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ReliaBill Engineer

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  1. ReliaBill Engineer
    Well, maybe CSP folks should reconsider. The alternative is….nothing. Just pics. So, if I said that I thought these sounded good, then left you with just pics, what would anyone learn? What gauge would you have?
  2. ReliaBill Engineer
    Exactly my point. Again, balance, clarity, definition, smoothness, lack of distortion were my goals. There exists no way to hear a “new, original” AR tweeter for these. I trust my dad’s memory. He’s old, but his hearing and memory are very good. He’s anxiously awaiting my dive into the other speaker, then to finish the cosmetic work.
  3. ReliaBill Engineer
    Problem here is that while we can see the XO response below target frequency, we can’t see relative output of the tweeter vs the mid-tweeter. That is a chart of only the tweeter response on, and off axis. As long as I can get balance by adjusting the pots, I’m satisfied. The fact that I can get balance within the adjustment range of both pots, tells me I’m where I need to be with the tweeter output. And getting balance with both, AND the woofer, is a wonderful sound! Currently I’m at 80% on the tweeter, 60% on the mid-tweet.
  4. ReliaBill Engineer
    There is a pot I can use to turn down the tweeter output. I’m looking for *balance* here; the biggest complaint I’ve read about in various groups/forums re: these original drivers is lack of balance between the mid and tweeter. I’ve seen folks add padding resistors to the mid, and I’ve seen folks replace the tweeter; I’ve seen folks replace the mid driver. As for duplicating results, that’s easy. But at this point, the second tweeter is exactly as received. Soon enough, I’ll take a look at it. But a huge question remains: Who out there has a brand new original tweeter for these? My dad is still alive, who had bought a pair of 2ax speakers new in early ‘65. He decided to trade them in late in ‘66 for a pair of Wharfdale W70Ds, with a Garrard Lab 80 turntable. He regretted it. For over 50 years, when we talk stereo stuff, he still mentions those AR 2ax speakers. That’s why I recorded the 1964 Billy Vaughn track, it was one of his favorite records he remembers hearing over the ARs. He says this one AR speaker is the way he remembers it. So there’s that. If anyone has a recording of a new original early AR 2ax tweeter, I’d love to hear it! Bass doesn’t come across well over cell phone speakers. But I can hear good mids/tweeter balance…or not. I can clearly hear how inadequate the tweeter was in my first recording pre-rebuild. And in my living room, this speaker sounds very good. Lacking nothing, and giving my Polks a run for the money in every area. The AR impressed me, even in a mono source.
  5. ReliaBill Engineer
    Here is an apples to apples comparison. Same track of music, same cartridge. Before tweeter rebuild and after. The next speaker in the pair will be the same. Before tweeter rebuild (caps replaced, pots cleaned and working): (Mid driver is overpowering the balance of sound) AFTER tweeter rebuild: The above are playing a 2022 recording from Octave records on vinyl. Below is a 1964 recording from Billy Vaughn, using the rebuilt tweeter. A new stereo album when these speakers were new (approximately):
  6. ReliaBill Engineer
    Such an amazing difference when the phenolic dome tweeter is working to its full potential!! It competes very well with modern speakers! Just a delight to listen to! Before the early 2ax Tweeter Rebuild: After the Tweeter Rebuild:
  7. ReliaBill Engineer
    Here is a comparison, before and after the tweeter rebuild, using the same music track. Jazz from one of my Octave Records Audiophile Masters recordings on vinyl. Balanced output from the tweeter and mid driver makes such a huge difference!! And now, the butyl rubber is completely cured and stable for many decades to come! Before: After:
  8. ReliaBill Engineer
    I need to record that same track I started with. After tweeter rebuild:
  9. ReliaBill Engineer
    Sure is quiet in here…… Was hoping for a bit of feedback.
  10. ReliaBill Engineer
    I’ll pretty up the baffle, then start on the 2nd speaker. If its tweeter needs work, I won’t add the 4 suspension points. I’m going to smooth the baffle, then use satin black finish.
  11. ReliaBill Engineer
    A sound test of the rebuilt tweeter:
  12. ReliaBill Engineer
    Been listening this evening. What a huge difference! Now I have balance. With the tweeter at 100% and the mid at 65%, the sound is no longer squawky and brash. My room is acoustically quite dead. Wall to wall carpet, drapes, cloth upholstered couch, loveseat, recliner. I can put my ear to the tweeter and hear plenty of output where I could barely hear anything before. It shimmers sweetly, not irritating at all. Could this be better? Probably. I don’t think it needs the 4-point suspension add-on. I think the clear butyl surround membrane is all it needs. It just needs a filler at those 4 notches surrounding the VC gap. That’s what I started to do originally. I was going to insert a strip of parchment paper, rolled into a tube. Then fill in the 4 notches flush to the top of the face plate with butyl. Let cure. Then remove the parchment to match the circumference of the faceplate gap. Position the tweeter in the gap. Clamp it down. Then just apply the thin membrane butyl seal. Let cure. The 4 notches in the faceplate. Still has remnants of yellow foam in them (I forgot to take a pic after cleaning out the gap and notches.):
  13. ReliaBill Engineer
    The other tweeter hasn’t been molested. I haven’t even removed the grill; it’s still stapled. Still original condition as I received it. Currently the tweeter makes no sound. Mid is muted.
  14. ReliaBill Engineer
    I only used RTV silicone on the leads. I don’t like the electrical tape looks, although I did keep that 1 strip on the plywood. So that’s black RTV. The rest is clear butyl. The red is a mix I came up with 4 years ago, for repairing GE VR1000 styli (and VR22). It gives the butyl rubber a more “spungy” quality to it. (I normally use gray butyl; for this I used clear.) I should have thinned it a bit more for easier application. But I didn’t want the mix to run; I wanted it to bridge between the faceplate and the dome. The red mix has silicone grease micro encapsulated in it, by using my ultrasonic tank; mixed the clear butyl with my red “dope”, putting it in the ultrasonic tank on Saran Wrap, then mixing a small amount of silicone dielectric grease in. After curing, if you slice it with a razor blade, then examine the cross section under a 25x loupe, you’ll see the itty-bitty beads of grease. It’s more flexible than butyl, and damps vibration really well. It controls the iron cantilever of the VR1000 and VR22 styli, giving an amazing level of tracking and clarity to the cartridges’ sound. So rather than use foam, I used this red mix. I won’t be able to give it a long listening session until tonight, after work. I briefly listened earlier, to make sure all was well. It sounded great for the minute or so I had it connected. Nice and clear.
  15. ReliaBill Engineer
    Looks a tad messy. But it sounds really good! Clear, focused, dynamic, well damped. Loud, too! Plenty of tweeter sound at 50% pot setting. I decided to secure the leads with black RTV silicone.
  16. ReliaBill Engineer
    I clamped the dome down flush with the steel mounting plate. I used that steel washer with 3 legs soldered to it. The magnet clamps the washer down. A magnetic jig, if you will. Then I applied the red butyl at the 4 points. Let it cure for an hour. Then thinned the clear butyl so I could apply it with a brush. Now letting it cure overnight. Once cured, when I release the jig, the preload from the batting should push the dome out, giving it clearance to move when a music signal is applied. Fingers crossed….. Thinned butyl sealant:
  17. ReliaBill Engineer
    I got the gap cleaned and the voice coil cleaned. Pretty obvious that AR allowed the glue to get into the gap and on the voice coil, pretty much glueing the foam at the 4 points and on the coil windings. Very little clearance between the center magnet and inside edge of the coil.Besides all of that, the stack of polyester batting inside the dome puts a VERY substantial preload on the dome. I put a HEAVY steel washer on the dome, and it isn’t enough to force the dome and voice coil down into the gap! I tried a 1.2 volt battery on the leads, to center the voice coil…. It expelled the dome with tremendous force! I won’t do that again.The batting: Using the heavy steel washer. I need a biggerweight!
  18. ReliaBill Engineer
    Anatomy of the early 2ax Dome Tweeter: This dome tweeter has a unique build. The cloth-phenolic dome is light, although heavy by modern soft dome standards. It uses enameled aluminum wire on the voice coil, which is why you don’t see solder on the brass binding posts below the tweeter’s mount; the wires are twisted on the posts. The suspension assembly is very unique. When in the voice coil gap, the stack of batting inside the dome supplies an upward (outward) spring pre-load to the dome. Of course, it also damps vibration and kills sonic energy inside the dome. The 4 liquid-foam deposits (yellow, applied as a foam liquid during assembly, then allowed to cure) anchor down the dome, against the pressure of the dome’s internal batting. The faceplate has 4 cutouts for anchoring the foam away from the voice coil. Then, a thin, sticky, clear elastomer sealant is applied on top of the foam, and on both the perimeter of the dome, as well as on the perimeter of the face plate. This elastomer sealant is allowed to cure. When all is cured, the dome is suspended by the batting that pushes the dome outward, and held in place by the 4 dollops of yellow foam and the clear elastomer membrane. Below, the polyester batting that is compressed below the dome. It provides damping and spring force outward: The four foam cutouts in the faceplate for anchoring the liquid foam: Below, the four foam suspending anchors to “float” the dome: Below, with the clear elastomer sealant applied, that forms a dust seal, and a resilient retaining membrane, to allow the dome to achieve pistonic motion when a music signal is applied.
  19. ReliaBill Engineer
    I spent last night formulating my plan for repair, the sequence and materials I’ll use. I tested using a silicone membrane for the sealant. Also the 4-point suspension. Hopefully I can get this done over the weekend.
  20. ReliaBill Engineer
    So now I feel I have no option except to remove the dome. So I did. I’ll have to carefully clean the windings and the motor gap. Then put the damping back in and replace the suspension and sealant. Sealant removed: The dome freed: The damping batting inside the dome: Dome completely freed:
  21. ReliaBill Engineer
    Pretty sure I figured out the problem. I don’t think my ears were lying to me. Output is greatly reduced. Looking closely at the tweeter dome, it was messed up at the factory 58 years ago. In these pics, on the right side vs the left, the voice coil is wedged in the gap; halfway out on the right side and flush on the left, and glued that way. Gently pushing down, there is no movement. Below, VC windings visible near leads: Below, windings visible: Below, other side of dome is flush with mounting plate: :
  22. ReliaBill Engineer
    Roy, you are correct in every aspect! The sample that I scraped from my tweeter was a drop of grill glue that managed to get dropped near the tweeter perimeter, just on the edge of the elastomer sealant. Boy! Do I feel embarrassed!! I was being *too* careful in my “sampling” of the sealant. Yup! I am learning much about AR-dom here. So….in your trials and travels, are these phenolic domes capable of more output by modifying their suspension, or renewing it? Or in other words, what is your experience in their change in output after *you’ve* changed out their suspension? I haven’t yet molested the original tweeter. I’m being very cautious… I’m going to attach a 1-minute clip of the speaker here. Only the caps replaced and pots cleaned. Tweeter at full output on its pot, midrange at 65% on its pot setting. I move my phone’s mic to within 1” of the tweeter. You can hear the tweeter’s output. Playing Bert Kaempfert’s “Wonderland By Night” from the 1960 Stereo LP. _________Everyone let me know what you think. Does this seem normal for this tweeter?
  23. ReliaBill Engineer
    I tested the “ear” theory last night. Like you said, I needed to verify whether my ears were fooling me, or the tweeter output was low. Using a frequency generator app on my phone, I injected signals from 1kHz to 15kHz into my AR speaker. At 8kHz the sound from the tweeter was barely audible. At 9kHz and above, the sound disappeared. So I rotated the balance knob on my amp from right to left. Amp is in mono mode, to ensure L and R speakers see the same signal. AR speaker on the right channel, my Polk on the L channel. As I went up in frequency (1kHz steps) from 1kHz to 15kHz, my Polk was very audible up to 13kHz, the limit of my hearing. On the AR, the XO does seem to be at 5kHz, as I had output from the tweeter. But its output dropped precipitously after 8kHz. This should be an interesting project going forward. My wife loves the Polks, the 1989 RTA-8T, and is losing patience with my fiddling on the “old” AR speaker. What she doesn’t understand is that I hear greatness from this AR. But it can’t be realized with the tweeter not producing in the highest octaves. I know they’ll sound great once I get the tweeter working to its full potential. Without the upper octaves, the speaker will suffer from an apparent lack of “air”, detail, and balanced sound. Edit: As an added tidbit, my father’s 1966 Wharfdale W70D speakers were his “cat’s meow.” He was very proud of them, bought new in ‘66. But they suffered from a beaming quality, and a sizzling paper cone tweeter with a felt surround. Already these little AR speakers have a promise of a more open, more spacious and detailed sound. My dad is still alive. In talking to him, he said he was sold on the “British” sound, and his Garrard turntable with Shure M44 cartridge. He considered the AR speakers, but got a “good deal” on the Garrard Lab 80 table and Wharfdale speakers….
  24. ReliaBill Engineer
    Thanks for the heads up! Replacing the tweeter would be an absolute last resort. But if I should, I have several great candidates. But the impedance would require a new XO design, or at least a new value of capacitor. The tweeter output, as is, is woefully inadequate. It’s very restrained, even at max setting. I had already known the heavier dome requires a stiffer suspension, and at 5 kHz+ the displacement was small. But I doubt the clear sealant is butyl. It’s hard as a rock on my tweeters. Butyl rubber doesn’t usually fail in that mode. Butyl rubber is what I’m going to use for the 4-point suspension. But a softer, more compliant mix. I may try a compound which uses micro encapsulated silicone grease; it has compliance yet damps extremely well. I’m going to try a thinned clear silicone for sealant. Membrane thin. It’s stable and won’t harden. (I used to work for Goodyear Tire and Rubber as a technical engineer with the compounding engineer) Butyl rubber is used for the inner case of tires; it’s stable and doesn’t react to oxygen or nitrogen, it’s heat stable, and is stable under constant flexing. I’ll do before and after vids of this track. This is before: https://youtu.be/I9tDWEOLOgs
  25. ReliaBill Engineer
    My backup plan is to replace the tweeter. I’ve got many in inventory to choose from, including a couple of Dynaudio 28 mm soft domes. But, I’ve done a lot of small work like this before. Fact is, my rebuild of a Shure VN35E stylus, and an (Micro Acoustics) MA 309, and Shure VN5MR and VN5HE styli was more demanding than this. Of course, I’d rather keep these original tweeters. So here’s my plan: Using a 10x loupe goggles and powerful LED headlight, use a razor to cut the sealant around the dome, except for where the yellow blobs are. Scrape away the sealant from the base of the dome, but not ON the dome. Then apply my own elastomer “blobs” next to the original yellow blobs (X 4). Let it cure. Then cut away the yellow blobs. Then apply a clear sealant I’ll make from thinned clear silicone. A very, very thin coat. Let it cure. This way I won’t come close to the VC windings, nor mess up the centering and spacing of the original dome or windings. Im actually a little surprised by how non-precise these domes were originally assembled. The yellow blobs are all different sizes, and the sealant looks to be painted on by hand.
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