Tyll measured three PM3s, I believe, and while they weren't entirely different headphones, they did have enough variance alone to explain subjective differences. With a bit of fiddling, they worked as over-the-ear for me and sealed very nicely. Boom, tons of powerful, thick bass. Break that even a tiny bit, and bye bye. Even then, from measurements, there seem to be pairs floating around that have lacking bass even with a good seal. One thing I can't take into account as easily is personal taste. One man's too much bass is another man's too little bass, or could be track dependent even.