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Old 15th February 2009, 11:53 PM   #1
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Default easiest way for voice coil alignnent

What technique is the easiet for voice coil align between cone speakers 1 speakers I have specs the other I dont
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Old 16th February 2009, 12:15 AM   #2
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Are you speaking of "time alignment" between multiple speaker cone drivers and need to find the position the voice coils rest at relative to the baffle, or about replacing the cone assembly of a driver (field replaceable unit)?
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Old 16th February 2009, 12:17 AM   #3
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Default for phase time alignment of speakers in build the cabinet

voice coil alignment for time phasing of work speakers
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Old 16th February 2009, 12:29 AM   #4
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Default I am working on aligning a mid/woofer and tweeter

I am working aligning a Silverflute mid/woofer cone speaker and coned tweeter
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Old 16th February 2009, 01:00 AM   #5
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Hmm, thats a tricky one then. You'll need to locate the front pole plate on each driver and measure the distance between them I believe.

Not having tried it this could potentially work. In the image, thin cotton cord loops are hung over the pole plate part of each motor with a small weight on the end, akin to a plumb line. This is with both drivers in the final baffle ideally. the distance is measured. A problem you will encounter is the tweeters cord colliding with the woofers basket, I dont know how much accuracy would be lost trying to divert it. Might be worh a go anyhow
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Old 16th February 2009, 10:32 AM   #6
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Default so the best place for reference is the terminals

if that is the case I have and idea of how I can align them I can use a laser aim a scale and measure the difference and then I can use that as a guide. I needed a reference on where to measure for the voice. Thanks for the help
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Old 16th February 2009, 06:00 PM   #7
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Not at the electrical connection terminals, they can be anywhere. You need to locate the front pole plate, this is where the voice coil rests centrally with no input. It'll usually be on the side of the magnet attaching to the basket

A laser scale could certainly be put to use here I'd have thought, not considered how yet though.

Should be noted that the measured distance and theory don't entirely match up with reality in all cases. You're almost certainly best getting a moderately accurate measurement then tuning the circuit guided by microphone measurement. Read here for more insight:

http://sound.westhost.com/pcmm.htm


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Old 16th February 2009, 06:32 PM   #8
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This is incorrect. The acoustic center of the driver does not necessarily coincide with the voice coil. Additionally, the center can change with frequency. The best way to determine this is to acoustically measure the drivers.
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Old 16th February 2009, 06:43 PM   #9
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That would be the best option, it is inevitable there will be some difference, as Rod experienced.

As a general query, in a metal dome (or cone) for instance, is the acoustic center where the voice coil joins to the dome/cone, or is it at the tip of the dome since the sound actually travels faster to here through the metal than through the air from the outer edges of the dome? It'd be a tiny difference anyhow, but just wondered. In a deep metal cone there could be some difference, but I don't think it'd work the same here.
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Old 16th February 2009, 07:04 PM   #10
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The acoustic centre of a driver does not equate to any specific point of its mechanical structure and it can/will change with frequency. You need to measure to get appropriate offset,

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