Which diaphragm shape has the greatest dispersion?

454Casull · 19th July 2004, 11:46 PM

Or do they all equally radiate sound off-axis? The reason I ask is this:

"The concave dome allows a smaller diameter voice coil which is then better coupled to any given point on the dome. This concave shape also produces an almost perfect waveform (its main strength), reproducing the original signal with an accuracy that a convex dome never can. This accurate sound is also dispersed widely (its second main strength), down only a few dB at the highest frequencies even at 180 degrees off axis."

http://humanspeakers.com/diy/drivers.htm

GRollins · 19th July 2004, 11:54 PM

The smallest one--relative to the wavelength being reproduced--is going to be the one with the best dispersion. The tradeoff being that smaller diaphrams produce less SPL for a given excursion.

Grey

Ron E · 20th July 2004, 12:09 AM

The reasoning behind the human speakers blurb is that dome tweeters when they break up degenerate into a ring radiator the size of the voice coil. Using a smaller voice coil will give you better dispersion if the dome is breaking up. For hard domes where the breakup is outside the audible range, there would be no difference between concave/small VC and convex/large VC. As it is, even with soft domes, there is precious little difference.....

Focal domes use this technique, and it seems to cause more problems than it solves in the HF region. Both their kevlar and metal (Ti) domes have nasty peaks in the 15-20kHz range. IT would be interesting to find out if the human has this problem as well.

454Casull · 20th July 2004, 12:18 AM

Ah, that clears it up a lot! I guess their claim of being down only a few dB 180 degrees OA is pretty off.

19th July 2004, 11:46 PM	#1
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	Which diaphragm shape has the greatest dispersion? Or do they all equally radiate sound off-axis? The reason I ask is this: "The concave dome allows a smaller diameter voice coil which is then better coupled to any given point on the dome. This concave shape also produces an almost perfect waveform (its main strength), reproducing the original signal with an accuracy that a convex dome never can. This accurate sound is also dispersed widely (its second main strength), down only a few dB at the highest frequencies even at 180 degrees off axis." http://humanspeakers.com/diy/drivers.htm

20th July 2004, 12:09 AM	#3
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	The reasoning behind the human speakers blurb is that dome tweeters when they break up degenerate into a ring radiator the size of the voice coil. Using a smaller voice coil will give you better dispersion if the dome is breaking up. For hard domes where the breakup is outside the audible range, there would be no difference between concave/small VC and convex/large VC. As it is, even with soft domes, there is precious little difference..... Focal domes use this technique, and it seems to cause more problems than it solves in the HF region. Both their kevlar and metal (Ti) domes have nasty peaks in the 15-20kHz range. IT would be interesting to find out if the human has this problem as well. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

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19th July 2004, 11:54 PM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	The smallest one--relative to the wavelength being reproduced--is going to be the one with the best dispersion. The tradeoff being that smaller diaphrams produce less SPL for a given excursion. Grey

20th July 2004, 12:18 AM	#4
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	Ah, that clears it up a lot! I guess their claim of being down only a few dB 180 degrees OA is pretty off.

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