Sennheiser HD 650's thin sounding?

They will break in. However, I just replaced my 570's with AKG 701s and the difference is like moving from bose mini cubes to Thiels.

580 is way better than 570. It is pretty much the same thing as HD-600 with the same drivers. HD-600 is tuned a little bit better (position of the drivers).

HD650s deliver more bass than HD580 but needs 250-500hrs break-in time according to one review I read. HD-580 was one of the best bargains when Sennheiser discontinued it - I bought mine for $140.

Even new the 650 will not sound thin, and will produce more bass energy than the 580 or 600.

I having the same experience with my "near new" HD650. I don't believe it is a defective pair. When compared to my well-used HD600, the HD600 has more bass, more extended high, more air, and bigger sound stage - almost better in all areas. I hope the 250-500 hour break-in period is true, or I will be very disappointed.

I briefly owned the 650s but sold them cause I couldn't stand them. Moved up to the Denon AH-D7000 and haven't looked back.