Have you seen any of the discussions on other boards cautioning about using UltraTouch in speaker cabinets with critical internal dimensions? The discussions have been so few so far that I can't quickly find them for reference, but in short it seems that, unlike FiberFill, rayon, or fiberglass materials, UltraTouch is not air-permeable. And the problem with this, it seems, is that rather than offering the apparent expansion of cabinet volume realized with permeable materials (up to 10% if I remember correctly), UltraTouch actually occupies space, and makes the cabinet volume smaller.
Not only that, it has no loft, so no absorption and the hard, dense nature reflects sound.
Those attempting to use UltraTouch in a Bozak—infinite baffle cabinet, so absorption is crucial—have experienced a severe loss of bass and poor sound from internal reflections. Removing it and going back to cotton batting restored the bass.
Biggles had a nightmare experience with his Bozak, and he's not the only one.
Of course, this supposition does not ignore the superior sound absorption characteristics of UltraTouch, and in situations where absorption is desired, UT is the way to go.
Those characteristics are a fabrication based upon wishful thinking (recycled denim has a nice appeal to it) that is endlessly recirculated without analysis. Here are the facts. UltraTouch has no absorption. It should
NEVER be used in a loudspeaker. Insulation installers don't like it, either. I've seen not one chart showing any benefit to using it, but I have heard numerous anecdotal stories about poor sound.
Cotton batting is the superior absorber, which is why it is used in Bozaks. Everyone who has ripped out the UltraTouch and gone back to the original stuffing has undone the sonic damage.
But in most cases, when it comes to loudspeaker construction, the purpose of insulation (stuffing, etc.) is not to absorb sound waves (wherein the energy is lost), but to break up their movement within a cabinet, and especially as a deterrent to standing waves.
Not exactly. Here's a summary.
The stuffing acts as friction to the backwave. Think of trying to blow through filter material. The tighter the material, the greater the resistance encountered. Most loudspeakers have two resonance peaks: driver and cabinet. The cabinet cannot be neglected. Damping certain portions of the backwave can reduce cabinet resonance which can suck neighboring frequencies into a peak. Hence the "one note" bass phenomenon.
In an acoustic suspension, the backwave compresses air in the cabinet and serves as a restoring force to return the cone to its rest position. The cone is quite floppy. Villchur hand-made his prototype surround to get that floppy behavior. The stuffing in AS disproportionately absorbs the higher frequencies, while leaving the lower ones unmolested, which helps to damp cabinet resonance, while not overly affecting the restoring force and not reducing the bass response.
In an infinite baffle (sealed cabinet) like the Bozak the goal is to absorb the entirety of the backwave, damping out the energy so it cannot put pressure on the cone. This also has the effect of reducing cabinet resonance, since the energy to excite the cabinet is no longer present. The cotton batting not only lines the sides, but forms a curtain dual-chambering the box, much like a muffler, so the backwave passes around the curtain and is then lost.
In a ported or T/L cabinet the goal is absorption as well as to slow certain waves through the pipe. This is why the pipe is stuffed with material like lambswool to add friction.
Jordan's ARU is an aperiodic port which adds acoustic friction.