AR-6 restoration - expert help sought

[radine]

I brought home a pair of AR-6 (euro version?) today. They have the 3 position switch on the back. I bought them from a guy who remembers going to buy them with his parents (now deceased) in 1974 or 1975 here in Glasgow, Scotland. They are all original and have never been touched. The grills are of a type I have never seen before but he assures me that his parents never changed them. Anyway, the grills are the least of my problems!

My problem is that on opening up the speakers there are two different woofers.

In speaker 1, the woofer is serial no 200001-4. This has a cardboard spacer on the metal frame and a cap and resistor wired to the terminals. So I think this matches Crossover type B in the pic attached.

In speaker 2 the woofer is serial no 200001-1 and has no card spacer and nothing wired across the terminals.

Also the crossover in speaker 1 has a coil clearly marked with a 4 and a big blue Sprague cap that I think is marked 10uF. Again I think this matches Crossver type B in attached pic.

The crossover from speaker 2 also has a coil but it has no markings and the cap too has no markings.

In the crossover pic attached, Crossover type C references woofer serial no 200001-1 but Crossover C has no coil at all and is for a two position switch.

So my question is how best to move this forward?

1. The cap and resistor on the terminals of speaker 1 look like they are toast. Do I replace them or just cut them off?

2. If I replace them should I also wire up the other woofer in the same way?

3. Also is it safe to assume that the big blue caps are identical? They look in good condition. Should I just leave them? If I replace them do I go with 10uF as per crossover B given these have the 3 position switch? Also can I assume the coils are the same?

I am a bit lost with this and any help would be very welcome. Thanks in advance.

I added this picture of the two woofers. They have different dust caps: left (200001-4) is flat, right (200001-1) is domed. Also left woofer has card spacer for outer foam ring and right does not. Cone material seems the same. It is the left speaker that has the cap and resistor across the terminals. The right does not.

 

[elnaldo]

I think you have to decide wich crossover sounds better. But having 2 different Woofers could be the reason for that network removed in crossover C.

I'd get some cheap capacitors so you can swap them and try. Try matching crossovers to see If both speakers sound the same.

Those blue caps are quite old. I'd replace them with modern film caps. But get some 6 uf and 3.3, so you can try both, putting 6 & 3.3 in parallel gives 9.3, quite close to the 10uf.

A capacitor in parallel with the woofer cuts the high freqs, so I guess in one crossover the tweeter is crossed lower ( with a larger cap), and in the other crossover, the woofer is reproducing higher freqs (without the cap in parallel ) so the tweeter is crossed higher (with a smaller cap).

It seems you have some model in between those 2 crossovers, since the caps looks the same and the attenuator has 3 positions.

I'd assume the coils are the same. You could measure their DC resistance to see if they match ( or take them to somebody with a meter to measure inductance ). But If they look like the same size, they are probably identical.

 

[GD70]

Roy C. is our resident AR expert. You may want to shoot him a PM for advice.

BTW, those look very nice.

Good luck, Glenn

 

[ra.ra]

About the various numbers, I'd be curious to know the cabinet serial numbers which usually show up on the backside, either on a printed card or a small tag near the wire terminals. The numbers you refer to (200001-1 and 200001-4) are part numbers for the two versions of 8" woofers you have. Also, the 001-4 woofer shows a 7509 number which means 9th week of 1975, which closely correlates with the April 75 stamps I see inside the cabinets. I would expect to see a similar number on the 001-1 woofer.

This situation is mildly perplexing, but I have a few thoughts. First off, despite the different woofer configurations (which would probably irk me somewhat), I think you still have a measured factory "pair" of speakers. Crossover C, despite the woofer part number, shows a different circuit than you have - - it shows only one resistor, no coil, and a 6uF cap. Even tho' we cannot see the marking on the second blue cap, my guess is that it, too, is 10 uF just like the other. Similarly, I suspect the coil is the same, also a #4.

As you've most likely discovered, there are at least three versions of AR-6 crossover, and several components comprise these variations - - coil or no coil, cap value, two/three position switch or pot, and resistor values. I have some AR-6's, and I know it can be a little confusing.

I think your speakers are identical except for the woofers. The 001-1 woofer is known as the 'universal' 8" woofer, and found its way into several models. The flat dust cap 001-4 woofer was probably intended specifically for the AR-6, and it includes the cap and resistor attached to its rear, known as a Zobel circuit (don't ask me why). Assembly workers used whatever parts were on hand to make the product work correctly (they were all tested before leaving factory). My guess is the 001-0 woofer and the 001-4 woofer (w/Zobel) meet precisely the same performance standards, and should simply be updated (foams and caps, if necessary) and replaced in original cabinets.

 

[kingscoins83]

Hello,

Did you managed to sort it out with the woofers/crossover configuration? I found a pair localy with the exact same configuration and would like to buy them, but I'm affraid they would not sound the same.... Any thoughts?

Thank you.

 

[stevo137]

Hello folks!
I think I've found the latest thread for the AR-6 restoration.

I found these today. They work but woofers need surrounds.

Is it better to find the replacement woofers I have heard about or restore the woofers?

Both woofers are stamped 1972.

Thanks in advance!

 

[RxDx]

Personal choice. A lot of people like matching numbers restorations... I'd
probably try to fix the originals, then look for a used one if I couldn't.

 

[ra.ra]

Hi stevo. From what we can see, those speakers look very promising. If you've already identified stamped dates on the woofers, maybe you can provide a pic of the woofer backside to show the magnet type - - - these might be the earliest AR-6 woofers. I don't know what type of replacement woofers you've "heard about", but unless these original woofers are non-functional, you should abandon all thoughts about replacing them. These woofers should be properly restored with new compliant foams.

Can you also share serial numbers and pics of the crossovers? AR-6's are very nice speakers......congrats on the great find.

 

[stevo137]

Okay, let me look again.
Thanks for your response.

I don't recall serial numbers but I do know that they both were stamped 1972.
One was from Feb one from March.

I got these from an older gent who bought them new and I know that I was the first to remove the covers.

These are all original despite one woofer looking a bit different on the front.

 

[stevo137]

A few photos

 

[ra.ra]

Thx for new pics - - I was hoping to see pics of the woofer magnet and crossover as well, but at least it's good to see the serial numbers. Your serial numbers at 16XXX and 19XXX seem to make sense for 1972 based on my own limited experience - - - I have two pairs of 6's: one pair is 04XXX from 1971; and the other pair is 40XXX from 1974. Without having yet seen the woofer backside (magnet), I'd hazard a guess that your woofers with the ribbed cones are the early type with the big Alnico slug magnet, as shown in attached pic. Don't concern yourself at all with the one cone that has the tic-tac-toe marks: some had it, and others did not.

 

[GD70]

Reforming is easy on those woofers, BUT, get the correct surrounds for AR woofers, not generic from fleabay which are often too thick and stiff, which will effect their performance. Vintage -ar on eBay should have the surrounds you need. The larger dust cap on the one woofer is actually cosmetic, and covers the flatter style dust cap on your other woofer. Regardless, the caps need to be carefully cut so the VC's can be shimmed. When I cut dust caps, I leave a little still attached and flip them open like a can lid. After the surrounds are finished being glued, regluing the dust caps back into their original position is easy.
Glenn

 

[GD70]

Another note, those Sprague caps are very good, and I wouldn't immediately change them without checking them first to see if they are in spec.
My LST-2's have those caps, and Roy told me this, and I left them in place. They sound great.

 

[ra.ra]

Hey stevo137, I saw your post in the photography thread - - - are you a Hoosier?

GD70 is correct about the blue Sprague caps, but he is possibly getting your set of speakers mixed up with those of the OP (radine), who was posting from Scotland in 2014. The OP's speakers were a different version with the Zobel circuit on the woofer and a switch for tweeter control.

If you have the blue caps, you might want to measure them to confirm, but they are more than likely to still measure close to original 10uF spec. I have confirmed this myself in pairs of AR-6 and AR-7 (6uF) speakers that had blue Sprague caps. My suspicion, however, is that you probably have the wax block caps (see pic), in which case you'd be well-advised to replace them.

Glenn is also right about the replacement woofer foams - - be sure to get highly compliant foam surrounds. If you do have the alnico woofer that I showed in post #11, it has exceptionally long range of movement of the voice coil - - - see pic attached that shows this coil in compressed, neutral, and extended positions.

 

[michiganpat]

FWIW I've refoamed 4 pair of AR 8" woofers (along with AR58S 12" woofers, 2ax 10" woofers, some ROLA 12" woofers, smaller advent woofers, and realistic Mach 1 woofers), and have always used the test tone method successfully without cutting the dustcaps off and shimming. the AR 8" have pretty generous voice coil gaps. as far as foams, 8" filled fillet foams for Boston Acoustics woofers are recommended for AR 8" drivers by RoyC among other AR gurus....

 

[stevo137]

Yes, Hoosier here!

Wow, thanks for your responses!
Great information.
I'll pull those woofs out and get pics later.

I did find out that unfortunately one of the tweets does not work, probably potentiometer?

The other one is working but need to fiddle with the adjustment knob to get it working.

You guys impress me with your patience and knowledge restoring these but it looks like this set really needs some expert attention that I can't give them.

I was hoping to listen to these with my Yamaha receiver and M-35 amp but thats not happening at this point.

I will pull those woofers and post the pics.

Thanks!

 

[stevo137]

Photos attached...

 

[stevo137]

Here's the junk!
Man, these are packed!

 

[GD70]

Here's the junk!
Man, these are packed!

That's an easy recap. Just need one.
Pull the pot and open it up. Usually there's lots of green corrosion.if there is, soak it in a distilled clear vinegar and salt solution for an hour or two, then wash and rice with soap and water. Now you can inspect the condition of the disk and pot wiper. Post pics and we can help you evaluate its condition.

 

[ra.ra]

Yep, you've indeed got the somewhat rare and coveted huge magnet early woofers, and these AR-6 speakers do require slow and careful restoration. Pots will need inspection and cleaning - - hopefully resulting in only a restoration effort, but in worst case, a replacement with new variable controls. Be forewarned that when working with the small nichrome wire, it can sometimes be difficult (it is very stiff, and it is short in length). Regarding the capacitors, replacement with any good quality new 10uF cap should make a noticeable improvement, but as an opening thought, I might suggest consideration of this one:

https://www.madisoundspeakerstore.com/carli-capacitors/carli-mylar-10-mfd/

Yo, I am a Hoosier by birth and for many subsequent years and therefore forever, but I've lived elsewhere for a long time since. If you need more help from someone closer, you might try to contact AK member larrybody - - - he has much experience and vast knowledge with AR speakers.