Curious... Are you finding optimal HD650 tubes to be less than optimal with your RS1i ? One of the problems I have always had with my Millet, it was voiced by its builder for the HD580, and it sounds very shouty and edgy in the upper mids with my RS1 and K701. I have used other members HD650 voiced amps with my brighter cans and had similar results with all of them.
Not entirely true. You can look through the perf mesh earcup and see the reflective/metallic mesh of the HD650 baffle. I do not know how to decipher the actual drivers though. It would not take much for someone to transplant HD580/600 driver "lollipops" into the HD650 silver mesh baffle plate. At that point its anyones best guess I think.
Hardly, Headbands have been known to crack/break on all of them (580/600/650). While replacement parts can be ordered from senn, availability varies greatly. In the case of the headband, they don't sell just the headband by itself. You have to purchase the whole assembly (headband + "Y" yokes). Thats the most expensive part on the bill of materials at ~$90 +S/H.
The small spring contacts in the earcups have a well documented history of intermittency. For a while a few years ago Senn was offering replacement springs. Never tried it myself, but knowing how thin the lead wires are on these cans... replacing that spring definitely looks like a nerve-racking repair. When my 580 springs developed a contact failure, I just re-bent the coils back using a bamboo BBQ skewer.
I find the higher gain 12AX7 a beautiful match for my HD650....but not as good for the RS1i....I much prefer the 5751 Sylvania TM black plate for those.....the synergy is just much greater.
When I switch headphones, I just also swap tubes.....then both cans have fantastic synergy.
Edited by whirlwind - 4/20/14 at 5:41pm