Sennheiser HD 650's thin sounding?

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.

Yeah...I had them for much longer than 500 hours. To be blunt - they are piece of...you know. Even 50000 won't change them. Resolution is not bad but the rest of them is totally unacceptable. Cheapest Grado sound much better overall. Sorry.