sub making pulsing noise, no music?

[sawychri06]

hi guys
i have got a 600 watt sub and a 760 watt 4 channel amp i have had it wired and working for 2 odd years now and now i have gone to put it in anouther car its gone weird? I have got the ground on a seat bracket, all my RCA are good wire from the headunit to the amp and my power is fused close to the battery. Problem is i turn the headunit on and within a few seconds the sub will just start pulsing and going into repetative and random base before it turns the protect light on? Anybody tell whats wrong?

[m1lky]

Try unplugging the rcas (with ignition off), make sure they aren't touching metal or each other and turn it back on. Is the noise there?
Get an RCA to headphone jack. Plug this into the amp connected to your phone iPod etc, does it do it now?

Check low pass is around 80hz, gain is under half and bassboost is off too. Otherwise chances are your amp is delivering frequencies above what the sub can handle or clipping. Either way it's not good for the sub (or amp).

On a side note how do you have it wired up? Is the sub dual voice coil? If so are the coils in phase? Are you dropping below the minimum impedance for the amp? If you tell me what the amp and sub are I might be able to help with wiring.

[Thomas1]

Try unplugging the rcas (with ignition off)

Why does the ignition have to be off?

Anyway, it sounds like you've wired something wrong. I'm tipping it's to do with the voice coils on the sub not being wired properly and the amp not liking the impedance. As said, post up the exact specs of the whole system and we might be able to point you in the right direction

[m1lky]

If you unplug them or plug them in with the headunit on. It can blow the fuseable link in some headunits and will lead to terrible whining.

[Thomas1]

If you unplug them or plug them in with the headunit on. It can blow the fuseable link in some headunits and will lead to terrible whining.

Never knew that. I always unplug/plug them with the system on when tuning and have never had a problem.

[HCVP]

I don't even think i was in the right forum

[m1lky]

Never knew that. I always unplug/plug them with the system on when tuning and have never had a problem.

Pioneers are chronic for doing it. Others do too. Better safe than sorry.

To the op, the more I think about it I think that the subs wired incorrectly

[sawychri06]

the sub is unknown its a 600watt slimline audioline but other specs unknown
amp is a jensen 760watt 4 channel 75watt per channel

sub is wired as normal
power from battery to amp (fuse is fine)
the blue wire is connected and plugged into the amp( sorry forgot the name of the wire)
RCA cables connected and all good( only thing i havent checked was the ipod jack to them)
ground is grounded

+ from sub to + to amp
- from sub to - to amp ( these are bridged )

i have checked with a multimeter
ground is dead
power is about 11.75volts
headunit is about 11.65volts
+/- from amp are making strange volt changes dipping up and down
so i am thinking it maybe something wrong there ?

any help would be great
thanks guys

[MAG00]

This sub?
and this Amp?

How is it bridged? What channels are bridged?

[sawychri06]

+ to channel 1. - to channel 2
I had it this way in my commodore and it was ok
Says above the wire ports bridgeable with arrows between them

[sawychri06]

And yes both of those items thanks MAG00

[m1lky]

So your only using half the amp? What are the other two channels connected to?

Voltage drops would indicate a problem with power supply. (you do not need a capacitor!!!). Try replacing the fuse, sometimes they still work but have high resistance across them when they partially blown. (edit: assuming this is on the power supply not the amp output. What voltages do you get on the remote wire and +12v at the amp with the car running? 11.5 is quite low even with it off, what size wire are you using?

Powerwise those aren't badly matched. 190wrms into 200wrms (max ratings are marketing rubbish).

How have you got the amp setup? Lowpass gains and bassboost?

[sawychri06]

i reckon i am goin to check the head unit this weekend and check to make sure things are wired correctly.
and yea because i only have a sub on the amp so only using the bridgeable +/- on channels 1 and 2
amp is adjustable so i a adjusting bass and max/min

[sawychri06]

ripped out the headunit last night and found nothing wrong with the wireing, only thing i can think is its a differnt head unit
and an old 1 pioneer DEH-440 still has rca cables but not sure if they work

[m1lky]

Did you try unplugging the rcas and turning it on? Or using a iPod etc as a source in the boot?

[sawychri06]

Yea rcas are fine unplugged and thats the only thing I haven't tried might see if I can get my hands on 1