Ronnie,

The stuffing the back chamber in upper bass horn and stuffing a sealed enclosure have totally different purposes. In the firs case we need to decrease volume of the chamber in the second to increase it. The polyurethane foam spray is not foam acoustically speaking but juts a filler of the back chamber space with wish the resonant frequency of the horn might be tuned. The foam that used in the sealed boxes is actual furniture foam, the swift airy material. They are available in different density. When I mentioned the “very light and has hair from one side” I revered to the cloth that I hanged atop on the sealant. When I referred to the Altec horns it was the multi-sell Altec horn that I have seen at your picture.

Rgs,
Romy the Cas