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In Reply to: Speculation about cause... posted by Al Sekela on March 7, 2007 at 11:43:58:
"Since we don't hear the frequencies these devices produce as sound, there is a question of whether they do anything that could affect what we do hear."My thought is that they provide constructive and destructive interference with the existing tweeter in the range that their outputs overlap and, perhaps, intermodulation at audible frequencies. Of course, I am not talking about extending the frequency response, per se, but about doing it with an add-on device. Of necessity, they are situated many times more than 1/2 wavelength apart and cannot act as a single source.
Follow Ups:
and have a large roll off before the get close these can be mated to a super tweeter.And tweeters with ultra sonic range are not a good canidate for a ST. A 3/4in tweeter again is not the best to mate a ST to. But adding to full range drivers, electrosatic or planars.Or systems with reduce hifrequincy they can work well of course you need to take account of spacing etc.And I think you forgot ribbons which wave launch diferant from cones domes etc.
... I first heard a pair of supertweeters at Max Townshend's home. These were protoypes so that must be taken into account. However Max demonstrated them with his huge full range speakers and I was then impressed by the added sense of spaciousness. However, later in the day the supertweeters were run without the other speakers and I could still hear a "twittering" sound from them. This was quite audible and I would estimate within my normal range of hearing (which being over 50 years old is not, according to the last audiology test that I had, very extended).A couple of years later and a friend had bought a pair of production samples and had mated them with a pair of Sonus Fabers. When I entered his room he had a BBC radio play on FM playing. The speech was unusually sibilant which is a factor that I neither associate with BBC engineering nor with the Sonus Fabers. As my friend left the room to make some coffee I took the opportunity to be a bit naughty and turned down the supertweeters to minimum and then off (they have level controls). The sibilance disappeared. Now FM radio only has a programme bandwidth extending to 15kHz so whatever the supertweeters were doing it wasn't extending the envelope from 20kHz to some supersonic (from a conventional viewpoint) frequency. They were doing something below 15kHz.
Moving forward to a few months later, Keith Howard measured a pair in a review in Hi Fi News and got useable output below 10kHz.
To echo Mr. Howard's review - until one finds a supertweeter with brick wall lower cut off at 20kHz then their touted effect is highly questionable.
"To echo Mr. Howard's review - until one finds a supertweeter with brick wall lower cut off at 20kHz then their touted effect is highly questionable." Questionable, even then.
US Army researchers in the early 50's and Cal State researchers in the mid 90's verifed that even though humans can not "hear" untrasonic frequencies they are still aware of their presence. While ultrasonic frequencies are not heard, they excite the auditory mechanism, sending data to the brain, which is aknowledged on a subconscious level. The subconscious sensation enhances the percpetion of what is heard. In addition the same process is part of the reason why some consider the nyquist frequency to have a negative impact on the sound of RedBook digital.Best,
several manufacturer's websites (manufacturers of supertweeters), aparently we do no listen to those ultra high frecuencies but we perceive them. Best, Antonio Machado.
let's have the references to those papers, please.
Hello there: first to tell you thank you very much since during many years your comments and opinions on this Forums (and sometimes your answers to my specific questions) have helped me to get a better sound from my very fine two-chanel system. Now I have two questions for you: (a) when you say "off necessity, they are situated many times more than 1/2 wavelength apart and can not act as a single source" I don't understand what you mean, could you please elaborate and explain me more that statement ? (b) I am also considering a pair of supertweeters as an interesting addition to my Ambience Superslim 1800se Ribbon Hybrid speakers, kindly check them out at www.ambiencespeakers.com.au and I have some space limitations. Do you think I would get the same benefits from the supertweeters any place I can place them, let's say over the audio rack, or at the buttom of my actual speakers, or next to them, or on top of them, etc. ? I understand they are not directional so placement shouldn't be an issue, but again I have no previous experience with supertweeters and I would like to listen to your insights. Best, Antonio Machado
The Murata supertweeters are quite good Antonio, you might want to add those to your list to research.
Where you put any driver in relation to another is very important. In order for two drivers reproducing the same signal to act as a single source and NOT produce constructive/destructive interference (resulting in reduced dispersion, Venetian Blind effects and, possibly, lobing), they must be within 1/2 wavelength of each other. This applies to multiple drivers in the same bandpass (e.g., multiple woofers) or to two drivers sharing a band of frequencies at crossover.Consequently, I do not believe that any add-on supertweeter, regardless of how extended or smooth its FR is, can peacefully co-exist with another tweeter. Of course, that doesn't mean that someone might find (or imagine) the effect to be an improvement.
All that aside, why are you thinking of adding such to your speakers?
Hello there: I have a pair of Ribbon Speakers, Ambience Superslim 1800se and they are great in the middle range, transparency, clarity, abundant inner detail, very musical speakers. Nevertheless Ribbons are not good enough at the bass area, so I recently added a Velodyne DD15 Subwoofer better the bass, with extraordinary, excellent results. So I was wondering if a Supertweeter could help me to extend my spectrum in the high area. I have been reading about it and I might try a pair. On the other hand, I have heard that Supertweeters better the sound not just in the highs but in the middle range and the bass area as well. Not being a knowledge person myself, I just guess it is about Physic laws. Field of Supertweeters is a very interesting, intriguing one. Thanks again, Best, Antonio Machado.
I think that you should see if you can get them on loan or with return privilege. Then you can try them and see if they will do what you want.
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