left-side car audio weak

[DaveNP]

Originally Posted by markthomas

...
Not really clear on what capacitative coupling is, but it does indeed seem like the left-hand audio is an insubstantial "shadow" of what is sounding so much sonorously across the right-hand side...

Again I'm a fumbler not a fixer but in my simplistic terms

A capacitor is two conductors separated by an insulator, DC will not pass through it due to the insulator, but when we apply a voltage to one terminal the charge appearing on one side will induce a charge on the other (in the way of static electricity), in DC that is insignificant but with AC the charge changing on one side will cause the charge to change on the other and the AC voltage shows up on the other terminal, the higher the frequency the more effective this becomes so sound becomes more tinny and less sonorous. If you've got a wire with a poor conductor the AC voltage can thereby jump the gap (with very little current flow), but a proper capacitor uses a relatively large area of two pieces of foil separated by a special insulator rather than the tiny area of the end of a wire with an air gap.

I'm scratching about now and this may need to go to a better qualified person but-
You could try each signal wire for DC resistance (and compare to the same wire from the right side) although as it appears to be on all left side speakers they may use a common earth return which may be the problem.

[Donmac]

Originally Posted by markthomas

Hello again. Yes, Dave NP, the problem must surely be the wiring (as opposed to the HU itself, because again, I have even swapped HUs, with no change)... but where would be the wiring glitch be that would at once affect all three left-hand speakers (even as each of them is on its own circuit, if I'm not mistaken)? .

Is there a small black brick in the door that serves to filter and direct the sound frequencies to the correct speakers,( i.e. bass to woofers, treble to tweeters)? Failure of one would account for what you're hearing. If there is then try swapping left and right.

After this I fear your best bet is to check/clean the multipin connectors between door and HU for corrosion from weather ingress.

Good luck!

[markthomas]

Originally Posted by DaveNP

You could try each signal wire for DC resistance (and compare to the same wire from the right side) although as it appears to be on all left side speakers they may use a common earth return which may be the problem.

I have indeed confirmed that every speaker wire on the left side (i.e., each + and - wire for left tweeter/left door cone/left rear cone) is clean, showing 0.00 DC resistance. Which did indeed lead me to suspect a bad common ground (earth return) for the left-hand side.

I thought I had correctly surmised, from the pin diagram, that pin 1 was the ground for all the left-hand speaker pins. But there is 0.00 resistance in the (constantly powered) circuit at pins 1 and 3 (same for the one at pins 7 and 9). Also 0.00 resistance in the (switched) circuit between pins 1 and 8 (same for the one at 7 and 8). Full 12V DC between all these pairs as well. So the ground wires at both pins 1 and 7 seem healthy.

If there is any other sort of reading I need to be taking somewhere here, I will jump on it!

Originally Posted by Donmac

Is there a small black brick in the door that serves to filter and direct the sound frequencies to the correct speakers,( i.e. bass to woofers, treble to tweeters)? Failure of one would account for what you're hearing. If there is then try swapping left and right.

Is there an image I can see for reference? Is it near the door hinge? Is it possible for this "brick" to be garbage but for the wires from left-hand speakers to corresponding connectors/pins at HU to still read clean?

I truly appreciate everyone's willingness to chime in here...

[DaveNP]

I'm afraid I've reached the limits of my fumbling ability on this one so can't suggest any more