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.