Thoughts on adding a Super tweeter .

I agree with the Tennis man on the overabundance of upper mid / lower treble energy. I base this assertion on my experience at CES / THE this year. Room after room had this characteristic. Even my own system has it to a degree, which annoyed me until I came home from CES. Then I turned on my system and it was a relief, because many (most?) of the rooms at the show had it far worse than my system does.

Also, keep in mind that a CD can not reproduce sounds above 20KHz. While it may theoretically be capable of producing "perfect sound" below this frequency, it has never been billed as having any capability above that point. So what you will be reproducing from a CD is not the musical content,but the residual digital noise that doesn't get filtered out by the player's filters. The better your player, the less of this there should be. Maybe if you're playing analog, there would be some content from the original event buried in the grooves.

I heard a super tweeter on a neighbor's SET system. Although there was
noticeable HF extension over his single driver speakers, the superimposed
lower HF brought on a heightened upward tilt that I didn't care for.

My experience is a bit different than most of what has been reported here.

I am definitely not an insect: my hearing dies well short of 15kHz, however the addition of the Townsend supertweeters to my Quads was a revelation: the entire sound stage became better developed (source is vinyl). I did not hear increased upper frequency 'hash': in fact the upper midrange is where I heard the most dramatic improvements (perceived improved clarity, lucidity). The overall effect: 'it sounds more real'.

I don't really 'hear' the supertweeters when listening, but it is quite noticable if you take them away. My non-audiophile wife was listening with me and clearly heard the difference when the tweets where taken out and put back into my system. I have also heard from other quad owners that the Townsend's enhanced their systems in a similar manner. The Quads do not have 'dc to light' frequency response so YMMV.

The addition of the supertweets is somewhat akin to the addition of a good, well integrated subwoofer; with a 'woof it's not merely the lower frequencies that are audibly improved, the upper frequency ranges also benefit.

I think this is one of those 'listen for yourself in your own system' situations. Supertweets cannot be dismissed as 'crackpot audiophile psuedoscience'. They can make an audible improvment in a high resolution audio system.

Cjsmithmd,et al...The reason for my post was for a couple of reasons(thanks to all,for responding).I have heard the Townshends(I like the Muratas,but they come in too low,to consider)in a fellow music lover's wonderful set-up.He was sporting the "shockingly good" Sonus Faber Extremas,a design long since gone(what a mistake,to discontinue these),and since I believe those had a tweeter roll off of 17khz,he gave the Townshends their day in court.BOY,the difference was NOT subtle.Better air/texture!For sure!Much more palpable.
So,with the non- stop talk of Berrylium/Diamond tweets,I simply felt,maybe,I could get that extra something,I read so much about.Bear in mind I felt my own speakers,which are flat to 25khz,had more air/extension,than the stock Extremas,but the Townshend demo was amazing.
Now,some time ago I added a Rel Stentor sub,to integrate with my system.I have my speakers almost 9 feet out from the rear wall,and have a very deep "stage presentation".However,as my speaker is a sealed box design,I suspected I could gain a touch(that's all I was looking for)of added heft/depth,in the lowest frequencies.
My friends were all dead set against this,as my speakers are amazingly fast,and articulate in the midbass.They did not think I could get a good blend.They were wrong,thankfully.Though it took me a long time to get past the "WOW I have loads of bass,and isn't it fun" factor.The blend is now,absolutely seamless,and hence my having a sneaky suspicion that I could pull a "touch" more off,in high freq air,or whatever.
Believe me,I could be making a mistake here,and am aware of it,as the Townshend comes in,and will overlap my own tweets by about 5khz.This can be trouble,and if my bass experience is an example(any overlap in low frequencies came off as "tubbyness") I can easily screw up something I have no actual criticisms of.YET,AND YET...I am always trying to push the envelope,and believe in my system.This could spell trouble,but as I see it,I may have to scratch the issue,or take a trial run.
I hope to get some meaningful feedback by those(few?)who have possibly tried or heard a supertweeter on a speaker with an,already extended high freq response.
Thanks,so much.