AR5 re-wire problem

[Guest hilltroll67]

I'm (trying to) replace the pots in my AR5's with wire-wound resistors during the surround replacing process. Completed one speaker and tested it - no sound from either mid or tweeter, and the woofer sounds like it's trying to do all the work. I think maybe I've screwed up the 'extra' connections that went to the pots, the wire-wound spool that looks like sort-of-a choke and the thing that looks like an electrolytic cap only there's a connection top and bottom instead of two on top.

The pots have 3 posts of course, and the resistors have just 2, and I think I guessed wrong. Anybody done this and will set me on the right path?

Bob

[RoyC]

Check out the AR-3a schematics in this website's library. The AR-5 crossover is set up exactly the same way as the AR-3a but with different component values. The level controls are the same 15 ohm pots.

Roy

[Guest hilltroll67]

I'e seen the schematics, and copied a couole of them. They are of no use (to me) for the purpose of replacing the pots with resistors. Still have no notion of how to wire to 2 posts instead of 3.

Bob

[Guest dogmeninreno]

>I'm (trying to) replace the pots in my AR5's with wire-wound

>resistors during the surround replacing process. Completed one

>speaker and tested it - no sound from either mid or tweeter,

>and the woofer sounds like it's trying to do all the work. I

>think maybe I've screwed up the 'extra' connections that went

>to the pots, the wire-wound spool that looks like sort-of-a

>choke and the thing that looks like an electrolytic cap only

>there's a connection top and bottom instead of two on top.

>

>The pots have 3 posts of course, and the resistors have just

>2, and I think I guessed wrong. Anybody done this and will set

>me on the right path?

>

>Bob

Bob, First be sure that the jumper is in place on the connecting posts between 2 and T. Assuming thie xover schematic I have used is correct:

http://www.classicspeakerpages.net/ar/clas...a/ar3axover.jpg

Connect your new Xover resistors as shown with the exception of the single wire that connects to the slider on the old pots (shown with an arrow on the old pot) This single wire should be connected to bottom of your resistor along with choke/cap wires. You of corse will have no control over the loudness of tweeters or mids.

Another option is a slidewire resistor which has 3 terminals.

Larry usually has replacement newer style pots on eBay.

I also can rebuild your original pots if they are not completly corroded. Dale in Reno

[RoyC]

Bob,

Each pot/level control represents 2 resistors, one in series and one in parallel with each driver. You need to know your optimum pot settings to determine what resistance to use. If you want to approximate the pot setting representing the "dots" for the AR-5, do as follows:

Tweeter: Connect a 3 to 4 ohm resistor to the wire coming from the tweeter capacitor (formerly the resistance between terminal "1" and "B"). The other end of this resistor should be connected to a 12 ohm resistor (formerly the resistance between terminal "B" and #2) AS WELL AS the black wire going up to the tweeter. The other end of the 12 ohm resistor connects to the yellow wire going up to the tweeter and mid which also connects to the "T" binding post (and formerly the #2 terminals of the pots).

Mid: Connect a 5 to 6 ohm resistor to the coil wire formerly attached to the pot. Connect the other end of this resistor to the green wire leading up to the mid as well as a 10 ohm resistor. The other end of the 10 ohm resistor also attaches to the same yellow wire described above.

The total impedance of the resistors for each driver should be 15 to 16 ohms to provide a similar effect to the pot settings. If you change one you need to change the other. The AR pots can vary by as much as an ohm, so you probably don't have to be exact. Shoot for a total of about 15.5 ohms for each driver.

If you have the ability to measure the impedance of your favorite pot settings between terminal #"1" and "B" and terminal #"2" and "B" use those values for your resistors.

Hope this helps...

Roy

By The way, what are the values marked on the tweeter and mid capacitors in your AR-5's?

[Guest hilltroll67]

Ah, thankyou sir. This is exactly what I wished to learn.

Bob

[Guest hilltroll67]

>

>By The way, what are the values marked on the tweeter and mid

>capacitors in your AR-5's?

24uf and 72uf Sprague Compulytic 50VNP.

[Guest hilltroll67]

>Bob,

>Each pot/level control represents 2 resistors, one in series

>and one in parallel with each driver. You need to know your

>optimum pot settings to determine what resistance to use. If

>you want to approximate the pot setting representing the

>"dots" for the AR-5, do as follows:

>

[detailed info snipped]

Thanks Roy, very clear/detailed instructions. I now have 3 recipes for the operation:

1. Replace each pot with 2 resistors, in an arrangement that emulates one fixed setting of the pot.

(I like this for durability, and xover freqs shouldn't change, but it takes up more space than I had in mind, and I'm not sure where to get resistors with the right ohms.)

2. Replace each pot with 1 resistor, placed correctly this time.

(I like this for durability and simplicity, but now {belatedly}wonder how xover frequency is affected.)

3. Replace each pot with a new pot.

(I am approaching my 68th birthday, so the pots ought to last longer than I do. One more dumb question though: Will 8 ohm L-pads throw off the xover frequencies? I can get 16 ohm pots in a couple weeks, but the 8 ohm ones are here now.)

Bob

[RoyC]

Bob,

Unless you run the parallel resistance the crossover will be affected. One resistor in series therefore is probably not the best way to go.

The AR-5 is considered to be an 8 ohm speaker, so as with the AR-2ax, everyday 8 ohm l-pads are worth trying if you are not concerned about authenticity.

If the pots aren't badly corroded, its worth taking a shot at cleaning them. After cleaning put a (very) light coating of automotive dielectric grease on the innards. Small tubes of the stuff are cheap and easy to find at any auto parts store.

My AR-5's had the older Industrial Condenser Corp 50V plastic encapsulated block caps for the mid and woofer with the values (28mfd and 78mfd) blacked out and different values stamped on them (24mfd and 72 mfd). Interestingly they both measured 28 and 78 anyway! The tweeter cap is a large cylinderical plastic encapsulated 4mfd (same company).

What are the serial #'s of your 5's? Mine are 22228 and 22355 (late 1971).

Roy

[Guest hilltroll67]

>

>What are the serial #'s of your 5's? Mine are 22228 and 22355

>(late 1971).

>

>Roy

27410 and 27474. Don't remember when I bought them (new), but the 27474 was a replacement for one that died shortly after I got it. The finish doesn't match the earlier one (it's darker). If the serial numbers are model specific, there may be thousands of AR5's stashed in dusty attic corners, acoustic jewels deteriorating unheard. Ah, the shame, the shame.

Bob

[Guest hilltroll67]

Reporting success! New surrounds, caps and pots (well, L-pads). They sound fine. Now on to re-finishing the cabinets and replacing the grille cloths. A labor of love.

Bob