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AR3a Woofer voice coil exchange?


dick

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I've been advised that it is a bit of a trick to get a new voice coil properly aligned, hooked up. That said, here's the deal:

There's a pair of AR3a's for sale for $80--Craigslist in Connecticut from Oct 10. Called the fellow this morning to learn that the woofers need new foam surrounds, one needs a new voice coil, the grilles are shot, and the cabinetry might be somewhere between very used and abused. If interested: in Connecticut, (860) 537-6622. He name is Mark.

I thought it would be sort of fun to do another 3a restoration, then the complications of the voice coil for an amateur diddler came into play, then...frankly...I could not escape the reality that I have no need for them, although I do have one AR3 cloth surround woofer with good voice coil and a Carl-modified cone....

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Would a shot AR3a woofer voice coil be the same voice coil found in an AR3's woofer? (Foam surround woofer) Would the exchange be doable?

Dick,

I suspect by this you mean changing out the entire cone/voice-coil assembly from an Alnico-magnet AR-3 woofer to a Ceramic-magnet AR-3a woofer, or vice-versa. If this is the case, I don’t believe you could align the coil properly, because the AR-3 voice coil -- wound on a bronze bobbin -- has a coil wire that is slightly smaller-gauge than the AR-3a coil, but the bobbin diameter is not precisely identical in the two woofers, so it is possible that the AR-3 woofer might rub in the AR-3a magnet assembly. The AR-3 woofer coil is also 1/8-inch longer (more overhang), but this shouldn’t make any difference as the diameter is still basically 2-inches (50mm) for both woofers. However, I believe that the total height of the cone with voice coil on one woofer is slightly different from the other, so voice-coil alignment would be more difficult as well. I’ve got both assemblies outside the magnet assemblies, and I will cross check to see if this could be done. Most likely, it’s not going to be worth the effort.

As for grafting a voice coil itself from one woofer onto another cone, this is very difficult to do because of the difficulty in epoxying the assemblies together without an alignment jig, and the difficulty of attaching the voice coils to the tinsel-lead output wires.

It sounds as though you have given up on this anyway, so it’s probably a moot point.

--Tom Tyson

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