Two Subs...Gain Matching vs Level Matching - Page 3 - AVS Forum
Forum Jump: 
 5Likes
 
Thread Tools
Old 10-22-2010, 12:36 PM
AVS Special Member
 
deepstang's Avatar
 
Join Date: Sep 2007
Location: Dallas-Irving, TX (from Nawlins!)
Posts: 1,708
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
In continuing the comments I wrote earlier on level matching, here is an excerpt from the Audyssey set-up guide for dual subs:

http://www.avsforum.com/avs-vb/showt...5#post14456895

F. Attempt to match the output level of both subwoofers.

1. Use the receiver / processor internal LFE test tone while adjusting the volume control on the subwoofer to perform the following:

2. Turn one subwoofer on, and adjust the output level to 80 dB using an SPL meter.
a. Ensure the SPL meter is located where the first Audyssey measurement position will be taken (see section V.), and is set to “C” and “Slow”.
b. If you do not have an SPL meter, adjust the level by ear.

3. Turn off the first subwoofer, turn on the second subwoofer, and repeat the procedure.

4. Turn on both subwoofers and calibrate with Audyssey.
deepstang is offline  
Sponsored Links
Advertisement
 
Old 10-22-2010, 12:37 PM
Advanced Member
 
nith's Avatar
 
Join Date: Dec 2006
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 11
I thought I read a couple pages back that a variation of 1-3dB is not discernible if crossover at 80Hz or lower. This is probably good enough for me...

I admire you guys pursue of perfection!
nith is offline  
Old 10-22-2010, 01:01 PM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by deepstang View Post

Glad to hear that GAIN matching seems to yield the best results for many.

I too have dual subs, but here are my concerns with gain matching:

(1) I like the idea of ensuring not to bottom out one sub quicker than the other when gain matching. OTOH, I also think it is possible to have situations where one may have a lot of sub-woofer headroom (where both subs are not pushed to their limits), and the subs will never reach their max. A user can also have a sub (like those made by Epik), which almost never bottom out.

As I said on the previous page, in a system where you are not playing back at levels that are near the limits of your subs, you may not need to gain-match. However, "bottoming" is the final symptom of driving the sub close to the limits. Compression and distortion hopefully precede bottoming, and you can tell when to turn the system down. Bottoming a sub can be destructive.

(Edit: Just to be clear, compression is not "audible". Compression happens when you add volume to the sub and it does not add linear SPL to the output. IOW, you reach a point where you add 3 dB of signal, but the sub only outputs 2 dB of sound. Add another 3 dB, and the sub only outputs 1 dB of additional sound. You won't "hear" this necessarily, but it will be your sub hitting it's limits.)

Quote:
Originally Posted by deepstang View Post

(2) My other concern with having each sub having a different SPL output at the LP is how Audyssey would calibrate them if a single LFE out is used with a y-splitter. I would think that maybe more calibration would be applied to the sub with greatest room reinforcement.

Not sure I understand this question. You can't apply more "calibration" to one sub than the other. If you only have one subwoofer output, the same EQ filters are applied to both subs.

If you gain-match, both subs will be at the same amplifier output level and the same driver excursion at all times. If you level-match, and the subs have widely different room reinforcement environments, you could end up with one sub set significantly higher, (the sub with *less* room reinforcement), than the other. The higher-set sub would reach it's limits sooner than the lower set sub. It would become the limiting factor for the entire *system*.

Quote:
Originally Posted by deepstang View Post

I actually have not had the time to try to GAIN match my subs.....so I should retract my earlier post until I can experience it for myself.

If your subs are not equidistant to the LP, and if they have significantly different room environments, and you can hear some distortion from your subs, I suggest you try gain-matching. If you don't have any of those issues, level-matching may be just as effective for you.

Quote:
Originally Posted by deepstang View Post

In continuing the comments I wrote earlier on level matching, here is an excerpt from the Audyssey set-up guide for dual subs:

http://www.avsforum.com/avs-vb/showt...5#post14456895

F. Attempt to match the output level of both subwoofers.

1. Use the receiver / processor internal LFE test tone while adjusting the volume control on the subwoofer to perform the following:

2. Turn one subwoofer on, and adjust the output level to 80 dB using an SPL meter.
a. Ensure the SPL meter is located where the first Audyssey measurement position will be taken (see section V.), and is set to “C” and “Slow”.
b. If you do not have an SPL meter, adjust the level by ear.

3. Turn off the first subwoofer, turn on the second subwoofer, and repeat the procedure.

4. Turn on both subwoofers and calibrate with Audyssey.

Audyssey uses level-matching. In their stand-alone products, the SubEQ and the AS-EQ1, and in their new XT32 systems, the first step is to level-match the subs.

Myself, I replace this step with gain-matching as it makes more sense to me, and it certainly works in my room and system. I will be getting an Integra DHC-80.2 with XT32 on Monday. I intend to keep my subs configured just the way they are now... Y-connected and gain-matched off 1 subwoofer output. (Of course, I have 3 subs, so using 2 outputs would be dicey anyway.)

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 10-23-2010, 02:38 PM
AVS Special Member
 
deepstang's Avatar
 
Join Date: Sep 2007
Location: Dallas-Irving, TX (from Nawlins!)
Posts: 1,708
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by craig john View Post

Not sure I understand this question. You can't apply more "calibration" to one sub than the other. If you only have one subwoofer output, the same EQ filters are applied to both subs.

Thanks for the response Craig. What I was trying to express is that when dual subs are connected to a sub processor (like Audyssey) via a single LFE out, that the processor will set distance/delay to the louder sub (b/c of room reinforcement). It would also cause the sub calibration to favor one sub over the other...when in-fact both subs should be equally considered in the calibration.

Quote:


If you gain-match, both subs will be at the same amplifier output level and the same driver excursion at all times. If you level-match, and the subs have widely different room reinforcement environments, you could end up with one sub set significantly higher, (the sub with *less* room reinforcement), than the other. The higher-set sub would reach it's limits sooner than the lower set sub. It would become the limiting factor for the entire *system*.

I guess this all goes back to our initial disclaimer of how close a sub is to its max (ie. how much sub headroom is available). First off, with dual subs, the system should gain at least +3dbs (if not co-located (+6db if it is) ), so there should be more headroom. You are right that if a sub is reaching it's limits in a given set-up, GAIN matching is the way to go. My concern is that I am not squeezing out the most LFE SPLs from my sub set-up. I think that may happen if I am allowing a single sub to produce more SPLs than the other, and the trim level is set based on that single sub with extra room reinforcement.


Quote:


Audyssey uses level-matching. In their stand-alone products, the SubEQ and the AS-EQ1, and in their new XT32 systems, the first step is to level-match the subs.

Myself, I replace this step with gain-matching as it makes more sense to me, and it certainly works in my room and system. I will be getting an Integra DHC-80.2 with XT32 on Monday. I intend to keep my subs configured just the way they are now... Y-connected and gain-matched off 1 subwoofer output. (Of course, I have 3 subs, so using 2 outputs would be dicey anyway.)

Craig


If the Audyssey product has 2 LFE outs, I believe Audyssey will set both subs to have the same SPL (IE. level matching). When I quoted the Audyssey set-up guide above, that was my interpretation of their advice (level matching when using dual subs, than run Audyssey). Someone correct me if I am wrong, but that is my understanding.
deepstang is offline  
Old 10-23-2010, 04:55 PM
AVS Special Member
 
bsoko2's Avatar
 
Join Date: Apr 2007
Location: Olympia, WA
Posts: 4,387
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 53 Post(s)
Liked: 68
deepstang - The way Audyssey handles subs is one reason that I went back to MCACC. More freedom of settings for subs with MCACC as MCACC leaves the sub LFE alone except for the trim settings.
bsoko2 is online now  
Old 10-24-2010, 03:38 PM
Senior Member
 
Hurk's Avatar
 
Join Date: Apr 2008
Location: Vancouver BC
Posts: 307
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by craig john View Post

As I said on the previous page, in a system where you are not playing back at levels that are near the limits of your subs, you may not need to gain-match. However, "bottoming" is the final symptom of driving the sub close to the limits. Compression and distortion hopefully precede bottoming, and you can tell when to turn the system down. Bottoming a sub can be destructive.

(Edit: Just to be clear, compression is not "audible". Compression happens when you add volume to the sub and it does not add linear SPL to the output. IOW, you reach a point where you add 3 dB of signal, but the sub only outputs 2 dB of sound. Add another 3 dB, and the sub only outputs 1 dB of additional sound. You won't "hear" this necessarily, but it will be your sub hitting it's limits.)


Not sure I understand this question. You can't apply more "calibration" to one sub than the other. If you only have one subwoofer output, the same EQ filters are applied to both subs.

If you gain-match, both subs will be at the same amplifier output level and the same driver excursion at all times. If you level-match, and the subs have widely different room reinforcement environments, you could end up with one sub set significantly higher, (the sub with *less* room reinforcement), than the other. The higher-set sub would reach it's limits sooner than the lower set sub. It would become the limiting factor for the entire *system*.


If your subs are not equidistant to the LP, and if they have significantly different room environments, and you can hear some distortion from your subs, I suggest you try gain-matching. If you don't have any of those issues, level-matching may be just as effective for you.


Audyssey uses level-matching. In their stand-alone products, the SubEQ and the AS-EQ1, and in their new XT32 systems, the first step is to level-match the subs.

Myself, I replace this step with gain-matching as it makes more sense to me, and it certainly works in my room and system. I will be getting an Integra DHC-80.2 with XT32 on Monday. I intend to keep my subs configured just the way they are now... Y-connected and gain-matched off 1 subwoofer output. (Of course, I have 3 subs, so using 2 outputs would be dicey anyway.)

Craig

I ran audyssey with 8 positions with main sub only (Polk PSw1000) and got great results. I then took sub #2 (Energy ES10) and gain matched it to #1 sub. I then placed #2 sub equa distance from LP as per #1 sub on opposite wall, both at rear of room. I played system with BD Iron Man 2, bass was very good with #1 sub but with 2 subs a lot more chest pounding bass, althought it didn't sound as smooth as just 1 sub but not bad.

I will now run audyssey with both subs and see if it smooths out the bass. Interesting to see how audyssey handles the 2 subs?

Hurk

I ran audyssey with the above noted parameters, 8 positions, the results seemed great.
The 2 subs were each measured with tape 78" to LP, audyssey calibration put the subs at 84", not bad?
Calibation set sound level at -8.0; with just 1 sub it was -4.5 so I picked up 3.5 dbs which was predictable.

All in all it did a great job gave me the chest pounding bass and seems to be as smooth as 1 sub.

Hurk
Hurk is offline  
Old 10-24-2010, 03:58 PM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by bsoko2 View Post

deepstang - The way Audyssey handles subs is one reason that I went back to MCACC. More freedom of settings for subs with MCACC as MCACC leaves the sub LFE alone except for the trim settings.

Hi Bill,

I thought you went back to Audyssey? Are back to Pioneer again?

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 10-24-2010, 06:36 PM
AVS Special Member
 
bsoko2's Avatar
 
Join Date: Apr 2007
Location: Olympia, WA
Posts: 4,387
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 53 Post(s)
Liked: 68
Quote:
Originally Posted by craig john View Post

Hi Bill,

I thought you went back to Audyssey? Are back to Pioneer again?

Craig

Yes, Pioneer SC-37 and the Anti Mode & SMS-1 for my quad Empires. The Anti Mode is excellent for doing a automatic check of the room and then I use the SMS-1 to see what the Anti Mode has done. I then tweak and set a house curve and EQ the lower end out to 16 hz for the quads. Chad had talked to me about the Empire rolling off at 20 hz. Chad said that multiple Empires could handle a deeper rolloff due to having alot of headroom. It works for me having 4 subs, but it would be real hard on a single Empire to do. Too much risk of blowing the amp or driver with setting that low of a eq.
bsoko2 is online now  
Old 10-24-2010, 07:33 PM
AVS Special Member
 
Gary J's Avatar
 
Join Date: Mar 2000
Location: 4000' or sea level
Posts: 7,650
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 67 Post(s)
Liked: 97
Quote:
Originally Posted by craig john View Post

I am a proponent of gain-matching. I have 3 Submersives, asymmetrically placed around my room. I want them all to drive the room with same energy, no matter what the relative SPL's are at any one listening position. This ensures they all have the same headroom, and they are all contributing equally to the sound. I don't hear any directionality from any of the subs anywhere in the room, even if I stand or sit very close to one of them.

To gain-match identical subs, the most rigorous method is to move each sub to the middle of the room, place a mic very close to the driver, and measure the SPL. Then move each of the other subs to the exact same position with the mic exactly the same distance away, and set the level to the same SPL as the first one. I place tape on the floor around the first sub, so I can ensure the subsequent subs are located in the exact same place. I don't move the mic between measurements. This works for identical subs, and the level knobs should be at the exact same point, assuming the amps are consistent from unit to unit. It also works for different subs, but then you should expect different settings on the amps.

I have yet to see a chart of an uncorrected sub that did not have a null, in fact several of them. When you put the subs back in place they will have different nulls, possibly deeper ones. Then when you apply room EQ to boost those nulls you are lessening the amount of headroom. This is why there are max boost levels in room EQ. It seems to me a better way to maximize headroom would be to compare measurements of before and after charts to see how much boost is applied between various sub positions in the room.
Gary J is offline  
Old 10-24-2010, 07:49 PM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by Gary J View Post

I have yet to see a chart of an uncorrected sub that did not have a null, in fact several of them. When you put the subs back in place they will have different nulls, possibly deeper ones. Then when you apply room EQ to boost those nulls you are lessening the amount of headroom. This is why there are max boost levels in room EQ. It seems to me a better way to maximize headroom would be to compare measurements of before and after charts to see how much boost is applied between various sub positions in the room.

What you say is true, but I'm not sure what this has to do with gain vs. level matching. Please elaborate.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 10-24-2010, 07:57 PM
AVS Special Member
 
Gary J's Avatar
 
Join Date: Mar 2000
Location: 4000' or sea level
Posts: 7,650
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 67 Post(s)
Liked: 97
If the reason for gain matching is not a concern for headroom what is it?
Gary J is offline  
Old 10-24-2010, 10:27 PM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
OK, I didn't understand your previous post. Let me see if I understand your position now...

What you're saying is that one should measure the FR with the subs gain-matched, then again with the subs level-matched, and use the one that has the fewest nulls, so that your EQ has less positive correction to do on the nulls? Is that right? If so...

First, one would hope that the EQ system, (whether it is automated or manual), is smart enough not to try to boost true nulls. True nulls can't be corrected with EQ.

Second, with multiple subs, true nulls are usually addressed with positioning of the subs. It's unusual to see steep, narrow nulls which can't be corrected with slight adjustments of the positioning of one or the other of the subs. This is one of the biggest advantages of multiple, non-co-located subs. Nulls, (and peaks), are both significantly reduced. What you're left with are much less dramatic peaks and troughs.

Third, once the subs are in-place, the difference between level matching and gain-matching will not affect the overall "shape" of the FR curve. It will only impact the magnitude of the affect of each sub on the other. Those differences will be moderate to subtle, depending on the level differences between the subs.

Bottom line, I would *NOT* make a decision about level-matching vs. gain-matching based on one or the other's ability to reduce nulls, (which will only be subtly different), especially if the goal is to increase headroom after implementing room correction. If there is a significant difference in FR between one or the other level-setting techniques, I would be more inclined to change the sub positioning than to go backwards to changing the relative levels of the subs.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 10-25-2010, 07:21 AM
AVS Special Member
 
Gary J's Avatar
 
Join Date: Mar 2000
Location: 4000' or sea level
Posts: 7,650
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 67 Post(s)
Liked: 97
Quote:
Originally Posted by craig john View Post


First, one would hope that the EQ system, (whether it is automated or manual), is smart enough not to try to boost true nulls. True nulls can't be corrected with EQ.

Audyssey will add boost (thus reducing headroom) up to +9 dB to all dips, including nulls.

Quote:
Originally Posted by craig john View Post

Second, with multiple subs, true nulls are usually addressed with positioning of the subs. It's unusual to see steep, narrow nulls which can't be corrected with slight adjustments of the positioning of one or the other of the subs. This is one of the biggest advantages of multiple, non-co-located subs. Nulls, (and peaks), are both significantly reduced. What you're left with are much less dramatic peaks and troughs.

Exactly, making the whole center of the room exercise rather pointless. If headroom is a concern only comparison of differences in measurements with subs in various possible final positions will give an indication of available headroom after room eq.
Gary J is offline  
Old 10-28-2010, 01:39 PM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by Gary J View Post

Audyssey will add boost (thus reducing headroom) up to +9 dB to all dips, including nulls.



Exactly, making the whole center of the room exercise rather pointless. If headroom is a concern only comparison of differences in measurements with subs in various possible final positions will give an indication of available headroom after room eq.



If you've gain-matched, and if the EQ is applied equally to both subs, then they'll still both be outputting the exact same signal, at the exact same levels, with the exact same electro-mechanical energy, the same headroom and the same compression and distortion points.

If the EQ is applied separately to both subs, (different EQ curves for each sub), or if they levels were set differently to begin with, then you might have a point.

And that is my point... level matching that results in different gain settings will force the higher set sub, (or the sub with higher EQ boost levels), to reach it's maximum potential before the lower set sub.

Have you ever set up multiple subs Gary?

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 11-06-2010, 06:54 PM
AVS Special Member
 
laugsbach's Avatar
 
Join Date: Jun 2007
Location: Cincinnati, Ohio
Posts: 2,678
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 54 Post(s)
Liked: 135
Quote:
Originally Posted by craig john View Post
To gain-match identical subs, the most rigorous method is to move each sub to the middle of the room, place a mic very close to the driver, and measure the SPL. Then move each of the other subs to the exact same position with the mic exactly the same distance away, and set the level to the same SPL as the first one. I place tape on the floor around the first sub, so I can ensure the subsequent subs are located in the exact same place. I don't move the mic between measurements. This works for identical subs, and the level knobs should be at the exact same point, assuming the amps are consistent from unit to unit. It also works for different subs, but then you should expect different settings on the amps.

Mark Seaton was the one who suggested this method to me, and if it's good enough for him, it's good enough for me.

Craig
Hi Craig, I want to thank you for this write up and to let you know that I followed your gain-matching method for my 4 Outlaw subs. I have slight differences with the gain knob on all 4 subs and my total output is down slightly from before (81dB now vs. 85dB before) but the "energy" is great in my room and I feel all 4 subs are not as stressed at reference level listening.

I always use the THX trailer "Amazing Life" as my quick, subjective listening test. My LP is 14' from all four subs (located on the front wall) and I matched the previous set-up SPL of 117.5dB with a MV of 0.0 on my Onkyo 805. I just love the THX mushrooms...

BTW, I really appreciate reading your reviews/thoughts on the various threads around AVS...thanks for being such a cool member here...
laugsbach is online now  
Old 11-07-2010, 10:46 AM
Member
 
HIMS's Avatar
 
Join Date: Jan 2009
Posts: 184
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 10
I redid everything using the gain matching technique that you guys have talked about with much better results than I have previously had. Just thought I would pass that on to anyone else that was wondering. Much better than level matching in my case......
HIMS is offline  
Old 11-07-2010, 11:25 AM
AVS Special Member
 
hometheatergeek's Avatar
 
Join Date: Jan 2008
Location: Georgia
Posts: 2,338
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked: 34
Quote:
Originally Posted by HIMS View Post

I redid everything using the gain matching technique that you guys have talked about with much better results than I have previously had. Just thought I would pass that on to anyone else that was wondering. Much better than level matching in my case......

Looks like we have another believer Craig. Glad you at least gave it a try HIMS. What subs were they?

Hometheatergeek

aka AL
----------
My Current System
hometheatergeek is offline  
Old 11-07-2010, 02:40 PM
Member
 
HIMS's Avatar
 
Join Date: Jan 2009
Posts: 184
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 10
DIY dayton 12" 240w ported built into the cabinets with an eD A5s-300 on the other side. I have been struggling to tone down the boom, I had no problem with output, but this tightened it up quite a bit. Thanks again.
HIMS is offline  
Old 11-07-2010, 02:54 PM
Advanced Member
 
Mantis10's Avatar
 
Join Date: Apr 2005
Location: Pa
Posts: 676
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 14
Everyone seems to have some technic or another so I will post how I set up multi subs in a room with a preamp or receiver with only one sub out suing Y splitters and such.

1) Set up sub's in the position they are going to live in.( This is after you figure out placement, I could go into that but thats another setup technic)
2) Unplug all subs but 1.
3) Run LFE and measure the SPL at the listening position with a quality SPL meter.
4) leave LFE preamp output to "0"
5) Use the Subwoofer gain or volume control to get the SPL to 75db.
6) Unplug this sub and move onto the next woofer and repeat steps 2 to 5.
7) Once all subs are reading 75db one at a time at the listening position , connect all subs and run your calibration tools or manual with a SPL , your choice of calibration and expertise.

This will allow very even coverage over the listening room. This helps with peaks and dips. Calibration of a theater system can take a few hours of figuring out problems in the room , speaker and sub/s placement and correcting. Once this is all figured out , you will get the most of the given system.

Note:
Adding more subs isn't for louder SPL , it's for even coverage. Giving everyone in the room a good experience with the system.
I prefer to use the exact sub all around but this is a personal opinion but an exact science. I find using the same sub keeps dynamic range matched to a point. Room gains does make some subs appear to have more dynamic range over others just due to placement. So it's not a bad idea to spend quality time choosing the correct placement of each sub to match the others room gain. If you can control this by all means this will make a huge difference in performance.

Good luck with your calibration and I hope this helps.
Mantis10 is offline  
Old 11-07-2010, 04:13 PM
AVS Special Member
 
warlord260's Avatar
 
Join Date: Aug 2007
Location: kent,wa.
Posts: 1,350
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
wouldnt that be level matching?
warlord260 is offline  
Old 11-11-2010, 11:58 AM
AVS Special Member
 
deepstang's Avatar
 
Join Date: Sep 2007
Location: Dallas-Irving, TX (from Nawlins!)
Posts: 1,708
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by Mantis10 View Post

Everyone seems to have some technic or another so I will post how I set up multi subs in a room with a preamp or receiver with only one sub out suing Y splitters and such.

1) Set up sub's in the position they are going to live in.( This is after you figure out placement, I could go into that but thats another setup technic)
2) Unplug all subs but 1.
3) Run LFE and measure the SPL at the listening position with a quality SPL meter.
4) leave LFE preamp output to "0"
5) Use the Subwoofer gain or volume control to get the SPL to 75db.
6) Unplug this sub and move onto the next woofer and repeat steps 2 to 5.
7) Once all subs are reading 75db one at a time at the listening position , connect all subs and run your calibration tools or manual with a SPL , your choice of calibration and expertise.

This will allow very even coverage over the listening room. This helps with peaks and dips. Calibration of a theater system can take a few hours of figuring out problems in the room , speaker and sub/s placement and correcting. Once this is all figured out , you will get the most of the given system.

Note:
Adding more subs isn't for louder SPL , it's for even coverage. Giving everyone in the room a good experience with the system.
I prefer to use the exact sub all around but this is a personal opinion but an exact science. I find using the same sub keeps dynamic range matched to a point. Room gains does make some subs appear to have more dynamic range over others just due to placement. So it's not a bad idea to spend quality time choosing the correct placement of each sub to match the others room gain. If you can control this by all means this will make a huge difference in performance.

Good luck with your calibration and I hope this helps.

Quote:
Originally Posted by warlord260 View Post

wouldnt that be level matching?

Mantis DID describe LEVEL matching. On step 6, if the other sub was moved into the 1st subs position and level matched....that should be close to GAIN matching if both subs are identical.

Correct me if I am wrong, but GAIN matching is having the exact gain for any 2 subs (example, gain at 12 o'clock for both subs). I ask, b/c today I finally checked the gain on my dual sub set-up. I realized that both subs were at the same gain (1 o'clock). I than noticed that the sub that would have the most room reinforcement was set to a PHASE of 180. I changed it to 0, and that single sub became violently loud. It was so loud that it was very noticeable that there was a lot more energy coming from that location. My intent was to try GAIN matching, and I realized I accidentally already had them gain matched. I did noticed that the sound was much more accurate once I changed to phase from 180 back to 0. That was an oversight on my part.

I think that turning down the gain at the room reinforced sub would yield a more balanced sound to me. Comments are welcome.
deepstang is offline  
Old 11-11-2010, 12:27 PM
AVS Special Member
 
hometheatergeek's Avatar
 
Join Date: Jan 2008
Location: Georgia
Posts: 2,338
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked: 34
Quote:
Originally Posted by deepstang View Post

Mantis DID describe LEVEL matching. On step 6, if the other sub was moved into the 1st subs position and level matched....that should be close to GAIN matching if both subs are identical.

Correct me if I am wrong, but GAIN matching is having the exact gain for any 2 subs (example, gain at 12 o'clock for both subs). I ask, b/c today I finally checked the gain on my dual sub set-up. I realized that both subs were at the same gain (1 o'clock). I than noticed that the sub that would have the most room reinforcement was set to a PHASE of 180. I changed it to 0, and that single sub became violently loud. It was so loud that it was very noticeable that there was a lot more energy coming from that location. My intent was to try GAIN matching, and I realized I accidentally did. I think that turning down the gain at the room reinforced sub would yield a more balanced sound to me.

I did noticed that the sound was much more accurate once I changed to phase from 180 back to 0. That was an oversight on my part.

Comments are welcome.

Hi Deepstang.

Just because both subs volume knobs are set at the exact same mark on the subs does not mean they are gain match. Every amplifier knob will have some variations in relationship to the output of their respectful amp. If you were to place your sub in the middle of the room and play the test tone, then do the other one, you will find in most cases that one sub will be playing louder then the other one, due to this variation in output. IOW What you would probably see is one of your subs (set at 1:00) is outputting 75dB and the other one would be outputting 78dB. The second one would then run out of steam sooner (during high SPL demands) then the first one. In order for them to be truely set by gain matching the second sub amp knob would need to be turned down to something like 12:30 in order to output the equal 75dB setting of the first one. This is what gain matching is.

Again I have found this to be true for most subwoofers but I have come across on a rare occasion that two subs did end up having identical output when both subs volume knobs were set identical to each other. But unless you try this process you can not be sure.

Hometheatergeek

aka AL
----------
My Current System
hometheatergeek is offline  
Old 11-11-2010, 04:24 PM
AVS Special Member
 
bsoko2's Avatar
 
Join Date: Apr 2007
Location: Olympia, WA
Posts: 4,387
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 53 Post(s)
Liked: 68
Even Audyssey Pro considers a 3 db of difference between subs to being matched.
bsoko2 is online now  
Old 11-11-2010, 05:25 PM
AVS Special Member
 
hometheatergeek's Avatar
 
Join Date: Jan 2008
Location: Georgia
Posts: 2,338
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked: 34
Quote:
Originally Posted by bsoko2 View Post

Even Audyssey Pro considers a 3 db of difference between subs to being matched.

Bill,

My response was an example. It could be off more then 3dB.

Hometheatergeek

aka AL
----------
My Current System
hometheatergeek is offline  
Old 11-12-2010, 07:11 AM
AVS Special Member
 
deepstang's Avatar
 
Join Date: Sep 2007
Location: Dallas-Irving, TX (from Nawlins!)
Posts: 1,708
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
I will shake this sub eq'n tree even more.

After hearing how much louder my room reinforced sub was after gain matching (not fully true, because I gain matched on the dial setting of my identical subs), I started to wonder about level matchings drawbacks. So, in my set-up I will have to definitely turn down the gain on my receiver. This would tame the overly hot LFE, and cause the 1 sub that is highly reinforced to fall within balance with the rest of the system. That would cause my other capable Epik Sentinel to have almost a 25% lower spl at my lp. I know I have enough headroom where I can easily turn my other sub up by 25%.

Correct me if I am wrong, but in my situation, level matching may be better.
deepstang is offline  
Old 11-12-2010, 09:43 AM
AVS Special Member
 
Kimwyn's Avatar
 
Join Date: Dec 2008
Location: Barbados
Posts: 1,411
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 14
hey guys, heres a little twist i would like to know about in your scenarios:

if a mid-bass module was added to the mix of a multiple sub woofer system, how would that be integrated? would that be gain-matched also or would it be level matched?

Why i asked this because a mid-bass module frequency tune stops at a certain Hz and if that is the case what would a user do if the test tone used to gain match is below the frequency allowed for the mid-bass module?
Kimwyn is offline  
Old 11-12-2010, 10:29 AM
Advanced Member
 
LF911's Avatar
 
Join Date: Mar 2010
Location: New Hampshire Seacoast
Posts: 686
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I want to try gain matching this weekend....via, for lack of a better term, "Craig's" method...move the sub to the middle of the room.

Both of my subs are ported...one has 1x6" port then other has 2 x 6" ports..

How should I position the meter? Do I position it half way between the ports and driver? How far away from the sub should it be positioned?
LF911 is offline  
Old 11-12-2010, 11:49 AM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by bsoko2 View Post

Even Audyssey Pro considers a 3 db of difference between subs to being matched.

Audyssey Pro uses level-matching, not gain-matching.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 11-12-2010, 11:55 AM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by deepstang View Post

I will shake this sub eq'n tree even more.

After hearing how much louder my room reinforced sub was after gain matching (not fully true, because I gain matched on the dial setting of my identical subs), I started to wonder about level matchings drawbacks. So, in my set-up I will have to definitely turn down the gain on my receiver. This would tame the overly hot LFE, and cause the 1 sub that is highly reinforced to fall within balance with the rest of the system. That would cause my other capable Epik Sentinel to have almost a 25% lower spl at my lp. I know I have enough headroom where I can easily turn my other sub up by 25%.

Correct me if I am wrong, but in my situation, level matching may be better.

Actually, what would probably be best is if both subs had more similar room reinforcement. Do you have any other placements that are more "equal" in room reinforcement?

If you can't move them to more equal placements, then level-matching would be preferred in your situation, as long as you don't overdrive, compress or distort the higher-set sub. If you are getting close to the limits of the higher-set sub, then a compromise between gain-matching and level-matching would be beneficial.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
Old 11-12-2010, 11:58 AM
AVS Club Gold
 
craig john's Avatar
 
Join Date: Oct 2003
Location: Lancaster, PA
Posts: 10,389
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 131 Post(s)
Liked: 363
Quote:
Originally Posted by Kimwyn View Post

hey guys, heres a little twist i would like to know about in your scenarios:

if a mid-bass module was added to the mix of a multiple sub woofer system, how would that be integrated? would that be gain-matched also or would it be level matched?

Why i asked this because a mid-bass module frequency tune stops at a certain Hz and if that is the case what would a user do if the test tone used to gain match is below the frequency allowed for the mid-bass module?

You can't gain-match such a system. The amps will have totally different gain structures. You can match the nearfield SPl of of the MBM with the nearfield SPL of the LF sub, but that's not really gain-matching. However, depending on placement and LP, level-matching at the LP may be the best result, as long as neither sub is run near it's limits.

Craig

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

My System

craig john is offline  
 

Tags
Outlaw Audio Lfm 1 Ex
Thread Tools


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off