPL C scale compensation when you use any SPL meter in C scale. That being said the RS SPL meter is not to be trusted on the high end (above 8 kHz) regardless of the compensation scheme being used.


The RS SPL meter's electronics follows the SPL C scale in a near perfect manner. The accuracy weakness in the mike element itself.



1/24 octave unsmoothed sweep of Digital RS meter's electronics with no mike installed. Green is SPL C scale. Red is SPL A scale.

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post #5 of 154 Old 07-07-2009, 10:41 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

not sure quite where you are coming from with your post penn. can you clarify a bit?

I was not acually involved but there was a discussion in the Audyssey thread about using the RS meter to manual measure a subwoofer's in room response. He has found some issues and he is asking if Audyssey is creating the problem. All opinions just fly back in his face telling him not to use a RS meter.


IMO, for his case I think the RS meter gives him enough of an accurate picture and I think instead of arguing the merits of using the RS meter they should maybe help him figure out why audyssey isnt doing a great job with his bass response.


I think this topic on using an RS meter for bass measurements is a generic one and Im sure there have been threads in the past. I create this thread so that we do not go that far OT in the audyssey thread. I posted in that thread saying I would create a thread here because we are the majority of RS meter users and we have enough experts on here to say "yes or no" to its viability.

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post #6 of 154 Old 07-07-2009, 10:44 AM - Thread Starter
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Quote:
Originally Posted by Kal Rubinson View Post

IMHO, the issue with the RS meter is not its accuracy (which can be ameliorated with calibration) nor with its repeatability (which is fine for A/B comparisons) but with its general use with pink/white noise broadband signals. The combination cannot distinguish between direct/reflected sound nor between early/late signals. It also is averaging across the signal spectrum. Combine it with REW (and its swept tones) and it becomes a useful device but, of course, there is better.


Yes there is better but its a viable option for doing simple measurements (20Hz to 200Hz) using free software like REW.

I think I follow what you are saying and that using the RS meter alone with just test tones can create those other in room issues, standing waves/direct/refected sound,etc and therefore the user wouldnt know what the true measurement was for any single frequency.

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post #7 of 154 Old 07-07-2009, 11:20 AM
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Quote:
Originally Posted by penngray View Post

Yes there is better but its a viable option for doing simple measurements (20Hz to 200Hz) using free software like REW.

I think I follow what you are saying and that using the RS meter alone with just test tones can create those other in room issues, standing waves/direct/refected sound,etc and therefore the user wouldnt know what the true measurement was for any single frequency.

Yes.

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post #8 of 154 Old 07-07-2009, 12:35 PM
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Hello everyone,

I guess I should start from the beginning. I have a Denon 1909 avr and absolutely love the low volume listening experience I get from the Audyssey room calibration and Dynamic EQ and Volume feature (listening at reference levels as a apartment dweller is not a option). I replaced a little Mirage omni S8 with it's larger sibling the Energy S10.3 subwoofer.

My issue is that when I placed my Radio Shack spl meter on a tripod at ear height in my main listening position i got a reading of 77db spl at 31.5hz and 76db at 25hz with the warble tones from Stereophile test CD #1. This was with Audyssey calibration meant for the smaller S8 sub. I replaced the meter with the Audyssey mic and ran the calibration for my main listening position. After recalibration I replaced the mic with the RS spl meter and measured 71db at 31.5hz and 62db at 25hz, with the same receiver vol, speaker level...etc. I would have expected a improvement in extension after recalibrating if anything.

I just wanted to know if anyone in the Audyssey thread had experienced this, and plan on re-calibrating this coming weekend. Unfortunately, it spiraled (with a lot of help from me) into a big debate on the validity of using a RS spl meter. I've found this little meter to be a useful tool. Any thoughts?
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post #9 of 154 Old 07-07-2009, 12:42 PM - Thread Starter
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77db spl at 31.5hz and 76db at 25hz = old sub, audyssey

vs

71db at 31.5hz and 62db at 25hz = new sub, audyssey

Correct?

Have you run measurements with Audyssey turned off?

It could be just your different sub and its placement creating a null at 25Hz, phase issue?

Other thoughts...

The sub itself could have a 30Hz cuttoff setting you are unaware of too
The old sub had a 25Hz BOOST setting that isnt on your new sub and therefore its down quiet a bit....

Many factors could contribute.

Do the tests without audyssey on, if you have not done so to see if its creating that -14dB difference.

btw, thanks for coming here......the Audyssey threads is not the best place for solving issues IMO. Anyone who remotely talks negative about Audyssey in that thread gets thrown to the wolves, its happened to me many times. In the end we just want discussion and answers. There should be zero emotion about the Audyssey product but people are strange in thinking its their baby to protect.

This isnt really a DIY thread either but atleast the passion, knowledge and level headed responses are good

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post #10 of 154 Old 07-07-2009, 12:46 PM
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Todd, it's very simple. If the mic is not calibrated and the software used (whatever it is) doesn't allow for the use of the calibration files for compensation, then you have no way of knowing whether you are getting an accurate response or not, ie is this +5dB hump because the mic is wrong or because it's true to what I'm measuring. For the money the RS one won't be and I seriously doubt that every AVR sold has a calibrated mic with the file for that one blown into the software.

When I calibrated my previous HT with the supplied mic and software it was weird. When I did it with my own software, mic etc, it was much better. I trust my gear far more than that supplied with the AVR.
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post #11 of 154 Old 07-07-2009, 12:50 PM - Thread Starter
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Quote:
Originally Posted by A9X-308 View Post

Todd, it's very simple. If the mic is not calibrated and the software used (whatever it is) doesn't allow for the use of the calibration files for compensation, then you have no way of knowing whether you are getting an accurate response or not, ie is this +5dB hump because the mic is wrong or because it's true to what I'm measuring. For the money the RS one won't be and I seriously doubt that every AVR sold has a calibrated mic with the file for that one blown into the software.

When I calibrated my previous HT with the supplied mic and software it was weird. When I did it with my own software, mic etc, it was much better. I trust my gear far more than that supplied with the AVR.

but if the same inaccurate mic is used for both tests then its going to be accurate within the comparison itself.

Example, if its +5 dB inaccurate @ 25Hz its +5 dB inaccurate for test A and test B.....therefore the difference between the tests are valid.


I think he is just using the RS meter to double check what Audyssey did, his question is simply why does he have a -15 dB dip when he simply upgraded his sub (I assume same sub position). He is asking why Audyssey created that -15dB dip, maybe too?

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post #12 of 154 Old 07-07-2009, 12:56 PM
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Is the new subwoofer in the EXACT same place as the old one?
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post #13 of 154 Old 07-07-2009, 01:17 PM
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Quote:
Originally Posted by penngray View Post

but if the same inaccurate mic is used for both tests then its going to be accurate within the comparison itself.

I was just thinking the same thing...

Quote:
Originally Posted by augerpro View Post

Is the new subwoofer in the EXACT same place as the old one?

More importantly, was the sub in the EXACT same place the second time (after rerunning audyssey for the new sub) as the first? I agree with Penn that checking with Audyssey off would be a good test as well. I don't suppose getting REW up and running is a possibility? It could help see what's going on here.
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post #14 of 154 Old 07-07-2009, 01:27 PM - Thread Starter
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I posted before (in other thread) asking him to get REW running...it will help him know the whole picture. He said he is working on it.

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post #15 of 154 Old 07-07-2009, 01:32 PM
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Quote:
Originally Posted by penngray View Post

77db spl at 31.5hz and 76db at 25hz = old sub, audyssey

vs

71db at 31.5hz and 62db at 25hz = new sub, audyssey

Correct?

Have you run measurements with Audyssey turned off?

It could be just your different sub and its placement creating a null at 25Hz, phase issue?

Other thoughts...

The sub itself could have a 30Hz cuttoff setting you are unaware of too
The old sub had a 25Hz BOOST setting that isnt on your new sub and therefore its down quiet a bit....

Many factors could contribute.

Do the tests without audyssey on, if you have not done so to see if its creating that -14dB difference.

btw, thanks for coming here......the Audyssey threads is not the best place for solving issues IMO. Anyone who remotely talks negative about Audyssey in that thread gets thrown to the wolves, its happened to me many times. In the end we just want discussion and answers. There should be zero emotion about the Audyssey product but people are strange in thinking its their baby to protect.

This isnt really a DIY thread either but atleast the passion, knowledge and level headed responses are good

Hey penngray,

Thank you very much for this, I really appreciated your being level headed about all of of this. Yes I definitely felt like I poked a hornets nest by questioning Audyssey, even though I qualified my statement by first saying how much I like it.

Actually the measurements I'm referring to are both with the new sub. First with Audyssey settings that were taking with the old S8 sub, then with the Audyssey settings calibrated using the new sub. Additionally they were taken with Dynamic Eq and Volume on. I did record one 100-20Hz set without the Audyssey multi Eq room correction on at all and 25Hz output was lower than 31.5Hz, I really need to take what I recorded off the notepad doc and put it in a spreadsheet.

Despite the two different company names the two subs are basically identical for except the energy is bigger, has 10" cone instead of a 8" and a 200 watt amp vs 100 for the mirage. The smaller mirage has solid response to 31.5Hz in my room and is rated to 27Hz. The larger energy is rated to 21Hz and I would therefore think that it should come close to that.

I've got to run to work, but I am determined to get the solid 25Hz response I felt back. Thank you so much for your help.
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post #16 of 154 Old 07-07-2009, 01:35 PM
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Pen,
Used one for a long time. A pain, but with a signal generator, step the tone, jot down the reading, repeat. That is all you are really doing with a fancy mic and pc analyzer.
I cheated a little as I user the RCA out to drive a old Heath AC VTVM that was easier to read and more accurate. In other words, just used the mic and amp in the RS meter.
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post #17 of 154 Old 07-07-2009, 01:43 PM - Thread Starter
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Quote:
Originally Posted by toddRiffic View Post

Hey penngray,

Thank you very much for this, I really appreciated your being level headed about all of of this. Yes I definitely felt like I poked a hornets nest by questioning Audyssey, even though I qualified my statement by first saying how much I like it.

Actually the measurements I'm referring to are both with the new sub. First with Audyssey settings that were taking with the old S8 sub, then with the Audyssey settings calibrated using the new sub. Additionally they were taken with Dynamic Eq and Volume on. I did record one 100-20Hz set without the Audyssey multi Eq room correction on at all and 25Hz output was lower than 31.5Hz, I really need to take what I recorded off the notepad doc and put it in a spreadsheet.

Despite the two different company names the two subs are basically identical for except the energy is bigger, has 10" cone instead of a 8" and a 200 watt amp vs 100 for the mirage. The smaller mirage has solid response to 31.5Hz in my room and is rated to 27Hz. The larger energy is rated to 21Hz and I would therefore think that it should come close to that.

I've got to run to work, but I am determined to get the solid 25Hz response I felt back. Thank you so much for your help.

No worries, I felt your pain in that thread.

My recent posts wrt a null at 120Hz had the same responses. All you and I care about is understanding it all and finding a solution...that gets lost in the back and forth because people love to nitpick, I do not really fault anyone because its the way online forums work and one phrase, incorrect wording sends a discussion in a death spiral.

If you could post the measurements with audyssey off that would be a good start and honestly I would just ignore what ever audyssey had calibrated based on the old sub. Your only goal is to calibrate your new sub and it might be impossible to answer why it happened.

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post #18 of 154 Old 07-07-2009, 01:45 PM
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Hey guys,

I got a -9dB dip at 25Hz after recalibrating Audyssey as measured by my RS spl meter with the warble tones from stereophile's test CD #1.

The new sub (Energy S10.3) was not moved at all.

Not one knob, switch, or button was touched on the sub. Phase set to 0 degrees, crossover bypassed and level knob at 12 o'clock.

I had the same level setting on my denon 1909. (SW -6, Volume -35dB, Audyssey multi EQ on with Dynamic EQ and Volume enabled.)

The tripod that I used to mount the Audyssey mic and RS spl meter was not moved.

The only thing I changed was to rerun Audyssey calibration. I had 9dB more output at 25Hz when using the old Audyssey's multi eq calibration based on my older smaller sub.

Thanks in advance
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post #19 of 154 Old 07-07-2009, 01:55 PM
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Quote:
Originally Posted by penngray View Post

No worries, I felt your pain in that thread.

My recent posts wrt a null at 120Hz had the same responses. All you and I care about is understanding it all and finding a solution...that gets lost in the back and forth because people love to nitpick, I do not really fault anyone because its the way online forums work and one phrase, incorrect wording sends a discussion in a death spiral.

If you could post the measurements with audyssey off that would be a good start and honestly I would just ignore what ever audyssey had calibrated based on the old sub. Your only goal is to calibrate your new sub and it might be impossible to answer why it happened.

Ok, I really have to get going to work now. but here is what I got without any Audyssey and with the audyssey room correction was based on the smaller sub, being used with the new bigger sub.


frequency spl without any Audyssey spl with old Audyssey values
100Hz 58 67
80Hz 61 75
63Hz 56 69
54Hz 57 66
40Hz 59 71
31.5Hz 63 77
25Hz 55 76
20Hz low 62
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post #20 of 154 Old 07-07-2009, 05:17 PM
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How does the new sub actually sound? Does the 10" seem to be down on the smaller 8" sub or is this just measurement games?
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post #21 of 154 Old 07-07-2009, 07:16 PM
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Quote:
Originally Posted by tsloms View Post

How does the new sub actually sound? Does the 10" seem to be down on the smaller 8" sub or is this just measurement games?

Hey tsloms,

Right now the 10" sounds the same as my 8" without listening to any reference material, I just have to keep it 6dB lower on my 1909 then I had the 8" at. A good test would be to play "Jurrasic lunch" on it. I had noticed that the 1st few ultra low rumble/footsteps were not very present with the 8" sub compared to hearing it on my cheap senhieser headphones. When I first installed the 10" in the 8's place, I listened to it and the first few ultra low footsteps Jurrasic lunch were being produced very nicely.

Back to work for me
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post #22 of 154 Old 07-07-2009, 08:39 PM
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Audyssey will do all sorts of things to the subwoofer response. Someone awhile back suggested EQ'ing the subs *after* using Audssey. At the time I thought that was a silly idea. But as of this weekend, I discovered the Hard Knee approached discussed at length on other forums. I applied it (as best I could) and found the results to be incredible. So next weekend when I mess around with all this again, I'll use Audyssey first. Then I'll tweak to my preferences using my BFD.

But for the sake of this thread, I'll share last weeks results for you. These don't reflect the hard knee approach, btw.

Quote:
Originally Posted by CZ Eddie View Post


BEFORE AUDYSSEY:




AFTER AUDYSSEY (NO OTHER CHANGES):
#9 EQ'd system using Audyssey MultEQ on Onkyo TX-SR805 a/v receiver.


Basically, what you're seeing is that Audssey will tame your subwoofer. But it's doing what it's supposed to. Make the response as flat as it's able to. What I'm looking forward to is the day when Audssey will include options. Like quick select settings for "tuned for h/t bass", or "tuned for party bass", or "tuned for flat response", etc.

You can see a bunch of other testing results I posted in this thread:

http://www.avsforum.com/avs-vb/showthread.php?t=1160611

"The boom is dead, long live the bass"
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post #23 of 154 Old 07-08-2009, 12:50 AM
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Quote:
Originally Posted by penngray View Post

but if the same inaccurate mic is used for both tests then its going to be accurate within the comparison itself.

Yes, but it's only going to be useful if you know what flat is from the start.
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post #24 of 154 Old 07-08-2009, 01:53 AM
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Quote:
Originally Posted by CZ Eddie View Post

Audyssey will do all sorts of things to the subwoofer response. Someone awhile back suggested EQ'ing the subs *after* using Audssey. At the time I thought that was a silly idea. But as of this weekend, I discovered the Hard Knee approached discussed at length on other forums. I applied it (as best I could) and found the results to be incredible. So next weekend when I mess around with all this again, I'll use Audyssey first. Then I'll tweak to my preferences using my BFD.

But for the sake of this thread, I'll share last weeks results for you. These don't reflect the hard knee approach, btw.



Basically, what you're seeing is that Audssey will tame your subwoofer. But it's doing what it's supposed to. Make the response as flat as it's able to. What I'm looking forward to is the day when Audssey will include options. Like quick select settings for "tuned for h/t bass", or "tuned for party bass", or "tuned for flat response", etc.

You can see a bunch of other testing results I posted in this thread:

http://www.avsforum.com/avs-vb/showthread.php?t=1160611

Hey cz,

Thanks for the post, I appreciate the helpfull contribution. It looks like audyssey really smoothed out your subs response for you. I did notice however, that you did not see a significant reduction in the lowest bass extension of your sub after audyssey calibration. My big question is why would audyssey calibration droped the 31.5Hz response with the warble tone from 77 to 71dB and then drop the 25Hz resonse from 76 to 62dB in order to smooth out bass response. I can understand lower a level at a specific frequency to smooth out response, but it doesn't make sense to me to have it cut my subs lowest extension that much.
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post #25 of 154 Old 07-08-2009, 05:30 AM - Thread Starter
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Quote:


Someone awhile back suggested EQ'ing the subs *after* using Audssey

I do this but Im buying the Audyssey Pro software to allow me to tweak as desired.

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post #26 of 154 Old 07-08-2009, 05:35 AM - Thread Starter
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Quote:
Originally Posted by toddRiffic View Post

Ok, I really have to get going to work now. but here is what I got without any Audyssey and with the audyssey room correction was based on the smaller sub, being used with the new bigger sub.


frequency spl without any Audyssey spl with old Audyssey values
100Hz 58 67
80Hz 61 75
63Hz 56 69
54Hz 57 66
40Hz 59 71
31.5Hz 63 77
25Hz 55 76
20Hz low 62

Why is your old subwoofer Audyssey calibration increasing your new sub SPL by 10+dBs more or less accross the board? I guess your old sub was extremely weak compared to your mains so does Audyssey set your Sub trim levels when you turn it on? I didnt think it did.

What is your Sub trim levels when Audyssey is off and when it is on?

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post #27 of 154 Old 07-08-2009, 05:41 AM
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Without knowing more of the big picture, it's difficult to assume anything. The 25hz mark may have been the victim of Audyssey making other things better. It doesn't have unlimited adjustments to make and can't fix everything. And every time you adjust one thing, it has an effect on the response somewhere else.

Why don't you make a chart of all the responses from 20-200hz. Then apply the correction factors to your meter.

Typically, you would add 3db to the 31hz reading and 5db to the 25hz reading.
So your 31hz is actually 74db and 25hz is actually 67db. Which is not too bad at all.

Here is a listing of other correction factors:
http://forum.audiogon.com/cgi-bin/fr...6&openflup&1&4

Or you could go all the way and learn how to make charts like I posted above:
www.hometheatershack.com/roomeq

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post #28 of 154 Old 07-08-2009, 05:55 AM
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Quote:
Originally Posted by toddRiffic View Post

Hey cz,

Thanks for the post, I appreciate the helpfull contribution. It looks like audyssey really smoothed out your subs response for you. I did notice however, that you did not see a significant reduction in the lowest bass extension of your sub after audyssey calibration. My big question is why would audyssey calibration droped the 31.5Hz response with the warble tone from 77 to 71dB and then drop the 25Hz resonse from 76 to 62dB in order to smooth out bass response. I can understand lower a level at a specific frequency to smooth out response, but it doesn't make sense to me to have it cut my subs lowest extension that much.

It might be to do with the width of the filter audyssey creates. Lets say you have a room mode of +10 db at 20hz which is extremely narrow and audyssey applied a filter of -10db at 20hz with a half octave Q. I doubt its that exagerated but you get the picture.


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Originally Posted by penngray View Post

I do this but Im buying the Audyssey Pro software to allow me to tweak as desired.

Can you post a review and maybe a high level step by step? I'm 99% ready to buy it too.

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post #29 of 154 Old 07-08-2009, 06:19 AM
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CZ,

What is this "Hard Knee" you are referring to?

James
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post #30 of 154 Old 07-08-2009, 07:50 AM
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CZ,

What is this "Hard Knee" you are referring to?

James

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