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$2 AR 4x pair, corroded pots, what to do?

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Guest Pickles

I found a pair of AR 4x speakers for $2 at a rummage sale. One speaker appears to be in pristine condition, but the other appears to be the long lost twin. The second speaker may have come into contact with water, as the pot is green with corrosion, and stuck in place. The speaker terminals also have light surface rust.

The walnut cabinets are salvagable, no chipping or peeling, and nothing a little steel wool and tung oil can't fix. They also match my AR-3s, so ideally, I would like to restore this pair.

I've read some restoration projects that completely bypass the pot altogether, and others that simply replace the pot. Although I am not a new AR owner, I am new to AR restoration, so my questions are, what are the pros/cons of bypassing the pot? & How easy of a job is it to repair a pair of AR 4x speakers?

as always, thanks in advance.

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Have you removed the pots and took them apart to take a look a their condition? If they are not completely corroded and you want to spend some time cleaning them then that is what you should do. I did the pots on my AR2ax's and they work like new but there was only a little bit of corrosion built up on the coils. Replacing them with new pots would be the second option with bypassing them the third. For me there is a great deal of satisfaction in knowing that some time and effort pays off in the end. I started to refurbish my AR's and today I got around to replacing the grill cloth and do they look good. I will take some pics of the "before and afters" and post tomorrow.

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I found a pair of AR 4x speakers for $2 at a rummage sale. One speaker appears to be in pristine condition, but the other appears to be the long lost twin. The second speaker may have come into contact with water, as the pot is green with corrosion, and stuck in place. The speaker terminals also have light surface rust.

The walnut cabinets are salvagable, no chipping or peeling, and nothing a little steel wool and tung oil can't fix. They also match my AR-3s, so ideally, I would like to restore this pair.

I've read some restoration projects that completely bypass the pot altogether, and others that simply replace the pot. Although I am not a new AR owner, I am new to AR restoration, so my questions are, what are the pros/cons of bypassing the pot? & How easy of a job is it to repair a pair of AR 4x speakers?

as always, thanks in advance.

Congrats on this find! I have restored some AR 4x's with advice from RoyC and johnnieo. Here is what I would recommend:

1. Try Watco Danish oil instead of Tung. You can use the steel wool, or if needed "wet sand" with #600 wet/dry paper and Watco oil. OR__I have recently discovered a product I like very much: Howard's Restor-a-Finish. Available online and in Home Depot, some hardware stores. Apply with steel wool and it will make old dull scratched veneer look great. Then follow up with Watco Oil or Minwax Antique Oil. See:

http://www.howardproducts.com/company.asp

2. You can take the pots apart and clean them. Lots of info in this forum about that. OR simply replace them with L-Pads from PartsExpress (they are about $4 each). According to Roy, the L-Pads are very good replacements on the 4x (I think he still likes to repair the pots on the 3s).

3. Replace the old caps--very easy to do. You can get them from PE also.

4. Check the cloth surrounds and if they need a little re-doping see RoyC's current thread on the "High Tack Gasket Sealant" he has tested:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4044

Good luck with this worthwhile project! Do you have a source for grille cloth to match your 3s?

Attached photos show my new xover, the old xover with John O'Hanlon's excellent and helpful notes, and my 4x woofer that will be receiving Roy's Loctite treatment. None of this is hard and you will have the satisfaction of doing it yourseld along with the joy of listening!

Kent.

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Hi Kent,

> According to Roy, the L-Pads are very good replacements on the 4x (I think he still likes to repair the pots on the 3s).

I've softened considerably on the use of l-pads for use in the tweeter circuits. The general effect of the 8 ohm l-pad is an increase in available tweeter output, and a slight lowering of the crossover point. Specifically, the old dome tweeters need all the help they can get, as they are diminished in output and are mostly at the end of their days. 8 ohm systems like the 4x, 2ax, 5, and 6 seem to work fine with them serving their tweeters, and I actually prefer their use with the AB Tech 3a replacement tweeter's new 12db/octave circuit (discussed elsewhere in the forum).

John O'Hanlon has prudently pointed out to me that increased energy to the old tweeters could put them in harm's way, as their crossover slopes are not steep (6db/octave), so this must be kept in mind if using the l-pads at full "increase". On the other hand, Ebay's "Vintage AR" has been selling literally hundreds of l-pads a year, with absolutely no negative feedback along those lines. He, as well as AB Tech Services, do not even offer pots for sale. If this were a significant problem we would have heard about it somewhere along the line. I suspect most classic AR owners are not driving them all that hard anyway...

The best "by-pass" option is to maintain the pot's 15 to 16 ohms across the tweeter by adding the "B" pot terminal wire to the #1 pot terminal. This is the same as leaving the pot at the full increase setting, and doesn't usually require removing, dismantling, or cleaning the pot.

>Check the cloth surrounds and if they need a little re-doping see RoyC's current thread on the "High Tack Gasket Sealant" he has tested.

I agree, only if needed...and it is a Permatex product, not Loctite :-).

Roy

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PS suggest you look at Jess's 2ax project. He outlines the steps. Same for the 4x but the 4x is a little simpler (fewer parts)

http://www.classicspeakerpages.net/IP.Boar...amp;#entry71588

Kent

I read both threads. Great info to bring back from the dead. A few questions. What value caps to use on the AR-4x? What is meant by resealing the woofers? Is there a parts list available for rebuilding/refurbishing these?

Tks,

Dr. Mux

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I read both threads. Great info to bring back from the dead. A few questions. What value caps to use on the AR-4x? What is meant by resealing the woofers? Is there a parts list available for rebuilding/refurbishing these?

Tks,

Dr. Mux

Welcome to the CSP!

You can find a schematic here:

http://www.classicspeakerpages.net/library..._schematic.html

The caps are 20uF. Choice of brand is up to you but film caps will last longer than non-polar electrolytics. Only reseal the the woofer surround IF the cloth is porous. In that case, send RoyC a private message--he has developed a sealant that will work. The pots should be cleaned as described in several threads here OR replaced with L-pads. When you pull the woofers either save the old caulk that seals the frame to the wood speaker enclosure or buy some duct sealant--dark gray putty that comes in a small brick and is sold in electric supply houses or HD/Lowes. Note: sealing the woofer to the cabinet is not the same as resealing the woofer surround. Be sure to look at the AR3a restoration manual, pinned to the top of the AR section here. Lots of good general tips even though the 3a is much more complex than the 4x.

http://www.classicspeakerpages.net/library...ring_the_ar-3a/

You can re-use the fiberglass stuffing IF it is fiberglass. If it's rock wool it should be replaced with fg.

So....

You need

2) 20uF caps

2) L-pads (if you don't clean the pots)

duct seal or Mortite window caulk

maybe new fiberglass if the old stuff is rock wool

Good luck

Kent

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I actually prefer their use with the AB Tech 3a replacement tweeter's new 12db/octave circuit (discussed elsewhere in the forum).

Hi Roy,

I installed AB-Tech tweeters in my AR-3a's with the requisite .07 mh parallel inductor coil. What subjective difference in sound did you notice with this configuration with L-Pads vs. Pots?

Best Regards,

Rich W

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1. Try Watco Danish oil instead of Tung. You can use the steel wool, or if needed "wet sand" with #600 wet/dry paper and Watco oil. OR__I have recently discovered a product I like very much: Howard's Restor-a-Finish. Available online and in Home Depot, some hardware stores. Apply with steel wool and it will make old dull scratched veneer look great. Then follow up with Watco Oil or Minwax Antique Oil. See:

I use Howards and like it. But I never use steel wool. A Danish furniture dealer put me on to using bronze wool instead, which can be picked up at a local hardware store, such as Ace. Also can get your Howards there also.

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A Danish furniture dealer put me on to using bronze wool instead

Great tip! Thanks! Steel wool fibers can rust and they are attracted to speaker magnets. I'll be sure to look for bronze wool.

Kent

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Hi Roy,

I installed AB-Tech tweeters in my AR-3a's with the requisite .07 mh parallel inductor coil. What subjective difference in sound did you notice with this configuration with L-Pads vs. Pots?

Best Regards,

Rich W

Hi Rich,

The primary difference, for better or worse, is greater upper midrange emphasis with the l-pad, as it lowers the tweeter's crossover frequency.

In the years since this thread was started, I have had the opportunity to experiment a bit more, and compare notes with others. The general consensus seems to be a preference for the original 16 ohm pots across the board for all models, including those with the AB Tech replacement tweeter installed.

BTW, when using a common 8 ohm l-pad, placing a 25 ohm resistor across the + and - terminals of the tweeter (in other words, "in parallel" with the tweeter) will bring the sound closer to that of the original pot through the first 1/3 to 1/2 of the l-pad's rotation. This arrangement can be used in place of the pots, or as a way to compare the effects of l-pads vs pots. It is a relatively easy and effective way to go when pots are not available.

Roy

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I use Howards and like it. But I never use steel wool. A Danish furniture dealer put me on to using bronze wool instead, which can be picked up at a local hardware store, such as Ace. Also can get your Howards there also.

Guys at Woodcraft recommended their Mirlon pads - like upscale scotchbrite - instead of steel wool. I tried them on my 4X's with very good results. Here's link:

http://www.woodcraft.com/Catalog/ProductPa...px?prodid=23086

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Congrats on this find! I have restored some AR 4x's with advice from RoyC and johnnieo. Here is what I would recommend:

1. Try Watco Danish oil instead of Tung. You can use the steel wool, or if needed "wet sand" with #600 wet/dry paper and Watco oil. OR__I have recently discovered a product I like very much: Howard's Restor-a-Finish. Available online and in Home Depot, some hardware stores. Apply with steel wool and it will make old dull scratched veneer look great. Then follow up with Watco Oil or Minwax Antique Oil. See:

http://www.howardproducts.com/company.asp

2. You can take the pots apart and clean them. Lots of info in this forum about that. OR simply replace them with L-Pads from PartsExpress (they are about $4 each). According to Roy, the L-Pads are very good replacements on the 4x (I think he still likes to repair the pots on the 3s).

3. Replace the old caps--very easy to do. You can get them from PE also.

4. Check the cloth surrounds and if they need a little re-doping see RoyC's current thread on the "High Tack Gasket Sealant" he has tested:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=4044

Good luck with this worthwhile project! Do you have a source for grille cloth to match your 3s?

Attached photos show my new xover, the old xover with John O'Hanlon's excellent and helpful notes, and my 4x woofer that will be receiving Roy's Loctite treatment. None of this is hard and you will have the satisfaction of doing it yourseld along with the joy of listening!

Kent.

Thanks for the LINK to Howard's Restore-A-Finish products. I need them for many projects!

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On 3/4/2010 at 9:57 AM, JKent said:

Great tip! Thanks! Steel wool fibers can rust and they are attracted to speaker magnets. I'll be sure to look for bronze wool.

Kent

 

Rocker Woodworking sells these synthetic abrasive pads which are supposedly better than steel wool. They come in different colors and the colors are indexed to the different grades of steel wool.  They supposedly don't leave fibers behind and they're reusable.  I haven't tried them yet but I plan to for my next finishing project. 

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