So I finally got around to building a small test box. Similar to what it would be in, if I ended up using it in my project. The AST series from Aurum Cantus are dipoles, so a box for me was necessary.
Frequency response in test box, roughly 2.5V/1meter, in-room, with a 450Hz 2nd order HPF.
Frequency Response with Parts Express Acousta-stuf polyfill. Was identical with Mundorf Angel Hair, for all practical purposes.
What I was interested in was if the box stuffing affected distortion performance. Here is what I found.
Felt pad in-place for one set of tests, then removed for the others.
20g Acousta-stuf vs 3.9g Mundorf Angel Hair. Angel hair looks like sticky icky itchy fiberglass. WRONG! It is the softest thing I've ever held, softer than a newborn baby! I just want to hold it up against my face, lol.
That bundle of Angel Hair was the same size as the Acoust-stuff, but it just keeps expanding and expanding to fill up all available space. I had to put it in the test box and seal it up because I thought it was going to engulf my whole room, lol.
Obviously not a huge difference, but I'll take it (and everything else) with Angel Hair!
Distortion seems a bit high compared to manufacturer specs, but this was with a class-D amp, where as previously (prior to 8 months) I was using a class A/B amp that I undoubtedly need to return to using.