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ra.ra

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About ra.ra

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  1. Pete, the drivers are identical in these two speaker models, and the crossovers are, too, with the exception of the switches and associated resistors included with the 91. Larry's objective here is to add the switching capability to the 58s which originally had no such control. From what I can tell, aside from significant variations in styling, the only other difference is the interior cabinet volume: 46.8L (1.65 cf) for the AR-91; and 43.6L (1.54 cf) for the AR-58s.
  2. Just a couple more illustrations from the assembly manual. The schematic is very clearly designated with all pertinent information (including the internal fuse, added by Heathkit); and the individual response curves present a wonderful, if perhaps oversimplified, view that assists an owner in understanding the various drivers' contributions to overall speaker performance.
  3. Protecting the open backside of these new pots is one matter, but I urge you to follow the sage advice that Kent has noted in his May 21 post regarding the rear metal plate. In your most recent pic, you can clearly see the rubber isolation washers (referred to by Heathkit as "binding post base insulator") where all three binding posts penetrate the metal plate, and this practice must be followed where the new pots are mechanically fastened to the metal plate. It is a little difficult to understand the entire assembly of these new pots, but because all of the exposed parts of these pots are metal (see pic attached), it would be prudent to use two rubber washers per pot shaft similar to the binding posts (see illustration). I do like the robust quality of those foreign pots but have never used them myself. And if interested, I have a copy of the entire Heathkit AS-103 assembly manual - - - it is a great little document with terrific illustrations. If you'd like your own copy, send me a PM with your email address and I will forward a file (1.4MB pdf) to you.
  4. The Ohmite controls do indeed have very open backs but their use as replacements in restorations should not require re-inventing the wheel. If preventing fiberglass or mineral wool fibers from interfering in the proper operation of these controls is the sole concern here, I see no reason why carefully draping a piece of Kimpac (or cheesecloth or.....) over the wired controls would not achieve this goal with far less effort. After all, this is exactly the intent of the Kimpac placed underneath the woofer in early AR speaker models. I do really enjoy seeing all of the creative solutions to this issue, but there are times when the KISS principle is often the most appropriate solution. Because of the rear metal plate used in the Heathkit version, this may be one of those times. Additionally, the original Aetna-Pollak pots used in hundreds of thousands of AR speakers do not have fully open backs, but they do have several open slots around the perimeter, and without additional screening, did allow for fibers to enter the working mechanisms.
  5. We were just discussing the 044 driver in another thread by Giorgio, and it is this paper by Tim Holl which explains the ferrofluid issue which differentiates the mid used in the three-way models (032 and 044) from the mid used in the four-way speakers (028). The entire paper by Holl is a good read.
  6. Wow, that was quick work! I wasn't even able to reply in the time it took you to dis-assemble this mid driver. That is great work. It appears that instead of the two-sided contact cement that I had expected based on the assembly note 9, your driver instead used a thin double-sided paper tape for this purpose. Your pics are very good, and in the "naked" pic of the front driver flange, you can clearly see the surround and the inner ring of the second adhesive. Thx so much for sharing - - - now I want to get one of those specialized spatulas!
  7. What you have done with the black paint looks terrific, but if you decide to try to remove the semi-horn from one of these drivers, you should be aware of where the factory adhesive is located. On the partial drawing shown, items 11 and 12 indicate locations of two different adhesives, as noted in assembly note 9. Item 11 is a contact adhesive applied to the wide outer flat surface of the horn; and item 12 is a second type of adhesive located under the narrow inner flat surface of the horn near the dome. This should be helpful if you attempt to pry off one of these plastic horns - - at least you'll know where you are trying to break the bond between parts. Be careful, work slowly.
  8. This thread might shed some useful light on your situation. You'll find confirmation of the 3a cabinets used for late-issue AR-3's, and see examples of Masonite grille frames. http://www.classicspeakerpages.net/IP.Board/index.php?/topic/8833-are-these-ar3s/
  9. Really helpful description with excellent results. You've created a very good new cone edge surface for attachment of new foam surround. Please keep us updated with the AR-16 restoration.
  10. These are very good points to add to this discussion, and since that combined mid-tweet used a single shared magnet that resulted in a combo driver with a reasonably small footprint, it might have easily fitted to a smaller cabinet compatible with an 8-inch woofer. Thanks for this reminder - - - these are great examples that often get overlooked. I really like that Allison Eight, but have never seen/heard a pair. Perhaps not considered a "big boy" speaker model because of its simple and inexpensive Peerless cone tweeter, but in the late 60's Rectilinear began marketing the Mini III, an acoustic suspension design which also used a fine 5-inch Phillips mid driver and 8-inch CTS woofer. I really like these speakers - - they are nearly identical (if a little deeper) in cabinet dimensions to the AR-6.
  11. Thx for clarification - - I kinda thought that was what you were posting. Indeed, all excellent drivers in that pic, but how do we know this combination would surpass the performance of the AR-38b or the AR-338?
  12. Jeepers, I find myself completely agreeing with Frank here. The masonite ring typically has considerable overlap on the top surface of the metal basket, so I seriously doubt if that is any type of "hole" which would compromise woofer performance. From my view, the re-foam appears very competent. I'm no expert on this series of mid drivers, but the rear sticker with big red dot appears to be an original AR marker. All Tonegen drivers I have seen have very different methods for identifying their driver nomenclature.
  13. Speaker model....what are we looking at here? That looks maybe like the top three drivers of a four-way AR speaker, but it's hard to tell from the cryptic pic and description.
  14. Just a few random comments from me, but I cannot really help you with the pricing. Before others might offer advice, it would be worth noting where you are located, what currency you use, and the type of markets where you may offer these up for sale. Those European 4xa's are gorgeous and appear to be in very fine shape, and the teak finish is relatively rare. Also of interest is seeing a single carton for a speaker pair (2) - - - this practice was not uncommon for the smaller AR-7 or AR-7x, but otherwise the only AR's I've seen packaged this way are MST's, always with Euro addresses. You might want to re-consider and maybe keep those speakers - - - you'll be hard pressed to ever find a better pair.
  15. Hi Giorgio, I'll gladly add my thoughts, but this rubbery "ring" is still something of a mystery to me. Last time I recall it being discussed here, one member more correctly referred to this elastic substance as being more like rubber cement, whereas I had originally mischaracterized it as silicone-like. Nevertheless, on both drawings for the 200001 and 200037 woofers, a substance titled "treatment" is shown in a detail where the foam surround laps over the cone. This material is not specified in either parts list on those drawings, but it is interesting to see it located below this juncture on the 037 woofer (left), but on the 001 woofer (right) it shows up on top. In either location, it certainly adds some small measure of weight to the moving cone assembly, but I cannot address any of the issues raised by Tunedguy, where he mentions: automated assembly process; dynamic shock; and break-up phenomena.
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