@cskippy,
Wonder if the headphone community modders might like to experiment with an extension of the Paper Towel mod.
From the mods on other types of hp's we see history of 2 ply & 1 ply toilet paper and paper towels, coffee filters, surgical mask plies, 3M breathable paper, ultra- thin sponge, porous thin foam types, chemistry filter paper discs of various grades etc, of varying material & different brands. These found use either behind (like M1060 PT mod) or in front of the driver (other hp's), often to flatten or eliminate treble peaks, and also affect other parts of the frequency response range and resulting sound tweaks.
Some modders went looking for a baseline standard, so last year it led to the SAATI Acoustex filters, described on InnerFidelity, in a preliminary intro article, and then the full testing/measurement article.
I think sheets of SAATI are expensive, but maybe also very large ( ? ), for many of pairs headphones use. The full article noted of the 9 grades of this standardized paper, 6 or 7 grades effectively worked in hp's to varying degrees.
So, just to point out, like in standardized pore sizes of chemistry filter paper/discs (those are cheap price), the SAATI Acoustex filters papers ratings are here -
Paper #, ... Air Flow Resistance in MKS rayls , ... Pore Size
-B003...3...285
-B006...6...105
-B010...10...120
-B025...25...53
-B047...47...38
-B090...90...41
-B115...115...21
-B160...160...21
-B260...260...18
Even if the sheets get pricey, if a few modders jump in together & share different sheets, a whole bunch of hp's can be tested for optimum grade sheet per hp type, and cost of sheets is distributed. Measurements & listening hone in on which grade paper fairs best. Just an idea as the standardization is really cool.