Best way to decrease the internal volume of a sealed speaker?

toddverrone,

Will the expandable foam absorb sound like the other products such as wool, fiberglass etc.? If so I think that would be the opposite of reducing the internal box volume. That's why I thought of sealing the exposed area with the Flex Seal spray.
Cutting the pieces of mdf wood and installing them as you suggested might work. I guess I worry that the glued wood may come loose and then rattle or move around.

theaudiotweak,

I will look into the Casacde V sounds interesting.

Geoffkait,

I agree and I was intending on limiting the amount of fill used.

pbnaudio,

Will the Styrofoam blocks absorb? Should I coat them with something?

ozzy

Ozzy

I agree with Geoff limit the amount of damping material. The Cascade reduces the drag of the glue and saw dust and increases the dispersive area of its solids. MDF which is probably in use here..sounds like a dark muffled congested cough..the Cascade seals out that character. The sheeps wool acts like a comb filter rather than damper of character. Tom

If you use Flex Seal, it may have petroleum distillates in it, as the more expensive rubber sprays at Wally World (10-12 bucks) will have. However, the cheaper stuff (2-4 bucks) doesn't have pd's. Pd's are rather corrosive to electronic circuitry.

Automotive undercoating spray (same thing as Flex Seal really and is what you'd be looking for at Walmart or your hardware store) will dry overnight to roughly half the thickness at which it was applied. However, after several days, the depth of the coating will continue to shrink and then be no thicker really than a coat of paint, so it might require simply too many coats and too much drying time to be of practical use as a way to reduce volume on its own...but good as a sealant, though. 

Flex Seal could possibly be thicker, but I have no idea if it contains distillates.

Styrofoam, I would think, would not absorb too much, although something that low mass may be excited to resonate a bit maybe, coating it with the rubber spray may help somewhat. 

Any object left inside the cabinet must Not be hollow, fill it with sand, if nothing else!

+1 Audiotweak

Best cutting edge advise so far

The last thing you want is flexible materials. They will increase your internal volume.

If you want to permanently increase it, and don't have room for the usual brick / wood block ideas I suggest a 2-part mixable epoxy that dries hard.

You may also experiment less permanently with buck shot. Placed in bags it's relatively easy to arrange and move.