AR series 3a

[Brian4561]

Dude, you CAN work on the crossover. Assuming, of course, that you know which end of the soldering iron to hold onto and can melt a little solder.

First off, the only things you would probably 'replace' is the capacitors. That involves mainly finding the right place in the circuit to put them, but that is really an exercise in following wires. Just pay close attention to the schematic (above) and the wire colors. After that, you snip the leads of the old ones and solder new ones in their place.

I've never seen inside an AR-3, but iin my AR-2 and AR4s, the capacitors are large wax-paper things. I cut the leads off and left them in place, since it looked like a PITA to pry them out.

Before I replaced the pots, I'd pull them out and see if they can be cleaned. you won't know until you pop them open what sort of condition they are in. If they are as corroded as the ones shown earlier in this thread, they are pretty much toast. If they are merely oxidized, a good cleaning should have them working pretty well. If I were cleaning AR pots to put them back in (and I am) I'd clean them up with Deoxit and then hit them with a good couple of sprays of Deoxit Shield.

 

[Jesse Garron]

Great, then I'll have the shop temporarily bypass the XO in a non-destructive manner and catch up with you guys about how to do the rest. Sounds easy enough.

I haven't seen the pots, but I have heard them. Sounds like a bunch of dried up leaves when you turn the knob.

 

[onplane]

Unless the material is replicated pretty closely, I would guess that a re-cone would affect the tonal quality of these drivers

Jesse, I second what ozmoid wrote.

That woofer is very special and to achieve the deep, undistorted bass the cone material was specially selected as was everything else in it.

Now, if the woofer can no longer produce sound under 40Hz, that would be a different story.

Regards,
Jerry

 

[ozmoid]

All of a sudden I feel like James Stockdale.

:lmao: The AR crowd here can be very vocal about their preferences, me included . That said, it is always a good idea to take the major gripes to PM guys, and not pi** all over someone else's thread with personal differences.

I have been guilty of the above myself, and have repented.

Jerry's mods have validity, as most modifications to vintage gear do. It all depends on what you're looking for. If you want that classic "AR sound", track down some replacements for those pots. If you want the best response for your system, that takes trying different things until you get it right for your ears.

Personally, I think using two amps without the pots in place would be a reasonable solution to the corroded rheostat issue. For my opinion, I would probably by-pass the wiper and leave the pots in place to keep that resistor (those old rheostats are replicating a resistor strap in the crossover) in place in the crossover.

But that's only an opinion - several members have done the by-pass-with-two amps-scenario and are very happy with the results. I have not tried it with two amps yet, but I will. And Jerry himself (onplane) has "modified the mod" over time, making changes to improve the result. I did much the same thing trying to figure out how to get the L-pads to replicate the pots when I was working on my first pair. I kept at it until I liked the result - what sounded good in the first 5 minutes was not so good sounding after a week or two of living with the speakers.

In the end, it's all about what sounds good to you - and the only way to find that out is try new stuff. :yes:

 

[Jesse Garron]

No sweat. Actually it wouldn't be right for me to complain as I took my own thread OT! I often do...

Speakers (repair) is new to me, so I'm just trying to take everything in...

I'd rather keep the speakers as originally designed - at least at first and modify if needed..

 

[shacky]

Perhaps your advice would mean more, Joe, if you read what AR wrote back in 1968. To achieve a "uniform energy output at all audible frequencies ... level controls must be turned all the way UP -- both the mid range and tweeter controls -- AND treble tone control of the pre-amp turned up slightly ... "


But don't believe me, Joe .... try reading what AR wrote :

So, Joe, unless you listen exclusively to vinyl records made prior to 1968, any reductions from FULL ON in the pots settings move you away from a flat response.

Lastly, "the AR-3a was designed mainly by a very competent man named Chuck McShane, under Roy Allison's direction." The recommendation to by-pass the tweeter pot came NOT from me, Joe, but from .... Chuck McShane!


Joe, do you have anything .... anything at all to refute what I've conveyed here??


Regards,
Jerry

Jerry,

Was not aware that Chuck McShane recommended bypassing tweeter pot. Is this from another article or are you talking about the recommended full on position?

I use to dabble in restoring cars - a '64 Grand Prix actually with a 421 tripower. In car restoration there are 2 approaches. The purist restores the car to the closest he or she can get to how it rolled off the assembly line. The second is to modify it to improve on the original.

I took the first route because I love these cars and wanted to keep a piece of history for future posterity. That's the same approach I take to audio gear including my AR 2AX's and project 3A's. I think it's part of the fun to make them work they way they were designed. Pots and all in place and with one receiver running the show. I don't think I'll ever get you to switch your system from the biamping approach and tweeter pot mod. At the same time you are not going to convince me to make your mods on my speakers. I'm enjoying them too much the way they were designed.

Your passion for your project and your enjoyment of the music using your mods is all fine and good. However, I think that the first approach should be to maintain the original and harken back to that magical time in music - the 60's. I'm glad I stuck with original approach. Maybe someday I'll try the biamping you recommend. Your passion is just as well intentioned as mine I am sure. Difference as I see it is you don't see me recommending that you put your speakers back to original on numerous posts.

 

[winters860]

Jerry,

I'm not as up on my AR lore as you are. I apologize to you, your family, your hometown, and Chuck McShane.

That being said, man, different strokes for different folks. I don't see anything in that document advocating modding the speakers. I can certainly see that bypassing the tweeter pot and fixing the wiper on the mid would bring about a close facsimile to cranking both pots and putting a slight treble boost on the tone controls. I know it's worked for you, ozmoid, and others and I might even try it myself one day, but you'll understand if I tire somewhat of your tenacity in promoting the One True Gospel.

Coincidentally, pots full-up with the treble slightly turned up is how I run my unmodded AR-2ax... Different strokes for different folks.

 

[onplane]

Jerry,

Was not aware that Chuck McShane recommended bypassing tweeter pot. Is this from another article or are you talking about the recommended full on position?

Hi, Jim!!

Nope, I'm talking about eliminating the tweeter pot and YES, Chuck McShane, the AR-3a designer, was the individual who first suggested.

AR Library

2nd article from the bottom titled comments from Jim McShane (Chuck's nephew).

At the same time you are not going to convince me to make your mods on my speakers. I'm enjoying them too much the way they were designed.

Well, Jim, thank you for giving me credit, but I'm really not really the inventor of these mods. Folks have been doing this for years. I'm merely an advocate for containing cost, yet still getting the best possible sound with MODERN media. These mods are NOT for folks who primarily listen to old vinyl records.

However, I think that the first approach should be to maintain the original and harken back to that magical time in music - the 60's. I'm glad I stuck with original approach. Maybe someday I'll try the biamping you recommend. Your passion is just as well intentioned as mine I am sure. Difference as I see it is you don't see me recommending that you put your speakers back to original on numerous posts.

Jim, I understand and appreciate the "purist" approach and I think that is fine. Just remember though that modern media (CD’s MP3’s, FM, etc) are totally different than those old vinyl records. So, while you are preserving the original design, you are actually veering away from the original sound; especially IF you mostly listen to modern media.

Now, as for bi-amping, I only mentioned it in passing on this thread. Jim, I no longer promote bi-amping to people who have recently acquired AR’s.

“Jerry-rigging” is neither for the faint of heart nor for folks who know little about electronics. There are risks associated with wiring amps together. Further, people who have just acquired AR’s can’t really appreciate the difference in sound it provides. This is a mod I will claim a small amount of credit, but I now believe it’s only for the long time AR owner who wishes to push these “old timers” to their maximum potential.

Jim, does this make sense or am I still coming on too strong?

Regards,
Jerry

 

[Jesse Garron]

I just want to add that "Chuck McShane" is a really cool sounding name. My previous favorite was "Tippsy McStagger" from The Simpsons, but that has been eclipsed.

 

[onplane]

Jerry,

I'm not as up on my AR lore as you are. I apologize to you, your family, your hometown, and Chuck McShane.

That being said, man, different strokes for different folks. I don't see anything in that document advocating modding the speakers. I can certainly see that bypassing the tweeter pot and fixing the wiper on the mid would bring about a close facsimile to cranking both pots and putting a slight treble boost on the tone controls. I know it's worked for you, ozmoid, and others and I might even try it myself one day, but you'll understand if I tire somewhat of your tenacity in promoting the One True Gospel.

Coincidentally, pots full-up with the treble slightly turned up is how I run my unmodded AR-2ax... Different strokes for different folks.

Joe, no offense taken and I apologize if my language was a bit shall we say "rough".

The Chuck McShane recommendation on the tweeter pot I referenced in my previous post. As for the mid-pot, I really don't know who first suggested it. I know that I read it prior to doing.

It was NOT the first thing I did. I ended up by-passing the mid-pot wiper out of total frustration. For years I'd lose ALL mid-range in my left speaker and I'd have to rotate the pot back and forth a few times to get it back.

So upon opening the speakers and itching like mad, I decided that I'd like to NOT have to go back in there again .... ever. In short, I by-passed not for sonics, but to avoid itching.

Joe, just out of curiosity, how are your 2ax's positioned? I see you have the pots set at the recommend position for modern media and am wondering whether you have your speakers on the floor where you get the deep bass reinforcement.

Regards,
Jerry

 

[winters860]

Jerry,

I like my 2ax pretty well on the floor, but I made some handsome (and obscenely heavy, being concrete) 8" speaker stands. I found getting them up off the floor got rid of the slight "boom" they had and gave them a better overall balance to my ears.

Cheers,

 

[shacky]

Jerry,

Looked the classicspeaker.net library article you mentioned. While interesting I wouldn't put that internet post in same category as "peer reveiwed" used in medical field. The pots are an integral part of the crossover circuit. My theoretical electronics are not up to your level but if you take a 15 OHM pot out of the ciruit it is going to effect the crossover frequency. Regardles of db gain, I can't imaging the crossover is going to be at factory setting so you have either frequency range missing or over-emphasized, ie doubled up from driver below.

Jim McShane's uncle may have indicate bypassing but I would bet he put something in place to maintain proper crossover.

AR's are deisgned to sound as though you are sitting a ways back from the stage. And they were designed to be as neutral as possible in regard to frequency response. Playing a new CD through them sounds wonderful - I don't think it's diminishing high frequency but I could be wrong. They are not near field monitors and in original spec they are the ultimate in non-fatigue. I tried L-Pads when I first refinished my 2AX and the 8 OHM L-Pad left a big whole in the midrange. Sounded pretty good and they were brighter than with original pots but I cleaned up a great pair of AR pots and put them in place of the L-Pads and will not go back.

I think any mod with the AR's needs to check frequency reponse not just DB to compare the reproduction of full spectrum vs. original set up. I don't buy the modern vs. 60's music. Full spectrum is full spectrum. AR's probably roll off in high end sooner than current speaker technology but increasing the DB up to that roll off isn't going to make the reproduction of music more accurate.

 

[shacky]

Jim, does this make sense or am I still coming on too strong?

Jerry,

You can never come on too strong for me. I've been in medical sales for over 20 years. I'm use to going toe-toe

Jim

 

[onplane]

Joe,

You made concrete speaker stands? That’s clearly unique! I can't recall ever seeing concrete speaker stands.

Sounds pretty impressive, Joe!! How about posting some pics??

When you went up 8 inches, did you notice any change in the balance between the low frequencies and the highs?

Lastly, Joe, it sounds like with the pots adjusted the way they are you feel the resulting sound is fairly well balanced ... right?? (I'm just curious as I don't own an AR-2.)

I have a set of AR-2 "clone" made by Jensen (my sister gave them to me), but it's a totally different animal. They sound OK ... nothing great ... as long as you are right it front of them. As soon as you move off axis, everything goes to he__!

Then I have a set of AR TSW-610's and they are a very respectable speaker. (3-way - acoustic suspension - 12 inch poly woofer - 4 ohms -made by AR in the late 80's)

For whatever reason, none of the TSW speakers have controls. I guess by the late 80's equalizers were fairly common and AR no longer saw a need to provide controls.


Regards,
Jerry

 

[onplane]

Jerry,

Looked the classicspeaker.net library article you mentioned. While interesting I wouldn't put that internet post in same category as "peer reveiwed" used in medical field. The pots are an integral part of the crossover circuit. My theoretical electronics are not up to your level but if you take a 15 OHM pot out of the ciruit it is going to effect the crossover frequency. Regardles of db gain, I can't imaging the crossover is going to be at factory setting so you have either frequency range missing or over-emphasized, ie doubled up from driver below.

Jim,

First off, there really isn't one factory set xover frequency. The very fact that you can adjust the level of the tweeter relative to the mid-driver, means that you can adjust the xover frequency. (For the sake of clarity let's agree that the xover frequency is the frequency at which each driver contributes 50% of the resulting sound.)

To evaluate a change like this, we need to understand what happens in the tweeter at various frequencies. Next, let's remember that we are eliminating a 16 ohm resistor that is in parallel with a 2.5 ohm (DCR) tweeter. Net effect of this is (see chart below):

1. Removing the pot INCREASES the impedance for the tweeter network
2. Higher impedance means LESS current flows through the tweeter network @ same voltage
3. Nevertheless, MORE current flows through the tweeter
4. On average 10% more current flows through the tweeter with the pot removed
5. Approx. 20% more power in the tweeter and 20% more SPL
6. Tweeter network increases in sensitivity for the same applied voltage
7. Reduction in xover frequency is really negligible (less than 2% difference between 4000 and 5000 hz)

Jim McShane's uncle may have indicate bypassing but I would bet he put something in place to maintain proper crossover.

Nope, because none is necessary. There is a thread in the AR forum where Jim confirms this. Finally, Jim, you can prove it to yourself. Just assume you set the pot to 2 ohms in series with the tweeter. The resulting resistance is far, far higher than the 2.5 ohms you get by simply removing the parallel 16 ohms.

Playing a new CD through them sounds wonderful - I don't think it's diminishing high frequency but I could be wrong.

It depends upon a number of factors. Where your pots are set, where your treble control is set and the amount of reflective surfaces vs. sound absorbing surfaces you have.

I have a late 80's vintage AR (Teledyne era) to compare against my 3a's. My 3a tweeter puts out no where near the sound output as the tweeter on my TSW-610. Jim, it's not even close, and I have my 3a's set, as you know, to the maximum output. Then on top of that the TSW-610 tweeter is surrounded by an acoustical blanket to absorb spurious reflections.

I tried L-Pads when I first refinished my 2AX and the 8 OHM L-Pad left a big whole in the midrange. Sounded pretty good and they were brighter than with original pots but I cleaned up a great pair of AR pots and put them in place of the L-Pads and will not go back.

L-Pads lack the adjustment range of pots. That is, the maximum series resistance is 8 ohms. With a pot you can have 16 ohms in series!

Consequently, an L-Pad at the mid point will be brighter than a pot at the mid point by a significant amount. Naturally, you can throttle an L-pad back, but you can't duplicate the same resulting xover frequency as a pot. (Roy has a very neat solution that makes an L-pad almost identical to a pot in the range of interest.)

I think any mod with the AR's needs to check frequency reponse not just DB to compare the reproduction of full spectrum vs. original set up. I don't buy the modern vs. 60's music. Full spectrum is full spectrum. AR's probably roll off in high end sooner than current speaker technology but increasing the DB up to that roll off isn't going to make the reproduction of music more accurate.

Absolutely!! Full spectrum is full spectrum and AR told us back in 1968 how to achieve "uniform energy output at all audible frequencies".

Increasing the db output of the tweeter will in no way, shape or from prevent the "roll off". Jim, once again you are correct! It may, however, delay very slightly ... the start of that roll off.

The other issue that no one really knows is whether those 40 year old tweeters are really putting out the same amount of db's as back then. Roy questions whether the buytl foam has degraded to the point where it impacts the resulting sound.

Regards,
Jerry

 

[shacky]

Quote from Ozmoid in another thread. I thought the AR pots kept constant 15OHM and adjusted level only not crossover.

Shacky, the difference in the original AR pot and the PE L-pad is two-fold:

1. The AR pot has a FIXED resistance across terminals 1 and 3 of 16 ohms. No matter where you move the control (wiper), this reading remains constant.

The L-pad varies resistance across terminals 1 and 3 as you move the control. Resistance will vary from 8 ohms at min to 40 ohms at max.

2. The AR pot output on terminal 2 varies from 0 ohms to 16 ohms as you move the control. this is the ONLY terminal affected by the control on the AR pot.

The L-pad varies terminal 2 output as you move the control from .5 ohms to 40 ohms.

These resistance changes are certainly changing how the crossover sounds, and is affecting the "voice" of the speakers. The easy solution with the L-pads is to just mark the point where terminals 1 and 3 read 16 ohms, and leave it there. At that point, terminal 2 is reading about 10 ohms - this is very close the "sweet spot" on the original control.

I have now measured over half-a-dozen AR pots, and the resistance varies from 15.5 to 17.3 so far. So if we have gotten within "an ohm or two", we are within the same tolerance AR used for the part.


Here is thread:

http://audiokarma.org/forums/showthread.php?t=71133&page=2

 

[onplane]

Quote from Ozmoid in another thread. I thought the AR pots kept constant 15ohm and adjusted level only not crossover.

While ozmoid is correct in that the 15 ohms never changes, the division between what part of the 15 ohms is in series vs. what part is in parallel ... changes. That's what the wiper does.

Jim, as soon as you alter the amount of series vs parallel resistance, there will most assuredly be a frequency response alteration. Guaranteed ... has to happen!

The simple rule is as you raise total resistance (naturally the cap is unchanged), lower frequencies will be impacted MORE than higher frequencies. Just look at how that very slight net resistance change in my chart impacts lower frequencies ... more.

The whole idea of L-Pads is to present a constant impedance to the xovers so that variations by frequency are minimized. Pots are an older technology and simply cannot do this!

L-Pad Description

Nevertheless, L-Pads alter the output of one driver vs. another. Let’s define the xover frequency as the frequency at which each driver contributes EXACTLY 50% of the resulting sound. With this definition in mind, even L-Pads will alter, although to a lesser degree, the resulting xover frequency.

Regards,
Jerry

 

[ozmoid]

I know it's worked for you, ozmoid, and others and I might even try it myself one day, but you'll understand if I tire somewhat of your tenacity in promoting the One True Gospel.

Coincidentally, pots full-up with the treble slightly turned up is how I run my unmodded AR-2ax... Different strokes for different folks.

Joe, for the record, I don't run any of my AR's with the pots bypassed, and do not advocate it. Other members here have tried the bi-amping approach that Jerry advocates and like it - as you said, different strokes for different folks.

I did do a lot of hands-on research into trying to replicate the effect of the original pot with readily available parts, and it works for me. I do not run the treble increased feeding my 2ax, and I run both pots just a fraction off what would be "full" in relation to the original pots. In my system, that seems to yield the richest sound, with a good balance between the three drivers.

And I DO listen to old vinyl LP's quite a bit - but I also listen to CD's and modern sources without changing how my speakers are set, or adjusting my tone controls. Good recordings in any media sound good.

 

[winters860]

When you went up 8 inches, did you notice any change in the balance between the low frequencies and the highs?

Lastly, Joe, it sounds like with the pots adjusted the way they are you feel the resulting sound is fairly well balanced ... right?? (I'm just curious as Idon't own an AR-2.)

I think I see what you're getting at.

Since I already run my speakers this way, why does it make sense for me to restore two pots that could potentially be bypassed for similar effect and keep my tone controls flat? Maybe it doesn't. You've about got me convinced to give it a go in my upcoming next AR-2ax project pair, but only because there will be a ready comparison. Has anyone actually done a side-by-side?

Running my speakers off the ground by 8" cuts the bass response somewhat. Doesn't this mean that I'm throwing away bass to compensate for the low output of the tweeter? In this case I think the bass sounds less flabby elevated a little bit and it doesn't have a thing to do with tweeter volume.

Sounds pretty impressive, Joe!! How about posting some pics??

I'm not big on flattery, but I'm proud, so I'll share. They're basically just the concrete blocks with the cross-shaped grooves on top that cheapskates use as deck pylons. I coated them with fleck-stone paint and the speakers are mounted with blue tack. My "high mass floor-coupling speaker stands" ran me $20, which I think compares favorably to the prices people pay one ebay for original AR stands.

Cheers,

 

[onplane]

I think I see what you're getting at.

Since I already run my speakers this way, why does it make sense for me to restore two pots that could potentially be bypassed for similar effect and keep my tone controls flat?

Running my speakers off the ground by 8" cuts the bass response somewhat. Doesn't this mean that I'm throwing away bass to compensate for the low output of the tweeter? In this case I think the bass sounds less flabby elevated a little bit and it doesn't have a thing to do with tweeter volume.

Cheers,

Joe, I think your speaker stands are very creative and look pretty darn good! A $20.00 creative solution is my kind of solution. I mean anybody can spend $40 to $60 on speaker stands.

On the balance issue, that wasn't what I was thinking. I've never heard the 2ax, but I know the drivers are somewhat similar to the 3a. I also know the 3a will put out more and deeper bass than the 2ax. My guess is the AR teamed "voiced" all of the AR's similar, but that's just a pure guess.

If I'm correct, your 2ax should be in balance with the pots at max positions, just like my 3a. If my guess is incorrect, I'd expect that in the max position the mid + tweeter would over power the woofer. Joe, I'm just trying to figure out what AR did some 40 years ago.

Switching subjects; raising the speakers off the floor will reduce the DEEP bass reinforcement. That doesn't mean, Joe, that you are "throwing away bass". It really depends upon the music you like. For most rock and popular music the bass line is handled by a bass guitar. I doubt you would notice a significant difference.

Now, if you listen a lot to classical or jazz where the acoustic double bass is used, then I expect you would notice a difference.

Lastly, Joe, I agree with your comment about the woofer having little impact on the tweeter. There is a strong relationship between the mid-driver and the woofer, however. In short, I can turn up the woofer so much that it seems as though the mid range has ... disappeared. It hasn't, of course, but you get that feeling and the end result is a total lack of clarity; vocals sound terrible and you have a hard time recognizing the instruments.

In short, balance between adjacent drivers is extremely important in achieving clarity. It seems to make less difference (as you observed) when the drivers are far apart in terms of frequency.

Regards,
Jerry