Regarding supertweeters

I believe in supertweeters, because I know, from personal experience, that auditory ability exists well above the frequency at which you can detect the pure sine wave that is used for testing.

However, I think you may be on to a point about CDs, and their 20KHz limitation. Some LPs can go a bit higher, but there is some argument about how high, and it certainly varies a lot between different LPs. If there is no signal at 30KHz, a supertweeter good to 50KHz is just an expensive paperweight. Probably the best application for a supertweeter (apart from some very exceptional vinyl systems) would be a SACD or DVDA system, where there is no doubt about the ability to have signal above 20KHz. Of course, the recording equipment must be good enough to include this signal.

Hifimannen, in order for the supertweet to contribute (musical) supersonic sound this content (sound) must be on the storage medium in the first place. It rarely is, as Eldartford notes.

Further, no cdp plays over 20k. What is there is often spurious hi frequency noise (unless you throw a sine at it).

Even further, if yr amp specifies 20kHz then its amplitude response will be much reduced beyond that --limiting the usefulness of a supertweet.

To make things worse, our ears' sensitivity typically goes down as the frequencies go up over 3kHz (i.e. to our ears, a louder signal at say 10kHz will sound as loud as a soft signal at 3kHz).

Ultimately, a supertweet usually functions as a "supratweet", intensifying (i.e.playing in conjunction with the nromal tweet) ordinary audio frequency signals over 13kHz or so -- thereby creating the effect of "spaceousness".

thank u! a little more clear on this now. Gregm, if the supertweeter helps the standard tweeter from as u say 13kHz or so,- will it not be very difficult to calibrate the two tweeters to eachother so the frequenses dont "crash"? maybe a stupid question, i dont know much about it. also, the Tannoy s.tweeters can be set to where they are supposed to "take over". from what i understood u are supposed to set them exactly where the standard cant follow anymore, but of course..u can set it to boost the standard as u say. but - as i understand u guys, if i dont get a cd player that can play above 20000, and do not have an amp. playing above 20000, theres no need for a supertweeter. other than helping out in the standard 20-20000 with ordinary cd's. lack of either that special cd player or amp. will also ruin the point..

also.. the reading on the back of most amps and cd players that say 20-20000.. isnt that meant just to say that either the cdp. or amp. give strong signals in 20-20K? it doesnt mean nothing under or above those figures are let through?
heh.. am i being difficult?

The wavelength of 20KHz sound is 0.66 inch. Therefore there is no need to carefully align the supertweeter and the tweeter for phasing reasons. Slight changes of listener position will affect the relative phasing of multiple drivers, so there is no "right" position. Perhaps the best approach is to aim the supertweeter at the wall behind the speaker, and many designs that include supertweeters do this.