Regarding the "general ratio", I don't think so. I also don't think there's much of a standard for what's peak.I should have been more clear, my question was specifically in relation to subwoofers and midbasses/midranges, not tweeters. Crest factor doesn't really help either, because we don't listen to the same song all the time.
Even "RMS" is kind of ridiculous because there really isn't anything called "RMS Power". RMS is a property of an AC voltage. So, RMS is a VOLTAGE that, when squared and divided by the load's impedance, provides some amount of power.
The ACTUAL rating should be "continuous average".
There are a lot of ways to measure this but standard procedure is to use a noise of some kind--pink noise, for example. So, if the speaker is to handle 100 watts, then the amplifier's output is calibrated using a voltage for the speaker's impedance that results in 100 watts. Then, pink noise is played through the speaker. Pink noise is white noise (equal energy at every frequency) passed through a pink filter, which is a 3dB/oct low pass filter. So, 20Hz is the only frequency that gets the full 100 watts. at 40Hz, it's 50 watts. At 80Hz it's 25 watts and so on and so forth until 20k is 0.1 watts.
So, for midbass and midrange, the rating depends a lot on whether it's tested with a crossover or without a crossover.
CTA has a standard for this. EIAJ apparently has a standard for this. Maybe DIN has a standard for this. And on and on and on and on.
But, whether the rating is RMS or continuous average, this is the amount of continuous power your speaker will handle if it's a sub. If it's a midbass, midrange or tweeter, then it has likely been tested using a high pass filter--because this is how speakers work.
And no matter what people THINK they're sending to their mids and tweeters, they're likely sending a lot less simply because of how power is distributed in most music.
It isn't straightforward at all and none of my attempts to explain it over that past 20 years has been sufficient. The notion that speakers should be "overpowered" should only apply to listeners who can hear distortion in their speakers and will manage the levels appropriately. Overpowering doesn't PREVENT damage.