Thanks for reply.   Actually the earpads are thicker on the "bad" pair, which is the newer one. I bought both pairs brand new, not refurbished.   I tried swapping the earpads, but no significant difference in sound. "Bad" pair still has much more bass. 

Hello All!   I have met a weird problem with 2 Sennheiser RS 170 s. I bought one of them in 2013 and another one a year after in March 2014.   The first one has a really nice and clear sound. Very clear and powerful mids and highs and the bass is not overwhelming (which i really like). The...