The latests on pots

[DavidDru]

I have started my AR 3 restoration and going in i am pretty confident the petontiometers are beyond salvage. I might yet get lucky, but they dont feel intact when turned and i can barely get a signal through them.

So what are the current options for replacement? I would like to keep it as original as possible.

[Sonnar]

Ohmite.pdf Hello David, try to press gently the pots rotating it slowly. Sometimes after many rotations You could hear the speaker. If so, clean the pots and everything will be right. However, if pots are dead, try Ohmite: a friend of mine used Ohmite pots in a DIY loudspeaker , very good quality.

[DavidDru]

Thanks. Believe me, I pushed, wiggled, pulled, you name it to get them to work just so I could hear something and confirm the drivers work. I found little sweet spots on each a couple times but the way they feel, I can't imagine they are going to be okay. I might know later today if I get that far in my efforts. I had one of the woofer screw t nuts come loose and it took me a while to figure it out and get it off last night so I lost a little time. I hate those things. They really are not designed for removal and you are asking for trouble every time you do, especially in old wood.

[Sonnar]

Certainly old acoustic suspension speakers aren' t made to be removed, it 's difficult to realize and maintain a perfect sealed cabinet . Remember KLH Six first series? In another thread I said " God bless compression drivers , simple , robust and eternal. If only it sounds less rugged " . Here I say God bless old giant bass reflex bins , a simple, well built empty box. If only it makes real bass. About pots, remove and clean the originals ones it 's not easy. You can see the process reading " Restoring AR 3a " on the site, but I think it' s better to use new Ohmite potentiometers.

[stupidhead]

Hi David,

Will be anxious to follow your progress, please post pics if possible. As for pots, here is a link to a thread I posted not too long ago. http://www.audiokarma.org/forums/showthread.php?t=617240 You shouldn't assume they are bad until you remove and inspect them. It does take a bit of effort to restore them, but they are worth it. I believe replacements are difficult to find with the proper ohm rating, but possibly the ohmite site may have a good alternative. I believe if you search you will also find links to auction site offerings from Russia.

Geoff

[xmas111]

I used the pots from Russia. They work fine. They're not enclosed like the original pots so you'll have to build an enclosure for them. Same with the Ohmite pots.

They're much cheaper in price than the Ohmite. I think the Ohmites are $45.00 a piece vs $16.00 (includes shipping) for the Russian pots.

With the Russian pots you'll have to cut the shaft to length and grind a flat on it, not a big deal to do.

Here's a link to the Russian pots on ebay.

http://www.ebay.com/itm/25W-15-OhM-CERAMIC-WIREWOUND-POTENTIOMETER-PPB-25G-SOVIET-MADE-ORIGINAL-BOX-/161206930532?pt=LH_DefaultDomain_0&hash=item2588ae8c64

Here's a a thread about them:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7990&hl=%2Bohmite+%2Bpots#entry98512

I used the Russian pots on the 2ax's I restored.

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7994

Hope this helps and good luck with your restoration.

John

[DavidDru]

Thanks for the good feedback guys. Getting the latest info on pot availability will be helpful if I end up needing them.

John, sounds like the imports are a good option and my dremmel can handle the cutting I would guess.

Pots from what other AR speakers would work with the 3? Are those from the 3a compatible?

[owlsplace]

Thanks for the good feedback guys. Getting the latest info on pot availability will be helpful if I end up needing them.

John, sounds like the imports are a good option and my dremmel can handle the cutting I would guess.

Pots from what other AR speakers would work with the 3? Are those from the 3a compatible?

I think all the "Classic" era speakers used those.

Just a quick look on the auction site turned up Miller's $68ea and these from HK at $9.99ea shipped:

http://www.ebay.com/itm/25W-15-15-Ohm-Power-Wirewound-Rheostat-Rotary-Potentiometer-25-WATT-/351106904764?pt=LH_DefaultDomain_0&hash=item51bf9a32bc

Should verify the dimensions on any new part to make sure it will fit in the space first.

Roger

[iso]

Mouser also stocks some Ohmites. Link is to mouser.fi... so priices in euros... but link may open as mouser.com in USA... don´t know.

http://fi.mouser.com/Ohmite/Passive-Components/Potentiometers-Trimmers-Rheostats/Rheostats/_/N-9q0yjZscv7?P=1z0zldmZ1z0x88kZ1z0x6wr

Best Regards

Kimmo

[JKent]

A mere $34 USD each!

http://www.mouser.com/Passive-Components/Potentiometers-Trimmers-Rheostats/Rheostats/_/N-9q0yj?P=1z0x88kZ1z0wn9m&Keyword=rheostat&FS=True

[Carlspeak]

Has anyone considered an 8 ohm L-pad with a paralleled 25 ohm resistor? Lots less $

[der]

Good point. Not sure about this one seems I've read others using it.

http://www.parts-express.com/parts-express-speaker-l-pad-attenuator-100w-mono-3-8-shaft-16-ohm--260-261

der

[Sonnar]

An L-pad is it identical to a potentiometer ( rheostat ) ? I have a pair of AR 3A '90 Teledyne replicas and it has L-pads instead of classic pots, but I 've heard it needs some modification in the crossover .

[iso]

Has anyone considered an 8 ohm L-pad with a paralleled 25 ohm resistor? Lots less $

I have tried to find out what is inside L-pad, but have not found any info. Probably 2 potentiometers are used inside L-pad ... but, how they are connected internally. Do these economy L-pads use wire wound tracks or carbon track? How they do maintain constant input impedance?

Best Regards

Kimmo

[Sonnar]

And this is my question: a rheostat maintain constant impedance, but an L-pad ?

[Carlspeak]

In order for an L-pad to work like a rheostat it must have a resistor wired in parallel.

More info on rheostats vs L-pads can be found here....

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=7409&hl=lpad

[DavidDru]

Are the 3a pots and those from the 3 the same and interchangeable?

[JKent]

Not sure about this one seems I've read others using it.

http://www.parts-express.com/parts-express-speaker-l-pad-attenuator-100w-mono-3-8-shaft-16-ohm--260-261

No--this one http://www.parts-express.com/speaker-l-pad-attenuator-15w-mono-3-8-shaft-8-ohm--260-248

[JKent]

Are the 3a pots and those from the 3 the same and interchangeable?

Yes.

Well, there were some changes along the line but basically the same.

Kent

[owlsplace]

A mere $34 USD each!

http://www.mouser.com/Passive-Components/Potentiometers-Trimmers-Rheostats/Rheostats/_/N-9q0yj?P=1z0x88kZ1z0wn9m&Keyword=rheostat&FS=True

Kent,

Nice link -- they are showing an enclosed model if 12.5 watt rating is adequate. Having to build a box is a pain. The original AP pots are not fully enclosed at any rate.

Carl, I was going to use L-pads on my current AR-5 rebuild but I found two complete crossovers with good pots so I'll be using those instead.

Roger

[DavidDru]

Well darn Roger. Would love to have seen your recap of an L pad effort! (You getting this snow too over there?)

A youtube video showing how to use an L pad to replace a pot within a crossover would be cool. So who's game? you could even do it with a progression of photos built into a slideshow and published as a video.

[der]

No--this one http://www.parts-express.com/speaker-l-pad-attenuator-15w-mono-3-8-shaft-8-ohm--260-248

OK, not sure where I got the idea that the original pots were 15-16 ohm units - but of course, those are pots, not L-pads.

der

[JKent]

OK, not sure where I got the idea that the original pots were 15-16 ohm units - but of course, those are pots, not L-pads.

der

You are correct. Original pots were 16 ohm but the L-pads to use are 8 ohm. See the restoration booklet, page 13.

Kent

[ra.ra]

Just a few more examples of various applications for tweeter control. None of these are my own speakers, and I don't quite understand everything that is going on here. First and third pics are beautifully constructed Asian mods (Japan, I think) and the second pic is a generic web image.

Pic 1. The AR-4 shows the common L-pad that JKent mentions in post 18 (but without the added resistor that is often recommended). Of curious interest to me are the two x-o frequencies - - - am not certain what cap value was actually installed here, but I had always thought the AR-4 with a 6uf cap delivered an x-o point at 2000 Hz.

Pic 2 shows the L-pad with added resistor that Carl mentions in post 11. Despite the messy wire management, it seems to have all of the common popular parts sold thru Parts Express.

Pic 3. I think these AR-4x speakers (with the earlier AR-4 woofer) were originally the oddball two-cap (20 and 24uf) version of 4x (that Kent and Roy helped me identify in an earlier thread over a year ago), but the "Orignal" x-o schematic shown here appears incorrect. Obviously, this project used some non-original bullet tweeters, but the point of my showing this is that the L-pad used is the 8-ohm version of the 100 watt P/E product that der noted in post 12.

[JKent]

Pic 2 shows the L-pad with added resistor that Carl mentions in post 11. Despite the messy wire management, it seems to have all of the common popular parts sold thru Parts Express.

I like that photo. It also shows it's OK to leave the old wax cap in place (disconnected of course). Here's a very clear photo provided by Roy.

Note for newbies: The numbers on the tabs differ. You can see where Roy labeled them on the L-pad. Tabs 3.2.1 on the L-pad correspond to 1, B, 2 on the pot.

-Kent