Harmonics don't fall neatly on divisions, but the first harmonic is at about 50% and the subsequent harmonics are at roughly double. I believe I'm correct on that. Feel free to fact check me.
And jerg, the difference between 12.5kHz and 15kHz might sound like a lot to you just by looking at numbers on a piece of paper. After all, that's a difference of 2,500 which is a whole lot, right?! But in actuality, it's only one note different on the musical scale... do, re, me, so, etc. Just from one note to the next- do to re. Human's hear about seven octaves (do to do). The difference between 12.5 and 15 represents less than 2% of the range of human hearing. That really isn't very much at all.
In addition to all that, 12.5kHz is higher in frequency than any musical instrument goes. It's higher than most of the harmonics that musical instruments produce. It's beyond the point where you can perceive a frequency as a musical note. Humans perceive that last octave of sound basically as noise.
Too many audiophiles worry about numbers on a spec sheet without a clue as to what kind of sound those numbers represent as sound. If you take the difference between a rolloff at 12.5kHz and a rolloff at 15kHz and relate it to actual human hearing, it flat out doesn't really matter. The truth is, you could roll off at 9kHz and it probably would only barely affect sound quality. There are other things that mean MUCH MUCH more and are much harder to achieve. And the Oppo PM-1s nail just about every one of those.