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graham

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  1. and a couple more photos I forgot. The crossover inside the enclosure, and a picture of the finished speakers. One with the grill cloth off to show you how ugly the mortite looks, but the grill cloth hides it of course. I wish I had take a before image of the grubby grill cloth. It is like new now.
  2. graham

    AR38S restoration on a dime.

    Thanks for the comment Pete. Yes NP caps do look small in comparison with the originals. I did not find an ESR ( equivalent series resistance) ohms value quoted for my capacitors or for a couple of well known brands I looked at. The originals were Unicorn 6uf 50v made in Japan Bi-polar size 0.5" x 1.12" Mine are Japan Chemical BP Series 6uF/50V 10% (on behalf of 5.6uF/6.8uF) (K) 85 C. $6.33 for packet of 30. size 0.25" x 0.5" I looked at what I could have got in axial with a well known brand name. packet of 4 SPRAGUE for $12.84. 5.6uF 50V DC solid-electrolyte Tantalex capacitor. Hermetically sealed, axial solid tinned nickel terminals. Case Code: R The size of these is 0.28" x 0.68" or a packet of 2 SIEMENS for $13.98, still sized at 0.28" x 0.68" So mine are practically the size as the recognized brand name ones, if size has anything to do with the ESR ohms resistance. I guess measuring the ESR would be the next step? I have an elenco M2795 multimeter but not sure if it can measure a capacitors ESR?
  3. graham

    AR38S restoration on a dime.

    I have now listened to about 30 CD's , played through the AR38S, and the sound is seems to get better and better, particularly after the first 10. These are good quality speakers, nice bass and lots of definition on the higher notes. Not top of the line audiophile quality, but certainly in the very good category, and can look down from a great height upon the majority of squawk boxes in mainstream use today. Some of my listening list are:- The gentler side of John Coltrane, The very best of Albert King , Compact Jazz by Harry James, and Chet Baker Jazz Masters 32. From the brushing of the drums , shining ambience of the cymbals, deep low pitch of the double base, the trumpets and the saxophones, all come out clear and warm on the A38S;s. My next project is to rebuild 2 sets of AR4X, After that I will feel confident to move on to a pair of AR9I which I picked up at auction about 8 years back for just $79 + premium and tax. The foam is in good shape, so I will likely just rebuild the crossovers. For the AR91 I will go for audiophile quality caps.
  4. I have just built two of Dave Smith's March 2010 AR4X crossovers (drawing and a schematic PDF a couple of posts back). The pair of AR4X I got from auction for $10 back in 2006, and they have sat in my basement since then. One of the Tweeters was blown and in March 2006 forum member RoyC got me a replacement in trade for some other old AR tweeters that wouldn't fit. If you are still here - thanks RoyC I am finally using that tweeter. AR4X with the blown tweeter was serial number FX227334. The woofer had a Black paper cone with cloth surrounds, it had black gauze each side of the magnet and had 4X 2748 137 6903D stamped on it. It was stuffed with Rockwool. It had the usual Brick 20uf wax capacitor and a number 5 coil inductor. The blown tweeter was dated Jan 31 1969. AR4X with the working tweeter unfortunately had the serial number paper peeled or ripped off. The woofer had a Brown paper cone with cloth surrounds but the sides of the magnet had brown paper tape sealing them. I believe this tape was original from the factory as it had the date JAN 31 1969 stamped on the paper ( see photos). It also was stuffed with Rockwool and had the same large 20uf brick wax capacitor and a number 5 coil inductor. The tweeter had the date Jan 28 1969 stamped on it. It is a mystery to me why one woofer had a black cone, and the other a brown cone? If only the 2nd serial number was there !. I soldered up the components according to the schematic. I built the crossovers outside the enclosures on 4" x 8" x 3/8" board which I then placed into the enclosure and screwed on top of the old board alongside the Input contacts and AETNA POLLACK Pot hole. One problem I hit was that in the new position for the crossover, the original wires on the Tweeter and Woofer were not quite long enough. I disconnected the speaker wires from the Woofer Tweeter and obtained new wires that were slightly longer. Of course the new wires had to be in the original blue, red, green, yellow colors. I dragged out of my basement an ancient tower PC that I had been meaning to scrap, it had a good supply of 18 AWG wire in red, blue, yellow going to the power transformer. The old PC power cord yielded another length in green. (see photos). Is 18 AWG thick enough ? it works great. Checkout the photo showing the solder and paste I used - out of an auction box, probably from the 1960's too. Solder had a 49c woolco sticker on it!. The pots had a few faint bits of green on the wires inside. I cleaned up with salt water and a toothbrush, then after thorough washing and drying, used 000 grade steel wool on the contacts, then a spray with MG chemicals Nu-Trol control cleaner. I used Mortite to seal the back of the Pots when I reinstalled. I used Mortite to seal the tweeter and woofer cutouts. ( see photos), On this forum I had read about the 11oz mini-packs of fiberglass from Walmart. I picked up two packs. Unrolled they are 4' ft. long 16" wide. I ripped them into 4 12" x 16" pieces. 16" is just about the inside length of the AR4x. One piece full length on right side, one on the left side. one piece in half to the back of the crossover under the tweeter, the remaining piece in middle front under the woofer. I used the 000 steel wool on the cabinets, to which I then applied Bri-Wax. The speaker grill cloths had a grimy appearance, but I thought I would have a go at cleaning them before resorting to buying new material. I unscrewed the one ARX badge remaining, then took the grills still on the frames to the sink. I had warm water flowing from the tap, wetted, gave a couple of squirts of dish soap, then very lightly used a nylon scrubbing brush. After about a minute each, I thoroughly rinsed them off, then took the to dry in the sun. They look great. Well, they are back to a clean tweedy beige look of the late 1960's. Could almost pass for new. These 49 year old speakers are now alive again. They sound magnificent. That crossover design of Dave Smith's works like a charm. I am playing Jazz on them now. The saxophone and trumpets are clear and ringing - Stan Getz knew how to blow a horn. Yes I am using CD's ! It seemed that the sound got more and more 'body' after about CD number 2 was played . I am now 3 days into using them for a couple of hours a day, and they are unbelievable. Here are the photos - comments appreciated... On the crossovers, the Blue, Red, Yellow, Green wires of course will go to the Woofer and Tweeter. The Orange goes off to #1 negative amplifier input. The white goes off to #2 positive amplifier input. Many thanks to Speaker Dave and RoyC for their contributions
  5. Hi All, I recently saw a pair of AR38S at auction in very rough shape. Left behind a written bid of $12. Was called later to be told I had got them for $10. I should have attended, I bet mine was the only bid, and If I had been there I would have probably got them for $2 !. I intend these to be a basement workshop pair, so I was not going to spend out on audiophile quality repair components. I decided to restore them on a dime. The woofers both needed a re-foam. I also decided to replace the 6uf 50v BP caps. I got a pair of generic 10" woofer foams from aliexpress, $3 the pair. Also from aliexpress, I got 6uf 50v Bipolar capacitors which came in a packet of 30 for $6.33. They are radial instead of the original axial, but I don't see it would matter. Following are the photos before and after. Yes I should have snipped out a small "V" from the foam where the screw holes go, but I forgot. When tightening the screws I was very careful not to rip into the foam by over-tightening. The original foam went underneath the woofer cone edge ( which is why it looks so clean from the top ). I glued the new woofers on top of the woofer cone edge. ( Is that acceptable? they work great). I also glued the foam directly to the speaker metal casing - is that acceptable? will it cause problems down the road? Anyhow they sound great - $10 + $3 + $6 = $19 for a pair of restored AR38S'. Comments? Kudos? Brickbats? questions? As purchased - both woofer foams completely disintergrated
  6. Thanks for the schematic Dave, and more thanks to RoyC for plugging it into a computer. If anyone has sourced the parts could they share the details of suppliers and prices please? the extra 0.10mH air coil inductor - parts-express have 14/15/18/20 gauge - which is best ? also what is the source for an iron core inductor of 0.25mH / 250uH ? part-express don't go down that low.
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