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View Full Version : Shared Enclosure Volume Gain?



bball09124
01-17-2009, 12:55 AM
I was reading some stuff on the Soundpressure DD forums and some guy was talking about how if you use multiple subs in a common chamber you can calculate a 20% gain in air space. I've never heard this, is there any truth in it or is it some BS? Here's his exact quote.


"remember when do multible subs in common chamber you can caculate a 20% gain in precieved air space when they share a common chamber so if 1 sub uses 1cf 2 can be tuned the same in a 1.6 cf box and 4 can work in 3.0 so keep this in mind when doing multiable subs"

bball09124
01-17-2009, 04:18 AM
I also saw on the soundpressure forums Louisiana CRX saying the same thing. More info on this? Is it true?

bball09124
01-17-2009, 05:05 PM
ttt

THUMPPER
01-17-2009, 09:16 PM
when multiple woofers are mounted in the same cavity keeping them with in the
voice coil diameter away from each other you get what is called a coupling effect
this can give up to a 6db gain in out put

bball09124
01-17-2009, 11:39 PM
when multiple woofers are mounted in the same cavity keeping them with in the
voice coil diameter away from each other you get what is called a coupling effect
this can give up to a 6db gain in out put

I've heard this, but it is not what I was referring to. I'm talking about enclosure volume, not output.

bball09124
01-18-2009, 06:17 PM
ttt

bball09124
01-18-2009, 10:23 PM
ttt

scoob8000
01-19-2009, 12:18 PM
Any more input on this? I'm intrigued!

Thumper, When you say once vc diameter apart do you mean keeping the motors that close (ie mounting subs at an opposite angle) or from the edge of one basket to the other?

I did a little searching on this coupling effect, but mostly everything I see are complex pro audio designs using all kind of crazy mounting angles.

bball09124
01-19-2009, 09:16 PM
ttt

bball09124
01-21-2009, 03:41 AM
I think I may never get an answer on this.....

teggybwoy
01-21-2009, 06:27 AM
so tell me if im hearing right, if i put 2 subs in an enclosure sharing the same port/chamber its gonna be louder than 2 subs that are seperated? so this is one big box for 2 subs?

pjhabit
01-21-2009, 09:00 AM
I was reading some stuff on the Soundpressure DD forums and some guy was talking about how if you use multiple subs in a common chamber you can calculate a 20% gain in air space. I've never heard this, is there any truth in it or is it some BS? Here's his exact quote.


"remember when do multible subs in common chamber you can caculate a 20% gain in precieved air space when they share a common chamber so if 1 sub uses 1cf 2 can be tuned the same in a 1.6 cf box and 4 can work in 3.0 so keep this in mind when doing multiable subs" If that were true. Wouldn't tuning get thrown out the window as you added woofers to a ported application?

bball09124
01-21-2009, 04:54 PM
If that were true. Wouldn't tuning get thrown out the window as you added woofers to a ported application?

You would still tune the box same as you normally would, taking into account displacement of the port and speakers used.

bball09124
01-21-2009, 04:57 PM
so tell me if im hearing right, if i put 2 subs in an enclosure sharing the same port/chamber its gonna be louder than 2 subs that are seperated? so this is one big box for 2 subs?

No. What I am discussing is that if you run 2 subs in the same enclosure, you should shrink it 20% in order to see the same performance.

pjhabit
01-21-2009, 08:21 PM
You would still tune the box same as you normally would, taking into account displacement of the port and speakers used. I don't think you quite understood. When you add airspace the tuning frequency changes. Meaning you'd also need to modify the port to keep the same tuning ie, you can't drop the same 6" aero's in 4 ft^3 & 2 ft^3 & expect the same tuning frequency.
So the question I propose. Is the port immune to this "perceived" airspace? If so how do the subs get so lucky?

BrianChia
01-21-2009, 08:31 PM
I don't think this is true... you'll get more net airspace from the same gross volume but only because separate chambers take up more volume. I think the notion just stems from the fact that when many people upgrade from a single sub to 2 subs, for example, they don't usually want to build a box that is twice as large so they'll just make it a little smaller than double even though it changes the properties of the enclosure/system.

I could be wrong, but I've never seen any evidence of why multiple identical subs in a common chamber would require less airspace per driver.