As someone who put in a (slightly off-topic
) post in this thread about the various ways of tuning the 12-tone scale a couple of years ago I feel that I can (and should) put in what would appear to me to be "the answer" to this question!!
And this "answer" is very simple:
RS-220s!
After many years of playing around with 130s - 160s - 185s etc etc, a couple of years ago I splashed out on a pair of RS-220s that were being "remaindered off" at a halfway-bearable price by a dealer in the 4thReich. They were being sold at 300
4thR$ which, by the time I got them here to Aotearoa/NZ, translated into about 700$NZ - the outer limit of what I could/would spend on a pair of wifi cans.
I'd coveted a pair of them (after reading their specs) when they first appeared a few years ago but, at that time, they were just a bit too expensive for me.
But: WOW!!! - what a sound!
Their THD figures (@ ≈.1%) are 5x better than
any other wireless cans on the market - which are all ≈.5% - and one can surely hear the difference/cleanersoundquality.
I quickly sold my pair of 185s - which I'd bought almost new from someone who didn't want them because they wouldn't do bluetooth or some other low-bitrate "drivel". Those 185s were the best wifi cans I'd had up to then but when compared to the 220s, they simply didn't "cut the mustard" - they were just so very "fuzzy" and blurred in comparison.
I've got a pair of 650s (which IMO are the best wired cans at a sensible price) and when doing an A/B test between them (the wired 650s) and my RS-220s I could hear little, if any, difference while listening to some very accoustically-demanding (=harpsichord) music.
I quickly bought myself another pair of 220s secondhand via eBay which were in effectively new condition.
And the sad/inexplicable thing is that Sennheiser stopped making them
!
They don't have a very long range - only ≈10-15m and not through too many walls - ie quite a bit shorter range than 185s etc.
And (at ≈6hours) they don't have as long a battery life as the 24-ish hours of the 160s-185s - but then I've not yet got anywhere near using the charge capacity of any pair of wifi cans.
And, with their very high static/charge voltage for their headset AAA rechargeables (1.5V+), they do seem to need a new pair of batteries occasionally.
But to me all these shortcomings are quite understandable and able to be tolerated in the light of their stunningly good soundquality - after all they must be transmitting/receiving a helluva lot more data than their markedly much inferior 165-195 siblings.
I've still got a couple of pairs of 160s for listening to TV and radio and other lowgrade material but for anything musically demanding IMO there is nothing I've found to compare with my 2 pairs of RS-220s when they are being fed coax SPDIF - optical SPDIF transmission is OK, but coax is that small but noticeable bit better.