open cell foam for entec subwoofer grill

I would construct a sturdy frame the same size and shape as your failing foam grill, then cover it with acoustically transparent black cloth.

The original foam will probably be difficult to find and probably offers no advantage musically.

The Entec grill material is completely transparent (and ugly).
I believe Wilson Audio used the same material on the Watt 3/Puppy 2.
Contact Crosby Audio Works for replacement grills.

Brian@Hello.lt