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

Cascade V bloc..Thick purple paint..sucked into the mdf..seals the contents of the wall material from the energy robbing glue and saw dust that kills the dynamics. This product drys hard like concrete.. You could add a quart of micro bearing steel to increase the amount of base solid content. Dont use sand, kitty litter, rice, or lead..Tom

Ozzy 

The Cascade can be applied by a heavy brush or even trowel like device. I have used this product on several cabinets. I kept track of the volume installed by using a platic cup filled to volume. You want the same = amount in each box. Apply more to all joint seams and corners as this will further stiffen these areas. Drys to a concrete like substance and grainular in feel. The micro bearing fill added in the gallan pale will add more mass and will be even more dispersive to resonance. I prefer long hair sheeps wool as fill material. You could even add non ferrous rods installed near each internal corner but this may alter the cabinet cosmetics while improving the sound. Dont add any right angle shapes to the cabinet..More you can do with the driver and mounting...good luck. Tom

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

Ozzy,

1 gallon displaces 241 cubic inches. So a gallon of Cascade when cured should shrink down to the volume you require..you would need a gallon for each box..They would be well sealed and more rigid. Tom 

Ozzy

I take that back ..3 coats would be enough..30 coats would take weeks to cure. Though the volume would be right. Tom 

Ozzy

Seal the sawdust and glue with something...varnish the inside a couple of coats or so.Tom

Google what is trex made of. All the same crap mdf is made of except trex has the added incredient of shredded plastic and probably more ga -luue as a binder for this compost pile. Tom