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subwoofer quantity versus room size (home theater)

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Anonymous
June 30, 2005 9:57:33 AM

Archived from groups: rec.audio.pro (More info?)

Regarding Home Theater, not live concert venue: are there any rules of
thumb for determining the appropriate number of subwoofers for a given
room size? Or is location more important than quantity?

I've read Sean Olive's white paper for Harmon, which seems to suggest a
case of diminishing returns for anything more than 4 subwoofers...or
maybe that's 4 subwoofer *locations* ? Eg., would you need more subs
for adequate SPL & coverage in a room that's 16' x 27' x 12' than you
would for a room that's 8' x 12' x 7.5', or is it just a matter of
turning up the subwoofer gain in the larger room? Thanks.
Anonymous
June 30, 2005 11:19:11 AM

Archived from groups: rec.audio.pro (More info?)

>Yes, placement is a big deal, and in a small room where there are almost
>always major standing wave problems it becomes an even bigger deal.
>--scott

Many believe that putting the sub in the corner is best. It's said that
way all the modes get excited rather than a few. Would you agree with
that in general?
Anonymous
June 30, 2005 11:31:51 AM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> For the most part, with a theatre install where there is no attempt at
> getting bass imaging, I think using any more than one subwoofer is asking
> for trouble because you run into interference issues. Yes, it's possible
> to do tricks like stacking subs to get some bass directionality and avoid
> leakage, but that's something that needs some careful engineering rather
> than just tossing speakers into a room.
>
> If you need more bass, get a subwoofer capable of producing more bass.
> If a single Servodrive can handle a 2,000-seat auditorium, there should be
> no need for multiple cabinets in a smaller room, right?


Oops, it was Todd Welti's paper, not Sean Olive's, that I was thinking
of. AES preprint #5602, also available here:

http://www.harman.com/wp/pdf/multsubs.pdf

He offers some well-reasoned indications that 2 or 4 subs far
outperform a single sub in terms of linear bass response & even
coverage over the seating area.
Related resources
Anonymous
June 30, 2005 1:13:14 PM

Archived from groups: rec.audio.pro (More info?)

Roscoe East <roscoeeast@yahoo.com> wrote:
>Regarding Home Theater, not live concert venue: are there any rules of
>thumb for determining the appropriate number of subwoofers for a given
>room size? Or is location more important than quantity?
>
>I've read Sean Olive's white paper for Harmon, which seems to suggest a
>case of diminishing returns for anything more than 4 subwoofers...or
>maybe that's 4 subwoofer *locations* ? Eg., would you need more subs
>for adequate SPL & coverage in a room that's 16' x 27' x 12' than you
>would for a room that's 8' x 12' x 7.5', or is it just a matter of
>turning up the subwoofer gain in the larger room? Thanks.

For the most part, with a theatre install where there is no attempt at
getting bass imaging, I think using any more than one subwoofer is asking
for trouble because you run into interference issues. Yes, it's possible
to do tricks like stacking subs to get some bass directionality and avoid
leakage, but that's something that needs some careful engineering rather
than just tossing speakers into a room.

If you need more bass, get a subwoofer capable of producing more bass.
If a single Servodrive can handle a 2,000-seat auditorium, there should be
no need for multiple cabinets in a smaller room, right?

Yes, placement is a big deal, and in a small room where there are almost
always major standing wave problems it becomes an even bigger deal.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 3:37:20 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
>
> And of course, JBL does want you to buy as many subwoofers as possible,
> so they aren't utterly impartial on the subject.
>



You would think. His conclusion seems to be that more than 4 is totally
unnecessary, and 2 is in most cases as good or better than 4,
especially for low frequency extension (or maybe it was linearity, I
forget).

Also, note the slide where he models what would happen if you installed
5000 subwoofers in a small room!
Anonymous
June 30, 2005 4:04:17 PM

Archived from groups: rec.audio.pro (More info?)

In article <1120141151.961143.84080@g14g2000cwa.googlegroups.com>,
<tymish@hotmail.com> wrote:
>>Yes, placement is a big deal, and in a small room where there are almost
>>always major standing wave problems it becomes an even bigger deal.
>
>Many believe that putting the sub in the corner is best. It's said that
>way all the modes get excited rather than a few. Would you agree with
>that in general?

No. It depends entirely on the room. Rooms are all different.

If you aren't going to spend the time to fix room problems, put the sub
at the listener's position, play a sweep tone, and walk around the room
listening. When you find a place near the floor where you can hear
as much of the sweep as possible, put the sub there. If you don't have
a bass sweep tone, a Jaco Pastorius record will work.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 5:02:02 PM

Archived from groups: rec.audio.pro (More info?)

Roscoe East <roscoeeast@yahoo.com> wrote:
>
>
>Oops, it was Todd Welti's paper, not Sean Olive's, that I was thinking
>of. AES preprint #5602, also available here:
>
>http://www.harman.com/wp/pdf/multsubs.pdf
>
>He offers some well-reasoned indications that 2 or 4 subs far
>outperform a single sub in terms of linear bass response & even
>coverage over the seating area.

He makes a good argument for a small room. The basic tenet here seems
to be that if you have a lot of serious room modes you're better off
exciting as many as possible rather than just one. That seems kind of
misguided if your goal is to get the flattest possible bass, but for
home theatre systems that usually isn't the goal at all.

On the other hand, the real-world tests that are cited don't seem to
involve particularly careful placement or setup. Although you could
argue this is typical of home theatre installs, it does seem a little
insufficient.

And of course, JBL does want you to buy as many subwoofers as possible,
so they aren't utterly impartial on the subject.

I hadn't seen this thing before. Thanks for pointing it out!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 30, 2005 7:43:00 PM

Archived from groups: rec.audio.pro (More info?)

In article <1120141151.961143.84080@g14g2000cwa.googlegroups.com> tymish@hotmail.com writes:

> Many believe that putting the sub in the corner is best. It's said that
> way all the modes get excited rather than a few. Would you agree with
> that in general?

I read of a recommended placement procedure that involved (if I have
this straight) putting the subwoofer in the prime listening position,
firing it up, then walking around the room to find the place where the
bass is loudest, and put the subwoofer there. This seems like a
perfect setup for maximizing standing waves, but if you want
boomandthump, that's probably just the right place. It might be just
at one frequency, but oh, what a great frequency!


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
July 1, 2005 4:43:53 PM

Archived from groups: rec.audio.pro (More info?)

Roscoe,

> He offers some well-reasoned indications that 2 or 4 subs far outperform a
single sub in terms of linear bass response & even coverage over the seating
area. <

The problem with that kind of thinking is it considers only raw LF response,
and ignores modal ringing and decay times. High-Q modal ringing is at least
as a big a contributor to flabby, muddy, "one note" bass as the skewed
response present in all small rooms. All the subs in the world will do
nothing to reduce ringing.

In my mid-sized (25 by 16 by 10) home theater I have one killer subwoofer in
the corner and 35 bass traps. I have yet to hear anyone else's home theater
that has bass as good as mine.

--Ethan
Anonymous
July 1, 2005 5:10:14 PM

Archived from groups: rec.audio.pro (More info?)

Ethan Winer <ethanw at ethanwiner dot com> wrote:
>The problem with that kind of thinking is it considers only raw LF response,
>and ignores modal ringing and decay times. High-Q modal ringing is at least
>as a big a contributor to flabby, muddy, "one note" bass as the skewed
>response present in all small rooms. All the subs in the world will do
>nothing to reduce ringing.

That's true, but again we are talking about theatre systems where precision
of bass is not a huge issue.

>In my mid-sized (25 by 16 by 10) home theater I have one killer subwoofer in
>the corner and 35 bass traps. I have yet to hear anyone else's home theater
>that has bass as good as mine.

I found that when I set a home theatre system up with very deeply extended
and accurate bass that everyone wanted to throw up when a splice ran
through the projector. Running optical track, the extended low end was
not as good a thing as I had thought.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 2, 2005 6:08:54 PM

Archived from groups: rec.audio.pro (More info?)

Scott,

> That's true, but again we are talking about theatre systems where
precision of bass is not a huge issue. <

We're still talking about a *home* theater, right? Why would "precision" of
the bass not matter? Flabby boomy bass is always a problem in my book. Also,
a lot of people are like me and have a single system for both 5.1 HT and
regular stereo.

> I found that when I set a home theatre system up with very deeply extended
and accurate bass that everyone wanted to throw up when a splice ran through
the projector. <

Who's home theater these days has an optical projector? :->)

--Ethan
Anonymous
July 3, 2005 2:05:09 AM

Archived from groups: rec.audio.pro (More info?)

Ethan Winer <ethanw at ethanwiner dot com> wrote:
>
>> That's true, but again we are talking about theatre systems where
>precision of bass is not a huge issue. <
>
>We're still talking about a *home* theater, right? Why would "precision" of
>the bass not matter? Flabby boomy bass is always a problem in my book. Also,
>a lot of people are like me and have a single system for both 5.1 HT and
>regular stereo.

Because most of the tracks out there have mostly wideband effects on the
LFE channel. The effects don't have enough of a sense of tone to begin
with.

It's not like you're trying to accurately reproduce the exact sound and
position of Jaco Pastorius' bass in a the room, with the complete
reproduction of the ambience that comes along with it.

You're just reproducing a thump track the vast majority of the time. When
there _is_ a real sense of tone in the LFE it's a nice change, though.

>> I found that when I set a home theatre system up with very deeply extended
>and accurate bass that everyone wanted to throw up when a splice ran through
>the projector. <
>
>Who's home theater these days has an optical projector? :->)

Mine does, although I have a dts decoder in the garage that I need to get
installed at some point. The projector needs some modification to put
the timecode reader on it and it's going to mean taking the top reel arm
off and taking the projector body off to the machine shop, I fear.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
July 3, 2005 10:46:52 AM

Archived from groups: rec.audio.pro (More info?)

If you're a FOB (friend of Bud -- Irving M. "Bud" Fried, founder of IMF and
promoter of transmission-line woofers), you know how insistent he was that
you need two woofers, not one.

I'm inclined to agree, for a number of reasons -- the preservation of LF
directional effects, smoother overall response for mono signal components,
etc.

I realize the LFE channel is for a single woofer. But if price isn't a
consideration, why not put subwoofers on your main channels, as well?
Anonymous
July 3, 2005 12:50:04 PM

Archived from groups: rec.audio.pro (More info?)

Scott,

> most of the tracks out there have mostly wideband effects on the LFE
channel. The effects don't have enough of a sense of tone to begin with.
It's not like you're trying to accurately reproduce the exact sound and
position of Jaco Pastorius' bass <

Understand that in most home theater setups, music goes through the
subwoofer too. The "standard" crossover frequency is 80 Hz, but many are set
to 100 Hz. So in most cases you *are* hearing some of Jaco's bass through
the sub.

--Ethan
Anonymous
July 3, 2005 5:23:11 PM

Archived from groups: rec.audio.pro (More info?)

Ethan Winer <ethanw at ethanwiner dot com> wrote:
>
>> most of the tracks out there have mostly wideband effects on the LFE
>channel. The effects don't have enough of a sense of tone to begin with.
>It's not like you're trying to accurately reproduce the exact sound and
>position of Jaco Pastorius' bass <
>
>Understand that in most home theater setups, music goes through the
>subwoofer too. The "standard" crossover frequency is 80 Hz, but many are set
>to 100 Hz. So in most cases you *are* hearing some of Jaco's bass through
>the sub.

Ahh! That's with the "bass management" setup, which throws crossovers on
the front three channels and directs some bass to the sub, in order to
compensate for front speakers without enough low end extension.

Even with the bass management on, the stuff that is in the low end on
most soundtracks is pretty artificial and lacks imaging, because it's
mixed to sound good on a lowest-common denominator theatre system.

Now, if you're talking about a system that you want to reproduce music
recordings and not just film soundtracks, that's a totally different animal
altogether. And a much more difficult and expensive one to do right.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!