component speakers.

[jhnkvn]

True on the broad side of things. However, on the general car and home audio side of things, there's no matching on amplifier and speakers. Because more than 95% of loudspeakers will typically be in the nominal loads of 1-16Ω -- they're close enough that matching impedance shouldn't be an issue and insignificant. Head-fi has since resistance load of headphones varies wildly from 16Ω to 600Ω and you try to match them with an amplifier that would minimize its impact on the sound curve of the speaker (hence there's hi-gain and low-gain in some headphone amplifiers).

For home audio, 8Ω drivers are the most common, 6Ω can also be found and 4Ω is also rather common. For car audio, 4Ω nominal is pretty much the standard. The reason for the lower impedance is that unlike in home audio where we have 220V on tap, in a car we usually get 12-13.8V -- a lot less than what your household plug has.

As much as I do recommend you optimize your amplifier-speaker combo by trying to get the nominal ratings that best takes advantage of your amplifier. I don't think this should deter anybody from using high impedance speakers. For one, I have a 8Ω driver that's just sitting waiting to be used on my next project. Second, there are people who professionally competes with higher impedance speakers in a car and win.

I might not recommend people run a 1Ω load to a 4Ω-stable amplifier.. but can you use it and actually play it? Yes, you can. Your amplifier simply anticipates the load a speaker will give out. If the resistance is higher, it'll play. If the resistance is lower, it'll protect. Will you cause significant damage to your amplifier? Not really.. well as long as your thermal protection is working properly.

Going from 8Ω to 4Ω usually means a halving of received wattage. However, power isn't really significant in car audio. Too many people are led stray by power ratings. Is 100W twice as loud as 50W? No. It's only +3dB more. Many people think: oh, I need 100W of power to match that 100W of speaker RMS but do they when most background listening only sucks up <30W of power? Remember, given all else the same.. 23W to 100W is simply +6.4dB. Whether those additional decibels is important is up to how loudly one listens.

P.S. Speaker wire skin effect does have an effect but the question is: is it significant? In that light, I'll answer no. In fact, temperature changes would probably yield a bigger effect on our perception of sound. For wires, resistance is king for me. Inductance is too.. but that's more of a PITA as a metric to go for.