Duntech Felt

Felt used for anti-diffraction purposes in loudspeakers is most commonly F26 or F13 grades. Acoustic performance of the two is very similar, with F13 being a higher grade and more attractive.

I haven't seen a Duntech in many years, but from memory I would guess the material to be F26 (or equivalent).

As previously mentioned, McMaster-Carr is an excellent source. This link goes direct to the F26 page:

McMaster-Carr
 
Felt used for anti-diffraction purposes on speaker baffles is most often F13 or F26 grades. Acoustical performance is almost identical (in this particular application), F13 is a higher grade with better appearance, so is often chosen when the felt surface will be readily visible.

I have not seen a Duntech loudspeaker in many years, but based on memory i would guess the material to be f26.

As mentioned above, McMaster-Carr is an excellent supply source for felt. (You can even get it adhesive backed to make installation easier. :)