Acoustic Center?

angsuman · 17th April 2006, 11:27 PM

I've looked for it everywhere, but i'm curious what defines the acoustic center for a driver with a phase plug? Not that i'm seeking time-alignment in a future design, but i'm curious if the acoustic center is always located at the voicecoil or if its at other parts. For example in a dome tweeter is the acoustic center at the voice coil edges or at the tip or the dome. Same question for a phase plug? Is the end of the phase plug considered the acoustic center of a driver.

soongsc · 18th April 2006, 12:51 AM

Quote:

Originally posted by angsuman
I've looked for it everywhere, but i'm curious what defines the acoustic center for a driver with a phase plug? Not that i'm seeking time-alignment in a future design, but i'm curious if the acoustic center is always located at the voicecoil or if its at other parts. For example in a dome tweeter is the acoustic center at the voice coil edges or at the tip or the dome. Same question for a phase plug? Is the end of the phase plug considered the acoustic center of a driver.

According to measurements, it seems closer to the tip of the center part whether cap or phase plug.

David Gatti · 18th April 2006, 12:55 AM

I usually approximate the acoustic centre as the point at which the voicecoil former attaches to the diaphram, whether it's a cone with/without a phase plug, or dome.
This seem to be a pretty accurate estimate in my subsequent measurements. Some say it's slightly forward of this point which may be the case but it depends on diaphragm material, cone geometry etc.

angsuman · 18th April 2006, 04:57 AM

Oh so a phase plug doesn't have an affect on where the acoustic center is? So generally its at the former to cone joint?

Curmudgeon · 18th April 2006, 06:32 AM

IIRC Dickason says that it is nominally at the air gap, and my measurements of mid and tweets confirmed that. (Although it's so close to the former/cone joint that the difference is probably not usually a matter of concern. )

lndm · 18th April 2006, 10:25 AM

Just a shot in the dark here, but doesn't the phase plug reduce the volume of air where the dustcap would be causing flow to be accelerated past it and pushing the acoustic centre forward? and the shape of the phase plug is to ensure the correct effect at all frequencies of interest? I did read something about this once (about 10 years ago).

17th April 2006, 11:27 PM	#1
angsuman diyAudio Member Join Date: Mar 2005 Location: Las Vegas NV	Acoustic Center? I've looked for it everywhere, but i'm curious what defines the acoustic center for a driver with a phase plug? Not that i'm seeking time-alignment in a future design, but i'm curious if the acoustic center is always located at the voicecoil or if its at other parts. For example in a dome tweeter is the acoustic center at the voice coil edges or at the tip or the dome. Same question for a phase plug? Is the end of the phase plug considered the acoustic center of a driver.

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18th April 2006, 12:55 AM	#3
David Gatti diyAudio Member Join Date: Mar 2004 Location: Melbourne, Australia	I usually approximate the acoustic centre as the point at which the voicecoil former attaches to the diaphram, whether it's a cone with/without a phase plug, or dome. This seem to be a pretty accurate estimate in my subsequent measurements. Some say it's slightly forward of this point which may be the case but it depends on diaphragm material, cone geometry etc.

18th April 2006, 04:57 AM	#4
angsuman diyAudio Member Join Date: Mar 2005 Location: Las Vegas NV	Oh so a phase plug doesn't have an affect on where the acoustic center is? So generally its at the former to cone joint?

18th April 2006, 06:32 AM	#5
Curmudgeon diyAudio Member Join Date: Nov 2005	IIRC Dickason says that it is nominally at the air gap, and my measurements of mid and tweets confirmed that. (Although it's so close to the former/cone joint that the difference is probably not usually a matter of concern. )

18th April 2006, 10:25 AM	#6
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Just a shot in the dark here, but doesn't the phase plug reduce the volume of air where the dustcap would be causing flow to be accelerated past it and pushing the acoustic centre forward? and the shape of the phase plug is to ensure the correct effect at all frequencies of interest? I did read something about this once (about 10 years ago).

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