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Multi-Way Conventional loudspeakers with crossovers

Acoustical center relative to front
Acoustical center relative to front
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Old 28th April 2015, 01:25 PM   #1
forr is offline forr  France
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Default Acoustical center relative to front

Hi... qufon mentioned for its tweeters
acoustical center relative to front : -11.3 mm
( Hiquphon OWI (OW1) dome tweeter, technical data )

I wonder by which ways it was measured so precisely.

I made many experiences to find a method to determine the acoustical center of a driver.

This morning, I fed two different tweeters (ScanSpeak D2905, Audax TW010F1) with a 5 kHz pulse signal directly from the ouput of a function generator.
I placed the front of a Behringer ECM8000 microphone as close as possible of the dome of the tweeters, about 1 mm (1/25 in).
The mike output signal was amplified by a IMG MPA-102 preamp and then applied to the input of a dual trace oscillocsope, giving the yellow trace.
The other input was fed by the reference signal from the generator, it is the blue trace.

I found similar results for the two drivers. They confirm other previous tests made with different drivers.

The beginning of the visible reaction of the driver can be estimated to be about 35 ÁS after the beginning of the start of the pulse.
The top of the driver response is about 60 ÁS after the top of the electrical pulse.

35 ÁS and 60 ÁS correspond to a geometric delay of 12 mm (0.5 in) and 20 mm (0.8 in).
I think that I have to take in account :
- the distance between the sensor of the mike and its front plate
- the group delay of the inherent low-pass filter of the mike behavior.
What can they be ?
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Last edited by forr; 28th April 2015 at 01:27 PM.
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