A Palfreyman Posted August 18, 2016 Author Report Share Posted August 18, 2016 Thanks for the useful "side" info and great pics guys. Right, my woofers are open-frame type covered with tape and looking at the coil, it appeared slightly "tilted" so i have lifted the foam from the frame with IPA and will attempt to re-glue over the weekend using shims. Even carefully manipulating the cone by hand, it was difficult to get it to move without some slight rubbing, so I cut the dust-cap out with a very sharp scalpel and found there are a couple of slight "high-spots" seen in the photos as the small circumferential black marks. These are near the centre of the V/C former at the 1-o'clock (0017) and 5-o'clock (0018) positions, shown in the photos (sorry about the quality, mobile phone). Not sure anything can be done, so I have put some thin card between the former and the pole-piece to apply some pressure at both positions in the hopes these will "flatten" out. With regards the tweeters, I actually carefully scraped some varnish off the flying wires from the coil as the soldered joints to the tinsels looked a bit naff. Even that showed open-circuit. What i'd love to attempt is to get some 3/4" v/c tweeter membranes and have a go at re-doming. Can't find anything suitable, but if cheap enough, could be worth a go as nothing to loose. In the meantime I had some second-hand 1" mylar domes which I have padded down (22R //, 1R8 series) and these are running on 3uF with the pots about 2/3 way up. These ar mounted on a 1/4 ply adaptor plate. AP Link to comment Share on other sites More sharing options...
A Palfreyman Posted August 22, 2016 Author Report Share Posted August 22, 2016 Shimmed the v/c of the sticking woofer over the weekend and re-glued the foam surround which was about 1/16" different to how it was glued previously and although it rubbed very slightly (I couldn't get it any better), this disappeared after about 5 mins of use so thanks for the heads-up on that one. According to the vintage speaker review, the resonance in-enclosure should be 56Hz and that is pretty much exactly what I measured as the peak in impedance was 55-56Hz for both drivers. I couldn't measure the driver itself because I was getting unreliable voltage readings from my meter below about 35Hz. I have still had some very minor problems though but I think that this is due to the lower frequencies which are reproduced on CD compared to vinyl and is very much track dependent so I used an oscilloscope on the speaker input to verify this. Where the frequency was very low, this was seen as quite large excursion coupled with some slight rubbing so I think it is sensible to be careful about the type of recording used with these, so i will try with some vinyl in next few days and if all OK I will put the recovered baffles back on. Thanks to all again for your pointers, AP Link to comment Share on other sites More sharing options...
LouB Posted August 31, 2016 Report Share Posted August 31, 2016 Hi all, Been lurking for years and just had to post to this one. I have been a big fan of AR & KLH since the 70's I have pairs of AR-2, AR-2a, AR-2x and AR-2ax Also a recently acquired pair of 3a's that I have not had time to examine yet. The most problematic of the bunch has been the 2ax. Mine have the cloth surrounds. The surround retention ring glue has come loose, requiring re-glueing. The phenolic spider retention ring also detatched, requiring reglue. Positioning during reglue is a touchy affair, as you all must know. The cloth surround doping was reduced to powder, that too needed attention. Best regards, Lou Link to comment Share on other sites More sharing options...
ra.ra Posted August 31, 2016 Report Share Posted August 31, 2016 Hi Lou, and welcome to the CSP Forum. With that many excellent AR's, it's about time we heard from you, and I think you already occupy a fairly rare subset of members - - - those who have pairs of virtually the entire "2" series (not counting the very rare 2xa). I decided to chime in here only because your dilemma with the 2ax cloth woofers is exactly what I was trying to learn about earlier today, since I may be soon trying to correct the same situation on a similar pair. The assumption is that you have not experienced the same problem with the woofers from the AR-2 or AR-2a, which I presume are virtually identical to your 2ax woofers. Even the early 2x used the same cloth woofer. From what I read earlier, there are a variety of adhesives that can be used to re-attach the ring to the smooth metal basket, but it is unclear to me what the preferred method is for ensuring a centered voice coil. I am normally comfortable cutting dust caps and using shims for this purpose, but in the case of these woofers I was hoping to avoid cutting the cap and shimming, and have not located any threads which clearly describe this process. And BTW, the rings are not phenolic - - they are hardboard, sometimes referred to as Masonite. As for re-doping cloth on AR's, the brush-on butyl liquid is the only product to use, and with a light touch. To the OP, A Palfreyman, any further report on your rebuilt speakers? Link to comment Share on other sites More sharing options...
LouB Posted September 1, 2016 Report Share Posted September 1, 2016 Hi rara Actually, I have relocated voice coils by shimming, positioning with multiple gage pins and also just by exercising the cone. What I have realized by trial and mostly error is that of paramount importance is that the coil and pole piece be angularly aligned, not just centered at the point of rest. If the coil is held by the spider and the cone is improperly located, the travel of the cone will attempt to move in a fashion out of angular alignment with the center line of the pole piece. I have had the result of unpleasant unexpected rubbing sounds! Oops. I was unaware of the doping fluid you refer to, I was using Shoe Goo waterproofing goop. regards, Lou KLH 6 & 17 faves too... Link to comment Share on other sites More sharing options...
LouB Posted September 1, 2016 Report Share Posted September 1, 2016 What is the name of the doping compound and who sells it? Link to comment Share on other sites More sharing options...
dxho Posted September 1, 2016 Report Share Posted September 1, 2016 RoyC, on this forum, sells the sealer. It's a combination of butyl rubber and toluene. Shoe Goo looks like it's in the ball park: toluene 30-60% Styrene Butadiene Copolymer 30-60% Solvent Naphtha 10-30% But the discussion has gone on for years, concerning various compounds and how they work. The bottom line is most of them have some level of solids or ash that eventually hardens speaker surrounds. Roy's mix is the best. Link to comment Share on other sites More sharing options...
lARrybody Posted September 1, 2016 Report Share Posted September 1, 2016 This is the stuff I use. I believe it is RoC's formula. You really don't want to use anything else. http://www.ebay.com/itm/ACOUSTIC-RESEARCH-CLOTH-SURROUND-WOOFERS-SEALANT-KIT-ALSO-KLH-/162184720559?hash=item25c2f670af Link to comment Share on other sites More sharing options...
LouB Posted September 1, 2016 Report Share Posted September 1, 2016 Thanks! So long to shoe goo! Link to comment Share on other sites More sharing options...
A Palfreyman Posted December 20, 2016 Author Report Share Posted December 20, 2016 On 8/31/2016 at 10:50 PM, ra.ra said: Hi Lou, and welcome to the CSP Forum. With that many excellent AR's, it's about time we heard from you, and I think you already occupy a fairly rare subset of members - - - those who have pairs of virtually the entire "2" series (not counting the very rare 2xa). I decided to chime in here only because your dilemma with the 2ax cloth woofers is exactly what I was trying to learn about earlier today, since I may be soon trying to correct the same situation on a similar pair. The assumption is that you have not experienced the same problem with the woofers from the AR-2 or AR-2a, which I presume are virtually identical to your 2ax woofers. Even the early 2x used the same cloth woofer. From what I read earlier, there are a variety of adhesives that can be used to re-attach the ring to the smooth metal basket, but it is unclear to me what the preferred method is for ensuring a centered voice coil. I am normally comfortable cutting dust caps and using shims for this purpose, but in the case of these woofers I was hoping to avoid cutting the cap and shimming, and have not located any threads which clearly describe this process. And BTW, the rings are not phenolic - - they are hardboard, sometimes referred to as Masonite. As for re-doping cloth on AR's, the brush-on butyl liquid is the only product to use, and with a light touch. To the OP, A Palfreyman, any further report on your rebuilt speakers? Not had much chance to listen to these, other things non-hifi to sort unfortunately. However, the mids seem a bit down on output too. I replaced the original caps with mylars as the wax / paper originals measured somewhere in the 20s of uF. Can the mids lose output (thought I'd read somewhere about demagnetisation) or do I need to give them more space as they were used about 4" from the back wall but placed roughly in the middle of adjacent walls firing diagonally across a square floor-plan of 12' x 12'? Link to comment Share on other sites More sharing options...
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