I've done some comparisons on the Signature and Lambda norm with the pro on an SRM-T1. To me the Pro has a smooth sound with a somewhat sucked out mid-range. Its bass isn't as strong is the Lambda and is about as defined (maybe more) as the Lambda, but stronger and not as well-defined as the Signature's bass. Its not bright like the signature, not too dark, just laid back. It worked decently with electronic music, but not so great with vocals. Those were my thoughts on it before I sold it them about two months ago, I was fairly happy with it.