subaru legacy speaker fault???

hi lads,ive just replaced my old speakers for new alpines 5inch in the front, ive got a standard subaru head unit, only thin i had to change was the connectors as the new speakers has smaller pinns. all done and sounds ok apart from when theres high pitch sounds or voices it sounds distorted like fuzzy,anyone know whats the story here???thanks

+ and - mixed up?
Head unit not out putting enough watts.

the pins wearnt marked or anything,the lad in halfords said it wouldnt matter unless it was marked red,but ill try tomorrow switchin them around,funny thing was on one speaker there was a small and a medium pin,on the other there was a small and a large pin so i needed to use one of my old connectors,why was one pin very big???its possible the power is too much for my head unit,here is the speakers i got
http://www.halfords.ie/webapp/wcs/s..._productId_237965_langId_-1_categoryId_212533

There was a factory amplifier in my legacy it could have something to do with that

sorry lads false alarm,speakers are fine,was playing music through my fone on that radio receiver thing,sounded fuzzy cus wrong frequency!!!tested a couple of cd...sounds crisp...thank god for that!!!