350ZOWNZ

Ok i got these speakers and for some reason the midbass SUCKS *** on them.. I mean ive heard other pioneer speakers and there much better. These speakers are pretty good SQ tho. Now my question is. I didnt install my amp. So i was thinking is it possible the guy that installed my amp put the + and - backwords for the speakers wire connected to the amp? Would it sound totally messed up if he did?

My setup is:

Alpine MRV-F450
STOCK HU
CD CL-61 up front and the pioneers in the rear
Bazooka tube (ya it sucks but it was free)