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Gaston

Restoring the AR-6 (and some other questions about them)

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Hi everyone, I am new to the forum.
I’ve been reading those pages previously a lot, but now, since I obtained a lovely sounding AR-6’s, I will need some help from you guys.

So, I would like to restore my AR-6's and make them not only perfectly functional, but also would like to restore the cabinets and grilles.
The cabinets will be sanded, repainted and oiled, maybe even lacquered but for that to be nicely done I will have to remove the LF and HF drivers.

- Is it a good idea to have the cabinets veneered with natural veneer or it would be best to leave them as they are?

- While restoring the cabinets, perhaps it would be a good idea to replace the capacitor(s) and the foam surrounds too? The capacitors have never been replaced.

The surrounds look like new but the job was not done with love obviously. They sound great, but the foams are twisted at some places and not nicely glued and I would like this to be done by a professional.

- Will I also need to replace/change the "cabinet sealer" material that I see it protrudes from both drivers?

Mine are with 3 position switch on the back (normal/decrease/increase), those are referred as European model and the previous owner told me they have the ceramic LF driver.

I also have some other questions:

I am driving them with NAD 3020. Is this amp enough for them? Will they benefit from extra power?

And there's one thing that concerns me... while listening several songs that are bass heavy (on high volume but far from distortion level) I've heard a reaping/braking sound... I was afraid that I have damaged the LF drivers for good, cause it sounded just like the paper cones were teared. Very unpleasant sound. Nothing was damaged luckily. Now I never cross that volume threshold but I do feel like they are not close to their maximum potential. After all, NAD 3020 is 25W per channel and they should handle up to 100 wpc.

Can this be due to the sealing material not doing his job properly?

Thank you for reading this long post, I know I am asking too much but I am new in the vintage world and this is an unknown territory for me.

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Hi Gaston, and welcome to CSP.

Congrats on your new speakers - - I am a huge fan of the smaller AR two-way speakers, so I am always pleased to find others with similar enthusiasm. All of your initial thoughts are valid concerns, and several voices will weigh in to give solid advice and opinions on all of your questions.

The best thing you can do is to upload several good photos of your speakers, and then we can all assess your cabinets, crossovers, grilles and speaker drivers. With a few good pics, the advice you get will be much more specific and helpful to your efforts. If you cannot figure out how to upload pics, just ask, and you will get assistance. Typically, if you keep the images under 100 KB, the image quality should be more than sufficient.

Looking forward to your follow-up post.

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I agree with ra.ra, pictures are necessary in order to give proper advice, if possible also inside the cabinets with the woofer removed.

Your model should have 2 capacitors, a 10 uF and a 24 uF, and depending on what make they are, I think that the sound would benefit if at least the 10 uF being replaced.

Regarding changing the foam surrounds, I think you answered the question yourself.

"- Is it a good idea to have the cabinets veneered with natural veneer or it would be best to leave them as they are?"

What are they? (again pictures would help)

BRgds Klaus

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Thank you friends.

I will post pictures as soon as I can. Next day or two.

Since I have a small flat, the speakers are now at my parents house. My father has a workshop with nice tools where I can work on them peacefully.

In the meantime, could you please tell me if NAD 3020 is enough to "feed" them? Should I consider another amp? I've been offered a NAD 3300 PE (60 wpc), but I am not sure if it will sound as nice as 3020.

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Welcome Gaston

Are you in Europe? Just guessing. If you are in the US I would recommend MillerSound to repair your woofers but if you're on the other side of the pond some of our European members will have to advise you on that.

Yes, you will have to replace the sealant if you pull the woofers to repair them or replace caps. "Duct seal", Mortite putty or foam gasket tape (from Parts Express) are all good choices.

I have no first-hand experience with the AR-6, so I'll let others give a more informed opinion on the NAD/AR-6 question but just as a point of reference, my first system included a pair of AR-4x's, which I believe had the same drivers and the same cabinet volume as your 6s, powered by a Dynaco ST-35 tube amp that delivered 17wpc. They sounded wonderful.

The NAD 3020 is an excellent amp. My guess is the AR-6s will be quite happy with it.

Kent

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Yes, I am in Europe.

There's a service in my neighborhood that has a good "renommé" here and is very popular among Tannoy Gold owners.

I don't know if he stocks foams for AR's but I really hope he do cause I have seen his work and can say that he is very penchant about details, practically a perfectionist.

So maybe he can replace the duct seal too.

So 3020 should be enough? That's great, because I really like the sweet, friendly sound of this little amp.

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Gaston, even though many people (here, and on other audio sites) rave about the virtues of amplifiers with 100W per channel and more, I totally agree with Kent's assessment about the suitability of your NAD 3020 to be compatible with the AR-6's. The classic AR's have certainly never been lauded for their efficiency, but then again, NAD is known to publish rather conservative power ratings for their amplifiers, so my guess is that these components should work well together. In my own listening world, I have some AR's from this vintage hooked up to a very modest 18W Sherwood receiver (circa 1971), and for many years I've powered these and similar AR's (model 4's, 4x's, 6's, 7's and 2ax's) with a Scott integrated tube amp from 1964 rated for no more than 22 or 24 watts per channel ..... and it all sounds very good to me.

Good to know you are in Europe - - - Klaus seems to be the reigning expert on many Euro models, and in particular the AR-6. You're in good hands for advice, so just post some pics when you can and the advice will flow.

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The Euro AR-6 with three-position switch uses a single 24uF 30V capacitor (the model with the 10uF cap only has a two-position switch).

You may or may not notice much change in the sound if you change the caps now, but 10 years from now is another matter.

Minimum rated power for this model is 20wpc, a bit less won't be a problem in a small room and not very high volumes. Maximum rating is 100wpc.

Inadequate sealing normally produces reduced bass. Breakup sound at moderate volumes indicates an issue with the woofer. I would start with that less than stellar refoam. Whoever did it may not have properly centered the cone.

Pictures definitely needed before advice about cabinets.

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Thanx everyone for your replies!

You are giving me an enthusiasm to restore them as best as I can. And I will definitely have them refoamed since that can be the reason for breakup sound.

About the cabinets - the previous owner, painted them with some reddish color which I want to change with a wenge/rosewood veneer. So, should they be re-veneered or repainted only?

The pictures:

I will have to make a triple post since I have 30 pictures and max allowed is 10 (I appologize for that).

post-131024-0-79036900-1369163033_thumb.post-131024-0-67191600-1369163036_thumb.post-131024-0-89898200-1369163039_thumb.post-131024-0-41927700-1369163043_thumb.post-131024-0-88454500-1369163047_thumb.post-131024-0-36594200-1369163051_thumb.post-131024-0-32527700-1369163055_thumb.post-131024-0-27180300-1369163059_thumb.post-131024-0-25690200-1369163063_thumb.post-131024-0-03710500-1369163067_thumb.

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Based on the pictures, I don't think the re-foam work looks bad, but the way the woofer was mounted is not good, and has some places twisted the foam; try to re-mount the woofers more thorough, avoiding that the screws "twists" the foam surround material.

It is the blue Sprague compulytic 10 uF capacitor you could consider to change with a film type (e.g. polypropylene), not because it has gone bad (they hold up pretty good) but modern film capacitors are considered better soundwise.

BRgds Klaus

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Not bad? Ok... maybe on the pics looks alright, but in truth, you can notice that the work is done just to be done.

But ok, will re-mount them first chance. Anyway, that will be the second thing on the list.

First thing will be to fix the cabinets and to find appropriate duct material since those rings between the drivers and the cabinets are ultra dry.

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Gaston, thanks for the excellent pics. My initial reaction was pretty similar to the one Klaus described - - - I do not think the re-foam is all that bad. Yes, I do see the small tear on the foam outer edge as well as the few pinched areas at the screw locations. Am not quite sure what Klaus is specifically suggesting with his recommendation for "re-mount", but I might suggest re-installing the woofers 180 degrees to their current position - - - not only would this allow for a wholly different position, it might also help to compensate for what some people describe as "cone sag", which may or may not occur over many years (assuming vertical positioning and normal earthly gravity forces). As for the small tear, a little glue will repair it just fine.

Where the foam is pinched at the screws, it might help to include an additional thin metal washer between the foam and the screw head. As the screw thread engages the T-nut in the baffle board, it will still be able to provide the necessary compression for an adequate acoustical seal, but the washer may prevent the screw head from twisting and pinching the foam. Your woofer gaskets look shot - - when re-assembling, replace them with new concentric foam gaskets or use a putty sealant as JKent has described.

Regarding your crossover electronics, I am a bit confused based on the comments from Klaus and genek, who are both excellent resources within this forum. It appears that you have several resistors and two capacitors in each cabinet, and although I cannot read the cap values and do not have all of the AR-6 schematics handy, I think you may have what is referred to as a 'Zobel' circuit, where the woofer has electronics directly attached. genek refers to a single cap crossover, whereas Klaus mentions two caps, with a potential improvement made by replacing the tweet cap.

Your linen grilles look great, but the cabinets are a mild mystery. As a first measure, I would suggest neither re-paint nor re-veneer. My guess is that the previous owner applied a very heavy-handed re-stain application, and the finished appearance is thick and unctuous, almost more opague than transparent. Do not despair - - - they are most likely restorable! Even though I do like a bit of red color in the walnut, your cabinets appear too intense and therefore, unnatural in color. This may indeed be an excellent situation for the application of a product like Howard's Restore-A-Finish, where it basically dissolves the original finish so that it can be either wiped out or rubbed in to the desired effect. From what we can see, the walnut veneer appears in good shape, and that open miter joint can be masked easily with an appropriate colored filler.

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I will rotate the woofers 180 degress, that's a logical and very easy thing to try. Thanx.

Yesterday, when I made the pics I hooked them to my parents old TRIO/Kenwood amp, that is only 35 watts per channel and even this poor amp made the woofers breakup at a bit higher volume levels.

Perhaps, before rotating the woofers it would be a good idea to lay them down with drivers pointing up and see if they will breakup this way?

One thing that cheers me up is that no one said anything negative about the drivers (both LF and HF), which means they are original and (I hope) in fairly good state. That Zobel, I guess it does not need to be changed, I will only replace the 10uF blue capacitor if that really makes an improvement.
A friend of mine, owns a pair of AR 11's, he replaced the caps last week and he explained that the difference was incredible and the sound improved dramatically.

I have to admit now, that while restoring those speakers I will have my wife as a small devil with a trident over my head, cause, I guess you all understand, those AR's have to fit with the rest of the room furniture. It is a small flat, but she has it "installed" in, what I must admit - the best possible way that this space allows. I wouldn't like to ruin her joy, so those speakers have to be perfect. Like brand new from the store. The color needs to be wenge or dark rosewood. And, those white linen grilles will have to go and to be replaced with black ones.
I have to do my best with the cabinets because of her. I've looked at Howard's Restor-A-Finish. Now that's one fine product, but it's not available in Europe. I don't know if anything similar can be found here.

Edit: I have been offered an almost mint pair of AR18S. How do they compare with AR6? (I don't intend to replace AR6. Those should replace a pair of Tannoy DC1000 - if they sound as nice and deep as AR6).

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I have attached the AR-6 schematic, in the most recent updated version (courtesy of Richard Lowe) for the AR-6 early models, the middle one is the one in your speakers.

When I wrote "re-mount" I meant re-installing, I guess I was a bit tired, could not find the right word. Could not remember the English word for washer either, meant to suggest that as well; It is an excellent idea to avoid the twisting of the foam when screws are tightened.

AR-18s are also excellent speakers, they are late versions of the (compared to AR-6) smaller AR-7, and therefore do not have the same deep bass, but again for their size, excellent speakers. AR-18 has a number of "professional followers" for use as a near-field monitor in studios.

BRgds Klaus

AR6-XoverUpdateOct12.pdf

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There are multiple variants of the 6 and no "official" schematics, so the ones we have are based on peoples' observations and get updated. I may have been looking at an out-of-date drawings.

With regard to the cabinets, there is no way that walnut can be made to pass for rosewood and reveneering would be required, but with the right stain a wenge look is achievable. Normally, I would prefer to use chemical stripper rather than sand to avoid distubing the patina that wood develops over time, but if the intent is to change the color it doesn't matter and you may as well sand it.

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I've tried rotating/re-installing the bass driver in every possible position without success. The breaking sound is there at high volumes :(

The only good thing is that it occurs only on one of the speakers. The other one is fine.

Could this be caused by a bad sealing or the thing is much more serious?

And I have bought those AR18S, fine sounding speakers. Much brighter than AR-6 in the upper range. I guess this is normal.

The bass is far from AR-6, so I had to connect a sub with those. That way the sound is lovely.

Here they are, the badges are missing but the seller promised that he will obtain badges for sure.

post-131024-0-62169200-1369852331_thumb.

However, there's something really strange with the metal housing of the LF drivers with those speakers.

Like someone was trying them to make wider opening with pliers or similar tools.

:blink:

post-131024-0-88041100-1369852736_thumb.

post-131024-0-17869300-1369853115_thumb.post-131024-0-59488300-1369853119_thumb.post-131024-0-23397300-1369853124_thumb.post-131024-0-58877900-1369853128_thumb.

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The woofer appears to have been refoamed, so my guess is a rather clumsy job of removing and cleaning off the old foam.

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Hi genek, thanx for your reply, but, fortunately, it seems that's not the case.

I was doing google and also ebay search for those drivers (200037) and other similar 8" LF drivers from that era.

Every picture that I have seen so far shows those ugly like plier bended casings.

Even here, ra.ra's post: http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7897, clearly shows that those drivers and other ones (200035) are bended.

And on ebay: http://www.ebay.com/itm/Acoustic-Research-8-Woofers-Refoamed-for-AR-4-4a-6-7-15-16-17-18-28-38-93-94-/251279527560?pt=Vintage_Electronics_R2&hash=item3a816d4e88

And everywhere...

That's relieving for me, but now the things are even more stranger...

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Hi Gaston. Just a couple brief comments here - - - I'm not quite sure what the point is that you are trying to make about your woofers. My suspicion is that you are concerned with the bent metal of the outer basket. In some pics, the basket looks just fine, but then in the close-ups, it can be seen that there is at least one edge that has been distorted. This edge is not in contact with either the cone or the surround, so I think it should not be a problem at all.

However, it sounds as if you are still having some poor performance from one of the woofers (breaking sound?), but it is difficult to give knowledgeable advice. Is it possible that the surround on the problem woof is not fully sealed against the concentric cone? Does high volume cause a flapping sound, or what exactly is going on?

Am surprised that your AR-18's are noticeably 'brighter' than the AR-6's since they employ almost identical tweeters. Am also curious about the colored tape at the speaker wire terminals. I always associate red with positive, and for this vintage of AR, positive (+) is normally the 2 terminal - - - however, your pic shows 1 as red and 2 as blue-yellow. Just wondering what these colors designate.....

"And, those white linen grilles will have to go and to be replaced with black ones." Am slightly surprised to hear this comment, too. Your white linen grilles look really terrific, and from the comments I have read about WAF (wife acceptance factor), it seems more typical for women to often find the soft look of raw linen more acceptable than the more severe appearance of black grille cloth. Not trying to stereotype an entire gender here, but's it's just my observation from the peanut gallery....

post-112624-0-26881200-1369966726_thumb. post-112624-0-67013100-1369966740_thumb.

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Hi Gaston
I don't want to confuse things or give you more anxiety, but I can't help but wonder about post #18. Now, admittedly I have no first-hand experience with the 6 or the 18S but I have lived with the 4x, 7 and 17 and I believe all of these 2-way 8" woofer speakers are quite similar. So when you comment that the 18S is much brighter than the 6 and lacks the 6's bass response I can only conclude there is something wrong with the 18S. Very likely, as Gene suggested, an air leak. Try placing 3 fingers in tripod fashion around the perimeter of the dust cap, then push in. The cone should take a second or so to return. Compare all 4 speakers. If the 18S woofer cones return faster than the 6's, that's your problem. Most likely culprit is the foam gaskets around the drivers.

OR.... as ra.ra. has suggested, make sure the woofers on the 18S are not out of phase. In one is wired in reverse, there goes your bass.
Kent

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The 6 did have significantly deeper bass than the 7/18 speakers. I'm not surprised by the observation of that. The 6's bass response was essentially identical to the 2ax/5. I believe the system resonance of the 6 was around 56 Hz, the 7/18 about 10 Hz higher. That's very audible.

As to the brightness, again an accurate and unsurprising observation. The 18 generation of speakers had FF cooled tweeters and therefore those tweeters could be driven "harder" than in the 7/6/4xa. The 18 was indeed brighter than the 7. In fact, that was the main performance difference--the FF-cooled tweeter (cosmetic differences aside).

Maybe my memory is fading after all these years, but that's how I remember things. So, neither the bass nor brightness comment strikes me as wrong.

Steve F.

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The 6 did have significantly deeper bass than the 7/18 speakers. . . . As to the brightness, again an accurate and unsurprising observation.

Thanks for clearing that up Steve. Hope I did not mislead Gaston.

Kent

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Steve's assessment sounds correct to me re: the development of this family of tweeters. My understanding is that the addition of ferro-fluid allowed the tweeter to handle increased power input. In post #18, Gaston mentions the problem with his woofer becoming apparent when played at "high volumes", which made me think to mention the ferro-fluid difference, but since his problem seems to be in the lower frequencies, I just left it at that. Still, despite the ability of the later tweets to be driven harder, I'm a bit surprised to hear that there were such pronounced audible performance differences.

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