ReliaBill Engineer
-
Posts
291 -
Joined
-
Last visited
Content Type
Profiles
Forums
Events
Posts posted by ReliaBill Engineer
-
-
Heat gun.
-
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.
-
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.
-
52 minutes ago, Aadams said:
I meant, you did a good job, getting them to match. Paul Desmond sounds good.
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. -
1 hour ago, Aadams said:
Good job getting them to match.
I added some content above.
-
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: -
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.
-
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.
-
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.
-
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.
-
I waited for a gently used pair of AR-2ax, early model. The wait/hunt has been very gratifying.
-
12.4 watt canned rheostat. Power-wise, it should work.
-
I have not had issues posting directly from my phone. This is 2.8 Mb:
-
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:
-
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.
-
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:
-
In my case, the 2 T-nuts were never driven into the plywood. There were no marks from where the barbs had ever touched the plywood. They had been only partially (half way) pushed in. Once I clamped the nuts into the plywood, the screws worked perfectly. The screws didn’t push the T-nuts out when I drove them in with a screw driver.
-
On 4/11/2023 at 5:38 PM, RoyC said:
It wasn't the variation in the pots. The notches were model specific and were there to place the arrow of the pot shaft in a specific position relative to the white dot. It was meant to position the pot so it would provide the appropriate amount of attenuation from full increase to the dot in accordance with that model's specifications. I only mentioned them to illustrate the fact that AR never intended, nor implied, that the dot was the halfway mark of the pot's rotation.
The comparison is always the interesting part when refurbishing these tweeters. Due to the nature of the construction of the old beasts, achieving consistent results is a challenge...regardless of the material used to suspend the dome.
I’m curious…..
Have you had occasion to measure crossover responses of the mids and tweeters (AR-3 series and AR-2 series) using the 15/16 ohm pots used as voltage dividers? Doing simple math, the impedance load on the capacitors changes with pot slider position.
-
I know you’re right, Roy. It made no difference in performance of the woofer. Just surprised to see it! All I did was use a pair of channel-lock pliers to press the T-nuts in, and the screws tightened up perfectly. I had to dig around to find a pan head screw that fit for the missing screw.
I decided not to “adjust” the pot positions. All I did was remove the retaining springs and open up and separate the pots. Then clean, lube the shafts with a smear of silicone dielectric grease, reassemble and replace the clips.
-
12 hours ago, Aadams said:
Did you skip the step where you compare the 2nd, untouched, tweeter to the restored tweeter? I can't find your analysis of that comparison.
Here is a direct comparison of the 2nd speaker with caps replaced. Original caps measured 5.8 uF and 8.7 uF. In both, pots are at 100% increase position:
Untouched:
Caps replaced. Pots wire brushed and reassembled; pots were clean and shiny. Original tweeter, untouched:
So I’m going to rebuild this tweeter also. Probably sounds like it did from the factory. I prefer the sound below.
-
As for replacing the pots, all 4 are perfect. Like they came out of the factory yesterday. They were never stored in a garage, barn, ministorage unit or attic.
I was very specific in how I clamped the domes, how I mixed the red elastomer and clear, and how I applied it. I’m not anticipating troubles duplicating it for the second dome. But I will test play the 2nd speaker after replacing the caps, prior to any work on the dome.
-
7 hours ago, Aadams said:
Did you skip the step where you compare the 2nd, untouched, tweeter to the restored tweeter? I can't find your analysis of that comparison.
I “analyzed”, or recorded a comparison. Same track, same cartridge, same preamp/amp. But the 2nd speaker has the original capacitors in it. I haven’t yet replaced the caps. Pots are clean and good; no dropouts or scratchiness, both drivers respond smoothly to pots being turned (ear at driver).
Untouched. Pots set to 100%:
The first one:Tweeter untouched:
Below, right side:
Below, left side:
-
Another thing on this second speaker. Some pretty shoddy factory assembly!
Where was the QC????
Of the 6 mounting screws in the woofer, only 4 were holding it in! 2 screws were covered in putty, complete with fingerprints. Left side, below. (Top positions of the woofer if set in vertical position.)
Below, close up of the putty-covered screws. The top screw in this pic is “stripped.” It’s there, but just turns in place. The bottom screw is missing. No screw!! Never added!
What happened? The “T-nuts” were only inserted half way. They were dangling in the holes and not fully clamped into the drilled holes in the baffle. So the top screw could not self tap. I guess the factory worker ran out of time to do it right. Must’ve been late on a Friday….
Below, you can see the nuts mounted only halfway into the baffle surface. The other 4 are firmly mounted into the plywood. Guess the assembly person was in a big hurry…
Below, original configuration of wiring, pots, coil, capacitor:
-
How many people who buy a new speaker want response curves, so they can compare to published response curves? And 58 year old speakers? Anyone who asks *me* for response curves is out of luck. What they can do, however, is feel free to adjust the pots to their liking. I’m confident that there are pot settings on these that will exactly match original response curves.
And from original: All original drivers, original pots, original wiring, original interior rock wool, all original veneer, original grills and original grill cloth, new capacitors.
Original AR-2 / 2a /2ax woofer damping ring
in Acoustic Research
Posted
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?