I got a pair of original Sigmas (low bias) in very good state today. What I like most about them is the looks . Honestly, I'm a bit underwhelmed. I was prepared for recessed highs and limited dynamics. I also knew that I couldn't count on deep bass, but the missing of pretty much anything below maybe 70 Hz is hard to take - despite the beautiful mids and the new kind of soundstage. Even plan b is at risk as I fear that the problem with bass persists when transforming the phones into Sigma/303's. Has anyone had success in experimenting with different types of damping material in order to improve low bass response?