I have Alpine SPR-174A's in my front doors, they aren't but maybe 9 months old... I have a amp driving them at 50w each, they sounded great up until this week, my passenger side one when its turned up and has any bass coming out of it, its kind of like a distorted sound, like treble is fine but any bass out of it like in rap songs it sounds like its hitting plastic or something, like a vibration of plastic i guess... driver side and my rear pioneer's are fine... i'm not sure what to think of it. I checked it out the other day and it started working just fine, then after another day or 2 it started acting up again??? I just got my windows tinted but the tinters claim they didnt take off the door panels so i'm not sure what to think...

 

I would pull the speaker out, [if you installed it yourself] and check the speaker, if you hold it up to your ear, [an inch or two away] and "thump" the magnet with your other hand, if the VC has "delaminated" you will hear it rattle, if you set the speaker down on its magnet, and using both hands move the speaker cone up and down and then with one hand, [fingers] gently push the cone down at 3 or 4 points around the cone. [offset test] at no point of moving the cone should you hear or feel "scraping" make sure the tinsel wire, [wire from term to speaker cone] is not and can not come in contact with each other the speaker basket or anything in the car when mounted, that gos for the speaker term and the speaker wire connected to them.

Normally you don't have intermittent problems with speakers, if you do, the problem is normally something else, mostly wiring or speaker mounting, or even an intermittent problem with the amp or HU.
If problem persists, [after checking] swap the front speakers, if problem moves to other side, it's a speaker problem, if problem stays on same side it could be the speaker wire or the amp, swap the speaker wires on the amp, if problem moves to other side it's the amp or HU, if problem stays on same side. its the speaker wire.
To check if it's the amp or HU, [when swapping speaker wires on amp problem moved to other speaker] swap the RCA inputs, if problem stays on the same side, the problem is in the amp. if it moves, problem is in RCAs or HU, swap the RCAs at the HU, if problem stays on the same speaker, problem is the RCAs if problem moves to other speaker, problem is in the HU.
That said, if you had the speakers installed at an Alpine dealer, take the car back and have them trouble shoot it. 94

 

Ok i'll try that tomorrow when I have some light, I think it's highly likely that it's the amp, I have my amp mounted under my passenger seat and when the tinters were working in the back seat, they moved my seat. Because the amp is a little too long, the seat can't be slid forward and backwards because the little lever assembly on the bottom of the seat hits the RCA plugs on the amp, I completely forgot to mention it to them, guess I just didn't think about them needing in the back seat. Oh well... it's not a very expensive amp and I want to get a smaller one so I can have full function of the seat anyhow, we'll see tomorrow.