My madisound kit came with their dampening foam sheets for the cabinet sidewalls. The stuff looks like 1" thick yellow furniture foam.
I was expecting some sort of denser black or grey acoustic foam.
What are you guys using for full range speakers. The speaker designer mentioned he used a thin rubberized material on the original design.
I'd rather get something decent if it's reasonable and use the madisound "furniture" foam for something else with less expensive drivers.
There is little difference between different damping materials. Use what came with the kit.