I'm currently using the SE215s and after a washing machine accident decided to try the SE425s. Richer Sounds have them at a pretty good price and have demo units so I went in to try them today. I was really surprised, all the comparisons on here seem to say that they are somewhat similar in terms of mids but slightly deficient in the bass and treble. This was completely not my experience. They were very very bass heavy. The bass on them was crazy, really powerful low bass. The bass was so powerful is kind of drowned out some of the other frequencies. I was so surprised I even checked that I didn't have a bass boost EQ set on my phone but I didn't. Could it be because I was using custom moulds and the perfect seal led to huge bass that would normally not be apparent?