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RoyC

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  1. I'm not aware of any rebuild parts for this mid. Roy
  2. Al W You have a long way to go if you are using non-AR woofers. They will not sound like AR-3's regardless of the repairs you have planned....and even if you were to use original AR woofers, the two speakers of your pair are not very likely to sound the same with the different mids (regardless of the questionable crossover changes). As far as the unusual crossover changes go, I have not seen these in 40+ years of repair and restoration of AR speakers. The crossover with the 3a type mid was already established, so it is unlikely they were done for this reason. I'm thinking the changes were made so late in the game that it is possible the woofers were replaced with the later ferrite magnet/foam surround version at that time as well. Based on my impressions of the AR-3 equipped with later AR woofers, those changes could make some sense. Later AR woofers are not the best replacement for the AR-3 using original crossover values. Roy
  3. It doesn't matter, but the series caps are on the negative side of the 3a crossover if you want to be consistent. Roy
  4. I agree with your assumption. The replacement mid, added capacitor, coil, and black glue all date to late 74 or 75. The cabinet stuffing was also replaced with the later AR type. There is no doubt this was a "factory authorized" repair involving the replacement of an original AR-3 midrange with a late AR-3a midrange. Assuming the added coil is .4mh, the mystery is why the parallel 50uf capacitor was added to the mix and not a 6uf cap as shown in the schematic posted in the Library. The 50uf cap in parallel with the existing 24uf value results in a total of 74uf. Alternatively, if the 6uf cap was added it would be 30uf. Big difference....which I have never seen before. The response of the later 3a type mid is not different enough from the early version of the 3a mid to warrant such a difference in capacitor value. Are your woofers the original AR-3 version with cloth surrounds or the later foam surround type? Roy
  5. der, Your assumption is correct. The addition of the 6uf series cap to the existing 6uf crossover cap decreases the total to 3uf, which raises the crossover frequency between the tweeter and the mid...reducing the tweeter's influence on the mid frequencies. Before adding the additional capacitor you should try a few things: 1) Do not reverse the polarity of the HiVi tweeter. If you have, change it back to that of the mid and woofer.. 2) Since you have stated you are using L-pads, place the 25 ohm resistor across the midrange if you haven't already done so. 3) if you have done #1 and #2, place a 25 ohm resistor across the tweeter. 4) If you have done all of the above and still feel the upper mid frequencies are too strong, try reducing the tweeter cap value as described above. Do some extended listening before deciding to implement this one. If you decide to go with rebuilt original tweeters, be sure to have 25 ohm resistors across the new tweeters as well as the mids if you continue to use L-pads. Roy
  6. Dirty switches in electronic equipment often cause the sound you describe, which is why my first recommendation was to check out your associated equipment. It is not, however, a common problem with the more passive switches in LST and LST-2 speakers. I hope it is that simple. Roy
  7. Bill, I respect Millersound's work a great deal, but "realigning" this type of AR midrange is not something I've ever heard of, nor possible in my experience. Furthermore, it is not something known to be required of this type of mid in my 40 years or so of repairing AR speakers. I know you have tried different speakers with the amp, but if you haven't already done so, simply swap the channels to see if the distortion follows the speaker wire from your amp or remains in the suspect speaker. Once you are sure it is the speaker and not the amp, it is just matter of repeating the problem until you nail it down. In this situation, I would be first suspicious of the electronics. If it is not the electronics, listen closely to each driver, including the woofers. The LST type switches are seldom the culprit. Before doing any of the above, by-pass or replace the fuse on the rear of each speaker. I'm not sure about the LST-2, as I have not seen many of these in recent years, but I recently found a number of old LST fuses to cause significant sound degradation. Roy
  8. To clarify...you are discussing a personal project using a pair of stripped AR cabinets? You connected new drivers to the old crossovers, you are obviously happy with the sound, and you are recommending it as an "upgrade" based on your listening impressions. Glad you are happy with it, but this thread should be in the "mods and tweaks" section of the forum. You are no longer discussing a pair of AR speakers. As an aside, there is much more engineering involved in designing a speaker system than than the cost of the drivers. You could plop $100 replacement tweeters into a pair of decently designed speakers and degrade the overall performance. "Engineers on a budget" are still engineers. What are your credentials? Roy
  9. No...but the AR-2 level control is only providing variable resistance (up to 10 ohms) in series with the high frequency driver, which is why only 2 of the 3 terminals of the control are used. Since it is doubtful the control would be used much below the maximum setting, you could easily replace it with the more common 15 ohm pot or a new 8 ohm L-pad. Since you would only be connecting the series leg either type of control will not change anything electrically, and will provide the appropriate amount of high frequency attenuation. Most users set the controls at maximum (no series resistance at all) or just off maximum. Also check the woofers' surround and spider mounting rings. They are very often loose or detached due to degraded adhesive. Send me a PM if you need assistance locating and assembling the appropriate replacement caps (if necessary) and level controls. Edit: I just read your other thread regarding the same speakers. You probably do not need to replace the capacitors. Photos would be helpful... Roy
  10. The response of AR-3 mids and tweeters is quite variable and often degraded today. In fact, it is not unusual for the level controls' "full on" position to not provide enough output for either driver, though it won't hurt anything to set them at that position. Consequently, it is very unlikely any responses to your question will provide much insight relative to your pair of speakers. Roy
  11. RoyC

    AR 2-ax

    I agree with Kent. Neat work. Yes, there is an enamel coating on inductor coil wire. Sand or scrape it off and tin it before making connections. Roy
  12. That pair would have originally been equipped with the 2nd AR-3 mid with the smaller rounder magnet...not to be confused with the AR-3a mid, which was used in the last iteration of the AR-3. Roy
  13. RoyC

    AR 2-ax

    Just a closer look at the schematics. I did overlook the fact that the first one was drawn around L-pads, not pots. The second one, however, is incorrect in a number of ways, especially for cabinets with serial numbers in the 209,000 range. -The "+" symbol is on the wrong side of the mid and tweeter -There was no resistor in series with the mid until much later (and it was 3 ohms, not 2 ohms). -The 1 3/8" phenolic dome tweeter was not original to the serial numbers, having been discontinued long before 200,000. I suspect this person did not have original 2ax's to begin with, and was simply documenting a project. The notes regarding the "2a" (not 2ax) tweeter and the reason for the mid's series resistor (which is questionable in itself) do not suggest originality. Roy
  14. RoyC

    AR 2-ax

    Just catching up with CSP threads. I believe this one may have become more complicated than necessary. To clarify some things based on my experience. -The first schematic is not typical, whether it be accurate to the author's speakers or not. I have only seen the yellow wire connected to the AR-2ax "B" pot terminals. -Kent's photo of the pot and L-pad connections was only meant to show the comparison between pot and L-pad terminals. It had nothing to do with AR-2ax wire connections. The bare wire on the pot was simply a wire stripped of insulation. -Late AR-2ax mids had a DCR of 9 ohms, not 6 ohms. During the transition, AR connected a series 3 ohm resistor to the earlier version. This mid was used in the later AR-2ax, which was equipped with the square modern-style ferrite magnet. -I would be very suspicious of any AR-2ax schematic showing a "+" symbol on the yellow wire side of the 2ax mid. I have checked the polarity on a number of these mids over the years and, without exception, the yellow dot side has been the negative side of the driver. Since the originating connection is to the cabinet's #1 input terminal, the mid's polarity would therefore not be connected in reverse to that of the woofer! I believe the person drawing the schematic assumed the yellow dot designated the "+" side of the mid, but did not remove the screen to check it. I have never seen reversed polarity connections for any AR-2ax. There is also frequent confusion due to AR's placement of the capacitors on the negative side of the circuit. -When using L-pads, the 25 ohm resistor simply connects across the driver served by the L-pad. This can be done anywhere from the "1" and "2" L-pad terminals on up to the driver. Bear in mind "1" and "2" L-pad terminals correspond to "2" and "B" pot terminals. The above considerations are much more important than very subjective tweaks such as by-pass caps, capacitor brands, etc, to 40+ year old drivers...which may or may not even be connected properly. The additional work and concern associated with these recommendations and opinions are not worth the effort (and confusion) for most people. I see Kent posted some photos while I was typing this. Below are two more photos, showing the only 2ax crossover connections I have ever seen (note the yellow wire connections), and a meter reading of the later 2ax mid. Roy
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