I bought the newer focus pads - the ones with the perforated pleather inside ring.
They appear better made, look much nicer and have softer velour ear pads than the stock he-500 velour - which look cheap and nasty by comparison. They cost me $50 here in Australia and I was predisposed to having a positive opinion.
Unfortunately I don't like their sound at all.
To me the Focus pads obscure textural/timbral detail and some lower midrange 'weight' - seriously compromising the realism of voices and acoustic instruments. With my equipment (Mac mini > ifi usb power/Gemini cable > Grace m903 dac > Violectric v281) the result with the focus pads is
far less musically engaging (than stock velour).
I've swapped the focus pads in on a number of different occasions - as I did again before posting this reply - and its always the same result.
Note: my he-500's are un-modded - except for reterminating the stock cable with a Neutrik xlr to allow balanced use. FWIW I get the same result from the M903's TRS HF output when using the focus pads.
Obviously there are people who prefer the Focus pads - but it's a complete mystery to me.
Not sure if the Focus A pads are still available (?) and I haven't heard them, so can't comment on their sound.