AR 3A tweeter problem

[carlbarry]

I thought my front left beloved AR 3A sounded off.  Turns out the tweeter is nor working.  I replaced both pots a few years ago, so I doubted that was the problem.

I did the easiest thing first: checked if there is a voltage going to the tweeter.  There is, hovering around 1 volt.

Can I safely assume the tweeter is shot and needs to be replaced?

Thanks.

[Aadams]

1 hour ago, carlbarry said:

Can I safely assume the tweeter is shot and needs to be replaced?

Original tweeters can be rebuilt and should be done in pairs.  You also have the option of the Hivi Q1R with mods.  Post a photo of both tweeters.

Adams

[JKent]

Hi carlbarry

I think you have 3 options and whatever you decide, you should replace both tweeters. Those half-century-old tweets are getting tired.

1. Replace them with Hi-Vi tweeters with inductors. I have thiese in my 3a's and they're fine. This is the cheapest option.
2. Have RoyC rebuild yours. He rebuilt a pair for some speakers I was working on and the results are excellent. And they are still original.
3. Have Chris1this1 rebuild them. I have no first-hand experience but other members (including Roy) say his work is excellent.

Since your speakers are "beloved" I'd go the rebuild route, unless cost is a major concern.

Kent

oops--Aadams gave similar advice while I was typing.

[ADVENTAGIOUS]

Disconnect wires from tweeter and measure across the driver terminal with an ohmeter. You should get a resistance value of 3-5 ohms. If the meter does not deflect then the driver coil "could"be open. It could also be a poor solder connection somewhere in the crossover, pots, or even at the voice coil connection on the driver. Don't rule anything out.

If $ are not a factor replace or rebuild them as mentioned by others. Good Luck!

[carlbarry]

Thank you.

I'm the original owner, and both speakers were bought at the same time.  Both are identical.

I see front wired replacements on ebay for around $88.  The HiVi are much cheaper, if I'm looking at the correct replacement, only $25.48.  But they have the back connections, not front like mine.

[JKent]

Don’t buy replacements. Have the originals rebuilt. Or go with HiVi. They can be front wired by drilling 2 little holes in the faceplate.

[carlbarry]

25 minutes ago, JKent said:

Don’t buy replacements. Have the originals rebuilt. Or go with HiVi. They can be front wired by drilling 2 little holes in the faceplate.

The HiVi option seems very good to me.  I used to be able to hear 20 kHz on the test records, but not any more!

If that is the solution, I'll do it.  Thanks.

[carlbarry]

I checked the resistance on the leads of the tweeter, after de-soldering, of course.  First problem was scraping the lacquer off the hair thin wires.

I checked with an ohm meter.  Infinite resistance.  So the voice coil is open? 

Is the HiVi Q1R a drop in, or does it need a modification to the crossover?

Thanks.

[JKent]

4 hours ago, carlbarry said:

Is the HiVi Q1R a drop in, or does it need a modification to the crossover?

Pretty much drop-in. You just put a 0.05mH coil on the back of the tweeter.

[carlbarry]

Aha!  Thanks.  I read something about a 3 uF polypropylene capacitor, and inverting the polarity.  I haven't fully researched it.  The speaker is out of stock until May.

[JKent]

This is really Roy's mod and he has experimented quite a lot and refined his approach. The most recent thing I found from him said "I prefer the .05mh coil, 5uf cap, L-pads/no resistor, and like-polarity."

You said you replaced the pots. If they are original pots the tweeter/coil should be enough. If you used L-pads you might consider replacing the 6uF cap with a 5uF cap but really the 6uF should be fine. You can tweak the sound with tone controls (and maybe room placement but that's often not possible).

Of course, if you never replaced the capacitors you may want to consider that. And be sure to download the AR-3a restoration guide. http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

Kent

[carlbarry]

6 minutes ago, JKent said:

This is really Roy's mod and he has experimented quite a lot and refined his approach. The most recent thing I found from him said "I prefer the .05mh coil, 5uf cap, L-pads/no resistor, and like-polarity."

You said you replaced the pots. If they are original pots the tweeter/coil should be enough. If you used L-pads you might consider replacing the 6uF cap with a 5uF cap but really the 6uF should be fine. You can tweak the sound with tone controls (and maybe room placement but that's often not possible).

Of course, if you never replaced the capacitors you may want to consider that. And be sure to download the AR-3a restoration guide. http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/

Kent

Thanks for all the help.

I couldn't fix the original pots, so I replaced them with new pots that were advertised as direct replacements.

I downloaded the restoration guide quite a while ago, and it is fantastic.

 

[JKent]

2 hours ago, carlbarry said:

I replaced them with new pots that were advertised as direct replacements.

If you bought them from ebay seller Vintage-AR they're L-pads.

[carlbarry]

34 minutes ago, JKent said:

If you bought them from ebay seller Vintage-AR they're L-pads.

Gee, I'm positive I bought them on ebay, but it was a few years ago.  I have to find the shipping box, where I saved the old pots.

[genek]

1 hour ago, JKent said:

If you bought them from ebay seller Vintage-AR they're L-pads.

Depends on how long ago. At one time, Larry was taking original pots apart and combining parts to reconstruct them to sell.

[carlbarry]

7 hours ago, genek said:

Depends on how long ago. At one time, Larry was taking original pots apart and combining parts to reconstruct them to sell.

No, the ones I used were not like the originals.  They looked like standard potentiometers.

[JKent]

When I did my 1st speaker restoration in 2004 I bought "replacement pots" from Vintage-AR. They were plain ol' L-pads from Parts Express with Larry's printed instructions. Useful for a novice but not pots.

The only "standard potentiometers" for these speakers are Ohmites (hard to find and absurdly overpriced) and some Soviet surplus ones being sold by an ebayer in some former Eastern bloc country. Standard potentiometers are open-back and would require an enclosure of some kind.

First picture below shows Ohmites in a plastic box in AR-3. Second shot is an original AP pot on the left and an L-pad on the right.

[carlbarry]

OK, I found the box with my originals.  It's from April  2007 (time flies when you're having fun; I would have sworn I replaced them about 5 years ago).  Return address is for Larry Lagace.  

The instructions for installing the new units says, "The VINTAGE-AR superior replacement level controls for all early year AR speakers utilize a different terminal layout than the original AR potentiometers . . ."  No mention if L-pads.

My originals are the ceramic bottoms with metal tops and red posts.

Just as a side note, I have the AR-3As because I built a Heathkit AR-15 receiver, as that was rated the best receiver by Consumer Reports.  We then bought the 3As at a place in Brooklyn called Stereo Warehouse for I believe $185 each, because again Consumer Reports rated them the best speakers.  I'm pretty sure that was 1968 when I was in high school.

[JKent]

No mention of L-pads because then customers would look for L-pads and find them at PE for $5. But they ARE L-pads. The giveaway is "different terminal layout ". Here's his current ad: https://www.ebay.com/itm/ACOUSTIC-RESEARCH-AR-3a-CONTROLS-INSTALLATION-KIT-LIFETIME-GUARANTEE/191490399538?hash=item2c95b79d32:g:MQoAAMXQk-FRESZQ

I'm not criticizing. Larry Lagace is Vintage-AR and his products are very useful. As I said, I bought his "replacement controls" for my first restoration and the printed instructions were very invaluable for a novice. But if you want to know what's in your speakers, they're L-pads.

So getting back to the quote from Roy (who btw does some work for Larry) "I prefer the .05mh coil, 5uf cap, L-pads/no resistor, and like-polarity." You have the L-pads. If you go with the Hi-Vi tweeters, do not use a resistor. Do not reverse polarity. Do add a .05mH coil. The cap is up to you. If you are re-capping anyway replace the 6uF with a 5uF. Otherwise just adjust the sound with the L-pads and the tone controls on your amp.

Kent

PS: If you search ebay for "AR 3, AR3a 5, 4x 2ax Pot Acoustic Research Speaker 16 Ohm Control potentiometer" you will find some actual closed-back pots offered by a seller in Brooklyn for $30 each and apparently identical ones being sold by CSP member Chris1this1 for $25 each.

[carlbarry]

Thanks again!

I see he's improved his packaging since I purchased mine.  Mine were just the L-pads and a photocopied instruction sheet, no wires, color directions, etc.

I'm just waiting for the speaker to be back in stock at Parts Express.

[JKent]

Try here:

https://www.madisoundspeakerstore.com/hi-vi-soft-dome-tweeters/hi-vi-q1r-1-fabric-dome-tweeter-116-mm-flange/

inductor:  https://www.madisoundspeakerstore.com/madisound-air-core-inductors-19-awg/madisound-0.05-mh-19-awg-air-core-inductor/

I'd phone or email to check availability.

[carlbarry]

1 hour ago, JKent said:

Try here:

https://www.madisoundspeakerstore.com/hi-vi-soft-dome-tweeters/hi-vi-q1r-1-fabric-dome-tweeter-116-mm-flange/

inductor:  https://www.madisoundspeakerstore.com/madisound-air-core-inductors-19-awg/madisound-0.05-mh-19-awg-air-core-inductor/

I'd phone or email to check availability.

Thanks.  I had looked at Madi Sound, too.  They want much more for shipping than Parts Express, and there is a notice that they don't know when they'll be able to ship.  So either way, I probably have to wait for the Apocalypse.  Until then I guess I'll just have to wear headphones.

[DonT]

I personally think the original pots can be rebuilt with no problem. You just need to polish the brass contacts and clean them up with a dremmel. Get several very fine grit grinding stones for use in the dremmel. And when done put some dielectric grease on them to keep it from corroding again.

[carlbarry]

I've replaced all of them in my 3As after unsuccessfully trying to rejuvenate them.  But when they go in my rear channel 4Xs, I will surely give it a try.

Thanks.

[JKent]

Some pots can be rebuilt and some are too far gone. I used L-pads in my 4x's. It was my first restoration. If you want authentic pots the ones from Chris1this1 are worth a try. While you're in there be sure to replace the capacitor. You'll need one 20uF per speaker.