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Old 11th July 2003, 03:10 PM   #1
jmiyake is offline jmiyake  United States
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Default Opinions on wall to wall subwoofer array

So in planning out my subwoofer array. Using the six 15" Dayton
Quatros in 4.8 cubic foot (closed) boxes across the front stage of
my 13'w x 20'l x 8'h listening room theater.

I have come across an interesting thing. I end up with a "Wall to
Wall subwoofer array."

So rather than radiate into open space, the woofers will couple
into a single low frequency line source. Since these reach wall to
wall, they would be a horizontal equvalent to the floor to ceiling
vertical line arrays, which behave like a virtually infinte line
source.

Thinking of this in low frequency terms. The 6 subwoofers
working in concert will will create a seamless pressure wave
towards the listener that is completely confined on three sides
(floor, left wall, right wall.) Think wave machine.

Another interesting fact:
The sd of the 15" Dayton quatro is about 127 square inches.
Times 6 that is about 5.3 square feet. The front of the room is 13'
wide by 8' tall, so that is 104 square feet. Therefore the sd
represents just over 5 percent of the area of the front wall.

Detail: six 15" Dayton Quatros (fs 21, vas 186.9 ltr, qts .41)
placed in a separate boxes with a qtc of .64, each with an
enclosure size of 4.8 cubic feet, across the front of the room. The
Quatros are a great value and model great in this regard. They
actually do better than the Tempest in resonable sized sealed
enclosures.

What opinions do you have on this approach?

See below the illustration of the front of the theater with the
subwoofer configuration. Click the url link for a view of the actual
room.

James
Click the image to open in full size.
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Old 11th July 2003, 03:33 PM   #2
7V is offline 7V  United Kingdom
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Provided the subs only handle the deep bass I can see no reason why it should make any difference whether you have the sub array horizontal or vertical. It should work fine in that respect.

The only question mark would be about how the subs react with the room. The fact that you're committing so much of your room to the system is obviously to be commended (although only by us and we should be locked away). Still, I wouldn't attempt to calculate the likely excitations of room nodes in this set up. You have to suck it and see. It will probably be fine (you'll have a volume control for the subs, won't you?) but some flexibility with sub placement may be a good thing if it all goes pear shaped.

Steve
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Old 15th July 2003, 02:57 AM   #3
jmiyake is offline jmiyake  United States
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7V said , in part:
The only question mark would be about how the subs react with the room. The fact that you're committing so much of your room to the system is obviously to be commended (although only by us and we should be locked away).
----------------------------------------
As long as it is my listening room... no problem.
----------------------------------------

7V said , in part:
Still, I wouldn't attempt to calculate the likely excitations of room nodes in this set up. You have to suck it and see. It will probably be fine (you'll have a volume control for the subs, won't you?) but some flexibility with sub placement may be a good thing if it all goes pear shaped.
----------------------------------------
That is always the issue with subwoofers, however you are in far better shape with a 15inch by 13 foot subwoofer than a small one in a corner somewhere.

James
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Old 15th July 2003, 05:07 AM   #4
Ken L is offline Ken L  United States
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Default Generally speaking a line array disperses at 90 degree perpendicular

I think you would be happier with the sound if they were in two vertical arrays - they would then disperse in a horizontal plane -

It's late and I'm not sure I'm wording this as well as I should.

But a vertical line arrray disperses sound in a horizontal plane.

A horizontal line array disperses sound in a vertical plane.

Given that your room is 13 wide versus 8 hi - I would think you would have better dispersion characteristics with a verical array on each side.

However, I really don't know what effect frequency extremes would have on this.

If you construct them so that they can be stacked three per side or lined up all six in front, you can try them both ways.

My guess, is that you're going to like them a lot more if they're stacked on the sides.

later

Ken L
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Old 15th July 2003, 05:14 AM   #5
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If you're going for a solid wave of sound comng at you (a VERY respectable goal, to be sure!!!) you might try using smaller drivers and T-lines, such that the drivers and the ends of the lines face the listener, and everything is mounted as close together as possible, to get as close to "solid wave of sound" as possible. Also consider using full-range drivers with lots of EQ. Just think of it--you'd be able to be anywhere within 3' of the sweet spot, and be in the sweet spot. :-)
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Old 15th July 2003, 05:47 AM   #6
jmiyake is offline jmiyake  United States
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Default Some interesting points Ken L.

Ken L. Said in part:
But a vertical line arrray disperses sound in a horizontal plane. A horizontal line array disperses sound in a vertical plane.
------------------------------------

This is a good point, and I am approaching it in an rather unconventional way I suppose. Here is the rational that I was using. If you create a stereo pair of subwoofers, and place the about 10 feet apart, you will get cancellation and boost - interference patterns.

This may be avoided by using a multi- driver horizontal sub array.
---------------------------------------

Ken L. Said in part:
Given that your room is 13 wide versus 8 hi - I would think you would have better dispersion characteristics with a verical array on each side.
--------------------------------------
Since the woofers are wall to wall, additional horizontal dispersion is not needed.
---------------------------------------

Ken L. Said in part:
If you construct them so that they can be stacked three per side or lined up all six in front, you can try them both ways.
---------------------------------------

This is a good idea. I will likely do this.
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Old 15th July 2003, 05:58 AM   #7
jmiyake is offline jmiyake  United States
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Default Wave of sound

Nappylady said, in part
you might try using smaller drivers and T-lines, such that the drivers and the ends of the lines face the listener, and everything is mounted as close together as possible, to get as close to "solid wave of sound" as possible. Also consider using full-range drivers with lots of EQ. Just think of it--you'd be able to be anywhere within 3' of the sweet spot, and be in the sweet spot. :-)
-------------------------------
I think I need deep speakers, at least 12", but I am likely to go with 15". A single 15" should have an area of about 2.5 12" speakers. So 6 15" speakers would need 15 12" woofers to equal the sd.

My mains:

Click the image to open in full size.

James
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Old 15th July 2003, 06:02 AM   #8
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Default Re: Some interesting points Ken L.

Quote:
But a vertical line arrray disperses sound in a horizontal plane. A horizontal line array disperses sound in a vertical plane.
At the frequencies of interest this should not be an issue at all. What will be an issue is getting the thing from being just a big lump ... your Qt is kinda high.

dave
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Old 15th July 2003, 06:21 AM   #9
jmiyake is offline jmiyake  United States
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Default Qt

Hi Planet10,
Love your website!

I am trying to understand your point more completely. Could you explain it a bit, in particular:

What do you see as the exact issue regarding the Qt?

What do you feel the goal should be in this area?

Thanks,

James
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Old 15th July 2003, 08:01 AM   #10
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Default Re: Qt

Quote:
Originally posted by jmiyake
What do you see as the exact issue regarding the Qt?

What do you feel the goal should be in this area?
If you design for flat anechoic response (ie in your modeling program) and then you put them into a room with gain of 3-6 dB/octave below a certain point you end up with a really lump at the bottom.

I like a design that starts rolling off fairly high (~100 hz) and slopes gently down from there (ie Qt=0.5). Often this isn't achievable with a reasonable size box in which case i go aperiodic (which i prefer anyway).

dave
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