can't find it listed on the speaker or on Eminence site, but acc. to Parts Express, it is 450 watts RMS. and there are some nice customer reviews on the Parts Express site for this speaker too, btw....
let me add that this was used in a Dr. Bass 115 cab (came w/ the cab), and it always sounded fantastic as a stand-alone (what i got it for, being 4 ohm).... in that Dr. Bass cab, even w/ the tweeter turned off there was a great range of tone coming out of the 15" b/c the Dr. Bass crossover is actually a hi-pass filter for the tweeter.. so the 15" gets full range... and this speaker really sounds great. w/ the tweeter dialed in, it gives you everything you could need, in a 4 ohm, perfect stand alone set up for medium size gigs...
thanks for looking!