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
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
Attachments
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
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
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.
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.
Is the best way to ensure things are aligned well to install the drivers in the baffle/enclosure and play a tone at crossover frequency with one driver out of phase. Then adjust the delay/phase for maximum null before putting the polarity back as it should be? Microphone presumably lined up at listening posistion/tweeter height. Driver output levels would need to be matched without moving the mic first.
No, not if you want best time alignment. That ensures good phase alignment, but you could be a full wavelength apart (or some other multiple). I'd play a sine wave at the crossover frequency and look at the difference in delay for each speaker from an electrical reference (the reference signal in a two channel measurement setup). Line them up that way and then fine tune using reversed phase.
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