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post #1 of 62 Old 09-29-2013, 09:48 PM - Thread Starter
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I have two subwoofers and my Denon AVR3312 manual says to individually calibrate the subwoofer SPL to 75dB before running audyssey using the AVR's test tones but it doesn't specify what the AVR volume should be at when running the test tones. Assuming the subwoofer channel gain should be 0.0dB but should the volume be at reference? And then adjust the subwoofer gain to achieve 75dB with my SPL meter?
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post #2 of 62 Old 09-29-2013, 11:09 PM
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The internal test tones of AVR are recorded at -30dBFS (75dB). When AVR test tones are playing, the master volume is internally defaulted to reference regardless of where it actually is. Also all the internal eq including audyssey is bypassed.

What it means is just simply run the internal test tone for the sub, best would be to keep the sub trim level at 00, and dial the gain knob on the subwoofer to the point where it is 75dB on spl meter. Since you have two subs, dial each to 72dB. Collectively it will be in 75dB ballpark

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post #3 of 62 Old 09-29-2013, 11:49 PM
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Originally Posted by brendelac View Post

Assuming the subwoofer channel gain should be 0.0dB but should the volume be at reference? And then adjust the subwoofer gain to achieve 75dB with my SPL meter?
Yes to both questions.

If you want to gain-match the subs, place one in the middle of the room, hold your SPL meter 6 inches away, dial the gain knob till the meter reads 75dB. Don't touch the gain knob after that (might even want to tape it). Move the sub to its intended location.

Move other sub to the exact same spot in the middle of the room and repeat the procedure. Return the second sub to its intended location. With the subs gain matched, they'll have the same amount of headroom (one sub won't run out of steam before the other).

Depending on subwoofer locations and how the subs interact, they may or may not give you double the output when running together. When you run your receiver's auto-calibration (Audyssey MultEQXT), it will set the level of your combined subs to match your speakers.

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post #4 of 62 Old 09-30-2013, 05:07 PM - Thread Starter
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Originally Posted by sdurani View Post

Yes to both questions.

If you want to gain-match the subs, place one in the middle of the room, hold your SPL meter 6 inches away, dial the gain knob till the meter reads 75dB. Don't touch the gain knob after that (might even want to tape it). Move the sub to its intended location.

Move other sub to the exact same spot in the middle of the room and repeat the procedure. Return the second sub to its intended location. With the subs gain matched, they'll have the same amount of headroom (one sub won't run out of steam before the other).

Depending on subwoofer locations and how the subs interact, they may or may not give you double the output when running together. When you run your receiver's auto-calibration (Audyssey MultEQXT), it will set the level of your combined subs to match your speakers.
75dB measured from 6 inches? I've been measuring from the main listening position. And does that center of the room method still work if my subs are not the same distance from the main listening position? I have one that is about 5 feet away and the other is about 13 feet away.
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post #5 of 62 Old 09-30-2013, 05:26 PM
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Originally Posted by brendelac View Post

75dB measured from 6 inches?
Yes, to minimize the contributions from the room while gain-matching the subs. BTW, it doesn't have to be 75dB. Turn the gain knob on one sub to its 12 o'clock position and measure. When measuring the second sub, turn its gain knob until you get the exact same level. Again, the subs should be in the same location when measuring and the SPL meter should be right next to the woofer cone.
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I've been measuring from the main listening position.
And will be doing so again when you calibrate using the Audyssey mic.
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And does that center of the room method still work if my subs are not the same distance from the main listening position?
Yes, because all you're doing initially is matching the gain on both subwoofer amps to the same level, so the both have the same amount of headroom and one doesn't run out of steam before the other. Matching the gain of 2 amps has nothing to do with the room or seating distance or listener position. All of that will be taken into account when you run Audyssey.

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post #6 of 62 Old 09-30-2013, 05:43 PM
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Originally Posted by sdurani View Post

Yes, to minimize the contributions from the room while gain-matching the subs. BTW, it doesn't have to be 75dB. Turn the gain knob on one sub to its 12 o'clock position and measure. When measuring the second sub, turn its gain knob until you get the exact same level. Again, the subs should be in the same location when measuring and the SPL meter should be right next to the woofer cone.
And will be doing so again when you calibrate using the Audyssey mic.
Yes, because all you're doing initially is matching the gain on both subwoofer amps to the same level, so the both have the same amount of headroom and one doesn't run out of steam before the other. Matching the gain of 2 amps has nothing to do with the room or seating distance or listener position. All of that will be taken into account when you run Audyssey.
If you gain-match before running Audyssey... and then let Audyssey do it's level-matching step... you've successfully defeated the gain-matching. eek.gif

I ignore Audyssey's level-matching step that runs at the beginning of the calibration. More importantly, when Audyssey is finished, if it has set different trims for Sub1 and Sub2, I "split the difference" and set both trims to the "mean" of the 2 trim settings. This ensures that the *signal* going to the gain-matched subs is still matched. In my experience this has ZERO impact on the EQ, but it ensures that all the subs are running "...the same level, so the both have the same amount of headroom and one doesn't run out of steam before the other."

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post #7 of 62 Old 09-30-2013, 05:48 PM
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Originally Posted by craig john View Post

If you gain-match before running Audyssey... and then let Audyssey do it's level-matching step... you've successfully defeated the gain-matching. eek.gif

I ignore Audyssey's level-matching step that runs at the beginning of the calibration. More importantly, when Audyssey is finished, if it has set different trims for Sub1 and Sub2, I "split the difference" and set both trims to the "mean" of the 2 trim settings. This ensures that the *signal* going to the gain-matched subs is still matched. In my experience this has ZERO impact on the EQ, but it ensures that all the subs are running "...the same level, so the both have the same amount of headroom and one doesn't run out of steam before the other."

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post #8 of 62 Old 09-30-2013, 07:16 PM
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Originally Posted by craig john View Post

If you gain-match before running Audyssey... and then let Audyssey do it's level-matching step... you've successfully defeated the gain-matching. eek.gif
Are you sure that Audyssey MultEQ (not even XT) in the OP's Denon 3312 sets separate levels for two subs?

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post #9 of 62 Old 10-01-2013, 04:29 AM
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Yes to both questions.

If you want to gain-match the subs, place one in the middle of the room, hold your SPL meter 6 inches away, dial the gain knob till the meter reads 75dB. Don't touch the gain knob after that (might even want to tape it). Move the sub to its intended location.

Move other sub to the exact same spot in the middle of the room and repeat the procedure. Return the second sub to its intended location. With the subs gain matched, they'll have the same amount of headroom (one sub won't run out of steam before the other).

Depending on subwoofer locations and how the subs interact, they may or may not give you double the output when running together. When you run your receiver's auto-calibration (Audyssey MultEQXT), it will set the level of your combined subs to match your speakers.
75dB measured from 6 inches? I've been measuring from the main listening position. And does that center of the room method still work if my subs are not the same distance from the main listening position? I have one that is about 5 feet away and the other is about 13 feet away.

 

There is some information on gain matching, how to do it, what it's benefits are, in this Audyssey FAQ answer, which you might find helpful:

 

f)8.    How does Audyssey handle complex multiple subwoofer setups?

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post #10 of 62 Old 10-01-2013, 04:31 AM
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Originally Posted by brendelac View Post

I have two subwoofers and my Denon AVR3312 manual says to individually calibrate the subwoofer SPL to 75dB before running audyssey using the AVR's test tones but it doesn't specify what the AVR volume should be at when running the test tones. Assuming the subwoofer channel gain should be 0.0dB but should the volume be at reference? And then adjust the subwoofer gain to achieve 75dB with my SPL meter?

 

Try this Audyssey FAQ answer - it has a lot of info on using dual subs with Audyssey.

 

f)2.    How do I connect and set up two subwoofers?

 

There is an entire FAQ section devoted to setting up subs, which may be useful to you.

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post #11 of 62 Old 10-01-2013, 05:05 AM
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Are you sure that Audyssey MultEQ (not even XT) in the OP's Denon 3312 sets separate levels for two subs?

Op is just gain matching two subs, not calibrating them independently. His avr can't set them up independently.

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post #12 of 62 Old 10-01-2013, 10:57 AM
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Originally Posted by braveheart123 View Post

His avr can't set them up independently.
In that case, I stand by my original recommendation, since running Audyssey in the OP's receiver won't have "successfully defeated the gain-matching".

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post #13 of 62 Old 10-01-2013, 12:08 PM
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In that case, I stand by my original recommendation, since running Audyssey in the OP's receiver won't have "successfully defeated the gain-matching".


I gain match from the MLP to take into account room reflections and also the differing distances of both subs from MLP. That has huge bearing on the eventual SPL at MLP.

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post #14 of 62 Old 10-01-2013, 01:54 PM
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I gain match from the MLP to take into account room reflections and also the differing distances of both subs from MLP.
That's level matching your subwoofers, not gain matching their amplifiers.

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post #15 of 62 Old 10-01-2013, 09:16 PM
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That's level matching your subwoofers, not gain matching their amplifiers.

I think you misread me. I gain match the sub amps, as well as, level match my subs from MLP for the reasons I listed above.

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I think you misread me. I gain match the sub amps, as well as, level match my subs from MLP for the reasons I listed above.
OK, but what you described as "gain match from the MLP to take into account room reflections and also the differing distances of both subs from MLP" is a description of level matching.

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post #17 of 62 Old 10-01-2013, 09:55 PM
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It was stark clear. I thought you could decipher the phrase "Gain Match" as it pertains to the different gain structure of the amps on the subs. I never used the phrase "Level Match".

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post #18 of 62 Old 10-01-2013, 10:38 PM
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It was stark clear. I thought you could decipher the phrase "Gain Match" as it pertains to the different gain structure of the amps on the subs.
Ending up with different gain on each amp (due to reflections and distance from MLP of each sub) is not gain matching. Not sure why I would have to "decipher" such a commonly used term.
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I never used the phrase "Level Match".
Didn't say you did, only that what you described as "gain match" was in fact level matching.

In order to gain match two amps, you have to eliminate differing "room reflections and also the differing distances of both subs from MLP" as variables. You described doing the opposite and still called it "gain match".

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post #19 of 62 Old 10-01-2013, 11:27 PM
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It's useless discussion. People do it either way.

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post #20 of 62 Old 10-02-2013, 12:01 AM
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It's useless discussion. People do it either way.
Their choice. I'm simply clarifying that there is a difference between gain matching a pair of amps and level matching a pair of subs. I don't see what you gain by blurring the distinction between those two terms.
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post #21 of 62 Old 10-02-2013, 12:12 AM
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What do you do when gain matching the subs away from reflecting walls @ close distance at, let's say, 75dB and then one sub goes into a location that has 5dB room gain and the other goes into another location where it has flat response from MLP? Perfectly gain matched subs are now 5dB apart within themselves in FR due to room reflections. What do you do now?

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post #22 of 62 Old 10-02-2013, 02:24 AM
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Originally Posted by braveheart123 View Post

What do you do when gain matching the subs away from reflecting walls @ close distance at, let's say, 75dB and then one sub goes into a location that has 5dB room gain and the other goes into another location where it has flat response from MLP? Perfectly gain matched subs are now 5dB apart within themselves in FR due to room reflections. What do you do now?
You can either leave them alone or (if your receiver has Audyssey Sub EQ HT and calibrates subs independently) you can split the difference between them post-calibration (in the receiver, move the -5dB trim up 2.5dB, move 0dB trim down 2.5dB, so that both will be at -2.5dB). In both cases, neither sub will compress or distort before the other sub does.

BTW, if you don't want to gain match, you don't have to. If setting them to the same level from the MLP and/or using delays to compensate for differing distances gives you better bass response, then that's your choice to dial them in that way. Just understand that they're not "gain matched". That's been my point all along.

Worth reading the Audyssey FAQ on multi-sub that Keith linked to a few posts up:
http://www.avsforum.com/t/795421/official-audyssey-thread-faq-in-post-1/51750#user_f8

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post #23 of 62 Old 10-02-2013, 04:16 AM
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You can either leave them alone or

And let them be 5dBs apart, though perfectly gain matched. Wowwww
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or (if your receiver has Audyssey Sub EQ HT and calibrates subs independently) you can split the difference between them post-calibration (in the receiver, move the -5dB trim up 2.5dB, move 0dB trim down 2.5dB, so that both will be at -2.5dB).

Not everybody has an avr equipped with Audyssey Sub EQ HT. In fact, OP doesn't have it either.

Audyssey directions are not carved in stone. I would like to gain match then level match multiple subs from MLP taking into account room modes also. There are plenty on this forum who have tried beyond what is deemed as best practice by Audyssey and have come up with better results.

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Originally Posted by braveheart123 View Post

What do you do when gain matching the subs away from reflecting walls @ close distance at, let's say, 75dB and then one sub goes into a location that has 5dB room gain and the other goes into another location where it has flat response from MLP? Perfectly gain matched subs are now 5dB apart within themselves in FR due to room reflections. What do you do now?

I happen to have three stand-alone parametric equalizers on hand, so I put one in line with each sub and balanced them and flattened them out before I ran Audyssey.
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post #25 of 62 Old 10-02-2013, 05:46 AM
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Originally Posted by braveheart123 View Post

It was stark clear. I thought you could decipher the phrase "Gain Match" as it pertains to the different gain structure of the amps on the subs. I never used the phrase "Level Match".

 

The idea is that the SPL levels on the subs read exactly the same when you measure them and have adjusted the amp gain knobs. If you then adjust the trims later to be different to each other (as you must if you are doing what you said) then you are no longer gain matched. You are now level matched. Here is a description of how to gain match properly:

 

f)8.    How does Audyssey handle complex multiple subwoofer setups?

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post #26 of 62 Old 10-02-2013, 05:47 AM
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Originally Posted by braveheart123 View Post

It's useless discussion. People do it either way.

 

It's a matter of choice which way you do it - level matching or gain matching. But it's useful to understand the difference between the two. They aren't interchangeable terms.

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post #27 of 62 Old 10-02-2013, 05:50 AM
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You can either leave them alone or

And let them be 5dBs apart, though perfectly gain matched. Wowwww
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or (if your receiver has Audyssey Sub EQ HT and calibrates subs independently) you can split the difference between them post-calibration (in the receiver, move the -5dB trim up 2.5dB, move 0dB trim down 2.5dB, so that both will be at -2.5dB).

Not everybody has an avr equipped with Audyssey Sub EQ HT. In fact, OP doesn't have it either.

Audyssey directions are not carved in stone. I would like to gain match then level match multiple subs from MLP taking into account room modes also. There are plenty on this forum who have tried beyond what is deemed as best practice by Audyssey and have come up with better results.

 

You're missing the point. If you gain match the sub amps, and then you level match afterwards, as you are suggesting, then you are no longer gain matched. You are level matched. Have a read of the FAQ answer I just posted - it explains it in some detail, along with the correct procedure. The procedure you are following is not correct IF you wish to gain match.

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post #28 of 62 Old 10-02-2013, 07:44 AM
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You're missing the point. If you gain match the sub amps, and then you level match afterwards, as you are suggesting, then you are no longer gain matched. You are level matched. Have a read of the FAQ answer I just posted - it explains it in some detail, along with the correct procedure. The procedure you are following is not correct IF you wish to gain match.

As I understand it, gain matching is done coz different sub amps have different gain structure. One tick on the gain knob of e.g. HSU sub amp won't be equal to the same on Rythmik sub amp. So, we set the gain knobs on both subs where they are equal in SPL. In this step the sub trim level is fixed, let's say at 00 in AVR. Now subs are gain matched between themselves.

In order to level match with the rest of the system, we use sub trim level in AVR. Now both subs will be collectively going up or down. I do it (Both Gain and Level Matching) from the MLP to account for room reflections.
That's what my point is. I don't know what the discussion is.

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post #29 of 62 Old 10-02-2013, 07:54 AM
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Originally Posted by braveheart123 View Post
 
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You're missing the point. If you gain match the sub amps, and then you level match afterwards, as you are suggesting, then you are no longer gain matched. You are level matched. Have a read of the FAQ answer I just posted - it explains it in some detail, along with the correct procedure. The procedure you are following is not correct IF you wish to gain match.

As I understand it, gain matching is done coz different sub amps have different gain structure. One tick on the gain knob of e.g. HSU sub amp won't be equal to the same on Rythmik sub amp. So, we set the gain knobs on both subs where they are equal in SPL. In this step the sub trim level is fixed, let's say at 00 in AVR. Now subs are gain matched between themselves.

 

No - gain matching can be, and is, done on identical subs. Once the subs have been gain matched, then run Audyssey. Observe the trims that Audyssey has calculated in order to calibrate to Reference. Then split the difference for the trims so that each trim has the same level set. EG, if trim for Sub 1 is -7dB and trim for Sub 2 is -4dB, then set both trims to -5.5dB.  It is very likely that the trim levels will be different after calibration if the subs are not equidistant from the MLP or room influences differ for each sub. By doing it this way, you will have a gain matched sub system.

 

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 In order to level match with the rest of the system, we use sub trim level in AVR. Now both subs will be collectively going up or down. I do it (Both Gain and Level Matching) from the MLP to account for room reflections.
That's what my point is. I don't know what the discussion is.

 

The point is, you are not doing it properly if you want to gain match. The trim levels must be set to the same as each other, as explained above and explained by Sanjay and the FAQ I referred you to.

 

EDIT: you do have an AVR that is capable of setting independent levels for two subs?

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post #30 of 62 Old 10-02-2013, 08:13 AM
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EDIT: you do have an AVR that is capable of setting independent levels for two subs?

No. And neither do I have identical subs.

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