Question on speaker quality??

I have 2 sets of pioneer 6 1/2 3way speakers in my civic. One pair is about a year old but in perfect condition, max watts like 160, and the other pair is new, max was like 200 watt. I think it was the same model, just different year. Anyway i have a 8400 pioneer head unti, 50*4 right? So how come if i have the bass up on the speakers, and turn off the sub, the speakers will start to sound distorted at about half the peak volume of the head unit??? It doesn't make any sense to me, since they'd be getting nowhere near what they could handle.

[Accord Man]

that size speaker isnt meant to handle much bass at all.. Thats why you should use a Xover.. If you use the one on your HU, then you wont be hearing bass thru your cabin speakers.. Thus you need a sub..

one reason is cuz the head unit only puts out about 20-24 watts RMS... if u used an external amp with an RMS rating closer 2 the speakers RMS rating then it would be clearer... but also use a crossover