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Thread: Is my subwoofer amp pooched?

  1. #1
    Constant Bitrate
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    Is my subwoofer amp pooched?

    So I just bought a del sol. Crappy car, I know, but it's sorta fun to cruise in.

    The car came with some half assed stereo installed in it, but I can't complain for what I paid. It has:

    Cheapo Kenwood Headunit with FRONT/REAR preouts at least, I dont think it has a subwoofer pre-out.

    1 4 channel amplifier in the trunk running interior speakers, no name but seems to get the job done. Somehow all interior speakers are wired to the front channel preout on the headunit

    1 500 watt rockford fosgate amplifier in the trunk powering a 12" alpine type s subwoofer. This amplifier is wired to the rear pre-out on the deck.

    I was told by the seller that the deck has no controls for the subwoofer, which after playing with the unit I determined he was right. I had assumed that the subwoofer was hooked up to a subwoofer preout (what a crazy idea). After trying to change the fade from rear to front a bit, I discovered that the subwoofer was controllable with the fade because it turns out the subwoofer was actually wired to the rear pre-outs.

    Due to cheap speakers in front and their close proximity to my head, and a good subwoofer in rear, I set the fade to about 70% subwoofer, 30% front. A song started playing that I liked and I cranked it. Little del sol's trunk started vibrating up and down about an inch, I could tell it would've sounded like a production of "STOMP" from outside the car, but inside it was nothing but clean bass and decent sounding highs. Ehh, i bought it off a typical honda owner, can't expect the stereo to be done right.

    Then, all of a sudden, my bass goes away. I pull over and pop the trunk, nothing is blown, or smoking or anything. I go to the front battery, which in itself is a fun little thing to look at, almost like an octopus on the positive terminal. The fuse on the power line wasn't blown either.

    So here I am, driving a car with no bass and crappy interior speakers. I am not sure I can handle this.




    So, after being bored and telling you guys my life story, what could be wrong here? Is the amp pooched? Are there more fuses I should check? What steps should I go through to fix this problem.

    Thanks stereo guys, you rock
    -dan

  2. #2
    Maximum Bitrate 3onDubs's Avatar
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    Check the fuse on the back of the head unit (if there is one)...check the fuse on the amp (if there is one)...check for amp protection lights. If none of these are the case, than i'm afraid you've fried your crappy headunit's rear out channel. The good news is that you can get a new one that is much better (with sub outs) for extremely cheap.
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  3. #3
    FLAC
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    Does the sub smell? Does the sub move f you push the cone? Is it scraping?Subs in trunk makes distortion inaudible. My guess is you distorted the hell out of your sub and melted it.

  4. #4
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    Subwoofer doesn't smell.
    Does move if I push the cone.
    Not scraping.
    Subwoofer appears to still be in good shape.

    I doubt the subwoofer is damaged. The amp is rated 500 watts rms and the subwoofer is designed to handle 900 watts rms.

    How often do preouts blow on decks... i've never heard of that. I might consider removing the deck and swapping connections to test the amp and subwoofer. I've no problem replacing the deck, it was a POS anyways put in just so the car had radio when I bought it, and this would be the preferable option. I've even been leaving the roof off in hopes of someone stealing this deck so I have reason to replace it, lol.

    We'll see
    -dan

  5. #5
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    If the two amps are in close proximity, just take the RCA's from the 4ch and put them on the sub amp, to test whether it's the rear preouts or not. I guess you could just swap them around, and see if you get sound on the 4channel amp from the rear RCA's.

    It's not totally unheard of for an amp to blow, but double check the fuses on the amp just to make sure.

  6. #6
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    Wonderful Idea. Easier than ripping apart my dash JIC.

    What would cause an amp to blow if that's the case, too much power? There appears to be 8 gauge wiring to power the 500 watt amp... is this insufficient... seems borderline at best to me... It also has some very shady connections to the battery and the wires might be fraying a bit.

    If the amp is dead, could these factors have contributed?

  7. #7
    FLAC
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    Quote Originally Posted by WoLLy

    I doubt the subwoofer is damaged. The amp is rated 500 watts rms and the subwoofer is designed to handle 900 watts rms.


    We'll see
    -dan
    Sorry bud but VERY VERY wrong. It is easier to blow up a speaker underpowering than overpowering. the forum for several discussions on it. ~100 distorted watts will fry a 900 watt speaker

    Get a multimeter and test the impedence of the speaker. It should be 4 ohms. Grab a little house speaker laying around and plug it into the amp output. Got sound? You need to troubleshoot and figure out if its the amp or speaker

  8. #8
    FLAC
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    Quote Originally Posted by WoLLy
    Wonderful Idea. Easier than ripping apart my dash JIC.

    What would cause an amp to blow if that's the case, too much power? There appears to be 8 gauge wiring to power the 500 watt amp... is this insufficient... seems borderline at best to me... It also has some very shady connections to the battery and the wires might be fraying a bit.

    If the amp is dead, could these factors have contributed?

    and sure, those could be factors, but i bet you pushed the bass too hard, turned up the bass on the headunit and had the loud button turned on. Combine that with choked wiring and grounds and you have the perfect scenario for extreme current draw and starving the voltage rails.

    A multimeter at the amplifier power inputs will tell you if you have power back there. Dont have a multimeter? Buy one, or close the trunk and take it to a shop that has them laying around.

  9. #9
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    Quote Originally Posted by Will Albers
    Sorry bud but VERY VERY wrong. It is easier to blow up a speaker underpowering than overpowering. the forum for several discussions on it. ~100 distorted watts will fry a 900 watt speaker

    Get a multimeter and test the impedence of the speaker. It should be 4 ohms. Grab a little house speaker laying around and plug it into the amp output. Got sound? You need to troubleshoot and figure out if its the amp or speaker

    Right, when you have your gains maxed out on an underpowered amp, thinking it will never blow your speaker, because it is underpowered is very bad. Amps put out a lot of distortion when pushed to their limits and will cause the voice coil to act like a heating element, not only that but the abnormal movement of the cone doesn't cool as efficiently as when the signal is clean, add those two together and you compound two bad problems into one huge one.

    As for the 8 gauge, I'd personally say it's not terrible, maybe borderline. I've seen 8 gauge kits rated for 1000 W; not saying I'd use 8gauge for 1000W but I have seen them.


    Quote Originally Posted by Will Albers
    and sure, those could be factors, but i bet you pushed the bass too hard, turned up the bass on the headunit and had the loud button turned on. .

    That's exactly how I blew my amp.

  10. #10
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    That's probably the cause then. I am at work now and cant check the settings on the amp, but I'm guessing the idiot had the gain maxed. It would just go perfectly with the ****hole job installing the rest of the system. I'll probably stop by my audio shop. I spent enough money there on my mr2 that they should be perfectly happy to look at it for me for free, or at least very cheap.

    Btw, The sub is rated at a min 300 watts rms, so I'm not severly underpowerng it, but I do assume that the gain is maxed along with distortion. The amp is probably being forced into a 1 ohm load due to bad hardware and wiring choices too, who knows. I'm tempted to drive to new york and kick the PO's ***

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