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RoyC

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  1. RoyC

    Ar3 midrange

    arken, The AR-3 tweeter held up better than the first two versions of the AR-3 mid. It is also much more available, having been used in the popular AR-2ax (first version), so your tweeters shouldn't be a problem. On the other hand, finding decent non-3a type AR-3 mids anytime soon will be very difficult. You are likely in for a very long, and ultimately costly, wait. If I were you I would go with a pair of AR-3a or later mids and use AR's .4mh coil/30uf cap modified crossover as mentioned above. I have not done any careful listening comparisons with the earlier versions of the AR-3, but I have made this repair a number of times for other people and it sounds quite good...certainly much better than any AR-3 with a typically degraded/non-restored earlier mid. Bear in mind, use of the later AR dome mid simply converts your speakers to a later version of the 3. They would still be considered "AR-3". If by some miracle, you were to find a couple of worthy earlier mids down the line, it would not be difficult to convert your speakers back to original. I have a hunch, however, you would not find it necessary to do so. The LST is not without issues (four typically degraded tweeters in each cabinet). They often start at $2500+/- a pair, and shipping them is an absolute nightmare. The last two restored pairs sold by "Vintage AR" went for $4000/pr. It is probably best to stick with your AR-3 project for now. Roy
  2. RoyC

    Acoustic Research AR-5 rebuild service

    Pete, Earlier front-wired 3a mids measure below 3 ohms. Later back-wired mids through the AR-9 typically measure 3.2 to 3.5 ohms. (Your AR-11 mid seems to be a bit on the high side.). Two later back-wired AR-5 mids I recently measured were both 5.2 ohms. All the AR-5 mids I've measured in the past have been around 5 ohms, with earlier front-wired specimens, like the 3a mids, being on the lower end of the range. I estimated the series resistance on the high side primarily because the white dot/"normal" setting of the AR-5 mid pot is nearly 50% off maximum (around 6.5 ohms in series), so there is plenty of output to be had with the AR-5 mid. The prudent way to go would be to measure dcr and add enough series resistance to the intended low impedance mid to achieve 5 ohms. This would put it well within the desired spec. It should also be noted that the original "15 ohm" pots can vary by as much as .5 to 1 ohm one way or the other, and should be measured as well. Roy
  3. RoyC

    Acoustic Research AR-5 rebuild service

    Yes...and all of the LST-2 drivers are the same as the AR-5 drivers. Roy
  4. RoyC

    Acoustic Research AR-5 rebuild service

    Sure, a 2.5 ohm resistor in series with an AR-3a mid will bring it very close to an AR-5 mid. Roy
  5. RoyC

    Acoustic Research AR-5 rebuild service

    Yes, they are constructed very differently. The AR-3 mid is essentially a large version of the orange phenolic dome AR-3 tweeter (foam suspension blobs, aluminum voice coil wire, etc). The 3a and 5 mids have more modern construction with a cloth dome/rolled cloth suspension, among other differences. Roy
  6. RoyC

    Acoustic Research AR-5 rebuild service

    Hi guys, I've been repairing the AR-3 mid, not the AR-3a/5 style mid. Roy
  7. RoyC

    Cloth surrounds

    I experimented with lots of materials, including that family of adhesives, Pete. It dries to a stiff rubber-like state (much worse than the Permatex materiel discussed above), and it unacceptably changes compliance and mass. "Might have to thin it" would be an understatement if it were to work at all. :) Roy
  8. RoyC

    New AR3a find and restoration thread

    Agreed, Jeff....the pots shown in dtafil's photos began being used sometime in the mid 70's . They had reinforced wipers, metal shafts (as opposed to the previous red or black plastic), and seem to be a bit more resistant to corrosion. Roy
  9. RoyC

    KLH 17, variance in impedance, pair of tweeters

    It's the woofers themselves. They are otherwise identical. Roy
  10. Thanks, Jeff...but based on our past dealings in other matters, I have nothing on you in the "unselfish" department. I will, however, take you up on that beer. Roy
  11. I'd like to meet this Roy guy and give him a piece of my mind. He's been unable to repair a number of AR-3 mids recently sent to him! There are some really nasty mids out there. Hey Glenn, I am planning to attend the September gathering. I really enjoyed meeting you, Robert, and Pete (finally!)...and that AR-3 pair of yours is something special. Your attention to detail is extraordinary. Roy
  12. RoyC

    Ar3 midrange

    Yikes...thanks, Pete. It is .4mh. I will correct it in the original post, so there is no confusion down the line. Roy
  13. RoyC

    Ar3 midrange

    More specifically...the addition of a .4 mh parallel coil to the 3a type midrange, and the addition of a 6uf to the 24uf mid capacitor to make 30uf will make an AR-3 the same as the last version of the model. See the Library section regarding AR-3 schematics. http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/thoughts_on_ar-3_schematics/thoughts_on_ar-3_schematics.pdf It is the last one on page 2. Roy
  14. RoyC

    Opinions on these pots....

    It should have nothing to do with the definition of a "rheostat". AR pots (potentiometers) and variable L-pads both vary series and parallel resistance using 3 legs. A traditional definition of a rheostat says it varies resistance with two legs. Others say variable L-pads and potentiometers are both types of rheostats. The new controls under discussion look very good from here, but the scare tactics this Ebay seller is using to steer people away from L-pads is nonsense. By far, the most numerous malfunctioning and melted controls (plastic shafts) I have seen are original AR pots. Roy
  15. RoyC

    Two years to get the AR-3a blues ...

    "but it turned out one of my solder connections from the mid pot to coil failed as in cold. Hard to believe I did that. This is a common issue due to failure to remove, or insufficient removal, of the coil wire's enamel coating prior to soldering. Roy
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