help please

btnhfan

wow. i have lots to say so please take your time to read it and help me out.

so the other day, my subs cut out. this is after having them running for 3 months now. i turned the volume up and it came back on. the next day, it cut out again and didnt come back on. i thought a wire came loose so i re-did the speaker wiring and during that, the + and - accidentally touched and sparked. anyway, nothing was working out, so i got a multimeter and tested the ohms at the sub and the amp.

i cant get reading on either really, or if i do it doesnt make sense. the amp is gettin a constant 13v throughout all of this. so i took the subs out of the trunk and again tried to get a reading. but i couldnt get anything, so i tried to undo the bottom part were the wire goes, and then i heard a hissing noise. what happens if my mm10 loses its airtight seal?

o and i also upgraded my ground wire finally, from 8 to 4 guage, cuz my power was 4 guage, and i never had time to do it

so is my amp or subs blown, and what about the seal?

i have 2 mm10's and a fosgate 1001bd
please help!

neomagus00

when you say you took the bottom part out, what do you mean? bottom part of what?

so you tested the +12V line, and got 13 volts... that's good. did you put it between the + terminal of the amp and the + terminal of each sub? that is, check each sub individually for ohms and volts... it should be around 4 (actually probably more like 3) ohms, and if the amp's going full power, maybe 30ish volts? what are your results for each sub?

did you check the fuse(s) on the amp from the spark? and the seal on the mm10's shouldn't just go...

oh, just for reference, when you're working on the system, you should unhook the +12V lead from the battery; since you have a fuse there (right?) it's easy to do

btnhfan

yea i forgot to unhook the battery, but i did after that. the bottom part that i tried to take out was at the bottom of the sub, where the terminals are. i did put it there. from what i remember, it was lower than 30v, in the 20's. and i didnt get anything on the ohm reading. like 1 or sometimes negative.

neomagus00

okay (yeah, you do kinda have to have the battery connected to get valid readings, huh?)... that strange reading of ohms sounds like a short through the sub. i forget what it's from - hey someone else, this is where you chime in - to confirm, hold the two multimeter leads together, and you should get a similar reading.

is this on one or both subs? and the subs are playing as you do this, yes?

the voltage in the 20s is fine, btw

btnhfan

subs are not even playing. and it is on both subs.

neomagus00

okay, let me get this perfectly clear - you have power, ground, RTO, and RCA's hooked up to the amp. you also have one subwoofer hooked to one channel of said amp. with music playing on the HU, there's no output from the sub? and when you keep this setup and change subs, same thing?

btnhfan

correct.

neomagus00

ouch... sounds like you blew both subs... i assume that you were running them in parallel, right? which still gives you 375 W/each, so you're well within their powerhandling capabilities.

do you have access to another amp to try them out? access to another speaker (any kind) to check the amp? did you try the leads across the sub's terminals (the multimeter should be able to put out its own power and test the resistance across the sub)? all this is just to make sure that your subs are toast, cause it could be something else i'm missing.

Systems

heres a tip someone gave me to test the subs. dissconnect the speaker wires from the amp, so it is still hooked up to the sub, and take a 9 volt battery, hook up the pos and neg, if you here a noise coming out of it, sounds almost like a small, faint pop. if it makes that noise, theyre still good,

btnhfan

i was running the subs so that they each ahd 2 ohm and 500w rms, like it reccomends. ill check that 9v battery and try to get another sub or amp to test. thanks for the help.

neomagus00

um... the mm10 have a rec'd rms of 400 W, and you're not getting any more than that out of that amp (unless it's severely underrated and you're pushing it to distortion).

yeah, try the 9v thing, you should see the cone move too... (get a new 9v to be sure)

btnhfan

then y does it say 500w rms on the subs?
the brith sheet on the amp says 1097 at 2 ohms, so then im giving it a lil over 500w to each sub wen i wire them to 2 ohms.

http://www.polkaudio.com/car/specs.php?name=mm10

neomagus00

a) my bad, it is 500
b) damn, that's a lot of power... and if you want to hear about the effects of overpowering the momos, talk to cody (exalted512), he'll tell you many many stories...

yeah, try the battery thing, and we can go from there... it sounds like both subs are toast tho... did you break them in properly?

btnhfan

im going to try the battery thing right now. i broke them in properly, just as the manual said. its been fine for 3+ months now though.

btnhfan

welp. the subs are blown or something else is wrong with them. i borrowed my friends mm12 and tested it with the battery and it popped, while my subs did not. then i hooked his up to the amp and it worked. what can i do now?

neomagus00

they may be covered under warranty... as to why they blew, no idea...

btnhfan

thanks for all your help.

btnhfan

o and one more thing. is this covered under polk's warranty?

MacLeod

This is concerning me. We seem to keep hearing reports of blown Momo subs. Im wondering if Polk is having quality control issues with their subs? Granted, virtually all the complainants were overpowering their subs but not by much and most manufactuers rate their speakers well below the actual limit for safety reasons. Hmmmm..

neomagus00

well, in the vast majority of cases recently, it's due to significant overpowering; some, like cody's most recent, it was only by 10% overpowering; and at least for this one we have no clue what caused it. i'm guessing only one sub went (cause as soon as one goes, the other gets the full amp input and blows up). but why?, we ask... overdriving the amp? a wire came loose on the second sub, driving the first with the full voltage of the amp? who knows...

the parallel wiring bit throws a new set of complications into the picture; now, if it was a 1 sub system, i'd agree wholeheartedly... as it is, i agree maybe 65%-heartedly ...

btnhfan

what were the otehr cases of blown subs? cuz i might have been over the limit by like 30w or less. and it was always on a fairly low volume. the subs blowing perplexes me.

neomagus00

yeah, in your case i'm totally flummoxed... check all your wiring, just in case; not only the way it's wired, but also the physical state of the wires; i.e. are there cuts or gashes, or, if they're crimped anywhere, could the two wires of a pair be touching there, etc.

exalted512

my bd1000 was rated at 1236 watts and i blew my first set of momo's while running them off of it...it was clean power though
i dont run my subs to distortion, or at least it wasnt audible and i have a really good ear for that kind of stuff
ive blown my momos from anywhere to 75 watts over to 115 watts over
they work great and never show signs of distress then...bam...
you sparking the wires mightve caused a huge surge and thus blowing the speakers...that gets my vote
-Cody

neomagus00

assuming there was still a sub in the circuit when the wires sparked

btnhfan

there are no wires there any more, they werent touching at all. they were on opposite sides of my trunk basically. is there a way i could tell what actually happend to them?

the spark happend after the subs stopped working, and the subs werent even hooked up to the wires when they sparked.

neomagus00

damn, i thought he was on to something... i have no idea whether you can find out what happened or not, maybe ask a local shop?

exalted512

something might be wrong with the amp and it mightve sent a surge to the speakers
ummm
your fuse wasnt blown correct?
push your speakers in really fast...does it sound like sand paper or a spring or something?
last time i blew mine thats what it sounded like and i had(im guessing) fried the voice coil
the other 4 momos i blew were still making sound
have you checked the leads both on the terminal and where they connect with the cone?
the tinsel leads were a big problem on the original momo's, havent heard of a problem with the new ones--but worth a look--i had to repair the tinsel lead on my mm6 midwoofer
-Cody

neomagus00

i vote exorcism, it can't hurt

AustinKP

Originally posted by neomagus00
(cause as soon as one goes, the other gets the full amp input and blows up). but why?, we ask... overdriving the amp? a wire came loose on the second sub, driving the first with the full voltage of the amp? who knows...

the parallel wiring bit throws a new set of complications into the picture; now, if it was a 1 sub system, i'd agree wholeheartedly... as it is, i agree maybe 65%-heartedly ...

Neo, I don't think this could happen. As soon as one sub blew, the amp would be seeing twice the impedance, thus it would only be giving half the watts to the single sub. In other words, two 4ohm subs in parallel would be 2 ohms, thus 1000 watts. If one blew, it would just be one 4 ohm sub immediately receiving only 500 watts. That's my theory...

exalted512

Originally posted by AustinKP
Neo, I don't think this could happen. As soon as one sub blew, the amp would be seeing twice the impedance, thus it would only be giving half the watts to the single sub. In other words, two 4ohm subs in parallel would be 2 ohms, thus 1000 watts. If one blew, it would just be one 4 ohm sub immediately receiving only 500 watts. That's my theory...

hes right...itll put the impedance back to 4 ohms and the amp puts out 500w @ 4 ohms
-Cody

neomagus00

yeah, you guys are right; i didnt think about how the impedance would change when one sub blew. man, that's 2 biggies on this thread for me.

so that's pretty strange, to get both subs blowing at the same time then; maybe it's the amp, like cody said; is it still under warranty, maybe you can exchange it, just in case?