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AR-6 Restoration


Gabriel
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Hi everyone! My name is Gabriel and since a few days I'm a possessor of a pair of AR-6.

These loudspeakers were from my grandpa and have been stocked in a humid cellar for a few years. They're in decent conditions, but I think there are some problem with mid-high frequencies.

I'm not an audiophile so I cant judge, but the high frequencies are kinda muffled. The response is better if I set the Treble of my amplifier (Akai AM-U04) to the maximum.

I already bypassed the potentiometer and the mid-high are slightly better. 

What can I do to identify the problem? Is there any kind of test i can perform?

I've read that sometimes is useful to change the capacitor, but I would like to avoid useless expenses. 

 

Thanks, Gabriel

 

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Hi Gabriel - - welcome to the forum - - and congrats on getting your grandpa's speakers. The AR-6 is a terrific bookshelf speaker and I'm sure you will get these performing up to snuff, but they weren't helped by the humid basement conditions, which may have accelerated corrosion of the pots.     

There were a few variations of AR-6 throughout its production - - different woofers, different crossovers, different tweeters. Since you mention that yours have a potentiometer, I suspect yours are the earliest version, and these most likely have a wax block cap (see pic attached). If so, probably a good idea to replace the 10uF cap, which is not a useless expense if you wish to restore these properly. Also, there is a good chance that the woofers may need new foam surrounds. Please include some pics (cabinets, grilles, drivers and crossover, etc.) and I'm sure you'll receive further explicit assistance on all matters.

Two new caps for these could be purchased for between $2 and $15, and a couple new foams should be under $20, too. 

AR 6 x-o.jpg

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I've opened up the loudspeaker and I discovered that the woofers have been replaced. Perhaps my aunt has already renovated them. 

The woofers are peerless kp 825 pp. Is it a good woofer? I think it may be the reason why the loudspeakers sounds weird.

Also one of the tweeters connection is broken. I've tried to fix it soldering a think copper wire to it but  the vibrations have broken it again.

Here are some pictures.

Do you think it's worth to renovate these loudspeakers? 

 

Cheers, Gabriel

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I think I can help you to a set  of 8" AR woofers, but you can also look on ebay.de .

Has anybody the right type-no's of these woofers

They need new surrounds, but this can easily be done, it is very easy to align them properly when you put a 20-100Hz signal (from youtube) on the drivers, I did glueing with bison-tix, but any tixotropic glue will work, regards  Jurgen Prinsen weldtech@online.nl

 

 

 

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I don't know anything about those Peerless woofers, but it's really too bad that the originals are lost and have been replaced. Regarding the blue 10uF Sprague cap, genek is correct that these very well might still be good, but the only way to confirm this is to measure them when out-of-circuit. I have a different version of AR-6 that uses the identical cap, and mine recently measured within spec so I left them alone and the restored speakers are performing extremely well.

Your speakers show a few other curiosities, and it would be of interest to see the speaker backside and label - - it is unclear if you have US or European assembled models, and these seem to reveal elements of a hybrid that has perhaps not been identified yet. On the exterior, your speakers exhibit the thin reveal edge that is consistent with the Euro profile. On the inside, the stuffing is yellow fiberglass - - - this was always used in the US, but Euro production typically used a multi-color poly stuffing. If these are in fact Euro models, they are probably relatively early issues, as exemplified by FG stuffing, pot control, and front-wired tweeter - - all more normally associated with US production.

But the real unique curiosity is this particular combination of crossover components. The inside of your cabinet clearly shows what we've referred to as Schematic A, which was typically associated with the early Alnico magnet woofer. However, even though the woofers have been replaced with non-AR drivers, that attached cap and resistor shown appears to be consistent with Schematic B, which used the square ceramic magnet woofer. I have never seen these two features together in the same cabinet. I would assume this cap (24uF) and resistor (10 ohm) were removed from the original woofers and simply moved to the Peerless woofers, regardless of performance parameters. Also attached is a pic of this similar assembly from an original AR-6 woofer.

I was also unable to find suitable drivers in current ebay UK listings, but be patient (or send a personal message to jurgen 59). Others may know more about this, but I think either woofer should work for your replacements - - - but the added resistor and cap on the woofer should only be used with the square magnet woofer. I will try to post other pics of the Alnico woofer a bit later....        

AR-6 schematic (A).jpg

AR-6 schematic (B).jpg

woofer zobel.jpg

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Here is the label and a picture of the backside.

Should i remove the caps and the resistors from the peerless? I'm not able to found a datasheet, this is the closest I found.

I found 2 tweeter on ebay.it are them good to replace mine?

http://www.ebay.it/itm/ACOUSTIC-RESEARCH-TWEETER-AR8-18-17-ETC-/132343241748?hash=item1ed0459c14:g:ubcAAOSw8aVZy9jp
 

Thanks a lot

 

Gabriel

 

 

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My guess is that whoever put the Peerless woofers in added those components to try and compensate for the difference between them and the original AR woofers. If I'm right, removing them will probably make  everything you don't like about the way the speakers sound now even worse.

About the muffled highs, have you checked to make sure there's actually sound coming from the tweeters? 

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I think that the muffled highs are due to the peerless woofer. There's sound coming out from them, but it is probably covered by the woofers. 

The real problem about the tweeter is that one of the tiny wire is broken in the middle. I fixed it soldering another small copper wire, but after some vibrations it has broken again. 

I'd need to change just one of them, but I prefer to change both to avoid steteo unbalancements in the highs. 

 

Gabriel

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Well, it's now clear that you have a Euro model (Holland), but the handwritten serial number offers no further clues as to this speaker's provenance. I am unable to comment at all about the Peerless woofer, and that includes anything about its general quality or its impact on your "muffled highs".

Now I understand the problem with your tweeters - - - one of those tiny tinsel wires has become a problem (underneath the grey tape), and your first attempt at a fix was unsuccessful. Your tweeters are fully original, and it might be worth a second try to repair and patch the broken wire before thinking about purchasing new ones, because your primary issue really is finding the correct woofers. 

Two more thoughts about the tweeters - - - actually, one rant and one caution. My rant (as stated previously in this forum) is that as much as I like the performance of these early 1-1/4" tweeters, I really find these exposed tinsel wires found on several AR drivers to be a serious flaw in the mechanical engineering or industrial design of these drivers - - - it is simply a bad, bad, bad idea to have the wires inside the cabinet, then bring them outboard, and then poke them under the cones while trying to hide behind flimsy electrical tape. My caution is this: the tweeters in the link you provided look excellent - - great condition, correct part number, spot-on DCR readings - - but these appear to have the larger magnet, and you need to first be sure that they will fit in the holes that have been cut in your speaker's baffle board.

Particularly if the cabinets and grilles are in good shape, but these speakers are worth restoring, yet it may require some patience and some expense.        

 

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These comments here are only about the woofers. I want to look closely at some AR-6 speakers I have before commenting further on the tweeter issue, but will try to get back to you soon.

Pics shown here are the two versions of woofer I've encountered in AR-6's - - both of these used foam surrounds. The first three-part image shows the Alnico woofer, with large slug magnet, ribbed cone, and flat dust cap. These do not show up very often, and were only used in early manufacturing runs. The second two-part image shows the more common woofer (p/n 200001) with square magnet, smooth cone, and flat dust cap.

The woofers you posted in the link (shown here also, third pic) are excellent 8" woofers, and they will "fit" in your cabinets. However that particular woofer (cloth surround, alnico slug magnet, fine mesh dust cap) was developed for and used in the AR-4x and AR-4xa.  It was typically used with a #5 coil (1.18 mh) whereas the AR-6 used a #4 coil (0.88 mh) on the woofer, so I would suspect this woofer used as a replacement in an AR-6 would deliver different characteristics. 

AR-6 Alnico woofer.jpg

AR-6 woof w:foam.jpg

4xa 3.jpg

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I had also found a pair of AR-6 Woofer from Italy but the  seller asked me for 160€ for the couple.  I decided to get these because I got them at a much cheaper price.

Regarding the tweeters I tried to fix the tiny wire again, but I totally broke them.  I decided to buy a pair of the tweeter i linked before. I'll update you once I'll receive them.

Gabriel

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18 hours ago, Gabriel said:

I decided to buy a pair of the tweeter i linked before.

I suspect this is what you should expect to find - - the pics shown are both AR-6 tweeters. The front-wired tweeter on the left is dated 1971 and appears identical to your original tweeters - - it has the smaller magnet. The rear-wired tweeter on the right is dated 1979 and appears identical to the first link you posted - - this one has the larger magnet.

AR-6 tweeters.jpg

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The seller told me that the tweeters have the big magnet, but he also said that they will fit without problems in my cabinet.

Today I  made some tests with my AR-6. I excluded the cross-over and i bi-amped them using L for Hi and R for low. Then I used a software digital crossover to cut the frequencies. I managed to get out a much better sound than before. Obvoiusly, since I don't have 2 amps, I cannot use this bi-amp system normally. So I wired the speaker as before, but removing the capacitor and the resistor soldered to the pearless cones. I think that the sound is much better now.

In my opinion the Low-Pass filter made for the AR woofer was cutting to low for this cones, making a gap in the mid-high frequencies.

I'll update you once the new woofers and tweeters arrive.

Gabriel

 

 

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Hi!  I received the woofers and the tweeters. Now the loudspeakers sounds much better.

I have 2 questions.

1)There are 2 different crossovers' schematics around. One with the capacitor and the resistor in parallel of the woofer and one without. Wich one should I use?

2) How can i bypass the potentiometer? I think what I did is not exactly correct.

 

Thanks, Gabriel

 

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Hello Gabriel.

I am still a little confused about exactly what you are trying to do, so here are a few more comments and questions.

On October 16, 2017 at 11:26 AM, Gabriel said:

1)There are 2 different crossovers' schematics around.

Actually, there are three versions of AR-6 crossovers, but we do not need to discuss version C which was used in Europe for later models (it had no coil and employed a two-position switch).

On October 16, 2017 at 11:26 AM, Gabriel said:

Which one should I use?

It is not entirely clear yet how best to advise - - can you post pics of the actual woofers that you are intending to use?

On October 16, 2017 at 11:26 AM, Gabriel said:

2) How can i bypass the potentiometer?

Exactly why do you wish to do this?

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Reading this thread go me thinking what version of AR 6's I have.  These particular speakers were advertised on the local shop goodwill as AR 7 speakers and that's what I thought I was buying. When i went to pick them up they turned out to be AR 6's. Here is a picture of one of them next to a AR7. Quite a difference.

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They have basically been waiting in the wings because other projects are always put ahead of them.  One woofer pulled, fiberglass removed and there is the crossover. These must be earlier versions with the woofer dated September 29, 1971. Not the grill cloth you would expect to find, but I believe it to be original. Would these woofers be considered 200001-1 even though they have alnico magnets? 

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Gabriel, my opinion is to either clean the Potentiometers up or replace with others, but definitely don't eliminate them.  I am glad they are back together and you are enjoying them. Keep looking and you will probably run across the correct woofer (200001-1 with the square ceramic magnet and flat dustcap), and you probably easily can get your investment back  on the cloth surround woofers. Keeping them in good shape will allow you to pass them down to the next generation. Mine deserve better than being in bubble wrap and stored away.

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Here are some pictures of my woofers. I installed the old cap and resistor on the new woofer. Do you think it's good?

I opened my potentiometer and I discovered that the spring inside is broken in one point. I tried to solder it but the tin does not hold on it.

How could I fix it?

 

 

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That last picture looks just like a AR 4xa. Maybe someone here has a extra spring or potentiometer. How close is a spring from a ball point pen?  Maybe it’s time to think about a some L-pads. Good luck. I am sure  with a little infinity it can be repaired.

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On 10/19/2017 at 4:52 PM, larrybody said:

Reading this thread go me thinking what version of AR 6's I have. 

Those AR-6's look really nice, Larry. I've never seen that grille cloth before but kinda like it - - do you think it might be original? I'm curious about their history - - the paper labels do not show either of the Euro addresses, but the serial number has a two-letter prefix which often shows up on Euro speakers, plus there is that "international guarantee" stamp". :wacko:

Also, you've got those great early-issue woofers with the massive Alnico magnet with the long throw (see below).

AR-6 woofer voice coil.jpg

AR-6 review excerpt.jpg

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On 10/22/2017 at 9:20 AM, Gabriel said:

Do you think it's good?

Gabriel, it appears to me like you've currently got a mismatched combination of parts you are trying to assemble, and I hope that my Oct 9 post about various woofers did not add to the confusion. To clarify, that post was trying to state that the ribbedcone/alnico woofer was found in early AR-6's using Crossover A; and the smooth cone/square ferrite magnet woofer was found in later AR-6's which used Crossover B (and C, not shown in this thread). The third woofer shown in that post is the cloth surround alnico woofer found in the AR-4x and 4xa models, which employed crossovers different from all versions of the AR-6. 

If I am following your current configuration, your cabinets have the two-coil Crossover A as shown in your Oct 5 post; your woofers are alnico-cloth drivers intended for the AR-4x or 4xa; and you have now attached a coil/cap combo to the woofer that was originally used with a ferrite magnet woofer in Crossover B of the AR-6. 

I guess it's possible that you may have created an excellent hybrid of sorts, but I can't imagine that your assembly as shown is going to perform very well. Added to that, there has not yet been any attention paid to the original tweeter cap (does it still measure close to 10uF?), and the pot control now has a new problem with the wiper spring.

On 10/22/2017 at 12:50 PM, larrybody said:

That last picture looks just like a AR 4xa.

Since the AR-6 and AR-4xa models have identical cabinet volumes and you now have drivers that are consistent with the AR-4xa, perhaps your best option is to simplify the crossover to comply with the 4xa model. Attached are pics of 4xa crossover: version with pot; version with switch; and schematic showing switch version.  

AR-4xa x-o with pot.jpg

4xa crossover.jpg

AR-4xa schematic.jpg

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