Wow! These are interesting responses.
 
It never really registered to me how differently folks are hearing my music. I always knew that hearing high frequencies declined as we aged but never really thought that much about it.
 
Sometimes I think I want my cymbals to "sizzle" more and I'll adjust those frequencies. Then I'll listen back and swear that I can hear a difference. Perhaps I'm not hearing a difference but am just more focused while listening and I only think that I'm hearing a difference.

I can just hear the 15K if I turned my headphones up a lot. But nothing above that. I guess that's normal at 40, and pretty amazing considering all the 12 hour raves I went to in my youth, as well as being in a thrash metal band at 17, and of course a lifetime of headphone use. 
 
It's sad to know that there's nothing you can do to get the high frequencies back when you get older. I can still remember what it was like to hear as a kid....I used to hear ridiculously high pitched harmonics in people's voices that had an almost metallic quality. Can't really describe it better than that...but I certainly don't hear them anymore!
 
I take a high powered magnesium supplement every day (Natural Calm) and especially before I do any work on headphones. Magnesium is proven to protect the ears from noise exposure so I consider it worth doing. 

just remember
 
boosting ABOVE 15k still effects harmonic content of stuff BELOW 15k
 
 
but if you can't hear that, there's not much point
 
 

Oh and regarding that YouTube video, I wonder how many hearing specialists would endorse such an online test? I bet it's nowhere near as accurate as a proper medical hearing test. Nonetheless, it's scary how many people in the comments are reporting high frequency loss at young ages. This is the explosion of iPods and loud earbuds over the last 10 years or so. I read something in the papers a while ago saying that hearing loss is endemic among the young because of it. 
 

 
Thanks for all the responses. I think this is very interesting.
 
I checked out jbow's link in his above post and tried that test. If I kept the volume level static throughout the test I could hear until about 12,000. If turned the volume up extremely loud I could hear things all the way until the end but it sounded as though the signal was not a "steady" frequency but rather going up and down the spectrum of frequencies so I'm a bit confused about that one.

sharke
Oh and regarding that YouTube video, I wonder how many hearing specialists would endorse such an online test? I bet it's nowhere near as accurate as a proper medical hearing test. Nonetheless, it's scary how many people in the comments are reporting high frequency loss at young ages. This is the explosion of iPods and loud earbuds over the last 10 years or so. I read something in the papers a while ago saying that hearing loss is endemic among the young because of it. 
 

I've often wondered about that. It is sad. I ask my grand daughters all the time about it when they have buds in. I always encourage them to keep it LOW. Who ever heard of quiet RocknRoll though?
Do you remember the stereo wars of the 1970s? Mostly Pioneer and Sansui but Marantz and a few others. They made some KILLER home stereos. I have a Pioneer SX-1010 and a Sansui that runs about 70w per channel. I mostly use the Sansui because I have the matching speakers with the wood lattice but the Pioneer is a beast. It is 110w per channel (100w RMS at .05% THD). I don't have speakers I am willing to risk by using it yet. I need to get a pair that will shine with it. Now what were we talking about and why can't we hear??
J

Should the fact that I can hear 20Hz loud and clear offset the disappointment I have at not being able to hear above 15K? Think I'm going to concentrate on reggae and dubstep from now on 

you should search for the 'brown note'
 

I couldn't hear past 8K on the first test, but I just barely made it up to 11K on the second test.  

I could easily hear 15k, and possibly 16k, but I'm not sure about the frequencies above that (I could tell something was going on - just couldn't make out what).
 
Not bad when you're about 50!
 
Considering the loud stuff I've subjected myself to I'm a bit surprised.  80,000 watts at an underground club comes to mind. I actually saw a girl with very long hair put her head in front of a large speaker cab (one of several that made up a wall about 12' x 12') and her hair was going straight back due to the are coming out of the speaker...