Why are my car speakers distorting (not blown)

I purchased a Vauxhall Astra 09 (I've sold it now, keep reading), and the left speak whenever I turn the bass up (depending on certain songs), when the bass hits there's a slight crackle within the speaker, only certain frequencies cause this though. Some songs will play through fine, where as others will have a slightly different bass frequency (or so I think) and the speaker on the left will *crackle* but only for as long as the bass is there, then it ll disappear just as quick as it was there I'm not sure how to explain it. It's definitely the bass that s causing it. Vocals come and play through fine. I had the speakers replaced to what were known as performance speakers but still the problem persisted. I recently bought a 14 plate Clio, and this car has the same problem. As an audiophile this is driving me insane. I had the speaker replaced in the Clio also and this didn't fix the problem. I've taken it to two individual audio experts because Renault refuse to fix the problem and one has told me I can't get rid of the problem as the speakers aren t able to pass out that amount of bass (but it's not even high and some songs play fine remember). So he recommended having an amp and a crossover fitted to combat the speaker from distorting. The other audio expert recommended having the front doors soundproofed. I'm at my wits end. My previous two cars did not do this so it must be something other than the speakers. I had a Ford Focus and a Corsa and both were fine.

Maybe the old owner of the car installed a bazoka system and it damged the speaker.

Wires not thick enough for that much power