Adding Mass to Subwoofer Cabinet

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Ephai

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Joined 2012
I'm currently in the process of building a subwoofer cabinet - a Dayton RS 10" in a 1 cu. ft. sealed cabinet. I made the drawings by hand so can't post them, but for the construction I'm using 3/4" birch ply and extensive bracing (most of the unbraced panels are around 6 sq. in.).

While cutting the materials I noticed that the box may end up being rather light, is this something I should be concerned about? Has anyone added sand filled chambers to their subs in order to increase the cabinet mass and help to minimize vibrations? I'm thinking about adding a sand filled chamber on the side of the box opposite of the sub, just to add a little wieght and help to keep the box from moving.

Thanks for any replies.
 
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Ephai

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Joined 2012
Nope, no Bitumen pads being used. I've been going with the Planet 10 / Linkwitz Labs school of thought: use a stiff material and add enough bracing to raise the panel resonance out of the pass band of the speaker (or into a region where there is less energy available to excite the panel resonances). Adding Bitumen pads would add mass to the panels, and bring the panel resonance frequency down - the opposite of where I want to go.

Which leads me into another point I've been thinking about: Would adding a sand filled chamber have the same effect? It's not adding mass to the panels per se, but it is adding mass to the enclosure, so wouldn't this bring the resonant frequency of the enclosure down as well?
 
Rullknufs

Rullknufs

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Joined 2010
I have a feeling that the sand will lower the resonant frequency, but I don't know for sure.

Adding mass to the panels lowers the resonance. You want to add mass to the cabinet which should mean that you must add mass to at least some panels which in turn would lower resonance frequency.
 
Michael Bean

Michael Bean

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Joined 2004
There will be no panel resonances in a subwoofer box worth worrying about. the wavelengths involved are far larger than even the biggest panel likely to be found in a subwoofer box. Far more important in my opinion, is the strenghth of the box, especially for a sealed subwoofer. The intense vibrations coupled with the huge amount of internal pressure can tear a subwoofer box apart if it's not built strong enough.

Mike
 
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Ephai

Member
Joined 2012
richie00boy said:
If it is a downfiring design you won't have any real problems with it moving.

Adding a sand filled chamber is not the same thing as adding mass to a panel. The sand filled chamber would just weigh the sub down, not alter any panel resonances.
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Thanks, I had it drawn up as a side firing sub. I think a sand filled chamber might be the way I will go then.

There will be no panel resonances in a subwoofer box worth worrying about. the wavelengths involved are far larger than even the biggest panel likely to be found in a subwoofer box. Far more important in my opinion, is the strenghth of the box, especially for a sealed subwoofer. The intense vibrations coupled with the huge amount of internal pressure can tear a subwoofer box apart if it's not built strong enough.

Mike
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Thanks Mike, I'll keep that in mind. I think the bracing and joinery I have planned will make for a structurally sound box. Plenty of braces/reinforcement, but even with all the material it seems like it might end up being a bit light, which is why I thought adding some mass might be a good idea.
 
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chrisb

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Joined 2002
With the current popularity of synthetic stone ( Quartz, etc) counterops, you might well be able to find offcuts available at local fabricators that could yield a suitable sized piece. I've been able to reclaim sufficient for several base slabs at zero cost from a local shop, but unless you have appropriate wet saw and polishing tools, the cutting and finishing the exposed edges could cost set you back a few $ - (try the ole "Friday afternoon "24 pack" incentive)

A couple of dabs of silicone or even high strength double edge carpet tape, and that slab ain't going nowheres.
 
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Ephai

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Joined 2012
Rullknufs said:
I've added three garden stone slabs at 14kg/each + my two amplifiers on top of my subwoofers. They aren't going anywhere :D
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I'd say. :D I was thinking like a 0.4 cubic foot chamber for about 40 lbs. (~18kg) of extra weight would suffice.

Build a form to fit and pour a 2-3" thick concrete slab to sit directly on top of the cabinet, but detachable. Paint the slab to match.
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Unfortunately I have a bit of a height restriction since the sub will be placed behind a reclining couch, but have an unlimited amount of space available for the depth. Hence the thought to put a sand filled chamber on the end of the cabinet opposite the subwoofer.

I hope it will work. :D It might make for a slightly awkward looking enclosure though (long and skinny: 24" x 12.5" x 12.5").
 
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puppet

Member
Joined 2011
chrisb said:
With the current popularity of synthetic stone ( Quartz, etc) counterops, you might well be able to find offcuts available at local fabricators that could yield a suitable sized piece. I've been able to reclaim sufficient for several base slabs at zero cost from a local shop, but unless you have appropriate wet saw and polishing tools, the cutting and finishing the exposed edges could cost set you back a few $ - (try the ole "Friday afternoon "24 pack" incentive)

A couple of dabs of silicone or even high strength double edge carpet tape, and that slab ain't going nowheres.
Click to expand...
In contrast to that build a matching wooden frame and inset the stone. .. if on top, build the box sides/top edges to suit. Now a guy just has to worry about the edges of the stone .. 1/8" chamfer or so.
 
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