The next paragraph had been moved from the last line in this reply since the rest was incidental being merely comments on "stress & strain" etc.
However that was before soundman's last reply. But I think we concur. Besides, some amps can be bridged for higher impedance loads. And those that can't can usually be fitted with bridging kits - eg,signal inverters.
But back to my original reply....
That brings me to my only relevant comment in this thread, namely that often domestic speakers are not suited to vehicles for environmental reasons - heat, vibration, etc.
But subs and their enclosures are probably fine - bass vibration generally being worse than g-forces and bumps - provided they handle the heat, or sunlight if exposed.
Nice thread. And I'm far from expert on audio.
In fact a relatively recent learning was that "unconditionally stable" at an Ohmage meant it would handle anything above - eg, a "1 Ohm" amp will handle 2, 4, 8 Ohms etc.
Yes - it's less power, but supposedly fine. (In theory, power decreases by the resistance ratio, eg 8 Ohms will be 2/8 = 1/4 the power output of a 2 Ohm speaker. I also read that "all good amplifiers" exhibit such behavior - not that I see many car amps that do [maybe varying SMPS voltage?].)
I must have been working on too many "tuned" amplifiers where the output impedances were matched, eg transmitters and maybe old audio circuits.
But hence IMO the speaker is seen simply as a resistive load, and hence the higher the resistance, the less the current (and less power).
But thus one point - there is no added stress or strainn on the amplifier because of a higher resistance load/speaker. There is less current, hence generally longer component life and less heating.
[ At least this should be easier than my usual alternator related discussions when many often say adding caps (why?) or bigger batteries increases the alternator's strain, but they're not considering the long-term. It's the opposite that is true - bigger batts etc decreases the "strain" - it saves the alternator having to replace the extra 30% of battery inefficiency used whenever it discharges. And the batt supplies the shortfall instead of the alternator - isn't that less strain?
And as to "strain" - is that appropriate? Is a 1Ω amp strained supplying its spec'd power to a 1Ω load? Is it more strained than on a 2Ω load? For a component POV, IMO yeah, they are more electrically stressed supplying twice the current into the 1Ω load, but to suggest that is bad if that is what the amp is rated and intended to do, but I consider neither a "strain" if strain is a negative term meaning an undesirable state. Different if we were discussing extending life, but we aren't - we are either into rated life & performance, else whatever life given our needs. (Ergo, a 90A alternator outputting 80A instead of 70A is not suffering increased strain.) ]
Nice too to read again the higher the Ohmage (speaker) the better the sound. I've read so many times in (car audio) forums that "the lower the Ohmage, the better the sound". What - less sensitivity is better? I think they mean power output, ie more power (with more distortion).
Some will know my views on having the PSU integral to the amplifier. Even worse is the reduction in speaker impedance from the olde norms of 4 to 16 Ohms etc, though I guess fatalities need to be minimised at very high power outputs (above ~1kW per speaker?). Maybe one day I'll have an engine bay PSU sending HV to a remote amp that drives higher Ohmage performance speakers (as in live-gig musician performances - maybe a few Marshalls or Fender bass speakers in the back?).
And now to implement some executive writing... (LOL - I moved the next to up top.) Oh no - intervening replies!!!