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post #1 of 249 Old 06-11-2009, 06:46 AM - Thread Starter
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Hi, I'm setting up two subs with the AviaII disc and didn't know if I should calabrate them with the spl meter at the same time or shut one down calabrate the other then switch and do the other one?

Thanks!!!!
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post #2 of 249 Old 06-11-2009, 06:50 AM
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One at a time.

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post #3 of 249 Old 06-11-2009, 07:08 AM
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As far as level setting on an SSP or AVR, I would think you would want the combined output set via the SPL meter = to your other speaker levels. The combined output will be greater (at least 3db) than the individual. The tone source is irrelevant to this process.

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post #4 of 249 Old 06-11-2009, 08:17 AM - Thread Starter
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Ok now I'm confused!!!
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post #5 of 249 Old 06-11-2009, 09:21 AM
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Turn sub2 off, level match sub1 to the mains by using the gain knob on the sub only.
Turn sub1 off, level match sub2 to the mains using only the gain knob on the sub.
Turn on both subs and level match to the mains using the sub level in the AVR.
Done.


Edit: Nevermind, see craig john's post below for the correct way using two identical subs.
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post #6 of 249 Old 06-11-2009, 09:21 AM
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Quote:
Originally Posted by Rob Horvers View Post

Ok now I'm confused!!!

Set one sub, then set the other sub (both set by themselves). Then in the reciever speaker setup, run the pink tone for the sub and set the db with both subs on with the spl meter. Your final sub setting is with both subs on. Two subs in the room will have a 3 db gain, two subs near each other (within 4 feet) will have a 6 db gain. So if you are looking for a final setting of 75, you want each sub set to 69, then together with 6 db gain at 75.

Bill
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post #7 of 249 Old 06-11-2009, 10:27 AM
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Quote:
Originally Posted by Rob Horvers View Post

Hi, I'm setting up two subs with the AviaII disc and didn't know if I should calabrate them with the spl meter at the same time or shut one down calabrate the other then switch and do the other one?

Thanks!!!!

Are they the same model subs, or are you using 2 different subs?

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post #8 of 249 Old 06-11-2009, 10:31 AM - Thread Starter
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Same subs. Mirage prestige s8.
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post #9 of 249 Old 06-11-2009, 10:56 AM
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Quote:
Originally Posted by Rob Horvers View Post

Same subs. Mirage prestige s8.

In that case, I would "gain-match" them first. Level matching has the inherent problems of room acoustics and distance from the measuring position influencing the settings. In other words, if one sub is further away from the measurement location than the other, it's level will be set higher. Then, it won't have as much headroom as the other sub. When combined, the higher-set sub will peak before the lower-set sub. You'll either be overloading the higher-set sub or under-utilizing the lower-set sub.

Room acoustics can also influence this. If one sub has a big peak and the other sub has a big null, their "average" levels will be different. If you turn down the sub with the big peak and turn up the sub with the big null, you'll end up with 2 very different gain settings. Combine the two issues and you could really cripple your system. IOW, if the closer sub is also the sub with the big peak, it's gain could be set 15 dB or more lower than the other sub. The further-away sub with the null would be set so high it would be bottoming, while the closer sub would be loafing along with output to spare.

If you "gain-match" you don't have these problems. How do you gain match? You set the two gains to the exact same levels. If you are confident that setting both amps to the exact same point yields the exact same levels, that's all you need to do. If you want to check to be sure, move one sub to the middle of the room. Place the SPL meter 6" from the driver and measure the output. Then, move the other sub to the *exact* same position with the SPL meter the exact same distance from the driver. If they measure the same, you're done. If they don't, adjust the second sub's gain until it measures the same as the first sub. They are now "gain-matched".

When you place them in the room, they will both add the exact same amount of bass energy to the room. They will both have the same headroom and distortion characteristics. They will probably measure differently at the listening position, but that is immaterial. Just set their *combined" level to match the speaker level by using the trim controls in the Bass Management of the receiver or pre/pro.

This is the technique Mark Seaton uses when he installs a multi-sub system. If it's good enough for Mark Seaton, it's good enough for me.

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post #10 of 249 Old 06-11-2009, 10:59 AM
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Quote:
Originally Posted by craig john View Post

In that case, I would "gain-match" them first. Level matching has the inherent problems of room acoustics and distance from the measuring position influencing the settings. In other words, if one sub is further away from the measurement location than the other, it's level will be set higher. Then, it won't have as much headroom as the other sub. When combined, the higher-set sub will peak before the lower-set sub. You'll either be overloading the higher-set sub or under-utilizing the lower-set sub.

Good points all around. I rescind my earlier recommendation and second craig john's
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post #11 of 249 Old 06-11-2009, 11:21 AM
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Originally Posted by lennon_68 View Post

Good points all around. I rescind my earlier recommendation and second craig john's

Actually, these are Mark Seaton's rec's. I'm just repeating them.

My sub's, (JL Audio F112's), have a Master/Slave connection. The Master sets the gain, and all other parameters for the Slave. By definition, my subs are gain-matched. It works very well in my system, and after MS explained the concept to me, I understood why.

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post #12 of 249 Old 06-11-2009, 11:24 AM - Thread Starter
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My subs are on either side of the tv. Same distance from the listening position.
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post #13 of 249 Old 06-11-2009, 11:33 AM
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That they are identical subs makes things, easy, Rob Horvers. You can level match them, or you can gain match them. Level matching is what most people would probably do but, as craig john pointed out, gain matching has some benefits.

Do you understand the difference between level matching and gain matching?

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post #14 of 249 Old 06-11-2009, 12:06 PM
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Quote:
Originally Posted by Rob Horvers View Post

My subs are on either side of the tv. Same distance from the listening position.

Then the only concern is room acoustic influences on the levels. If the room adds and subtracts similarly to each sub, then, in your situation, gain-matching and level-matching will yield similar results.

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post #15 of 249 Old 06-11-2009, 01:19 PM
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Originally Posted by craig john View Post

Then the only concern is room acoustic influences on the levels. If the room adds and subtracts similarly to each sub, then, in your situation, gain-matching and level-matching will yield similar results.

Yeah, in this circumstance, hell, I'd probably just crudely gain-match them (set their volume knobs identically) and calibrate them together. That'd be easiest.

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post #16 of 249 Old 06-11-2009, 02:05 PM
 
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Interesting thread.

Regards,
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post #17 of 249 Old 06-15-2009, 08:30 AM - Thread Starter
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Thanks to everyone for the info. It was lots of help for my set up!!!!

Thanks again!!!!!!!!!!!
Rob
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post #18 of 249 Old 06-18-2009, 12:10 PM
 
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Originally Posted by Craig John View Post

Level matching has the inherent problems of room acoustics and distance from the measuring position influencing the settings. In other words, if one sub is further away from the measurement location than the other, it's level will be set higher.

Yes...well :

Gain matching two subwoofers at different location points will yield dissimilar output levels so you'll still have to set the one higher than the other.....robbing dynamics and headroom.

The other option, is, of course, using the acoustics to benefit the situation, because after all, it's free output. Using identical levels means that

A) You'll achieve better coupling
B) Less distortion.....even though two subwoofers may be spaced at weird distances in relation to each other, the coupling achieved when properly level matched will bring about lower levels of harmonic distortion.

So even though you might think that whatever free output you're gaining is void due to the gain level differential, you're actual gaining more than you realize. More so then just putting both gain knobs to the same level.

B) Not everyone has their subwoofers positioned in awkward dissimilar locations, so in the event that two subwoofers are spaced a few meters apart, coupling will be easy to achieve and the benefits are threesome (hmm...)

1) Woofer modulation effects will be reduced
2) Once matched in phase and in level will result in a 5-6 dB output improvement across the frequency band that falls to within 1/4 wavelength

3) Those that don't understand 1/4 wavelength sound wave summation, please read my explanation on that......it's somewhere in the archives...look for it....

4)It's just cool.

So basically, you have two subs, and you want to gain match them. Set both in the center of the room.....set both 6" away from the cone......then turn the gain knob to the same level........

But comb-filtering can effect the levels...even to within 1 inch ! Nevermind that one, I misspoke.

Quote:


Then, it won't have as much headroom as the other sub.

Yes...well....

Again..

Setting identical gain levels will yield different output levels if both subwoofers are located in different locations so if you want to compensate then you'll adjust the gain...ONCE AGAIN...and ONCE AGAIN you'll end up with more distortion, reduced dynamics...

Quote:


When combined, the higher-set sub will peak before the lower-set sub. You'll either be overloading the higher-set sub or under-utilizing the lower-set sub.

Or......Or...you'll end up with dissimilar output levels if both subs are evenly gain matched and both subs are in different locations...which means :

A) Each sub will have different proportionate SPL levels per location even though both subs are achieving the same amount of work required, their net SPL will be dissimilar....

B) A disproportionate amount of SPL per sub is not always a good thing. Oh no. Because if you measure your frequency response with two subwoofers, one achieving 80 dB's and the other measuring 75 dB's due to dissimilar locations but equal workload (because that's the great thing about gain matching, you've got equal workload power between both subs right ?) but...well, the levels will be offfffff.

So let me poke and prode...and change the gain just a tad, to equalize the levels.. Ooops...now I've just added 35.3% harmonic distortion products to the table because I've compensated for the distance irregularities.

Well, whatever.

Regards,
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post #19 of 249 Old 06-18-2009, 12:34 PM
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goneten,

Quote:
Quote:


Originally Posted by Craigsub
Level matching has the inherent problems of room acoustics and distance from the measuring position influencing the settings. In other words, if one sub is further away from the measurement location than the other, it's level will be set higher.

You attributed the above quote from me, "craig john", to "craigsub". I am not "craigsub", and I don't wish to be confused with him, (as I'm sure he does not wish to be confused with me. ). Please edit your post above and attribute the quote to me instead of craigsub. Thank you.

Oh, and BTW, the colors sure are pretty.

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post #20 of 249 Old 06-18-2009, 12:35 PM
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Originally Posted by goneten View Post

Gain matching two subwoofers at different location points will yield dissimilar output levels so you'll still have to set the one higher than the other.....robbing dynamics and headroom.

C'mon goneten. You set them to the same exact gain. You DON'T set one higher than the other. That's the whole point. Gain-matched properly, their output WILL be identical. What will probably be different is their individual contributions to the perceived SPL at the sweet spot. So, if you measure their SPL individually, at the sweet spot, they may very likely measure differently. One will be louder than the other. But their output IS identical.

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post #21 of 249 Old 06-18-2009, 12:54 PM
 
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Quote:
Originally Posted by craig john View Post

You attributed the above quote from me, "craig john", to "craigsub". I am not "craigsub", and I don't wish to be confused with him, (as I'm sure he does not wish to be confused with me. ). Please edit your post above and attribute the quote to me instead of craigsub. Thank you.

Apologies. I just haven't posted here in a while and I thought I might stir a little. Just having a little fun, no harm intended.

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post #22 of 249 Old 06-18-2009, 12:59 PM
 
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Originally Posted by sivadselim View Post

C'mon goneten. You set them to the same exact gain. You DON'T set one higher than the other. That's the whole point.

Um, yes, that might be true if both subwoofers were in identical locations but since many people I'm sure will position their subwoofers in dissimilar locations that will present a bit of a challenge. The workload might be the same, which is great, but the levels will always differ. Also, the big secret is that people tend to listen within their rooms, not outside so the room's acoustics need to be taken into consideration, not excluded.

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Gain-matched properly, their output WILL be identical. What will probably be different is their individual contributions to the perceived SPL at the sweet spot.

Don't be silly, output will not be identical. Even if both subwoofers were positioned three meters apart, using identical gain structure, it still wouldn't be the same and you know it. Heck, one meter apart wouldn't yield exactly the same levels.

Why ? Because of comb-filtering.

Quote:


So, if you measure their SPL individually, at the sweet spot, they may very likely measure differently. One will be louder than the other. But their output IS identical.

In a perfect world, yes, output would be identical. Unfortunately sound waves tend to combine in the air at different distances at different phase angles at different amplitudes, at different frequencies; the funny thing is that all frequencies are affected here.

Not trying to be a dick here, I'm just offering a different perspective. One which is obviously not biased.

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post #23 of 249 Old 06-18-2009, 01:29 PM
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Quote:
Originally Posted by sivadselim View Post

C'mon goneten. You set them to the same exact gain. You DON'T set one higher than the other. That's the whole point.

Quote:
Originally Posted by goneten View Post

Um, yes, that might be true if both subwoofers were in identical locations but since many people I'm sure will position their subwoofers in dissimilar locations that will present a bit of a challenge. The workload might be the same, which is great, but the levels will always differ. Also, the big secret is that people tend to listen within their rooms, not outside so the room's acoustics need to be taken into consideration, not excluded.

Right. In almost all cases gain-matching is going to produce a situation where each sub contributes differently to the perceived level at the sweet spot. No one has ever presented it otherwise. In fact, that has been clearly pointed out. That's a given. The argument (if that's what it is) is that that shouldn't matter; that, when their combined level is properly calibrated, the fact that each sub is contributing a different amount to the perceived level will not be noticeable. Sure, there could definitely be circumstances where that disparity might be obvious, in which case one might have to rethink things.

Have you tried it yourself, btw? In what I can remember from your pictures, it should work very well in your case.


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Originally Posted by sivadselim View Post

Gain-matched properly, their output WILL be identical. What will probably be different is their individual contributions to the perceived SPL at the sweet spot.

Quote:
Originally Posted by goneten View Post

Don't be silly, output will not be identical. Even if both subwoofers were positioned three meters apart, using identical gain structure, it still wouldn't be the same and you know it. Heck, one meter apart wouldn't yield exactly the same levels.

Of course their output would be identical. Again, that is the whole point. You set each sub so that their output is absolutely identical. You are confusing their loudness with their output. If you adjust two subs to the same output level and put one in the closet, obviously it will not sound as loud as the other. But it still has the same exact output.



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Originally Posted by sivadselim View Post

In a perfect world, yes, output would be identical. Unfortunately sound waves tend to combine in the air at different distances at different phase angles at different amplitudes, at different frequencies; the funny thing is that all frequencies are affected here.

But you're not talking about output. The subs' output IS identical. What happens after it is produced is something altogether different. And irrelevant, too. If you don't like the terminology, then let's say that with gain-matching the amps have identical output. Is that OK?



I always thought that when this was discussed several months back that you might have a fundamental misunderstanding of the concept. And I am not being a dick, either.

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post #24 of 249 Old 06-18-2009, 01:41 PM
 
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Originally Posted by sivadselim View Post

Of course their output would be identical. Again, that is the whole point. You set each sub so that their output is absolutely identical. You are confusing their loudness with their output. If you adjust two subs to the same output level and put one in the closet, obviously it will not sound as loud as the other. But it still has the same exact output.

You misunderstand. Obviously the workload (ie energy output will be identical but overall SPL will not because of a multitude of reasons that I've obviously outlined and are easy to understand).

Some choose to ignore the ramifications of disproportionate SPL per sub per distance given that comb-filtering excitation will happen (will happen which tends to skew results and could present problems in the overall response). Some say that it's just irrelevant and others look the other way because they don't know what comb-filtering even means or worse, they shoot multiple smiley icons at you to overcompensate for their lack of understanding.

Look, I'm not here to rain on anyone's parade but a gain matched approach has it's downsides too, just trying to 'even the playing field a tad' as it were as I get the impression that 'gain matched' calibrations are the one and only approach to setting up more than one sub. Or perhaps I'm just paranoid.

Quote:


You are confusing their loudness with their output.

That very well may be so I'll at least give you that.

Quote:


Have you tried it yourself, btw? In what I can remember from your pictures, it should work very well in your case.

I have tried it. I.....*cough* preferred *cough* a different approach. I just notice the flaws in both approaches and prefer the one that gives me the least compromise, which, in my case, and many other cases, is not a gain matched approach.

FYI, not insinuating that my approach is better than yours, as that would imply that I'm heavily biased or something.....*hiccup*....

And I realize you're not being a dick.

Regards,
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post #25 of 249 Old 06-18-2009, 01:53 PM
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............but overall SPL will not because of a multitude of reasons that I've obviously outlined and are easy to understand).

Exactly. No one EVER said otherwise. But a "gain-matcher" would say that that is irrelevant. That is doesn't matter if one sub is 12' away, midway along along front wall, and the other sub is 4' away in the rear corner, AND adjusted to be producing the same amount of output.

I can't make an argument that gain-matching is THE way to setup multiple subs, and I didn't imply that in this thread. At all. Both level-matching and gain-matching can be presented in a way that "makes sense".

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post #26 of 249 Old 06-18-2009, 01:54 PM
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I had set my subs up with individual settings and then adjusted all for the same for final db output. Now I set the gain the same for each, then all at the same time. Final gain setting is easy for me as I use a Paradigm X-30 volume controller to contol the volume for all subs at the same time. So setting the gain identical for my dual MBM-12's and dual A7S-450's have noticed a big improvement for me in output with clarity and distortion.

Bill
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post #27 of 249 Old 06-18-2009, 02:05 PM
 
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Quote:
Originally Posted by sivadselim View Post

That is doesn't matter if one sub is 12' away, midway along along front wall, and the other sub is 4' away in the rear corner, AND adjusted to be producing the same amount of output.

Well, if two subwoofers are putting out equal energy at their respective locations but, because of physics and all that other stuff, the SPL levels differ by 5 dB's between the two (or worse), I tend to think that that might pose a problem for several reasons.

But I suppose to each their own.

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post #28 of 249 Old 06-18-2009, 02:30 PM
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Quote:
Originally Posted by goneten View Post

Well, if two subwoofers are putting out equal energy at their respective locations but, because of physics and all that other stuff, the SPL levels differ by 5 dB's between the two (or worse), I tend to think that that might pose a problem for several reasons.

But I suppose to each their own.

Regards,

Well, if two subwoofers are set to measure equal loudness at one listening position but, because of physics and all that other stuff, the gains differ by 5 dB's between the two (or worse), I tend to think that that might pose an entirely different set of problem for several reasons.

But I suppose to each their own.

Regards,

----------------------------------------------------------------

Obviously, the "ideal" solution would be to find placements of the subs that provide identical measured levels at all possible listening positions when both sub's gains are set identically. This addresses *both* concerns. However, this is not possible. They will only yield identical measurements at one position. At any other position(s), they will measure differently. Therefore, I will take equal gains, (i.e., equal power output), into the room "as a whole", and let the measurements at any one position within the room be whatever they may be.

Craig

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craig john is offline  
post #29 of 249 Old 06-18-2009, 03:00 PM
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Originally Posted by goneten View Post

..............I tend to think that that might pose a problem for several reasons.

Why? The two subs operating together are each going to be less localizable than either one operating on its own, right? If you have a sub in the rear that is not localizable, then adding another one in the front is not going to contribute to its localizability. If anything, it will help to reduce it.

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post #30 of 249 Old 06-18-2009, 03:23 PM
 
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Originally Posted by sivadselim View Post

Why? The two subs operating together are each going to be less localizable than either one operating on its own, right? If you have a sub in the rear that is not localizable, then adding another one in the front is not going to contribute to its localizability. If anything, it will help to reduce it.

Hmmm, who cares about 'localizability' ? (is that even a real word ? ...lol ) Let me ask you a question : If one sub is positioned 100 meters away from you and another is 20 meters away from you, do both subwoofers contribute the same amount of energy at your location ?

Thanks !

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