TimmyTonga Posted June 30, 2016 Report Share Posted June 30, 2016 Hello everyone This is what I have; the piece of card with holes is stuck in pretty firmly with hardly any space around it. Question is; should I be removing this in order to shim? Or is that what this is? The cone, which was sitting rather low in the saddle, is moving freely and quietly now I have supported the edges with rolled-up paper towels to raise it up a bit. With the driver on its back the movement was rather scratchy otherwise. any helpful comments welcome, and much appreciated. regards/Tim Link to comment Share on other sites More sharing options...
Carlspeak Posted June 30, 2016 Report Share Posted June 30, 2016 That 'piece of card' is part of the voice coil. Leave it be. I suggest you remove the paper towel pcs you used to raise up the cone, then insert your shims. They should provide enough friction to allow you to raise up the cone without having to insert the paper towels. Centering the coil MUST take precedence. Link to comment Share on other sites More sharing options...
lARrybody Posted June 30, 2016 Report Share Posted June 30, 2016 That piece of card is called the voice coil former. That is the piece the coil the wires are wound around. Insert the shims in the gap between the former and pole piece. Hopefully that assembly is attached to the spider securely. Actually everything is looking good. Link to comment Share on other sites More sharing options...
TimmyTonga Posted June 30, 2016 Author Report Share Posted June 30, 2016 It's a salutary lesson in the importance of shimming. The tolerances are so very small, and a fraction of a millimetre in shim thickness means the difference between not enough friction or not being able to get a shim in all the way round. can I get a steer on how to know when you have the cone up at a good height? it's going to be really awkward glueing, as the symmetry is shot by virtue of the Masonite being out of true to the frame. regards/Tim Link to comment Share on other sites More sharing options...
TimmyTonga Posted June 30, 2016 Author Report Share Posted June 30, 2016 Now looking like this..... Link to comment Share on other sites More sharing options...
lARrybody Posted June 30, 2016 Report Share Posted June 30, 2016 No problems here. Raise the cone up enough so that the new foam is slightly above the Masonite ring. Center the inside lip on the cone. Remember my picture of how I use little tick marks on the cone to make sure the new surround is close to centered on the cone. I use Aleene's Tack Glue and spread it evenly around the edge of the cone and the lip of the new surround. I use small art/craft brushes like you would see in a watercolor kit. Place the surround on the cone and apply gentle pressure to the surround lip as it dries. Usually takes around 10 to 15 minutes. I like to use the blunt end of the brush to apply the pressure. Fingers also work good. I keep a damp wash cloth to clean up any glue that might ooze out. Keep it up till the glue is tacky and drying. Allow to dry for 2-3 hours. Then repeat the same process with the outside surround lip and the Masonite lip. Lower the cone enough so the new surround makes contact with the speaker frame. I let everything dry overnight before removing the shims. Make sure the voice coil gap is clean by using a vacuum. Re glue the dust cap and I like to add a small bead around the inside edge of the surround to make sure there are no air leaks. The next time you do this it will so much easier. Link to comment Share on other sites More sharing options...
TimmyTonga Posted June 30, 2016 Author Report Share Posted June 30, 2016 Thanks Larry. I do indeed remember the tick-marks, and did similarly. I am leaving the inner lip to dry overnight, but am confident the difficult stuff is behind me. Cutting the dust-cap was tricky psychologically, and although I have re-surrounded smaller ARs, it's the awareness that you could be wrecking a piece of sonic history that makes doing a 3a so nerve-shredding the first time. regards/Tim Link to comment Share on other sites More sharing options...
lARrybody Posted June 30, 2016 Report Share Posted June 30, 2016 The first set of AR 3a woofers I got a hold of, I thought, "Toto. I've got a feeling were not in Kansas anymore" Just the size and weight of the magnets told me these are something special. The low frequencies these produce rattle the china in the dining room hutch. You are going to like these 45 year old speakers. A little hard to drive, but using a Adcom GAF555II these really sing. Working on a second pair now. Stacked AR3a's? I will need another 555II. Link to comment Share on other sites More sharing options...
TimmyTonga Posted July 1, 2016 Author Report Share Posted July 1, 2016 This is number 3, and it might be worse than Kansas; Please advise..... Regards/Tim Link to comment Share on other sites More sharing options...
Carlspeak Posted July 1, 2016 Report Share Posted July 1, 2016 You've a mess there. AR3a voice coil formers are perforated with holes around the outside just above the windings to allow venting of heat. Unfortunately, the holes are in a single line and not staggered and thus the distance between the holes must provide the vertical strength component of the voice coil former. If the woofer is driven too hard, the back end of the voice coil bottoms out (read slams) against the steel top magnet plate. The force of that collision is absorbed up thru the former. Those lands between the holes can't absorb that shock and the former collapses like shown in your picture. At a minimum you'll need a new voice coil or a complete recone job. They are great speakers but do have their limitations with regard to overpowering them leading to your issue and also burnt out tweeters. Link to comment Share on other sites More sharing options...
TimmyTonga Posted July 1, 2016 Author Report Share Posted July 1, 2016 *sobs* Link to comment Share on other sites More sharing options...
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