Is a speaker's maximum power handling capacity an over rated specification?

[Acid Test]

Just thinking that what is more important to me is the speaker's maximum volume.

It seems, especially for 4x12" cabs, that in most cases, it would be difficult to exceed the speaker's power handling unless you are using an unusual amount of power or really low power handling speakers.

Even more to the point, if you are using a lot of power then are you not trying to get more volume. A speaker's maximum volume seems like a better spec.

[sharpshooter]

In a word,,yes. The wattage rating largely pertains to the ability of the speakers voice coil/motor to dissipate heat. At lower freqs, (dropped tuning, and/or bass), many speakers are really limited by the X-max excursion level, and will reach their mechanical limits long before their wattage limits.

[Tone_Terrific]

Wattage rating is critical to matching to amp power, even if the specs are wonky for both max power and pwr handling, you can get into the ballpark.
Max SPL level and a host of other specs are not published, partially because the cab design, acoustics, frequency chosen, etc., are all factors and difficult to quantify.
There is no substitute for trying it out yourself.....too bad.

[Jef Bardsley]

I wouldn't say it's over-rated, as the biggest concern for most players is not toasting the buggers.

And I'm not sure those using a lot of power are trying to get louder, in many cases they're simply trying to get "that sound" out of the tubes. Witness the popularity of 'small tube' amps and attenuators these days - both are means of getting that sound and keeping your ears intact.

But, if max volume is your goal, then sensitivity will move up the ladder of importance. Still, what sharpshooter and Tone Terrific say is true - Xmax is equally important, especially if you're down-tuning, and sensitivity isn't linear for guitar speakers. That is, the most efficient speaker at one watt may not be the most efficient at 50 watts.

[GCDEF]

It's a useful spec that some people seem to misinterpret. You certainly need to know how much power it can safely handle. You need to know that Greenback isn't going to work in your 100 watt combo, and its max SPL isn't going to tell you anything about that.

Wattage, sensitivity, max SPL, resonant frequency, frequency response... all the specs are useful in figuring out what the speaker will do for you.