Help troubleshooting my system!

I have a problem with my subs, but i cant figure out what it is at all.
I have two 12inch subs with an older MTX thunder (420 maybe) two channel amp bridged(the two subs came in a ported box with one set of inputs). I also have an Alpine active crossover.
Now randomly when im driving, the subs start to become really distorted and sometimes get a lot louder. I cant figure what the problem with it could be, ive checked all of the wiring.
Now here are a couple things wrong with my setup, but i dunno if this would cause the large distortion. I have a 4 gauge power wire but with an 8 gauge ground(soon to be fixed, but ive never had a problem with it in the last couple months ive had the system). Now what might be the cause, is a couple weeks ago I was messing with the RCA inputs on the crossover, and I might have accidentally touched the center connector to the outer ring of the input...when the system was on. I know im a dumbass, but could this of caused my to fry some circuits or something? But the thing is, the problem only occurs randomly like if i hit a bump or something, and the problems becoming more frequent.

Any help would be greatly appreciated, I cant figure out whats causing this at all, is it possible i somehow blew my amp or something??

you may have blown a sub ... that would change the impedance of the load.

crap, thats not good lol. is there any way to check to find out if that is infact the problem? would checking the resistance on the positive and negatives of the subs tell me if i did? i was thinking of upgrading my subs anyway because i did buy the really cheap and shitty 12in Dual's.
the problem im having though is also sparatic, like tonight driving home from work they were fine, but they were having the problem on the way there. could they still be blown?

thanks alot

you can take an ohm meter and probe across the sub terminals. Each voice coil should be around 4 ohms, if its considerably less, you have a blown sub.

my sub box only has one set of positive and negative terminals for two subs. should my reading still be about 4 ohms? i cant figure out how my subs are wired together, and they still have a 4 ohm impedence? could they be wired in parrallel? or is it series?

Unscrew the subwoofers from the box and take a look inside at how they are wired.

easier said then done, the only opening is really small and it would require taking apart the fairly complicated box

Is it a bandpass box or something?

yea, its the 2 12in Dual subs...i dont see how i blew the subs though, theyre supposed to be about 600watts rms i think, and with that amp? i couldnt find any stats on the amp though

What does it have so you can access the subwoofers, a piece of plexiglass?

yea i may end up removing it and taking out the subs because i just used an ohm meter and i think my subs are blown.
when i was taking the reading it was coming out with a -+1 and then spiking randomly up to as high as 12, which i think were just errors though. so does this mean i do need new subs?

pull each sub out, they are prob. svc 4ohms. set your ohm meter an make sure its on "ohm" setting, it should come out somethin close to 4, maybe like 3.85 or something. If your sub blew, the impedence reading will be alot lower, like 1.5 or somethin lower.

i havent had a chance to pull out the subs, i just got back from work, but wheni took the reading from the pos and neg terminals it gave me an impedence of less than 1.5ohms, so im pretty sure theyre blown.
ill keep you all updated if i have a chance to pull em out
thanks alot for all of your help, ive never had any experience with blown subs and im slowly learning alot about car audio.

thanks again

it's easy to blow subs in a bandpass because you can't actually hear the subs themselves - only the sound coming from the port. Also, you need a hi pass (subsonic) filter for a ported or banpass type box. At frequencies below the porttuning ferq, the sub is basically unloaded .... just like their in no box, so the power handdling is reduced GREATLY.

that helps alot and makes alot of sense, i did play alot of low frequency tones on the subs, probably causing them to blow

you can check for a blown speaker with an ohm meter, but - it'll be an open or shorted condition. speakers rarely (if ever) actually read in ohms what their impedence rating is. the reason is because this rating is an ohm reading that is an average derrived over the amount of power consumed when the speaker is operated within the specified frequency range. those of you out there who are into ham or radio repair, know what i'm talking about right away, as do some of you who have electronics backgrounds -- the impedence number is derrived by measuring how many amps are being drawn from an amlifiers output, and measuring the voltage of the amplifiers output - taking that voltage & dividing it by the amount of current = the amount of functional impedence that exists from the amplifiers point of view. a speaker can easily have a resistance of far less than 1 ohm, & still be rated at 8 ohms. this is because audio is dc biased AC, and at the frequency that the ac passes thru the speaker & the way that voice coils passing thru magnetic fields function at those frequencies, the effective resistance increases. lot of technical stuff, but really - don't think that your speakers are necessarily blown just because you're showing a less than 1 ohm reading. check each speaker independantly (wires disconnected from one another and from the amp) -- CAREFULLY move the cone with your hands while watching the ohm meters readings (use alligator clips to hold the leads on securely so you know there will be good connections). if while you're moving the cone you get a sudden wild spike, you've probably got a break or short somewhere in your voice coil & need to replace the speaker. remember to move them SLOWLY since moving the voice coil adjacent to the magnet will induce voltage! in fact, you can see by your meters movement while moving the cone, that indeed the apparent resistance it's seeing changes. hope your speaker isn't blown dude, sux when ya have to replace the $$$$$ stuff.