Newbie with question about my AR3A

[Guest CarlR]

Hi. I'll try to be brief. I have a pair of AR3As that I recently had new tweeters put in and also the potentiometers were replaced. They sounded good for about a month, but now I get a crackle (again!) out of one of the tweeters. This happens when the potentiometer is set toward to treble side. When I turn it back toward the low side, the crackle goes away. Does anyone know what might cause this? I'd hate to think I can't listen to these without having to set the pot to only one half of its range. I love these speakers. I listened to my older brother's when I was a kid, and they're outstanding! I'm kind of weak when it comes to electronics, but I could probably hold my own with an easy repair. Any thoughts on this matter are greatly appreciated! Carl

[Carlspeak]

You'll have to provide your audience some details so we can help you.

What exactly did you install for tweeters? Same as vintage types? or, a newly produced drop-in replacement? If so, what was the brand, ohms, etc.?

What were the pots you installed? Where they true 15 ohm rheostats? or, 8 ohm l-pads?

Where the tweeter caps replaced?

[Guest CarlR]

You'll have to provide your audience some details so we can help you.

What exactly did you install for tweeters? Same as vintage types? or, a newly produced drop-in replacement? If so, what was the brand, ohms, etc.?

What were the pots you installed? Where they true 15 ohm rheostats? or, 8 ohm l-pads?

Where the tweeter caps replaced?

Hmm. That's a tall order. Unfortunately, I had the speakers professionally fixed so I have no idea about what was put in. He told me they were original AR parts and I can only trust that they were. Sorry I don't have any more information than that. The speakers would have been the vintage type.

[RoyC]

Hmm. That's a tall order. Unfortunately, I had the speakers professionally fixed so I have no idea about what was put in. He told me they were original AR parts and I can only trust that they were. Sorry I don't have any more information than that. The speakers would have been the vintage type.

There are a number of possible reasons for the problem you describe, and I doubt any can be resolved with a quick fix. Since you have had them back for only a month, you should call the professional who performed the work to at least get the answers to Carl's questions. Since the tweeters are "new", the most obvious guess is a faulty level control, which means someone is going to have to take the speaker apart to repair or replace it.

Roy

[Guest CarlR]

There are a number of possible reasons for the problem you describe, and I doubt any can be resolved with a quick fix. Since you have had them back for only a month, you should call the professional who performed the work to at least get the answers to Carl's questions. Since the tweeters are "new", the most obvious guess is a faulty level control, which means someone is going to have to take the speaker apart to repair or replace it.

Roy

Carl's Custom Loudspeakers

Roy, the person who fixed it is unreliable. I would not use him again. What is involved in replacing the tweeter? Thanks!

[RoyC]

OK...that brings us back to what you have for tweeters, and are they "front-wired" or "back-wired"? Photos of the front of the speaker, as well as the level control shafts would be helpful.

Roy

[Guest CarlR]

OK...that brings us back to what you have for tweeters, and are they "front-wired" or "back-wired"? Photos of the front of the speaker, as well as the level control shafts would be helpful.

Thank you, Roy, I really appreciate your kindness here. I'm uploading photos of the tweeter. Funny thing today, I tried to reproduce the crackle and couldn't. I readjusted the potentiometer to its previous position - at the high end - and the speakers sounded terrific. But I'm sure it'll come back.

I look forward to hearing what you think of the replacements. thanks again for your time. Carl

[johnieo]

Greetings CarlR:

The tweeters that are shown in your attached photos are not AR original tweeters, but rather AB Tech Services replacement tweeters (could have been supplied via Simply Speakers). Not to be upset. These are new and will last many years, but they do need a change in the crossover. Ken Kantor has modeled these and found that for the AR-3a, they need a 0.7 mH coil connected across the tweeter directly to make them as close to the original as you will find today. If you cannot handle the electronics mods, it would be best if you found help - preferably close to where you live. If CSP members knew your location, perhaps there will be someone who could assist. As far as the scratching -- probably an incomplete job of pot cleaning.

Cheers,

[RoyC]

CarlR,

Oops, John posted his response while I was writing the one below. I agree with him :-).

Your tweeters are the current standard AR "replacement" tweeter sold by a small company called AB Tech Services, and your speakers are the later version of the AR-3a (probably 1975+ vintage), equipped with back-wired tweeters and mids. This means the tweeters are very easy to remove and replace, though I believe your intermittent noise is a level control issue. The old controls can be troublesome, even after cleaning.

If you want to get adventurous someday, there is a minor crossover modification that will make those tweeters sound more like the originals.

Roy

[Guest CarlR]

CarlR,

Oops, John posted his response while I was writing the one below. I agree with him :-).

Your tweeters are the current standard AR "replacement" tweeter sold by a small company called AB Tech Services, and your speakers are the later version of the AR-3a (probably 1975+ vintage), equipped with back-wired tweeters and mids. This means the tweeters are very easy to remove and replace, though I believe your intermittent noise is a level control issue. The old controls can be troublesome, even after cleaning.

If you want to get adventurous someday, there is a minor crossover modification that will make those tweeters sound more like the originals.

Roy

Thanks both!! I live in Monterey California, so if anyone were near by who could give me a heads up, I would greatly appreciate that. Regarding the pots, they were replaced; that's the funny thing about this. I had the speakers serviced at a shop in Sacramento (paid more than $250 for the service), where the pots were replaced in both speakers and the tweeters were both replaced. What is the crossover modification? I could take out the tweeters and do something behind them, if that's all that's needed. I'm fairly handy; just not a speaker expert. Thanks again to all who are helping here!

[Diamonds&Rust]

Regarding the pots, they were replaced

Hi Carl,

I've been following along. You have really high quality help coming your way already. I just noticed that you skipped a couple of could-be very important questions.

The "pots" being replaced, by a pro, could mean they used potentiometers or L-pads. Both things will work, but not exactly equally. That might become important to diagnose a crackle. It wouldn't be the *cause,* but the answer could be important for troubleshooting. Also important is whether or not new capacitors were installed on the tweeter.

There are a lot of possibilities.

The immediate thought is going to be dirty potentiometers, but if the ones in your speakers are really new, and not cleaned-up old ones, that's less likely.

If it isn't an old potentiometer, then a list of things needs to be ruled-out one at a time.

1) Can you tell by your invoice, or by looking at them, or just by knowing, if they did install "new" potentiometers, or new L-pads, or cleaned-up old potentiometers?

2) Do you know if they put new capacitors in the speakers?

3) When you experienced the noise and you say it happened when the controls were turned up, did the noise happen continuously, what were you playing (violin, a choir, Motley Crue) and how loudly? <the speaker should do it all equally well, again, this is a troubleshooting issue>

4) If it happens again, are the speakers where you can easily switch sides with the speaker wire and see if the noise stays with the same speaker, or the same channel on the amplifier?

John described the crossover modification, briefly. You have to install a new inductor (choke) across the tweeter. It has to be in the right place and be of the right size. I'm sure John will get back to you on exactly how it is done - with very clear instructions - if you are willing to spend the time to do it. A little solder, resizing an inductor or two...

Do you have an inductance meter?

Bret

[Guest paul]

Thanks both!! I live in Monterey California, so if anyone were near by who could give me a heads up, I would greatly appreciate that. Regarding the pots, they were replaced; that's the funny thing about this. I had the speakers serviced at a shop in Sacramento (paid more than $250 for the service), where the pots were replaced in both speakers and the tweeters were both replaced. What is the crossover modification? I could take out the tweeters and do something behind them, if that's all that's needed. I'm fairly handy; just not a speaker expert. Thanks again to all who are helping here!

Hello,CarIR

I am in San Jose,I am a engineer,I had collect many vintage speakers for fun and I do all the repair myself.I had the equipments to do the trobleshooting. I will not charge you anything,buy I need you to give me the old tweeters.if you interesting,email me your phone number.Thanks.

[RoyC]

CarlR,

As you can see there are seldom simple answers to most of the questions asked in this forum. Replacing capacitors and modifying the crossover for the new style tweeters are both desirable things to do, but you seem quite happy with the sound of your speakers with the exception of the crackling noise. I would concentrate on that issue first.

If the noise problem is not in the amplifier channel, the next easiest thing to do is to simply switch the tweeters and see if the noise stays in the same cabinet or follows the tweeter. Once again my money is on the level controls as that is where that type of noise is found 99% of the time in these old beasts. Even brand new 8 ohm l-pad-type controls can develop some static upon adjustment after a relatively short while, but not usually to the degree of having to dismantle your speakers.

Attached are two photos...one showing the difference between a typical 8 ohm l-pad and an original AR potentiometer, and the other of a quick mock-up of the easiest way to implement the crossover modification. You need to identify which type of level control you have, if for no other reason than to determine if they need to be replaced.

IF your guy replaced your old pots with new 8 ohm l-pads, you can purchase two off the shelf .05mh 18ga inductors (instead of "making" .07mh inductors) for a total cost of about $6 from Parts Express or Madisound, and easily implement the modification as shown. No inductance meter is necessary. (Actually I have a bunch of .05mh coils, along with the appropriate wire and connectors, which I would be happy to share with you.) I personally prefer the new l-pad/.05 mh inductor combo better than the .07mh inductor/original pot combo with the new tweeters. The .05mh inductor is easy to acquire, the l-pads are more reliable than the old pots, and it sounds better to my ear. IMO, that combo provides somewhat smoother tweeter output, and more useful level control settings.

Roy

[Guest CarlR]

OK. First, you'll be happy to know that I've figured out how NOT to include the previous post. Thank you all very much. The receipt says "4 AR Pots + labor" and "2 AR3A tweeters" then "check all components". That's it. Then, there is the fee. :-((

Anyway, I can email the guy and ask if he replaced the questioned parts. My name is Carl Richmond and my home email is carl.richmond@comcast.net if you'd like to reach me there. I really appreciate this help. You guys are really terrific. Thanks!

[Guest CarlR]

Roy, how can I tell which pot I have? Can I see this from behind, or do I need to go inside the cabinet? I've been inside before; you pull out the woofer, right? And then you can view the pots? If you tell me how to get in there and what I'm looking for, I might be able to do it. Thanks! of patients of patients

[Guest speedracer]

Roy, how can I tell which pot I have? Can I see this from behind, or do I need to go inside the cabinet? I've been inside before; you pull out the woofer, right? And then you can view the pots? If you tell me how to get in there and what I'm looking for, I might be able to do it. Thanks! of patients of patients

I think you "feel" the difference, "L" pots are smooth, "pots" are "scratchy"

[RoyC]

Roy, how can I tell which pot I have? Can I see this from behind, or do I need to go inside the cabinet? I've been inside before; you pull out the woofer, right? And then you can view the pots? If you tell me how to get in there and what I'm looking for, I might be able to do it. Thanks! of patients of patients

The control knobs on the shafts are easy to remove (look for the small set screw). You can get a pretty good idea by looking at the shafts. (Post a photo of 'em.) Most repair shops replace the pots with l-pads, as they are much easier to obtain and are much less expensive.

A pair of those ABT tweeters are pricey... around $150.

Roy

[JKent]

Roy, how can I tell which pot I have? Can I see this from behind, or do I need to go inside the cabinet? I've been inside before; you pull out the woofer, right? And then you can view the pots? If you tell me how to get in there and what I'm looking for, I might be able to do it. Thanks! of patients of patients

If you look at the control (L-pad or pot) shaft after removing the little knob, I think a pot will look like one of the photos below. The 4x's and 2ax's did not have knobs--just a shaft with a little arrow on it. They were usually red or black plastic, sometimes aluminum, and solid. The L-pads usually have splined split steel shafts, to take a push-on knob.

The link will show an L-Pad. The attached photos show a 4x (red shafts) and two 2ax's (black, aluminum) but the pots are all interchangeable, so I "think" the 3a pots will look like the 2ax aluminum ones. Roy and many other members here would know for sure. I unfortunately do not own a pair of 3a's so I can't be certain. But if the shaft is splined AND split, I think it would be an L-Pad.

http://www.partsexpress.com/pe/showdetl.cf...tnumber=260-248

Kent

[Guest speedracer]

If you look at the control (L-pad or pot) shaft after removing the little knob, I think a pot will look like one of the photos below. The 4x's and 2ax's did not have knobs--just a shaft with a little arrow on it. They were usually red or black plastic, sometimes aluminum, and solid. The L-pads usually have splined split steel shafts, to take a push-on knob.

The link will show an L-Pad. The attached photos show a 4x (red shafts) and two 2ax's (black, aluminum) but the pots are all interchangeable, so I "think" the 3a pots will look like the 2ax aluminum ones. Roy and many other members here would know for sure. I unfortunately do not own a pair of 3a's so I can't be certain. But if the shaft is splined AND split, I think it would be an L-Pad.

http://www.partsexpress.com/pe/showdetl.cf...tnumber=260-248

Kent

All my 2ax's, 3's, 3a's, and 4x's are red and or black plastic, one pair of 4's have aluminum pads that I had replaced about 10-12 yrs, ago.(?)

[RoyC]

The red, black and metal original AR pot shafts are interchangeable, as Kent and Speedracer suggested. Nice photos, Kent..

Attached are photos of an installed l-pad (in a 4x), and the 3a knob/set screw arrangement which must be removed to check out the shaft.

Roy

[dynaco_dan]

The red, black and metal original AR pot shafts are interchangeable, as Kent and Speedracer suggested. Nice photos, Kent..

Attached are photos of an installed l-pad (in a 4x), and the 3a knob/set screw arrangement which must be removed to check out the shaft.

Roy

Hi there;

It has been too long for me to remember all the melted pot shafts that I saw in the AR warantee depot here, as to what colour they were in colour order, black or red.

I should have said, "all of the shafts that I didn't see," come in. LOL

I believe that the aluminum shaft was the final answer to the meltdown of the plastic shafts.

AR wasn't Aetna-Pollock's only potentiometer customer, but judging by the number's used in AR speakers alone, AR was a major customer.

Did that supplier go under first or did AR change to the later switches and L-pads maybe causing that company to disappear?

The original A-P pots used a resista wire coil which is chromed in appearance, very smooth, when new.

One must use the least abrasive possible cleaner or an etching will take place to the coil encouraging more corrosion again.

I've seen pencil erasers mentioned, a soft abrasive if there ever was one.

[JKent]

It has been too long for me to remember all the melted pot shafts that I saw in the AR warantee depot here, as to what colour they were in colour order, black or red.

Hi Vern

How do you like this pot? Talk about melted shafts!!

[dynaco_dan]

Hi Vern

How do you like this pot? Talk about melted shafts!!

Hi Kent;

I would save all the parts to salvage what you can to try to re-build some spares.

The melted plastic can be discarded, unless there is a market for it. LOL

I know about automotive dielectric grease.

Do we plaster it inside a cleaned up pot housing or just swipe a smear on the rotors and coil?

I have finally given up on finding a stock, non-conductive and non-flammable shield for the rear of the pots.

This was to keep the insulation and wires away from the rear rotors.

You should see my varied collection of Chinese tea cups, cute little flower pots, shot glasses, Wendy's Ketchup cups and paper cups used by the doctors when giving you a small dose of medicine or pills.

I went to a dozen or more retail and wholesale sellers of these items.

I even went to Canadian Tire and bought some cute little clay flower pots.

The main problem I had was finding a large enough straight inside diameter cup, without it being too large an outside diameter, so that 2 can fit, side by side, where needed, for example an AR-2AX needs two.

A single pot wasn't so much of a problem but it had to be universal in it's fit.

There is the Ohmite and the Chinese pots, both slightly different in size.

The Ohmite appears to be discontinued (?), very well made in the USA.

The Chinese one is built like a tank and at least 1/2 the price of the Ohmites and appears to be an ongoing produced item, at the moment at least.

The physical problem I was having, was the rotors of the two pots.

The rotor was exposed and slightly extending over the edge of the coil.

That meant the tea cup had to clear the rotors tip, a difficult requirement, as I was to find.

I found a ceramics shop/workshop a few months ago.

They have ceramic eggs for sale.

They are small, medium and large I believe.

The large was about $10.00 each.

The egg sizes I did not measure but the shell thickness was quite on target for our requirements.

I would have had to buy some greenware eggs and cut the egg about in half, using 1/2 of it only, maybe.

I thought about it over and over a few times.

Now I would suggest buying at, Home Depot for one example, plastic electrical 2 hole pipe clamps.

I haven't measured the size yet but an 1 1/2" or 2" should do the trick.

If the clamp straddles the pot's rear area, there is the two screw holes as part of the flange which can be epoxied to the the masonite crossover boards.

If by chance there is adequate clearance from the 1 1/2" clamp, then maybe a 2" clamp can be kitty cornered across the smaller clamp, to double the insulation blockage.

If required down the road, it would not be too difficult to remove the clamp or clamps.

The 2" clamp should be ok by itself but this is another option, like I say, I have not measured the required size yet.

This is a non-conductive and non-metallic fix and with adequate clearance should not be a heat problem.

This is of course only my suggestion with the Chinese and the Ohmite pots, with the exposed backsides.

[RoyC]

Regarding the AB Tech tweeter modification...I just noticed that in a previous photo in this thread I should have shown the yellow wire (the 3a tweeter + lead) connect to the - terminal of the AB Tech tweeter, as shown in the attached photo. (The sonic difference is, at most, very subtle.) The addition of the inductor theoretically calls for the polarity reversal. The most important thing is to wire both speakers the same way.

Roy