Restoring 10pi's

[Guest JonM]

I've just started restoring a pair of 10pi's that I literally found by a dumpster. They're cosmetically in good shape, and all drivers seem to work, so it appears to be a matter of refoaming the woofers and light cleanup. (Reading Ken Kantor's paper on restoring AR-3a's , it looks like these are the second generation 10pi's with the ferrofluid tweeter.)

They also have foam around the tweeter and around the outer edge of the woofer basket (outside the gasket that the old surround was glued to). All that foam is disintegrating, and will have to come off. I assume the foam on the woofer was purely cosmetic, but the foam blanket on the tweeter may have had some acoustic effect. Is there some place I can find a suitable replacement for the tweeter foam? Can felt be used instead? Does it matter?

Also, I noticed that a spare AR-3a woofer surround I had lying around (probably from Simply Speakers - I have bought from them in the past and been happy) with a 1/2" roll had the correct inside dimension, but its outside dimension stuck out well past the outside of the gasket on the woofer basket. Where can I get a replacement surround that has all the right dimensions? Should I look for one with a 5/8" roll? (I have read the originals had 5/8" rolls.)

I've owned quite a few AR speakers (starting with 2ax's in about 1972, LST's briefly, 3a's and a single 3, and a pair of the little 7's). My favorites have actually been the 3a's (after I replaced their potentiometers, their sound was smooth and sweet). I am looking forward to listening to the 10pi's (especially considering what I paid for them :-). So any tips on getting them up and running again are appreciated. (I have refoamed quite a few AR's and Advents, and am handy with both a soldering iron and a schematic, so I am not afraid of getting my hands dirty.)

Thanks!

JonM

[Rlowe]

Hi,

You will find a number of articles if you do a search on

1 - AR10pi

&

2- Schematics

[ar_pro]

Not sure if it's the same type used in the 10pi, but there's a pair of AR-9 tweeter foam surrounds on ebay right now: item 270308486673

[kkantor]

Hi, Jon.

Hey, no way I can take credit for the 3a restoration document! I was happy to help, but the other authors are truely the experts here.

In my opinion, the addition of the foam to the tweeter faceplate was not a particularly good idea. (The "acoustic blanket" WAS a good idea, but the material and range of operating frequencies were different.)

-k

I've just started restoring a pair of 10pi's that I literally found by a dumpster. They're cosmetically in good shape, and all drivers seem to work, so it appears to be a matter of refoaming the woofers and light cleanup. (Reading Ken Kantor's paper on restoring AR-3a's , it looks like these are the second generation 10pi's with the ferrofluid tweeter.)

They also have foam around the tweeter and around the outer edge of the woofer basket (outside the gasket that the old surround was glued to). All that foam is disintegrating, and will have to come off. I assume the foam on the woofer was purely cosmetic, but the foam blanket on the tweeter may have had some acoustic effect. Is there some place I can find a suitable replacement for the tweeter foam? Can felt be used instead? Does it matter?

Also, I noticed that a spare AR-3a woofer surround I had lying around (probably from Simply Speakers - I have bought from them in the past and been happy) with a 1/2" roll had the correct inside dimension, but its outside dimension stuck out well past the outside of the gasket on the woofer basket. Where can I get a replacement surround that has all the right dimensions? Should I look for one with a 5/8" roll? (I have read the originals had 5/8" rolls.)

I've owned quite a few AR speakers (starting with 2ax's in about 1972, LST's briefly, 3a's and a single 3, and a pair of the little 7's). My favorites have actually been the 3a's (after I replaced their potentiometers, their sound was smooth and sweet). I am looking forward to listening to the 10pi's (especially considering what I paid for them :-). So any tips on getting them up and running again are appreciated. (I have refoamed quite a few AR's and Advents, and am handy with both a soldering iron and a schematic, so I am not afraid of getting my hands dirty.)

Thanks!

JonM

[Guest JonM]

Ken -

Thanks for the reply. The foam on the tweeter's front plate came off easily (rolled off under my fingers and got swept away by a vacuum). I left the plastic sheet under the foam undisturbed (it protects the wires to the voice coil), so I guess I can leave the tweeters like that till I decide whether to put on the felt replacements that Vintage AR sells on eBay. (Though I gather you would recommend leaving the tweeters as they are, with nothing on the front plate.)

As for giving you credit for the restoration doc, my apologies to your co-authors. It's a very useful piece of work - thank you to all of you.

Jon

[Carlspeak]

Welcome aboard Jon. You are in the right place for top notch AR advice.

I suggest before replacing the foam tweeter rings you had, give a careful listen to your speakers as they are now and decide if the tweeters sound a bit bright.

You may also want to visit the link below and download my tweeter diffraction ring study (post# 5). It compares two currently available ring types (foam and felt) and the thick felt used on Spica TC50 speakers. My conclusion: felt is definitely the way to go.

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4758

If you opt to get the felt rings, suggest you also consider ones sold by Madisound for considerably less $$ than Vintage AR. Also suggest you get 4 and layer if one on each speaker isn't enough attenuation.

[RoyC]

Welcome aboard Jon. You are in the right place for top notch AR advice.

I suggest before replacing the foam tweeter rings you had, give a careful listen to your speakers as they are now and decide if the tweeters sound a bit bright.

You may also want to visit the link below and download my tweeter diffraction ring study (post# 5). It compares two currently available ring types (foam and felt) and the thick felt used on Spica TC50 speakers. My conclusion: felt is definitely the way to go.

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4758

If you opt to get the felt rings, suggest you also consider ones sold by Madisound for considerably less $$ than Vintage AR. Also suggest you get 4 and layer if one on each speaker isn't enough attenuation.

I agree with Carl and Ken's cautionary notes regarding damping rings. Having experimented with many tweeters in the similar AR-3a, I have concluded that felt damping rings (Carl is correct, Madisound's and Vintage AR's are one in the same) suck too much life out of them, especially with regard to dispersion issues. If you do try the felt rings, tape them to the faceplate until you make a decision. The self-sticky glue can be quite difficult to remove.

Roy

[Guest JonM]

Thanks for the helpful advice. I'll look into the options you've suggested. This will be a project probably for the week between Christmas and New Years, when I'll have some time to spare. I'll check back in when I'm done and have had a chance to do some careful listening, just so you know how they turned out.

Happy Holidays to all!

[Diamonds&Rust]

Thanks for the helpful advice. I'll look into the options you've suggested. This will be a project probably for the week between Christmas and New Years, when I'll have some time to spare. I'll check back in when I'm done and have had a chance to do some careful listening, just so you know how they turned out.

There's some lucky dumpster-diving if I ever heard it.

I don't remember if I reported this in public or not, and I'm not prepared to argue the point, and I'm not going to re-re-re-recount the full story (sparing the long-time regulars here the tedium of reading it again).

A friend of mine and I restored two pairs of 10pis, simultaneously, but used different branded capacitors and different brands of resistor sand we goofed around and fooled around A/Bing for months and months, listening for hundreds of hours, to the point that we were absolutely sick of Steely Dan's "Aja" and a few other favorites.... and each other, I think.

When I finally was able to replace the big 2500uF capacitors in mine (the only caps I hadn't replaced as much as six months before) the first time my buddy heard them, after about 20-30 seconds of listening, he (in essence) said that he had to have some new big caps like mine.

I know that the difficulty of finding suitable single replacement capacitors for those big ones makes it tempting to say "Awww, they aren't hurting anything. I'll leave them alone." They are hurting things. Don't leave them alone.

You won't regret the time and effort.

BTW - I have given away, or given to my kids, or otherwise retired all my AR speakers except for my 10pis. In my not-humble, but not-arrogant either - just ego-neutral - opinion, the 10pi was something special and I'm looking forward to hearing your opinion.

I'm partial to pulling them away from all walls, lifting them a couple of feet into the air (resting them on another pair of speakers), toeing them slightly (like you might a mini-monitor), turning the woofers' switches up, and centering the tweeters' switches; then listening to well recorded "live" material. You owe it to yourself to try that once, even if it's impractical as a permanent placement. It isn't how they were intended to work (essentially like a really big pair of headphones), but it's fun!

Bret

[Guest JonM]

Bret -

Yeah, my eyes popped out when I saw what they were, sitting there on the pavement next to the dumpster. They were sitting face-to-face, so I had to go over and look to see what they were (I was expecting real garbage). 10pi's, woofer surrounds rotten, a little frost on the tops (it was cold that morning, but it hadn't rained over night, so nothing was actually wet) - I figured the worst that could happen is that the drivers were all burned out and I'd take them back to the dumpster where I found them. I was thrilled when I hooked them up and all drivers worked. They are now sitting on their backs, on the carpet, old foam largely removed and vacuumed up, waiting for me to order new woofer surrounds.

If they have big capacitors like that, I assume they have autoformer-based crossovers - I can understand why you say they're important (if it's like the LST, *everything* goes through them). I haven't pulled the woofers, so I don't know how hard it is to get to the crossovers (I've heard it's not easy). I imagine I can order the crossover parts I need from Digikey, except maybe the big caps? I wasn't planning on touching the crossover till I read your note - now I'm thinking about it. Time to go find a schematic so I know what I'm dealing with... And while I'm in there, what about changing out the other electrolytics for something like polypropylene films? Is that heresy? (I did it years ago on a pair of small Advents and I liked the little bit of extra openness I got.)

Thanks for your input. I'm looking forward to getting these making music again.

JonM

[Diamonds&Rust]

If they have big capacitors like that, I assume they have autoformer-based crossovers - I can understand why you say they're important (if it's like the LST, *everything* goes through them). I haven't pulled the woofers, so I don't know how hard it is to get to the crossovers (I've heard it's not easy). I imagine I can order the crossover parts I need from Digikey, except maybe the big caps? I wasn't planning on touching the crossover till I read your note - now I'm thinking about it. Time to go find a schematic so I know what I'm dealing with... And while I'm in there, what about changing out the other electrolytics for something like polypropylene films? Is that heresy? (I did it years ago on a pair of small Advents and I liked the little bit of extra openness I got.)

Sorry to be so long getting back around, but life's been busy.

You really should replace the capacitors. They are very old. In fact, they are so old that in one pair of speakers I had the former owner had replaced the capacitors and his *newer* capacitors were going bad, presumably from age.

I'd use poly or mylar if I were you, for longevity if for no other reason. The speakers are brighter with polys and so there must be a bump and/or dip in the response with poly. Still, my friend's sound fine with polys and no attenuation, probably because of the room and furnishings. Mine need a little attenuation (tweeter and mid) but I want it to be less than a full switch position most of the time.

Someone ought to be able to give some guidance based on the 3a, even though the speakers are different.

I lived the capacitor discussions here, paid a lot for a bunch of capacitors, and eventually concluded that the difference you *can* hear in capacitors isn't worth the huge difference in their prices. And in conclusion, I concluded that the most expensive capacitor may not be the best solution.

You could pay as much for a set of capacitors as a better, newer, speaker.

Yes, the 10pi has the 2500uF like the LST. Expensive, no matter what you use. I'm using a NPE for that one, but everything else is poly.

While you're in there, you might want to change the resistors, too. One of them, the one near the back on the crossover board, is prone to getting a little brittle. Can't be a good sign.

And yes, they are not easy to work-on. If you haven't already found it, the soldering rings on a strip must have made assembly easier when the crossover board was out of the cabinet, but it makes trying to work on it once the board is glued to the bottom of the cabinet very difficult.

You need a mirror, a good light source, a good eye to follow which lead is soldered where, a steady hand, desoldering tools, soldering tools, and the patience of Job. I'd tell you not to bother, just leave it alone, but I don't really think that's an option if you want them to sound good.

And I'd point you at a good 2500uF NPE electrolytic capacitor if I knew where one could be had. I don't.

Good luck with the project.

Bret

[Diamonds&Rust]

I found this snapshot the other day. It might help explain my "positioning" description, being worth 100 words and all that.

Ignore the mess. The maid left rather, uh... suddenly.

Bret

[Carlspeak]

The LST has a similar 2500 uF cap set up. For recapping those, I use 3 Bennic NPE's available from Madisound. Two 1000 UF and one 500 uF wired in parallel as a bundle. You also might want to consider a low uF bypass mylar or film cap.

[Guest JonM]

Bret -

Stacked 10pi's - quite something! I had stacked Advents for years (refoaming those is another project I have waiting for me).

I do notice that you have the woofers next to each other and the tweeters/mids on the top and bottom. Have you tried flipping them so the tweeters/mids are next to each other? (You'd probably want them on stands at that point, to get the bottom woofer off the floor.) When people stacked the Advents, they typically put the tweeters near each other - they still got enough coupling between the woofers to augment the low end, and the imaging was helped by keeping the tweeters together (though some claimed comb filter effects, I never noticed it). Just curious.

You and Carl have me thinking about the capacitors. I got the surrounds from John at Msound (nice guy!), and I have one woofer out ready to be worked on. Time to remove the stuffing and see what I'm up against with the crossover.

Thanks for the encouragement.

JonM

[Guest JonM]

Bret -

Oops - looking closer, you have a pair of 14's acting as stands. Forget what I said about stacked 10pi's (though the concept is mildly intriguing :-)

I have the stuffing out - thankfully it looks like the capacitors' leads are merely inserted in the terminal strip, and not wrapped before soldering. That will make things easier.

Taking this a step at a time. Will keep you all posted. Thanks again for the advice - much appreciated.

JonM

[Guest JonM]

Just a quick update. Spent a snowy Saturday putting on the new surrounds, which went smoothly (I've done AR and Advent woofers before, so I had an idea what I was doing). Now that the glue has had a chance to set over night, the 10pi's are reassembled and I'm giving them a nice, long listen. I don't have them critically set up, and you'd cringe at what I'm driving them with, but this is just to let the surrounds break in a little and maybe reform the crossover caps (which, judging from the condition of the original surrounds when I found them, probably haven't been used in many years).

Very initial impressions - the sound so far is very good. Good driver integration, deep smooth lows, highs that sound effortless (that cloth dome is really nice), and a midrange that is very open and listenable on well recorded vocals. These are clearly superior in all regards to my stacked large Advents (which sound cardboardy and closed in by comparison), and are definitely more open sounding than (but not as sweet as) my early AR-3a's (with the cloth surrounds). They are not "sweet" (I guess I'd call them "accurate", definitely brighter than the traditional "AR sound"), but they can sound a tiny bit dark/thick, and there is a hint of hardness/grain in the mids. But that could well be from what I am using to drive them, so when I improve the amplifier and source, I may declare them "simply wonderful" :-)

I've heard modern speakers that are better (the beneficiaries of modern materials, extensive computer modeling, and a small handful of extremely talented designers) but I've heard many more that are nowhere near as good as these 10pi's. I thought to myself this morning, when doing my initial listening, these are good enough that someone could easily live with them the rest of their lives and never feel the need for something better. For a 30 year old design, that's saying something.

Next part of this project? Well, the crossover caps are on the list (I am currently planning to stick with NPE's, closer to the original design, but I might change my mind as I think about it more), and I am thinking about making grills (the tweeter and midrange put out a tremendous magnetic field, and I don't want paper clips to find their way too close to those drivers :-) I figure a frame made of 1" square dowels (1" needed to get enough clearance over the midrange's cage, and they're cheap at Home Depot) covered by something suitable from the local fabric store will get the job done. (It doesn't matter to me that the grill won't be original - if it's easily removable, originality isn't as important as simply protecting the drivers.)

Cheers!

JonM

[Guest JonM]

I hooked up a better amp (a McIntosh MC502 - not great, but better than what I was using before), and my trusty Sony XA7-ES cd player, and these are some of the nicest speakers I've heard in a very long time. All the hardness I heard before is gone (it was the amp I was using). Boy these are nice, even with the original crossover caps still in them. Think how'd they sound with some really good modern gear driving them :-)

And to think someone had thrown them out...