Speaker Whine Fixed On R33

[diamondjo]

Hi guys,

Until recently I was a victim of the dreaded alternator whine and I thought I'd share my little story so that it might help someone else someday.

I've been putting up with this whining for weeks and I'd had just about enough of it. Well, the other day I bought a power filter from Jaycar, spent about an hour hooking it up and... no difference - still whining. The interesting thing is the whine would stay there even if the head unit was switched off with the facia removed. It was getting very frustrating because it spoiled the sound of the engine - which I was beginning to miss!

The speakers I have are the kevlar 6.5" coaxials from Jaycar and these speakers have an inline crossover that just looks like a heatshrinked matchbox. Turns out what was happening was this; when I was driving along, the crossover on the passanger side would dangle very close to the battery. With the alternator charging the battery while the engine was running, this was enough to enduce a current in the crossover which translated into a whine from the tweeter.

I have since fixed the crossover as far away from the battery as I can get and this has sorted the problem right out.

Hope this helps someone

Iain

[RANDY]

So when I ran my speakers off an amp, (tried two new amps) the fronts were making the whine. Headunit off or not, the whine was there. Changed cables and everything, and my crossovers are only for the fronts, and they are in the doors, well away from any power wiring. =-/

[diamondjo]

So when I ran my speakers off an amp, (tried two new amps) the fronts were making the whine. Headunit off or not, the whine was there. Changed cables and everything, and my crossovers are only for the fronts, and they are in the doors, well away from any power wiring. =-/

Did you try all the usual things like finding another earth for your head-unit/amp, power filter for headunit/amp, inline RCA filter for amp (but that spoils the sound).

Does the whine go up and down with the speed of the engine?

Perhaps you haven't got a good earth?

[RANDY]

Ah yeah.. i've posted in several of these threads...

different earth on HU, bigger earth, short cable.

Different earth on amp, bigger earth, short cable, resistance check with multimeter.

Power filter on amp, same deal. Swapped RCA cables, ran cables outside the car... I gave up on the idea in the end. It was the first time i'd ever amp'd speakers, so I just went back to amping the sub on its own like I have in my previous cars.

Whine goes up with revs, yeah. Alternator noise. If I hold the RCA's closer to the yellow plug behind the HU, it gets louder. I routed it as far out of the way as possible, but it was still quite loud. It didn't affect the rears, or if I swapped RCA cables (front for rear) then the rears would cop it more than the fronts.

I think my HU earthing for the RCA's is shot... it's the only thing I haven't been able to properly fix.

[diamondjo]

Ah yeah.. i've posted in several of these threads...

different earth on HU, bigger earth, short cable.

Different earth on amp, bigger earth, short cable, resistance check with multimeter.

Power filter on amp, same deal. Swapped RCA cables, ran cables outside the car... I gave up on the idea in the end. It was the first time i'd ever amp'd speakers, so I just went back to amping the sub on its own like I have in my previous cars.

Whine goes up with revs, yeah. Alternator noise. If I hold the RCA's closer to the yellow plug behind the HU, it gets louder. I routed it as far out of the way as possible, but it was still quite loud. It didn't affect the rears, or if I swapped RCA cables (front for rear) then the rears would cop it more than the fronts.

I think my HU earthing for the RCA's is shot... it's the only thing I haven't been able to properly fix.

When you say yellow plug, what do you mean? The larger yellow power cable? Hmmm, you didn't mention if you power filtered the head unit - have you tried that?

If you do mean the yellow power cable, I suppose it's entirely possible that this could be the source of your problem. Is your HU wired directly to the battery or are you taking a feed off something else (e.g. the existing HU power cable on your loom)? It sounds like the only thing you haven't changed in the equation is your HU and power filtering of the head unit.

I'd take the power filter off your amp and stick it on the HU to see if that will make any difference. Also, if you've got a spare HU lying around (lol, who hasn't), have you tried swapping that back in to see if it works okay?

Also, another thing to try is to buy an inline RCA filter (Dick Smith, Tandy, Altronics, Jaycar sell them). It can muddy out the sound a bit, but its worth it just to see if that's your problem or not. I missed where you live, but if your in Perth, I actually have one I'm not using.

Here's a link:

http://tinyurl.com/ylk2bh

[RANDY]

heh.. umm.. there is a large harness of wires behind the HU (factory) and the plug on it is yellow.

I used the power and ignition wiring from the factory loom... I didn't think this was an issue with the headunit because all the speakers are totally fine when they run directly from it.

it was only when I was moving the RCA cables around, that I noticed that the noise went louder when I pressed them against that yellow plug. I suspect that harness has the rev signal wire going through it.

I was going to try my other headunit, but at the time I remembered that I fitted it to my gf's car, and now I have no spare. So I gave up after LOTS of reading and searching and just ran it the way I have always run my stereo's before. Sub amped, speakers to headunit. Works a treat really.

thanks for the suggestions though... there doesn't seem to be ONE fix for this problem. I'm still convinced that it's an RCA grounding issue between amp and headunit though.

[diamondjo]

No worries mate. I'd really try filtering your HU though if you ever feel like doing it again. The reason you won't have noticed it through your speakers is because you have a lot more power running through them than you do have running through the RCAs.

That is to say, you're running at a higher signal to noise ratio.

There is a lot of power going through the speakers wires along with a little bit of alternator noise so it's not so noticable.

The line level going through your RCA's is very low powered, it doesn't need to be very high because it's the amplifiers job to make it louder. The problem is, you've got the same little amount of noise going through those cables along with a little amount of signal. The amplifier takes the noisy signal and just makes it louder. That's why the whine is a lot more noticable when you run your speakers off an amp.

I'm not very good at explaining this so I've drawn you a little diagram.

Hope this helps

Iain

P.S. There is no point in power filtering your amp if this is the case - you have to filer out the noise at it's source. The reason filtering the amp wasn't working for you was because the signal was already noisy by the time it got to the amp.

Edited November 22, 2006 by diamondjo

[RANDY]

Makes perfect sense =-]

I kinda already knew this. (2v along RCA) And the reason I don't hear it through my sub, which is now the only thing running off the amp, is because the amp is doing a low-pass filter which chops off the top of the frequency range, and the sub itself by nature doesn't reproduce those frequencies.

Oh well... my Skyline can't be perfect in EVERY way for me. ;o)

Thanks for the info though!