Subwoofer Problem

[Bailey]

Hi guys!

Ive got a problem with my subwoofer (Alpine Type R 12" running at 4 ohms)...... i.e. it used to work, and then suddenly stopped. I have sent the amp back to alpine and they didnt find a fault with it, plugged it in today and still no output

The amp (MRP M850) has power because the light on it is coming on, and the speaker is not blown because a) the reading across it with a multimeter is 4 ohms, and b) when the contacts are tapped with a 9v battery it makes a noise.

Does this mean my head unit has crapped out? I have checked all the wires in the boot and nothings shorting/cut, and the subwoofer is turned on on my head unit (Alpine 9887R, also brand new). I have tried taking an rca cable from an mp3 player to use as an input to the amp, but there is still no output, i am also measureing across the output of the amp on AC volts and there isnt anything, any help would be massively appreciated!

Bailey

[Coops]

Have you tried a different sub on the amp? I.e. a mates sub.

If it works then your subs fcukd.

If it doesnt then its something to do with the amp / car.

[Bailey]

None of my mates have a sub so its a bit tricky to test, but i was thinking even if the subs fecked the amplifier should be trying to output a signal to it.

Its an intermittant fault and im having difficulty tracking it down, it works fine, and then, without going anywhere (so say leaving car overnight), it wont work in the morning

Its just weird that when i tap the contacts with a battery the sub makes a noise, showing that its working

[Coops]

It actually sounds like an earth problem to me.

Have you checked you have a solid earth and not a loose connection? Make sure you have sanded any paint away so its a metal to metal connection

[Bailey]

I shall check my ground again tomorrow, but i have checked my ground to a totally seperate point on the car and theres no resistance between the terminal on the amp and that point

[skippy]

Have you checked the Fuse on the amp and the one on the amp lead running to your battery?

[Bailey]

Yeah ive checked all the fuses. If the fuse in the power line was blown the light on the amp would not turn on, i have 12V across the battery feed to ground, so the amp is getting power

[charlton_68]

Sounds like an earth problem to me

[eandjkustomaudio]

there may be a problem inside the amp stopping the signal being transfered to the sub. (had this problem with a mates amp, took it apart and the speaker outputs where damaged and there was also a stray bit of solder in the amp ratteling around aswell)

[jacko103]

Check all wiring - RCAs, Live, Ground, speaker wire.

Make sure they are all run without being squashed or compromised and are securely fastened.

[Bailey]

Have checked my ground and theres no problem there, intrestingly when the amp is off between the positive pole and the ground pole theres 12V........ when its on theres only 4 volts which means summats going funny somwhere :?

[SXi-Dan]

thats v strange, i was going to say check if the amp is actualy putting any signal out using a multimeter on ac voltage but the 4v things is v v strange, is everything else okay with the car electrically?

[Bailey]

Ive checked to see if the amp is giving out a signal and nothing, but im guessing thats summat to do with the 4v across the amp.. It has 4AWG wire for battery feed and ground so i dont think its anything to do with the wiring not being able to cope with the current, Found an ICE store up here that do installs so taking it along 2morrow for them to have a look at it, cos i cant narrow it down without an extra amp/sub to see if its the amp or sub and i guess they'll have subs they can try it on etc

[Bailey]

Thanks for all your help guys, found the problem today. Some of the wire from the battery was a bit fecked, replaced it and now ive got my bass back!