Do I really need a stiff enclosure???

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Hi All, I've been looking at all my option for two sub drivers I have. One option was to use two cabs I have already and just convert them. The other option is to use a small storage space that is built into the wall already. It measures approx. 4' x 6' x 3' and the opening is 24" x 24". I was thinking of framing in a very stiff baffle board into the opening and mounting the two subs there.

I already have two subs in the room so this one would be for smoothing.

Here is my question. The enclosure walls are 2x4 and sheet-rock construction but most of it is not in the room so does it matter that it is flimsy by sub cab standards?
 
If this is only for smoothing then technically two independent subs, in different locations would give you better results. The subs only need to extend as low as the room has room modes too, so absolute extension isn't required. If you are mainly doing this to get more 20Hz output though, and smoothing is just a nice benefit, then by all means go with the monster in the wall.

Perhaps the wall sub would end up being the main sub, with your other two being used as fillers.
 
Thanks all. I have two very good subs up in the front corners behind the speakers. I just happen to have these two sub drivers, an amp, 30 foot ICs and a cavity in the wall. I don't do HT and I don't have much pipe organ so going down really really low is not an issue. I just like to have good solid bass down to 30hz or so and want to be able to sit anywhere in the room and have the same output.

SO why do people brace the crap out of cabs???? is it because they are in the room and will cause cancellation if they can resonate?
 
Thanks all. I have two very good subs up in the front corners behind the speakers. I just happen to have these two sub drivers, an amp, 30 foot ICs and a cavity in the wall. I don't do HT and I don't have much pipe organ so going down really really low is not an issue. I just like to have good solid bass down to 30hz or so and want to be able to sit anywhere in the room and have the same output.

SO why do people brace the crap out of cabs???? is it because they are in the room and will cause cancellation if they can resonate?

An unbraced floppy cabinet will reduce output. And may make unwanted noises etc.

For an IB setup where you aren't really going for maximum SPL you should be fine. Like Cal said, if you're really concerned with more output from these you should consider building an enclosure into the space.
 
I always figure that the flex you have in a cabinet the more energy it is absorbing so long as you don't have to listen to the flexing walls you should be fine. In the case of a free standing cabinet I think you want cabinet wall flex to held to a minimum and pushed up as high as you can with bracing so that it will be easier to damp. In your case you want the door to be rigid and well damped. Have you considered placing the driver into the floor in front of the door, place a grill over the woofer and make a short plenum into the closet area with another grill. That way you only need stiffen and damp the door and make sure it seals well. A much neater arrangement if you can make it work, no woofers hanging off of doors. just a thought. Best regards Moray James
 
Absorbing in acoustics means transferring energy from sound waves into mechanical friction. Damping is the mechanical reduction in amplitude of the vibrating panels of an enclosure. Stiffness is the mechanical damping of an enclosure. When the enclosure is not stiff enough it will have its effect on the driver response. Even if the enclosure is not present in the room (flush mounted) the low stiffness of the enclosure will have its effect on definition and impulse response.

Strength and stiffness are often mixed but they are not the same. An enclosure only needs to be strong enough to resist the pressure changes inside the enclosure. Since the pressure is equally distributed over the entire surface of the panels that isn’t a big problem. Sheetrock isn’t strong but has good damping characteristics (material properties) even when used in a structure (loudspeaker enclosure). Therefore you can make an enclosure of something weak as sheetrock as long you make it rigid/stiff enough by using enough support braces. Just make sure you use several glued layers of sheetrock to give it enough strength. I suggest to paint the outside of the sheetrock enclosure to prevent it from absorbing moisture.
 
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