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ReliaBill Engineer

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  1. ReliaBill Engineer
    Using modern drivers, I think you’d have to use high and low pass filters to shape modern driver outputs to roll off their normally flat response. Or, use inexpensive drivers for mid and tweeters. I’m talking 1970 and older AR sound. It would be pretty difficult to make an old wineskin using new glass bottles, for 1976+ AR sound. Substituting a new driver for only 1 in an older AR speaker is certainly doable. Maybe 2. But not all 3 in a 3-way design. Matching Sound power response is only 1 aspect. Each driver has its own voice, and matching that with a modern driver would be difficult. Like Bob Carver matching voices of amplifiers, only more difficult.
  2. ReliaBill Engineer
    I don’t mess with the pots. They stay at 85% tweeter, 75% mid. Detail is not power response. It’s the ability to resolve slight variations and frequency mixtures in the signal from the amplifier. That detail and ability to resolve small nuances won’t show up in a sine wave sweep. So the pot has no bearing in resolution, just in relative power output. My “other” hobby has been collecting vintage cartridges. I’m used to being able to swap cartridges and hear the differences. I have 160. I can hear differences in ADC styli, or Empire carts, or between the V15V-HE and V15-IV HE. Or an ADC 10E MKIV and MKII. But with these AR-2ax’s, that gets very difficult. I love the sound I’m getting, great for enjoying music, but not for enjoying different sounds from different transducers. Hence, why I said I “crave” more detail. My main speakers are the 1989 Polk RTA-8Ts. Not big. But unique in the Polk line of that era. 2 midwoofers (MW) in parallel, with no crossover tricks to use both for bass, 1 for midrange duty. Ported, no PR. I installed the updated tweeters, but stock other than that. No XO rebuild, no recap. The parallel MW in D’Appolito vertical arrangement (MW-T-MW) resolves detail exceptionally well. Great imaging also.
  3. ReliaBill Engineer
    Yikes! Volkswagens, Newton, “crude vs simple”, sealed vs ported, 1% caps, etc.! I’ll just accept that the fiberglass batting is used to damp “rough edges” at the roll off higher frequencies.
  4. ReliaBill Engineer
    The XO to the midrange is at 1400 Hz, isn’t it? At 6 dB/ octave, the mid still has output at 700 Hz. So it carries output 700-8000 Hz. That’s where a great deal of detail is produced. The cartridges I’m using are known for their detail retrieval. That’s why I can hear a certain “numbness” of detail in these. The mid driver isn’t capable of reproducing it. I’m used to hearing that detail. When I switch from “Speaker A” to “Speaker B”, I can plainly hear the difference. Just an observation. I could correct it without making a visible difference in the speakers. But it’s a rabbit hole journey.
  5. ReliaBill Engineer
    Thank you! Makes sense. AR went through a lot of trouble to add the screen and pad, so I’m not going to mess with success. But I was curious. Having said that, I do crave a bit more mids detail than these offer. But that isn’t possible without molesting these and replacing the mid driver.
  6. ReliaBill Engineer
    Is it used to add dispersion? Tame a sizzling midrange? Acoustic (air) impedance matching? Or….add mystique?
  7. ReliaBill Engineer
    Anyone know why AR chose to put fiberglass padding over the paper cone midrange? Is the reason documented anywhere?
  8. ReliaBill Engineer
    To answer my own question, the foam ring is soft polyurethane foam. I guess to somewhat damp a possible source of distortion near the voice coil. Flexing of the cone?
  9. ReliaBill Engineer
    Was there ever an answer for this? I haven’t touched mine. I’m not going to, unless I find out more about what the original was made from, and whether it was soft foam or rigid foam. I sure don’t want to add weight to it. Anyone know? Soft foam, or rigid foam?
  10. ReliaBill Engineer
    Heat gun.
  11. ReliaBill Engineer
    My living room is 18x35 feet. Speakers are 8.5 feet apart, center to center, on the 18 foot wall, 3 feet from the wall. I can sit in any one of 4 places and the sound doesn’t change. All 4 seating positions are about 20 feet from the speakers. Speakers are 16” off the floor, tilted back about 10 degrees on stands.
  12. ReliaBill Engineer
    What I’ve found is that these phenolic domes do a very good job of dispersing their output, *if* they are allowed to have more output. The internal batting under the dome tends to suppress cone breakup and distortion. If the domes are allowed to move, produce greater output, 2 things are solved: wide dispersion and ample output. Off axis sound is very good from these. No additional tweeter of any kind is necessary. At 100% position of the tweeter pot, these tweeters overpower the mids. So 85% tweet and 75% mids is good.
  13. ReliaBill Engineer
    Thanks. I took notes and pictures on the first one. I used a 0.015” feeler gauge around the domes to get them set prior to applying sealant. I did a test patch of the sealant to see how thick one brush stroke left on a steel plate, after curing. I used a digital scale to measure butyl sealant and thinner. The hard part is carrying these back into the garage for cabinet refinishing. I enjoy listening to them.
  14. ReliaBill Engineer
    I added some content above.
  15. ReliaBill Engineer
    So, I fixed the woofer, checked the other one, it’s surround is secure. I’ve been listening to these a lot over the last several days. I’m not wanting for treble at all. These don’t need an “augmenting” super tweeter. I’ve read that many times from owners of both the 3/3a and 2ax. Long discussions about which tweeter and which crossover point to use. It isn’t needed on these. These have ample treble output that is clear as a bell. The tweeter surrounds are thoroughly “seated”, and stable. I’ve played them very loud, and thoroughly exercised them. They’ll sound good for the next 50 years. Below, 1963 recording of the Dave Brubeck Quartet, “Take 5.” Cymbals are clear, proper volume. Balanced with the sax, piano. Drums are fast, tight and low. This is from the 1963 compilation album commemorating Rexall Drug’s 60th Anniversary, 1903-1963. Using a Shure V15 Type IV cartridge with original stylus:
  16. ReliaBill Engineer
    Just found the left woofer has partially delaminated under the surround, where the surround is glued to the outer rim of the basket. Heard a buzzing noise. Not a big deal, but has to be repaired before I do anything else.
  17. ReliaBill Engineer
    Sound check. Stereo playback. Much less than ideal placement. Listening for buzzes, rattles, any distortion. Playing a track from a 1964 Billy Vaughn record using the Shure V15V-MR cartridge. Tweeter pot at 85%, Midrange at 75% settings on both speakers. Pretty much recommended factory settings.
  18. ReliaBill Engineer
    Just an FYI…. I bought these new for $12 each. I wasn’t sure what condition I’d find my pots in on this pair of early 2-ax. Turned out they were in like-new condition. I tried one of these out. It fits nicely. But 20 ohm. Sounded fine! It bleeds off less current from the tweeter or midrange, since these are used as voltage dividers, and sounds fine. But I’d have to make a cover for them to keep the fiberglass out of the wiper mechanism, but that’s easily done. Temporarily I used plastic from a 2-liter bottle to make a “hood” while I tested for sound/function. It displaces no volume, open on the ends.
  19. ReliaBill Engineer
    I bought these for $12 each. I wasn’t sure what condition I’d find my pots in on a pair of early 2-ax. Turned out they were in new condition. I tried one of these out. It fits nicely. But 20 ohm. Sounded fine! It bleeds off less current from the tweeter or midrange, and sounds fine. But I’d have to make a cover for them to keep the fiberglass out of the wiper mechanism, but that’s easily done.
  20. ReliaBill Engineer
    I waited for a gently used pair of AR-2ax, early model. The wait/hunt has been very gratifying.
  21. ReliaBill Engineer
    12.4 watt canned rheostat. Power-wise, it should work.
  22. ReliaBill Engineer
    I have not had issues posting directly from my phone. This is 2.8 Mb:
  23. ReliaBill Engineer
    Here is the second tweeter, rebuilt: Sounds just like the first one. I’m listening to them as a stereo pair, for the first time since both tweeter rebuilds. Wow!! Very gratifying. Before tweeter rebuild:
  24. ReliaBill Engineer
    Finished the 2nd tweeter rebuild last night. Sounds great! It sounds just like the first tweeter I rebuilt. Later today I’ll do another recording of this speaker, to compare the before and after.
  25. ReliaBill Engineer
    Just thought I’d ask, Roy. Maybe I can model the response. I don’t have any sophisticated test equipment for measuring actual output/response. I’ve started on the 2nd tweeter rebuild: Im going to try something different this time. I’m going to mask off around that strip of electrical tape under the lead wires. Then remove the electrical tape stuck to the faceplate and plywood. Then I’ll use black acid-free silicone sealant in place of the tape. Let the base silicone cure. Then after the dome is reset in the gap, I’ll more neatly cover the leads in the black silicone sealant. I don’t care for the tape. Below, dome carefully removed. Picking out the remaining yellow foam from the gap and notches:
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