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AR1 find and crossover research potentiometer help


donsof
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Hi all

I have been looking for info and how to approach using these speakers. They are super nice and very original, with no evidence of ever being tampered with.

Does anyone have internal pictures of the crossover parts, removed or still in place, inside this pot generation model? I did find the confusing schematic for them. I think I could live with the HF section at full gain if its possible to bypass the pot, without pulling driver? I cranked the pots up all the way to find a spot with little crackle.

I am considering pulling the grilles and 1 driver to apply deoxit to the pots. If anyone has a slick way to break the glue, let me know. It looks like I should peel the grille cloth, and work a thin knife under the 6 glue dots, holding on the masonite. Even if I later sell these, I think everyone will want to see the cones, so its not a bad thing. I plan to use velcro when replacing the covers.

The speakers sound ok, but the pots are really needing help.

Has anyone ever thought of drilling a hole, and filling it later to allow a deoxit tube?

If I am reading this right, I need to pull the 1-2 jumper to make these 8 ohm, as modern solid state amps are mostly 8 ohm ready, and a 4 load is not good with most solid state gear? Does that sound right? I am reading the label as saying these are 4 ohm speakers with the 1-2 jumper attached.

thanks Don (a first timer here)

pictures here

https://jpegbay.com/gallery/007555295-.html#1

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Welcome Don

You've come to the right place. Those are rare beauties, so to paraphrase Hippocrates, "first, do no harm."

Member Tom Tyson has experience with these and I believe Roy does too. Be patient and wait for them to chime in.

Don't drill any holes in anything.

You cannot "make these 8 ohm." When the time comes, you need to use a powerful 4 ohm amp. The jumpers are for using just the woofers.

Kent

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The Altec 8" driver has its own plywood sub-enclosure, so access to the level control would have to be through the woofer hole.

You could try rotating the level control back & forth a few dozen times, and you might find a good contact point. There's not a tremendous amount of HF output from the Altec, so running at "full gain" wouldn't be a problem for most listeners.

AR-1 speakers in original, unmolested condition have significant value; if you can avoid opening them up, you'd be doing your wallet a favor.

As Kent mentioned, the speaker is a 4 ohm model when used as a full-range system, so you'll need an amplifier that's powerful & stable at that impedance. 

How about some photos to show the condition of the cabinets?

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AR-1 has an additional jumper that puts a 3.5 ohm resistor into the crossover circuit for an 8 ohm connection. It was supposed to compensate for certain "unfavorable" speaker placements, but is really not the best solution for normal placement with the wrong amplifier because it doesn't really turn it into an 8 ohm speaker; the resister just converts some of the amplifier power into heat, and who needs a heater in a speaker cabinet?

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Thanks for the help... this site has caused me to use up 20 or more hours of reading! Its fun researching when you stumble into the estate sale find of the year. The AR's were found in a modest home with a decent looking EICO ST-70 tube amp, which is going into resto as well. Hopefully these speakers won't need much.

So I have been wanting to find out what the altec 755 is all about, and initially, my first impression is this set runs good, and is one of those pairs that would be considered on the high end of the value range. Taking off the grille shouldn't devalue them, I wish the AR's were more service friendly. I tried uploading pictures, but this site wouldn't allow my uploads for some reason, so I used the jpegbay link in the first post. It works great.

I will get one of my 5 tube amps rebuilt and running this winter, with 4 ohm loading available, thanks for the tip on that 8 ohm mystery.
Both drivers are 4 ohm models in this piece? I know the Altec is supposed to be 4 ohm anyway?

I understand there is one cap in the crossover, and its oil filled. I read someone say don't worry about that cap. I have been looking everywhere for pictures of this crossover, to no avail. I do research things pretty deep before digging inside, so thanks for the words of caution. I hope someone has a picture pile of this crossover they can share. I saw a set get parted on ebay that brought big money recently, but they didn't show the crossover very well.

thanks Don

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Don,

The jpegbay option works but if you want to post pics here resize them to about 100kb-ish. I use Photoshop Elements, resize to about 6" across, about 100 pixels/inch and save at Quality 8.

Looks like you do your research, so my initial fear that you would just tear into these very collectible speakers was unwarranted. 

Gene set me straight on that extra set of jumpers, so you were not wrong but as he said, generating heat inside the box may not be desirable.

Tom T is really the authority on these AFAIK and I sent him an email asking that he take a look at this thread.

Those Western Electric/Altec drivers are funny. I've never seen or heard one but from what I've read they were introduced in 1948 and were widely used as full-range speakers in PA systems in hospitals, schools and the like. Very well built and solid but never regarded as "hi-fi" until recently. The AR-1 seems to me to be a single driver speaker (the 755) with the addition of Vilchur's revolutionary woofer. AR also sold the AR-1W which was the original acoustic suspension subwoofer.

Asian audiophiles, especially in Japan, have a love for vintage American tube gear and the associated stuff. Based on photos, the 755 is beautiful to look at and has the feel of quality. Asian "USA Audio-philes" seek these out and have driven the prices way up. This has been abetted by some American reviewers who also praise the 755. As a result, many fine old AR-1s like yours have been torn apart just for the 755s. A pity IMHO.

btw, the 755 only goes up to about 13kHz so you won't get any true high end, even cranked all the way up. Back in the day people added electrostatic tweeters from JansZen or conventional tweeters from the misleadingly-named MicroStatic to augment the high end of early AR and KLH speakers.

Good luck with these. You probably saw this thread but just in case: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1106-ar-1-anomalies/

and the crossover schematics (there were different versions) are here 

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/1909-need-ar-1-schematic/

Kent

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The 755 had an unusually smooth response for a full-range speaker of its era, over a range from about 300Hz to 10kHz, though there are a couple of large dips under 1kHz. This made it a good choice as a high-range driver for the AR-1 crossing over at 1kHz. It also had the advantage of being widely available and relatively inexpensive.

By modern audio standards, its performance is utterly unworthy of the high prices it brings as a collectible.

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Here is the best I have so far, inside this AR-1 unit that just sold as a parts unit on ebay, there were some crossover parts visible. Can you tell me what are the parts in the metal cases labelled #10 - #11 - #12, and there seems to be something in tar under the masonite squares labelled BLK 1 and BLK 2? I will put an A-B-C- code to each part so we might talk about them easier.

Input 1 is +IN #1 terminal and its hidden
Terminal 2 is down and hidden by insulation
Input #3 is -3 IN and visible

The black pucks are the inductors? .4MH maybe?
or are the inductors next to the can at the bottom?
I assume the #11 can is the 24MFD capacitor?
see items 10-11-12
I think the HF wires are yellow and green?

Can you help fill in the blanks, and the pot may have the rear cap missing?
This is the only crossover picture I have.

pictures here
https://jpegbay.com/gallery/007555853-.html#1

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54 minutes ago, donsof said:

The black pucks are the inductors? .4MH maybe?

yup

54 minutes ago, donsof said:

I assume the #11 can is the 24MFD capacitor?

I'm sure. Looks like a multi-section cap wired together (10, 11, 12) to make 24uF but I've never seen that style myself.

54 minutes ago, donsof said:

the pot may have the rear cap missing?

Or it may not be an Aetna-Pollack like the AR-2 xo shown. Ohmite (and other) pots are open on the back.

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You guys are awesome, and its great how that one seller provided me with a look at the crossover. Though I wish I could see around the insulation. That ebay seller parted the pair out for appx 3900$
AR serial numbers were 14586 11162 both mahogany with potentiometers
Also I noticed that his woofers had red and blue wires, that were unsoldered or clipped from some point?
He personally sent me the 2 pictures of the crossover, they weren't in the listing.

I think the first version of the crossover would suit me better. I don't like pots, if I have to go through hell to service them.
If anyone has pictures (of the insides) of the early strapped version, please share.

I learned about the east coast vs west coast sound rivalry a few years ago, and always wanted to see what the AR fuss is all about. Its my first pair. I understand there may be some shortcomings to the original AR, so I will just be happy to listen to it properly, and at its best.

I have been working on JBL projects for the last several years, and loving my JBL C36 Bass Reflex speakers.
This week I stumbled across a JBL trend from 2006 called the econo-wave. It takes a JBL C36 from the 1950s - 1970s, seal the cabinet to be air suspension, and use a 12inch 123A-1 woofer, compression driver with dispersion wave horn, 1200 Hz network, and was a project "Zilch" worked on. I am very happy with the west coast sound in a 2 way, and love to horse around with all the old stuff. I do like looking and working on the JBL stuff, its easier to get apart!

thanks

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On 8/29/2019 at 8:25 PM, donsof said:

If anyone has pictures (of the insides) of the early strapped version, please share.

No picture of the earlier AR-1 crossover assembly to share, but nonetheless am providing this schematic and rear views FYI. I find it interesting that the earlier speaker label shown carries the Mt. Auburn address (Henry Kloss' loft), while the later speaker label shows a Thorndike St. address across the street from the well-known 24 Thorndike found on most early AR's.

With your rare specimens in such excellent condition, you'd be be well-advised to not consider any attempt to adapt to the multi-strap configuration. Yours most likely do have early robust pot controls, but even if the rotary controls are unserviceable, this project would be well worth the cost of some new heavy-duty Ohmite controls.     

AR-1 schematic strap.jpg

AR-1 #1225.jpg

AR-1 #2364.jpg

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  • 2 years later...
Hi all,
This is an old thread, but I waited long enough and found an early AR-1 crossover someone removed from a speaker. I thought I would share the pictures as its very hard to find someone who has broken one out, and the pics show its not easy to get these out.

https://jpegbay.com/gallery/008383189-1.html#1
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