BjarneAndersen Posted June 4, 2019 Report Share Posted June 4, 2019 Sorry for my bad English i am from Denmark. I have restored my old AR9LS from 1983. Rebuilding the crossover to AR9LSi with new capacitors and re foaming the 10" 12" 8" speakers. Now I've discovered that the 3/4" tweeter are blown in both speakers and no one on E bay for sale. I bought some 0,12 mm. copper wire and i will try to make a new coil at 4 ohm. Has anyone tried it?. Or someone who knows if you can take a coil and dome from another AR 3/4" tweeter that fits in the original?. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted June 5, 2019 Report Share Posted June 5, 2019 I'm on my tablet, and I can't 100% verify this comment, as my tablet can't open the .Tif files. But, double check the Library, in the AR Drawings section, for exact part tweeter numbers, as that looks like the standard 0.75" tweeter diaphragm. It's used across many AR speakers, including AR9s, AR90s, AR91s, AR92s, AR38Bs, AR48Bs, AR58Bs, and AR1MS speakers. The mid-tweeter plate, as used on the 38s, 48s, and 58s can be found fairly cheap, and those tweeters could be used for donor diaphragms, on your 9LS speakers. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted June 5, 2019 Report Share Posted June 5, 2019 Tweeter plates, from this series, are almost always on eBay. Quote Link to comment Share on other sites More sharing options...
Stimpy Posted June 5, 2019 Report Share Posted June 5, 2019 Quote Link to comment Share on other sites More sharing options...
Pete B Posted June 5, 2019 Report Share Posted June 5, 2019 That is great to know, are those also 4 ohm? Quote Link to comment Share on other sites More sharing options...
Stimpy Posted June 5, 2019 Report Share Posted June 5, 2019 7 hours ago, Pete B said: That is great to know, are those also 4 ohm? Yes, they are 4 Ohm tweeters. They look like this, with the face plate removed. Quote Link to comment Share on other sites More sharing options...
ra.ra Posted June 5, 2019 Report Share Posted June 5, 2019 On 6/4/2019 at 11:50 AM, BjarneAndersen said: ...if you can take a coil and dome from another AR 3/4" tweeter that fits in the original? The Library section on this website offers some very good information regarding your dual dome driver - - I believe this is part no. 200048 that employs the singular shared magnet structure. A low-resolution copy of the drawing for this driver(s) is attached which includes detailed assembly notes, but there is also a separate document regarding performance specs not shown here. A few portion of blow-ups are shown FYI, too. I think Stimpy makes a good suggestion here, but there are other drivers that might also be suitable parts donors. A quick look suggest that the tweeters from the AR-58s or the AR-9/90/91/92 series have similar construction - - the outer dome and underlying wood button are identical parts numbers ,but the voice coil/surround part number might be different. I suppose this might difference have an affect on performance, but it appears these parts should "fit". Quote Link to comment Share on other sites More sharing options...
BjarneAndersen Posted June 20, 2019 Author Report Share Posted June 20, 2019 Hello everyone. Thanks for all the inputs on restoration of AR 3/4 "tweeters. I have been able to make 2 new coils of 0.12 mm insulated copper wire 1.65 meters long, giving a coil of 4 ohms. they succeeded and when I added some magnetic cooling oil they played fine. Quote Link to comment Share on other sites More sharing options...
fedeleluigi Posted June 21, 2019 Report Share Posted June 21, 2019 @BjarneAndersen Hello Bjarne, Unfortunately the coil is out of focus. It seems that you made only one layer winding covering all the former. If so, this is not correct. 1) the winding must be a two layer winding and 2) the former must not be covered completely. In the AR Library I've found the tweeter voice coil drawing of the "Lamba driver" used in the AR 9 LS, 98 LS and 78 LS. It is the 241th drawing. As regards wire, even though the drawing reports: "2 wire: 22 to 24 turns of N° 38 AWG (a diameter of about 0.1 mm) copper……….. in two layers, 11 to 12 turns per layer", actually I have usually found an inner layer of 14 turns and an outer layer of 11 turns. Hope you removed the tweeter diaphragm only mechanically since solvents usually change tweeter suspension stiffness permanentely and consequentely the tweeter FS and Thiele-Small parameters. Luigi Quote Link to comment Share on other sites More sharing options...
BjarneAndersen Posted June 21, 2019 Author Report Share Posted June 21, 2019 Many thanks for your reply, I will now try to make some new coils after the drawing. Quote Link to comment Share on other sites More sharing options...
fedeleluigi Posted June 22, 2019 Report Share Posted June 22, 2019 15 hours ago, BjarneAndersen said: Many thanks for your reply, I will now try to make some new coils after the drawing. You can find a higher definition drawing in the library (AR drawings). The drawing is the 241th and is named "no image". Luigi Quote Link to comment Share on other sites More sharing options...
BjarneAndersen Posted June 30, 2019 Author Report Share Posted June 30, 2019 I managed to make 2 new coils in two layers, first layer in 12½ turns and second layer in 11 turns. But there is something strange for, according to the original drawing, the coil should be between 3 to 3.7 ohms. I measured the old wire with a micrometer screw to 0.12 mm and a length of 1.65 meters and measured it to 4 ohms. The new coil is also made of 0.12 mm. wire 1.65 meters long and measures 4 ohms. I don't know if they just had a bad day at the factory when they made it. But I am currently satisfied with the result. Quote Link to comment Share on other sites More sharing options...
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