Gave this mod a try
I gave this mod a try because like everyone else who has ever tried them, I was not impressed by how uncomfortable the 'zones are. While they're not awful, the pads are not fully circumaural, you can expect your slightly squished ears to touch the driver covers occasionally due to shallow pads.
I was using a pair of 650 trackmasters (mechanically identical to hfi-700, although I think the sound is possibly different). The pads I used were beyer 860 breathable pleather rather than 990, but they look to be of similar dimensions. Certainly these pads were circular rather than oval and much deeper than stock 'zone pads.
I used Mufto's helpful tutorial to make mounting rings. I found it to be surprisingly easy despite my poor cutting skills. I used the cover from a thick card file to make my rings and found the card to be dense and easily stiff enough.
After mounting the pads I needed to cover the drivers of the headphone. The 860 pads come with a small circular disk of foam for this purpose, compared to the very thin disk of cotton or whatever that 'zone pads use.
Immediately on using the pads I found two things;
Firstly, the headphones are much more comfortable in this configuration, less sweaty, less pressure on the ears and more depth for your ears.
Secondly, that the sound the phones were kicking out was significantly quieter and more muffled.
I figured that putting a much more damping material right in front of the drivers probably damps them. Pulling out the foam and listening to the drivers cover-less led to a big improvement. I covered the drivers with a bit of very thin tight from a pair of ladies tights (not mine!). Adding the tights didn't seem to change the sound from that of the naked driver, simply prevented the possibility of anything falling into the baffle holes, so success in this respect.
Listening to the new beyer padded, tight shielded 'zones led to some disappointment. Like Mufto, I don't like audiophiles exaggeration regarding sound and often far too much is made out of tiny, almost imperceptible changes.
Despite finding the new sound to be a significant step backward, I stuck with the 'zones in this configuration for a week, before switching back to the original pads today.
Changing back made me appreciate how good these phones usually sound. When they were beyer'ed they lost some of their body and detail. The midrange especially seemed to suffer on these phones and they lost some the great midrange detail and life that people enjoy in 'zones. Again, I don't want to exaggerate the changes because beyer'ed 'zones weren't unlistenable or rubbish, just weaker in some of their strong respects.
Having lived with them for a week and using them often, im convinced its not simply a case of getting used to the change, instead I think stock 'zones are simply noticeably better sounding. Beyer'ed zones never got muddy (and nor do the originals), but everything was a little less focused. I wondered if this might be partially because the driver on the 'zones is angled to fire towards a certain part of the ear, when your ears are more or less in the centre of the stock pads and that possibly adding deeper, wider pads upsets this.
I went into this mod willing to except a small amount of change to the sound. My reasoning is that generally people who say they JUST care about sound are kidding themselves or posers, what we want is a listening experience and part of that is comfort, audio lovers simply put SQ higher in the mix than normal folk. However, despite my pragmatic intentions I can say that for me, the loss of SQ outweighs the gains in comfort, my 650's are gonna remain stock.
I don't write this to 'trash' Mufto's mod, more to say that your mileage may vary and it might be worth thinking twice before ordering beyer pads specifically for this purpose. If you already have beyers, give it a try, you might like it.
So there you have it; an unasked for review, of a mod only a few people seem to have done, on a dead thread with atrocious punctuation to boot.
Happy listening.
