Wiring rear door speakers to HU

[Jay]

Since installing an aftermarket HU I have had a buzzing sound at low volumes which is getting quite irratating. Someone suggested that I need to wire the speakers directly to the HU instead of running them off the factory amp.

I spoke to someone in Halfrauds who said it may not cure the problem as the front and rear speakers may have different impedance. Is this correct?

How do i take the door cards off? i've looked all over but cant find any screws.

I'm planning on running the speaker wire along the amp power cable and rca cable down is this ok?

Has anyone had to do this or is there another way around it?

thanks

 

[AndyMac]

You asked someone at Halfords? Classic answer though, makes absolutely no sense even if it was true.
What's impedance got to do with alternator whine?
Might help with the door card if we knew what model Audi you have.
You don't have to run the cable all the way to the speakers in the door, you can run it to the amp in the rear and pick the speakers up from there.

 

[Jay]

Its a Audi A3 8L 5 door.

Running it to the back makes sense and sounds easier. Does this mean I can run both left and right speaker wires down the same side (passenger).

I'm using an ISO adapter and dont have a clue where i'd need to connect the speaker wires both at the head unit or in the boot.

Is this alternator whine? Why did it happen after installing the HU?
It seems to go away if I switch the engine off but leave the keys in.

thanks

 

[AndyMac]

On the A3 you maybe better actually running it to the doors as the rear speakers are powered off the same amp as the sub, which is actually inside the tupperware sub enclosure. Real pain to get to.
It is alternator whine and very common when installing an aftermarket HU. Audi use real mickey mouse wiring from the HU to the rear amp, basically the low level pre-outs run the length of the car and are unscreened, so have no protection from electrical interference.
It's worthwhile trying an additional earth from the chassis of the HU and the chassis of the car behind the glovebox, with the engine running and HU on quite loud try different locations until the buzz disappears.
I simply burned a CD with silence on it, and played that at full volume which makes it easier to locate the interference and get rid of it.
If all else fails then rewiring the rears is probably a better solution as the new HU will have more power than the feeble 2 x 20w amp in the sub, so you'll get a better balance with the fronts. The sub will ultimately be way too quiet though.
To connect the rears to the HU, you need a male and female ISO connector. The male end plugs into the existing Audi front speaker loom (brown, with only the middle 4 connections populated), the female plugs into the HU, then cut the 2 pairs of outside leads and connect the new rear speaker cable to them, ensuring +ve to +ve, -ve to -ve. If in doubt about +ve & --ve then simply connect a 1.5v battery between each pair and see if the speaker moves outwards or inwards. +ve on the battery to +ve on the speaker will move the cone outwards.
If you switch the engine off of course it goes away as there is no alternator running to create the interference. Does the buzz go up & down with the engine revs?

 

[Ibzzzzz]

Since installing an aftermarket HU I have had a buzzing sound at low volumes which is getting quite irratating. Someone suggested that I need to wire the speakers directly to the HU instead of running them off the factory amp.

I spoke to someone in Halfrauds who said it may not cure the problem as the front and rear speakers may have different impedance. Is this correct?

How do i take the door cards off? i've looked all over but cant find any screws.

I'm planning on running the speaker wire along the amp power cable and rca cable down is this ok?

Has anyone had to do this or is there another way around it?

thanks

i had the same problem. i was told that the ground wire for the amplifier is not thick enough i changed this and the problem was resolved but to be on the safe side i got better insulated power cable for the amp and better insulated rcas.
i appoligies in advance if this doesnt work for u.

 

[Jay]

Andy that method sounds like a headache! I might just leave it.

Ibzzz I get the same problem when I disconnect my amp so don't think its a problem with the earth lead.

 

[AndyMac]

Jay you didn't mention you're running an aftermarket amp, just an aftermarket HU.
What is the amp driving?
What amp is it?
How have you connected it to the HU?
Why are you still using any of the stock system?

 

[Jay]

Sorry Andy I assumed you knew because of my previous threads.

I'm running an Alpine V12 and a 12" Alpine Type R sub. I'm using the sub outs from the HU to connect to the amp.

The only reason i'm using the stock system is because if i disconnect the audi sub I lose the rear speakers. Sounds a bit ***** just running the front speakers alongside the sub.

 

[AndyMac]

That's actually the perfect setup. You really think the garbage Audi fit to the rears driven by a Nokia 2 x 20w amp is gonna transform the sound?
As you have a proper sub, then rewiring the rears is much easier as you can pick up the wiring off the loom that plugs into the stock tupperware sub.
So all you need to do is run 2 speaker cables from the HU to the boot. Unplug the stock sub and plug the new cables into the connector detailed below. You'll need to crimp some small spade terminals to the ends in order to plug them into the stock connector to avoid cutting the loom. It's a 40 minute job, well worthwhile to avoid compromising your new install.

 

[Jay]

Thanks for this.

Just to be clear I only need to worry about pins 2+3 and 9+10

What guage speaker wire should I use?

 

[Bran]

sorry to nick ur post, but is anyone from the manchester area, as i need help me fitting a system ??

 

[AndyMac]

Jay, yes that's right, any old speaker cable will do as the Audi wiring is already shockingly bad.