There are few methods for dampening the walls of loudspeaker enclosures.  All of these methods of adding mass to the cabinet wall are viable.  However, I believe with proper box construction they are unnecessary.  I have not used an accelerometer to test this.  I have only done some comparative testing using my wife’s ears.

One method suggested in Vance’s book is loading roofing cement with sand in a 50/50 ratio and placing a layer on the interior of cabinet walls.  I did this to one of the walls in my cabinets.  Not only did it smell profusely for many weeks, it still smelled slightly after about 1 year.  If I put my nose up to the porthole on a warm day, that stuff still smells!  If you are going insist on using roofing cement and sand to fix a resonant cabinet, use the latex variety.  It smells less.

I compared the sand/roofing cement treated cabinet with a non-treated cabinet, and found no audible difference.

This is likely because the largest spread I have between the vertical braces connecting the top and side walls in my cabinets is about 3 1/2″.  This means that there is some support structure every 3 1/2″.  The side walls are built from 3/4″ MDF, and the vertical braces are also 3/4″ + MDF.  My cabinets do very well with the “rap test”.  They feel very solid, and produces very tight bass.  With my cabinets, dampening cabinet vibrations is overkill, and it smells.

Some folks disagree with me on the issue of dampening materials to the inside of a cabinet.  Dennis Murphy did a test with Black Hole 5, and did find a slight increase in clarity in the lower bass region.  But this was in a cabinet that was relatively un-braced.  There were nice large open panels with no support.  This translates to panels that are weak/floppy and create that nice “warm” bass sound.   Dennis remarked that the Black Hole 5 effectively dampened some of the cabinet vibrations, and cleaned up the sound.  I would rather spend the $5 on some good braces during the construction process than @$100 on Black Hole 5 without them.  

I am not saying that Black Hole 5 has no other purpose, but IMO your $100 would be wiser spent elsewhere – perhaps on Goertz wire.

Again, if you do insist on using the roofing cement/sand brew – get the latex based variety.  You will pay slightly more for this, but it doesn’t smell.