Are exotic speaker cabinet materials overrated?

@gdaddy1 interesting post re: wood layers and Glop. pray tell, what ratio of clear silicone to sand did you use? And how thick of a layer did you put on the inside?

@simao  I can't take all the credit. The idea comes from the Northcreek cook book.

To get the stuff to stick properly I coated the inside cabinet walls with contact cement first. Then pumped several tubes of silicon into a bucket and mixed in sand to what I felt was a good consistancy. Then, with gloves, spread by hand the entire interior. No need to smooth it. Just glop it in there. Let it be rather bumpy and irregular. Drys in a day and seals the cabinet as well as adding dampening to every square inch. Goes thick into the corners. Takes a little bit more effort but I believe it's superior to ANY stick on dampening pad.

Thickness is variable but I use about 1/4" thick in some places a little more. It's really up to you. Then goes in the normal foam or fiber fill stuffing.

The stuff stays soft and rubbery for decades and adds a nice amount of mass to the cabinet.

@yoyoyaya  You're right, basic concrete is not a good choice. However, there are additives that can be mixed into concrete that makes it an excellent material to use especially when creating special shapes. It also requires a mold. The complexity becomes far greater.

Polymer modifiers, Latex/Acrylic polymers

• Increase tensile strength
• Increase internal damping
• Improve adhesion between aggregate and cement

Pros for speakers:

• Reduces brittleness

• Adds loss factor (less ringing)

• Improves edge integrity around driver cutouts

MDF is not “cheap” — it is acoustically well-behaved.
Concrete is not “high-end” unless engineered to avoid its own strengths.

The only advantage concrete may have is for molding shapes. MDF remains a superior product if properly braced and dampened.

Adding substances to Board Materials with the intent to improve the board materials Damping Factor, is known about for a long time in circles where there is a importance on such matters being aired.

Modellers Putty from the Brand Newplast, measures with a Damping Factor that is 50% better than Plasticene.

Newplast added to Board such as MDF has created a DF of 0.3, which is very attractive, but intrinsic properties for Dissipation is not attractive when measured.  Dissipation of most board type materials coated with a material that improves the DF, does not produce a board type that match's a RIDWB intrinsic properties.

Control of resonance through Dissipation is an extremely attractive intrinsic property for a material. High Damper Factor alone does not win over, hence Plinths for TT's using such a design have been Superseded in use for many years, where Dissipation is also a highly valued area of the designs. This same practice is now very evident that it is extending into Structures used for Speakers. 

@gdaddy1 thanks for the details. you do this when you have 5 sides of the cabinet glued and b4 the crossover instal?

also my son and I recently put together a Parts Express C- Note and decided to cut our own 3/4 inch BB in lieu of the 1/2 inch mdf you can get if you order the cabinets.