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Subwoofer / Low Frequency Optimization

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amirm

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watchnerd

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Assuming your room is a square, this is what the performance is for various number and locations of subs:

View attachment 23788

#3 is one sub in the middle. #4 is one sub in each front corner. I am surprised that their performance is so close to each other. Usually placing them in the corner gives you higher gain so two in the corner should have had more LF output.

If your room is not square/rectangular, none of these recommendations work. You would ideally have a smart audio-eq that can optimize all of them in which case you can put them where it is convenient.

Can I ask where this graph came from?
 
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Hypothetically:

Would 2 x 10" almost always be better than 1 x 12-15"?
From what point of view? For evenness of response, two is better than one.
 

Soniclife

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Hypothetically:

Would 2 x 10" almost always be better than 1 x 12-15"?
Simplistically, with everything else equal, 2 * 10 is more displacement than one 12, but less than one 15, so for max low and loud the 15" wins. If you were asking about movies you would be told to buy the 15.
 

DonH56

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Two 10" drivers have only about 89% of the cone area as a single 15" but there are a lot of other parameters... Just like comparing two subs that have different amplifier power ratings; not enough to really say which is better without some test results.

Yes, I know you said "simplistically"... :) In a contrary mood today, long week.

Still, I'd usually go for two good subs with lower output over a single larger one due to the uneven bass response in most rooms. Even better are two good subs, so sometimes the best advice is to buy one good one now and start saving for the next.
 

watchnerd

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Simplistically, with everything else equal, 2 * 10 is more displacement than one 12, but less than one 15, so for max low and loud the 15" wins. If you were asking about movies you would be told to buy the 15.

Yeah, I should clarify:

2 channel, music only
 

watchnerd

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Two 10" drivers have only about 89% of the cone area as a single 15" but there are a lot of other parameters... Just like comparing two subs that have different amplifier power ratings; not enough to really say which is better without some test results.

Yes, I know you said "simplistically"... :) In a contrary mood today, long week.

Still, I'd usually go for two good subs with lower output over a single larger one due to the uneven bass response in most rooms. Even better are two good subs, so sometimes the best advice is to buy one good one now and start saving for the next.

Luckily, or unfortunately, depending on your POV, I have the luxury / curse of optimizing for concealment as opposed to cost.

Basically, I have much more freedom of movement on cost than something big the wife will frown at, aesthetically.
 

RayDunzl

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Put a plant on it.

"Honey, the new plant stands are here..."
 

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watchnerd

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Here is a question for the academy:

Ceiling in my living room slopes, from about 8' up to about 14'.

Is that good, bad, or indifferent for bass production?
 

watchnerd

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Earl Geddes designed his speakers to be used with multiple subs.
Here are a couple of his papers that touch on LF behavior of small rooms.

http://www.gedlee.com/Papers/multiple subs.pdf
http://www.gedlee.com/Papers/Philosophy.pdf

Generally her recommends 1 sub in a corner, preferable in a front corner near the main speakers and the other 2 in positions to affet the room modes differently, even elevating to ear level.

Okay, there are some things he says that seems to contradict the Harman papers. Example:

"1)If there are corners, then one sub should probably go in a corner. Corners have the unique characteristic of see all of the modes. But using two corners is not an effective use of two subs because the symmetrical situation makes these two sources less statistically independent. A less symmetrical location for the second sub would be better.

2) One of the subs should be relatively close to the mains, but not too close. Ideal here might be to locate the first sub close to the mains, but back in a corner, if in fact the mains are pulled out slightly from the wall behind them, as they should be.

3) The rest of the subs locations become far less important if the first two points above are adhered to"

This seems quite different from the Harman stuff, which, with 2 subs, seems to recommend the 2 front corners.
 

kevinh

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This seems quite different from the Harman stuff, which, with 2 subs, seems to recommend the 2 front corners.


Here is a 1 hr presentation where he notes disagreements with Toole and the reasons for his approach. IMO Earl is one of the better speaker designers, however he has retired from speakerbuilding.



BTW Earl went to the MINIDSP for eq and crossovers of his stuff a few years ago this presentation os 6 years old now.
 
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kevinh

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Here is a question for the academy:

Ceiling in my living room slopes, from about 8' up to about 14'.

Is that good, bad, or indifferent for bass production?


Doesn't make a lot of difference.
 

Olli

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So that's pretty different views on subs placement discussed in this thread:

1) Harmann/Welti: Symmetric Sub placement is key (https://pdfs.semanticscholar.org/00da/51387c572cfd27c0256cb15e44e976a1a72e.pdf)
2) Geddes: Asymetrical Sub Placement is key (http://www.gedlee.com/Papers/multiple subs.pdf)

Is there any statistical evidence/furthere research on these 2 views?

I found this Celestinos/Nielsen paper that deals with some variation of the C.A.B.S approach (among them shifting into slightly asymetrical set-ups), but their basic finding is still that symetrical sub placement is best: http://webistem.com/acoustics2008/acoustics2008/cd1/data/articles/000837.pdf
 
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