Does speaker wire length matter between left and right channels?

Doesn't matter in the slightest.

IIRC electrons travel at 200,000 kilometres per second. So if your passenger door channel had a 125 mile long cable, you may notice a lag of 1 millisecond.

Those electrons are moving way to fast to make a difference at those distances.

Nope.

I believe those electrons are moving at a speed that would circle the planet 6 times a second (am I right?). More important is the distance of the listener from each speaker as the soundwaves travel much slower and you would potentially want to delay the sound from the closer speaker if your DSP allows.

In a car, no. The added length will add a tiny bit of resistance than will lower the volume level slightly, but given that we don’t sit at exactly the same distance from each speaker, it’s inconsequential.

Makes no difference. Obviously there won’t be any latency due to the distance, don’t add extra wire to compensate. Extra wire might just add noise depending on how you bunch it up.

Also, the electrons aren’t actually moving at the speed of light, the force carried by those charges is. Just a small correction to some of the replies here, doesn’t really matter though lol i’m just being pedantic. It’s interesting though, depending on the amperage, the electrons actually move very very slowly.

Edit: another comment mentioned the added resistance, yes this is true if your using less-than-adequate wiring. Always use OFC for all your wiring and this is a non issue.

We’ll only know if we measure it.

However I have heard longer wires have more capacitance, and they definitely have more resistance, so there could be an effect, but I don’t think anyone cares because it’s so minimal and a vehicle isn’t an ideal listening environment.