My velour pads
http://www.ebay.de/itm/261084114242?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_2912wt_857 just arrived.
First impressions:
Bass : does get reduced indeed. Will quantify by how many dBs time permitting. Does not change in definition. Definitely not something a basshead will crave for. I would call it about right, maybe a tad less than totally flat, but never gets overwhelming or fails to support the music with fundamentals needed. "Boring" in the positive meaning of the word, does not draw attention to itself.
Isolation : expectedly worse, but no biggie.
Treble/soundstage/airiness : I chose to rate these three as a single category due to the fact that these earpads literally transform HA-S500 from (bassy/ In your face/with occasional tendency to shout) headphone with constricted soundstage into something with much more rafined manners and much, much more satisfiying soundstage presentation, both in width and depth. Now you can almost "count wires" on delicate jazz cymbal work, for example. I do not have the time needed to do A/B against AKG K 1000 at the time, but the humongous gap between the two regarding soundstage/airiness is certainly reduced with these pads.
Midrange: improves further due to the above.
These earpads reduce the sound level compared to stock ones by about dB or two - you will have to open the volume a bit more. But BEWARE of Telarc 1812; they were on the very edge of possibility with stock pads, 2 dB more might prove too much for them; use caution and common sense.
Now they are much more comfortable and improvement in treble definition keeps freaking me out - listening to
http://www.amazon.com/Dafos-Hart/dp/B000008GEY at the moment from the Rykodisc CD. You can look for it on YT, but the usual blues regarding SQ applies too much for me to post any of the links available. Wish I still had my copy of the awesome Reference Recordings LP pressed on arguably the best thing EVER produced by the JVC - their vynil analogue LP records...
That much after about 90 minutes after opening the box and fitting the velour pads.
As always, enjoy your music !