sc-em Posted January 6, 2017 Author Report Share Posted January 6, 2017 Thanks Jeff. I have ordered the kit now so here's to a good refoaming. I will have to watch all the videos as I am not sure what the shims do. I am used to shims in part engines and suspension, but don't think they work the same way, just being a centralising method I assume. Link to comment Share on other sites More sharing options...
JKent Posted January 6, 2017 Report Share Posted January 6, 2017 When you remove the dust cap you will see a solid silver color cylinder in the center. That's the pole piece. Around that is a tube wrapped with thin copper wire. That's the voice coil (VC). There is a tiny gap between the VC and the pole piece and the shims are used to temporarily hold everything in the proper alignment as you work on it. They also have a secondary benefit of providing friction so you can raise or lower the cone while working on it. After the faom is all glued in place and dry, remove the shims, vacuum the pole piece and glue the dust cap on. -Kent Link to comment Share on other sites More sharing options...
Jeff_C Posted January 6, 2017 Report Share Posted January 6, 2017 If you do not fear removing the dust cap, then most repairers would say that shimming is the way to go. It is just a thin piece of card or similar that locates in 3 or 4 positions around the voice coil gap. So when you position the new foam surround there is no movement of the cone and voice coil. From my limited experience I would say that the smaller the woofer diameter the easier it is to get away without shimming. Sending a test tone helps to ensure the new surround is correctly positioned. Link to comment Share on other sites More sharing options...
djcheung Posted January 7, 2017 Report Share Posted January 7, 2017 This is the uk site that I have used once before. I use Goodhifi exclusively now. http://www.speaker-repairs.co.uk/shop/refoam/ar.html Link to comment Share on other sites More sharing options...
sc-em Posted January 8, 2017 Author Report Share Posted January 8, 2017 Yep. Thats where i have ordered the kit from. Having watched the videos i'm quite looking forward the giving it a go. I assume dust caps come with kit Where the screw go a guess you make sure the is enough glue around the hole to seal and then run a small drill through to open up the hole. Link to comment Share on other sites More sharing options...
djcheung Posted January 8, 2017 Report Share Posted January 8, 2017 You can always use some washers to minimise the distortion on the foam when you tighten the screws up. Link to comment Share on other sites More sharing options...
fedeleluigi Posted January 8, 2017 Report Share Posted January 8, 2017 @sc-em I usually never shim voice coil when refoaming. Anyway when refoaming the woofers, try not to use more glue than it was used originally (i.e don't let the glue dirty the paper cone). If you decide to shim the voice coil, save the original dust cup (see ra.ra's picture) and reuse it. It is not necessary to remove it completely cutting all its circumference along. You can leave it connected by a small part that allows you to bend it and shim the voice coil. So it is very easy to reglue it in the original position. Imho preserving the original appearance is very important with vintage drivers and speakers. If it is your first refoam, watch as many videos as you can before acting. Luigi Link to comment Share on other sites More sharing options...
sc-em Posted January 9, 2017 Author Report Share Posted January 9, 2017 On 30/12/2016 at 4:41 PM, ra.ra said: If those foams work for the AR-7 as shown in the link, they should work fine for the 8" woofer in the 18LS as well. I cannot tell exactly which woofer is used in your speakers, but it appears to have a dust cap similar to this one from woofer p/n 200037. If so, the cap is very thin and soft, but can be re-glued (as shown here) after being cut for shimming during the re-foam process. ra.ra. Did you cut the dust cover right up to the edge or where the sort of seem appears to be? The latter would seem more straightforward. I was going to use a razor to make it as thin a cut as possible so the glue will fill the smallest of gaps. Does this sound like a plan? Link to comment Share on other sites More sharing options...
JKent Posted January 9, 2017 Report Share Posted January 9, 2017 ra.ra. did a truly expert job on that. You can use a fresh razor blade. You want to be careful not to nick the voice coil or the thin leads to the vc, visible to the right of the cap in the photo. I use a thin X-Acto knife, held at a low angle (handle almost parallel with the woofer cone) and not cutting too deeply. Leave a bit uncut so you can hinge the cap back while shimming. When finished run a thin bead of white glue (Elmer's, Aleene's or the white glue that comes with the kit). It dries translucent. I outlined a portion of the cut on ra.ra.'s photo. Link to comment Share on other sites More sharing options...
sc-em Posted January 9, 2017 Author Report Share Posted January 9, 2017 Super. Just what I thought thanks. Link to comment Share on other sites More sharing options...
ra.ra Posted January 9, 2017 Report Share Posted January 9, 2017 The first pic attached shows this same woofer with the shims in place and the dust cap cut and hinged back. The second pic shows the cap after re-attachment. The third pic(s) show the re-gluing of a different AR-7 woofer flat dust cap using a similar process. Kent has accurately described the process of cutting the cap, regardless of the cap's material. It should be noted, however, that for me, this particularly dust cap (very thin, glossy, domed) was the most difficult type to work with. It is very flexible and floppy which makes the cutting a delicate process, and it is so thin and non-absorptive that it makes the re-gluing step also more difficult. Just take your time, work slowly, and use a sharp blade. Link to comment Share on other sites More sharing options...
sc-em Posted January 9, 2017 Author Report Share Posted January 9, 2017 So like this then? Not much room for the shims is there? Link to comment Share on other sites More sharing options...
JKent Posted January 9, 2017 Report Share Posted January 9, 2017 Not much but they will slip in between the pole and the voice coil. If you bought a kit that came with shims there may be different thicknesses included. Nice job of cleaning the metal frame btw. Notice in your photo that there are bits of debris on the pole piece. You DON'T want those getting lodged between the pole and the vc so be sure to vacuum them out. You can do it now and also before re-gluing the cap. Be careful not to distort the thin copper vc. So far so good. Link to comment Share on other sites More sharing options...
sc-em Posted January 9, 2017 Author Report Share Posted January 9, 2017 Thanks for that. A little light vacuum to remove the debris. Hopefully the kit will be here tomorrow and so I can have a go. I was going to use cotton buds to apply glue, but there may be a brush in the kit. The cotton fibre may also become detached I suppose. Good old scrape and then v fine wet and dry with a smidge of WD40. Cleaned enough car parts that way. Link to comment Share on other sites More sharing options...
sc-em Posted January 10, 2017 Author Report Share Posted January 10, 2017 Progress so far. The foam didn't seem a great fit around the inner edge some may try and run a bead of glue underneath. Link to comment Share on other sites More sharing options...
Jeff_C Posted January 10, 2017 Report Share Posted January 10, 2017 Yes you certainly need to glue from about 9 o clock to 2 o clock on your photo. When you do it, try and press the foam to the cone gently trough the holes in the basket, as the glue starts to cure. I hope others can give advice for you. Link to comment Share on other sites More sharing options...
sc-em Posted January 10, 2017 Author Report Share Posted January 10, 2017 Done that. Looks tidier. Think the second one i will do a better job. How long to leave before re sticking dust cover? Ivernight before a try? Link to comment Share on other sites More sharing options...
Jeff_C Posted January 10, 2017 Report Share Posted January 10, 2017 Overnight will not hurt. I don't know what to advise about re-sticking the dust cover before a test, because the partly attached dust cover could rattle/vibrate and could deflect from whether the re-foam is effective or not. As you have shimmed, your main concern should be whether there is any significant air leaks around the foam, not the centering of the VC. Remember I did not remove the dust covers when I did my woofers. Link to comment Share on other sites More sharing options...
michiganpat Posted January 10, 2017 Report Share Posted January 10, 2017 21 hours ago, JKent said: Not much but they will slip in between the pole and the voice coil. If you bought a kit that came with shims there may be different thicknesses included. Nice job of cleaning the metal frame btw. Notice in your photo that there are bits of debris on the pole piece. You DON'T want those getting lodged between the pole and the vc so be sure to vacuum them out. You can do it now and also before re-gluing the cap. Be careful not to distort the thin copper vc. So far so good. that's why I usually don't cut the cap, and use a 30hz test tone..... Link to comment Share on other sites More sharing options...
djcheung Posted January 10, 2017 Report Share Posted January 10, 2017 I haven't cut a single dust cap so far with all my repairs. Luckily AR driver are very forgiving. One thing I normally make sure is to check the sagging on the spiders. If they are sagging slightly, I normally put the driver upside down ( before installing the new foam surround) and use a hair dryer to warm the spider and then put some weight behind the cone to 'hopefully' push (away from the magnet) and restore the position of the cone before glueing the foam surround. 9 times out of 10 it works but sometime they get way beyond repair and you have have to make do !. Link to comment Share on other sites More sharing options...
sc-em Posted January 10, 2017 Author Report Share Posted January 10, 2017 Ah well it's my first set, so will see how they go. Maybe further experience and I will be checking saggy spiders and test tones....... Link to comment Share on other sites More sharing options...
sc-em Posted January 11, 2017 Author Report Share Posted January 11, 2017 Well they live again. Hooray. One forgets how good proper speakers can sound. Just warming up with a bit of Satriani. Just a thought though. I can't imagine speaker cable has advanced much, but is it worth investing in some new and if so what recommendation would you have without going to OTT? Thanks for all the help in putting the 18s back in working order. Link to comment Share on other sites More sharing options...
JKent Posted January 11, 2017 Report Share Posted January 11, 2017 Quote Well they live again. Hooray. Hooray indeed. Congratulations! Are you hooked yet on DIY speaker repair? Quote I can't imagine speaker cable has advanced much, but is it worth investing in some new It hasn't. And no. I use 18 ga lamp cord or for longer runs the 16 ga "hi-fi speaker wire" sold by PE. Some of the big box stores have perfectly good speaker wire. I'd just stay away from "CCA" wire--copper-coated aluminum. Pure copper is best. Link to comment Share on other sites More sharing options...
sc-em Posted January 11, 2017 Author Report Share Posted January 11, 2017 Hooked? Not so sure about that. lol. This the cable I have at the mo. The limitation seems to be the clamps I have in the back of the Rotel rather than the connectors like the back of the speakers. Other amps offer better options like the speaker backs (must have a name...posts?) My 58s have arrived......bugger they are big.... Link to comment Share on other sites More sharing options...
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