I did my aftermarket setup on my RX330.
I am running focal 6.5 components in the front as well as the back on a Hertz amp with an excellent alpine headunit.

Only now I realise the mp3 quality is appalling on some tracks! the Focal Performance series is excellent

Now the problem - I noticed that the left side tweeter emits distortion when the car revvs.

I checked if its because i ran one audio cable on the side of the power cable but while the car was powered up, i pulled out the crossover from under the dash and viola! the distortion stopped.

And the Focal crossovers came with thick wires so i let it hang against the carpet.

Have any of you guys had this problem and do you know any material that can be wrapped round the crossover to limit electromagnetic interference?

 

That's alternator whine. You can get a filter for that.