Hey Sludgenutz, I'm hoping this will make sense, it is sort of looser sounding whereas the series II's seem a little harder or maybe even tighter. The pl also seems just a bit more sensitive to a higher presence setting, making it a little easier to get a bit more "sizzle", when you want it that is. I have three series II's and only one proline and they are several years old. Very well broken in. I use the proline in an open back 1x12 for smaller stages, rehearsal etc. and it sounds just huge when you push it a little. It somehow gets the sound out so that it doesn't have that small, no bottom combo vibe. I also have one of the original 1982 EVM series II's. I has the rough paper pattern on the cone (the Black Shadow versions have a smooth cone.) It reminds me more of the proline.