Breaking news!!!
As I was going through my stock of materials to use to tune my new TH-900MK2, I came across these foam disks, still in the original packaging:
Thin & Thick Inside Foam Disk Ear Pads For HD545 HD565 HD600 HD650 Headphones
Thin & Thick Inside Foam Disk Ear Pads For K240 K241 K270 K271 K272 Headphons
I have originally bought the oval ones ("HD650" model) to tune Pro 80, and the round ones ("K272" model) to tune Hifiman HE-400, but never did anything with them.
Until today...
The oval ones seems to be an almost perfect fit, maybe just a bit too long:
Round ones are perfect length, but are too wide:
Both of these listings state 2mm and 4mm width.
The oval ones are actually 3mm and 4mm, while both pairs of the round ones are 2.5mm - but one of them is made from exact same material as the oval ones, while the other one is made of a much more porous material:
The left one is made out of the same material as the ovals (pretty dense), the right one is the more porous one.
I didn't want to take the pads off, so instead of placing the disks between the driver and the pad, I showed them inside the pads.
First, I tried the "thin" (3mm) oval one.
WOW
Bass - Slightly less controlled, but still tight enough and with a longer decay
Mids - No longer recessed! Vocals sound so much better! Yet it doesn't have the small thin veil that B8 has. Timbre is perfect.
Treble - Slightly less accentuated, but just as clean and as well extended.
Soundstage - Due to a decrease in treble, a bit smaller
Clarity - It no longer has the same estat-like clarity, but still probably is the best closed headphone in that department.
Overall, It's not mid-forward as B8 yet, but it's no longer U-shaped either. "Neutral" and "Balanced" are the best ways to describe it.
Then, I tried the "thin" ("porous") round one - it was easier to shove inside the pads than the oval ones.
Double WOW
Bass - Somewhere between the "oval" one and the original
Mids - Vocals sound very close to the "oval" one, maybe 1dB less forward. Still perfect timbre.
Treble - Same as the "oval" one
Soundstage - Almost as big as the original
Clarity - Better than with the "oval" one, almost unaffected.
Overall, I like it more than the "oval" one, because it retains the best characteristics of Pro 82 - its clarity and bass, while improving the mids.
I highly recommend anyone with Pro 82 to buy both oval and round ones.
I can't guarantee that you'll get the same combinations of width/materials, but you will have enough tuning possibilities by using different width/material/shape (alone or in combination) to get the signature you want.
Even placement (under/inside pads) or orientation (for the oval ones) can have an effect - have fun tuning!
P.S. If you will place them inside the pads, trimming a few mm will make it easier.