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Old 17th September 2014, 03:00 AM   #1
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Default Physical time-alignment of drivers

Hi All,
In cabinets where the mid and the tweet are located above the woofer and offset rearwards, by what method is the optimum offset calculated?
(Please don't tell me it can be done electronically. We all know that.)
Let's assume - for simplicity - that we have all cone drivers.
What point on a cone is taken to be the reference? The projected apex? The centre of the base? Something else?
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Old 17th September 2014, 03:02 AM   #2
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Its better to measure this using the interference between the output from two drivers and fitting the offset. There is a good explanation of this technique written by Jeff Bagby called "How To Use Passive Crossover Designer To Find The Relative Acoustic Offset". Just google it.
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Old 17th September 2014, 04:56 AM   #3
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Quote:
Originally Posted by Brisso57 View Post
Hi All,
In cabinets where the mid and the tweet are located above the woofer and offset rearwards, by what method is the optimum offset calculated?
(Please don't tell me it can be done electronically. We all know that.)
Let's assume - for simplicity - that we have all cone drivers.
What point on a cone is taken to be the reference? The projected apex? The centre of the base? Something else?
Good question, but we don't measure it with calipers and measuring tape.
We don't really even measure "absolute" offset.
As shown in the paper Charlie mentioned, what we measure is simply the phase response. by simulating different phase interactions between two drivers until it is identical to the measured simultaneous phase response, you get your z-offset from one driver to the next.
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Old 17th September 2014, 05:29 AM   #4
MiiB is offline MiiB  Denmark
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you have to measure the delay, The delay is a function of mass and the drivers acceleration-factor, I can't be judged from any geometry observations. most often speaker designers neglect this or doom it non important as they introduce a phase-shift over the crossover region anyway
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