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In Reply to: RE: Fostex alnico tweeters posted by Crazy Dave on December 16, 2016 at 12:38:00
Since the tweeter will aim all frequencies straight ahead whose wavelength is smaller than the tweeter's diameter, I have wondered why you wouldn't have to aim any supertweeter directly (horizontally & vertically) at the corresponding ear to even receive the higher frequency sounds at all.
For example, 20 kKz is 0.678" in length, so shouldn't any supertweeter have to be smaller than a half inch in diameter to be picked up by the listener off-axis (seemingly would require the left supertweeter to be aimed precisely at the listener's left ear and the same for the right channel)? 30 KHz (0.452") would seemingly require laser-like focus of the supertweeter at the listener's ears.
And yet I routinely see images of systems with the supertweeter aimed off-axis and often above the listener's ears as well.
Please correct me if I am wrong. I would love to understand this concept better.
Best regards,
Jim Smith
Follow Ups:
"Since the tweeter will aim all frequencies straight ahead whose wavelength is smaller than the tweeter's diameter, I have wondered why you wouldn't have to aim any supertweeter directly (horizontally & vertically) at the corresponding ear to even receive the higher frequency sounds at all."You're referring to theory. Harry Olson, in "Acoustical Engineering", described this. However, that isn't how it works in reality. Other factors come into play. Olson also noted this.
With regard to tweeters being "aimed" off-axis, this may be an attempt to improve the direct and/or ambient soundfield in some rooms with some speaker/room combinations.
Hope this helps.
:)
Edits: 12/21/16
Theoretically, the dispersion is narrow, because that is what is specified, even at lower frequencies. The Selenium ST200 tweeter is specified as 40 degrees x 40 degrees dispersion. However, I was more interested in what an advocate of this tweeter actually experienced, since theory does not aways predict what actually is experienced. Being in my late 50's, I don't expect I hear much at 20kHz.
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