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A 20½” square “AR-1 Special”


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Just recently, I had the opportunity to acquire this custom AR-1 from a seller in western Massachusetts. He found this speaker in the attic of a Boston area home a couple of years ago, along with a custom assembled mono preamp and amplifier which included an Acrosound TO-300 output transformer.

The label on the rear of the cabinet is the earliest label used by AR, and has a handwritten model number: AR-1 Special. The serial number is 3-digit and looks like 150 (the writing has faded considerably). Sadly, all letters but the letter G in the printed word ‘WARNING’ fell off in transit.

As you can see in the pictures, the cabinet is square, measuring 20 ½” on each side with a depth of 10 ¼”. The internal volume is approximately 1.67 cu ft, with 1.47 cu ft for the woofer section. The box for the 755A is 0.20 cu ft.

The cabinet construction appears to be all plywood, with the sides and top veneered (likely mahogany) and painted with gloss black. Interestingly, the grain runs front to back, instead of side to side like all other AR’s. The bottom is plywood painted flat black. Unlike other AR-1’s, the cabinet sides are butted to the bottom panel, on the top the panels are mitered.

The front grill frame has the same bevel and width as other AR-1’s. This one is painted gloss black with a painted gold pin stripe around the perimeter (matching the grill cloth).

The grill cloth is the black with random gold swirl typical of the earliest AR-1’s with mahogany veneer. Unfortunately, there is no logo tag, but the masonite grill board has the hole for it in the same location as my other AR-1, but on this speaker the logo tag would be upper left instead of the opposite corner.

The back panel still has the pencil marks made to determine the center for cutout of the hole for the crossover connections! ( I love it!)

The drivers are an AR-3 woofer, and an Altec 755A with a date code of 5/55. It looks like the original 12” pleated surround woofer was replaced for some reason, and the various glues on the grill board and front panel indicate that the grill was pried off successfully and re-glued after the woofer change. At some point the glue must have failed and the owner resorted to putting a carpet tack in each corner to hold the grill panel to the cabinet. Thankfully they kept the grill and it’s in good shape (though some fraying has reduced its size), the exact cloth is impossible to find!

I gave it a quick low level “test drive” and it works well. The woofer donut looks very dry, along with the foam ring just inside the surround, and the woofer springs back in about a ¼ second. I removed the woofer and as I suspected, the spider is coming loose on one side so I’ll need to apply some epoxy to it. The woofer surround will also get a coat of surround sealer (Roy’s, of course!).

This all fits with being stored in a warm, dry attic, instead of a damp basement.

The cabinet is stuffed with yellow fiberglass, with Kimpak between the woofer and stuffing.  Inside the cabinet, the crossover uses two coils (one marked ‘4’), one for each driver, and two US Navy can capacitors in the tweeter circuit. The 3.5Ω resistor is there along with the others used to adjust the tweeter output level.

The robust t-nuts are held in place with two carpet tacks each. One shim was tapped into place between the bottom of the 755A box and its supporting post and another spare was left in the bottom of the cabinet. I’m sure it’ll come in handy for something!

The price sheet from AR, dated 12-1-54 stated that “Cabinets with custom dimensions available for models AR-1W and AR-1WU only.” I never thought that I’d see an AR-1 in a custom enclosure. Unbelievable.

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It’s almost exciting too think of this as a one-off . And, not to minimize the excitement factor I’m feeling I need more information. Is it that it could’ve been made by ‘AR’ as a prototype?

From appearances, it could’ve been made by an employee after hours. Perhaps it was a special-order  though I think AR would’ve done a better job on the cabinet’s finish in terms of grain-direction, wood-corner joining construction and driver placement, etc.

Were there mounting brackets on the back that may have been removed at some point? Isn’t the internal cabinet volume supposed to be 1.7 cubic feet for the woofer?

In terms of the 755 driver cabinet location, it would normally be mounted higher and inline than the woofer as seen in the AR-1 typically and also used in general speaker design.  The mostly missing corners of the back paper label make me wonder if the corners once were stapled, though I've seen labels glued and stapled at different times of construction.

Out of AR owner curiosity, a number of years ago I thought of building a cabinet for using AR woofers as additional low-frequency support in a planned system but never got around to it. So, I’m still very curious.

In a way, this cabinet you acquired is puzzling at best and I can’t rest until some one more qualified such as RoyC expresses his opinion as he may be the site’s only fully knowledgeable remaining member left here. There may be others but, he is doing the ‘AR-Thing’ I’d guess everyday.

“johnieo” or “Ming”  and others haven’t been posting for a while (years) so, RoyC. is our leader and all-knowing, all-seeing Magical-Mystic-Guru-Ruler.


P.S. If my questioning is unnecessary or incorrect, so be it but, I can’t rest until I hear different. If I don’t hear differently, I’ll reluctantly accept this cabinet as being what you have implied or said it is. I generally enjoy ancient history of man and nature so I'll be checking back to read other opinions until we're sure 100%, this is  most interesting.









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It is a first for me as well, Frank.

From Jeff's post above..."The price sheet from AR, dated 12-1-54 stated that “Cabinets with custom dimensions available for models AR-1W and AR-1WU only.”  Based on the crude installation of the 755A, it appears to have been a "special" cabinet for the woofer (ie AR-1WU) which was converted to an AR-1 by installing a 755A and an AR-1 crossover. It seems unlikely it would have come out of the factory like that. This speaker was accompanied by other custom equipment suggesting the owner was an enthusiast capable of doing this type of modification. The AR parts would not have been difficult to acquire in those days.

I've also never seen that type of crossover wire in an AR speaker before. 


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Hi Roy, nice to hear from you.

I agree but failed to mention those lugs on the speaker wire, I never saw AR use lugs, simple solder was and is sufficient.

Your theory that the previous owner could've  built these very easily on his own with as you say; easily acquired drivers from AR direct, I agree with also.

I still have the occasional day-dream of mounting two AR 12” woofers in a cabinet as reinforcement however, I also think AR’s woofers as great as they are would be stressing in such use. For several hundred dollars one could find a singular ‘sub-woofer’ that’s powered and it would be enough for most medium size installations. Although  I may find like others a more exciting and dimensional sound through the use of a sub as it were, I also feel my speakers are properly set-up in my listening room and afford me more than adequate bass levels and stay within realistic levels. I enjoy a big sounding system but, I could never tolerate a fake, over-done or booming effect. My thinking their use for modern movie sound tracks if that's your thing and to bolster a small system such as one using two-way speakers.

Additionally, I have always found the rendition of bass frequencies that AR’s 12 “ woofer willfully projects is enough for realistic-listening levels of bass frequencies. I also feel that any more bass will defeat my speaker’s purpose of emanating un-colored bass-tones.

In general, I find the sound of sub-woofers entertaining for short term listening that could possibly become audibly boring with time, not to mention false sounding. I first purchased (in 1971), my AR-3a’s for a number of reasons, realistic and quality bass reproduction was a major buying consideration that hasn’t diminished in the 52+ years of my ownership.

So, have we debunked “JeffS’s great find? Perhaps but, if he were dissatisfied with them, he still has costly drivers to either use or sell for a profit and still come out ahead. Or, redesign and incorporate them into something else.

Now, let me get back to the ’National Geographic’ channel, showing specials on ancient Roman structures in England.


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5 hours ago, frankmarsi said:

Hello Frank and Roy,

This is an interesting one for sure. I'll address a number of the points you've made.

I've included pictures of the joints used in the construction of the cabinet. The miter joint looks similar to that used on AR cabinets. I don't recall seeing the butt joint being used before.

The label is the same label used by AR from inception through 1955 after which time the word "WARNING" was removed, and it was glued on. My other AR-1 (serial no. 0071) has the same glued label.

I don't believe the speaker is an AR-1W because the label states that it is an AR-1 Special. The model and serial number are both faded, but it's clear that they are handwritten. For comparison I've include the handwritten label from serial no. 0018. Notice that the handwritten 'AR-1' looks almost identical. Another piece to consider is that serial no. 0627 which is an early AR-1W, does not have a circular cutout for the connector, and it is not centered. Early AR-1's have the 7-post connector centered.

Regarding the serial number, for this speaker it is a 3-digit number. Practically all AR-1 serial numbers, up to 9999 are 4-digit, except two (that I've seen).

Serial no. 147 was assigned to the prototype speaker owned by Julian Hirsch. That AR-1 was the first to have the additional connection for choosing woofer only or entire system operation. The additional label attached to that speaker, and signed by Henry Kloss, stated that "The unit will be available in this form upon request to anyone."

The speaker in question here is the second I've seen with a 3-digit serial number, in this case 150 (or possibly 156). It's also not a standard AR-1, and if you look at the back panel, it looks like another label was attached at one time (on the narrow rectangular spot midway between the crossover and right cabinet edge).

My theory is that the last 2 digits of these 3-digit serial numbers fall in line with the 4-digit serials, and that the preceding digit (1) indicates a prototype. So 147 is 0047, and 150 is 0050. This falls in line with my other AR-1 with serial no. 0071, which has the woofer breakout connection, and 0074, which was once owned by Audio magazine reviewer Edward Canby, which also had the woofer breakout. Taking the serial numbers at face value, 71 and 74 should have preceded 147 which is actually the prototype for those lower numbered speakers.

Regarding the cutout for the 755A, I've included a picture of the cutout of serial no. 0633. The internal box looks identical. The wires to the driver are both the same color as they are in this speaker, the screws look identical, and both boxes have a wad of Kimpak behind the driver. The difference here is that it's mounted in the corner.

I found a picture of the crossover from serial no. 2835, which looks to have identical crossover components except for the capacitors which are Spraque.

My guess is that this was made in the loft at 23 Mt. Auburn Street in the first half of 1955, and that it was built as an AR prototype, or for a well connected friend or person in the industry to their specification (to fit a certain space or narrower bookshelf).

Lots of pictures, I hope I don't exceed my file size allotment!

Note that any pictures included here not of this speaker came from ebay.









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2835 crossover.jpg

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On 1/17/2024 at 1:47 PM, johnfalc said:

What a nice bit of AR history you've got there!

Thank you johnfalc,

This speaker offers AR history and a good dose of mystery!  I'd really like to know the backstory of this one. It looks like it worked near it's birthplace all of it's life.

One of the things that excite me about this unit is the easy ability to get inside the cabinet. The grill board had been glued on years ago but the glue stopped working, so someone wisely put a nail in each corner and fastened it back to the cabinet. Removing the grill was easy.

My guess is that anybody that keeps an intact AR-1 in their vintage audio collection doesn't try to remove the woofer. Even if the glue holding the grill cloth to the grill board has dried enough to cleanly remove the cloth, the grill board still has to be removed to get access to the woofer bolts, and there's a good chance that it will have to be removed in pieces. With this speaker I had easy access, and since the flat sides of the woofer frame aren't tight to the front molding like a conventional AR-1, woofer removal was also easy. That allowed me to shine light into an AR-1 that hasn't been opened since the woofer was replaced (probably in the 1960's), and be able to see the internal woodwork and crossover. This box, like other AR-1's, is very well built.

So, it's a lot of fun to be able to acquire, examine, and share this find with the members of the CSP. I never thought that I'd see an AR-1 with a custom cabinet.

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Jeff, I think this uncommon speaker was an AR-1W “custom cabinet,” with Altec 755A and AR-1 crossover components added to make it an AR-1 “custom cabinet.”  This is the first time I’ve ever seen this cabinet style, but I’ve heard and read about custom cabinets being offered by AR in the past.  It was very likely a one-off prototype built in 1955 by Henry Kloss in his Mt. Auburn, Massachusetts loft—the first home of Acoustic Research.  It has the earmarks of a Kloss-built cabinet; for one thing, he liked the square shape, and he later built several KLH speakers (Model One, Two, Seven, and Twelve) in that general configuration, though most were floor-standing models.  It may well be the only one ever made.

On your speaker, one corner of the 755A inner-box cutout is rounded and custom-fabricated because it is too close to the edge of the baffle board and is practically on top of the woofer opening, demonstrating how tight and impractical this would have been for a production version and impractical for a production model.  In other words, the 755A box could not comfortably fit on the front panel in this configuration.  Other cut marks for the 755A sub enclosure are obviously hand-cut.  In addition, the crossover-component placement is much cleaner and neater than normal—depicting careful hand fabrication—and the wiring is different (heavier) from typical AR-1s from this very early period. 

Insofar as this speaker has a standard AR label on the back, standard components (perhaps except for the crossover wiring), front-molding material and so forth, it was most likely built alongside the first AR-1s and 1Ws fabricated by AR in the Mt. Auburn location.  The handwriting on the label appears to be Kloss’ handwriting, very similar to my AR-1 #0006 prototype. 








According to the December, 1955 price list, “cabinets to custom dimensions available for models AR-1W and AR-1WU only.”  This might have been a one-off prototype or one-off special for a specific customer.  I remember hearing that a point of contention (there were several) between Villchur and Kloss was to offer “specials” from the factory, and these were eventually reduced in number over time.  The two men did not get along well and finally parted in February, 1957.  Kloss was a cabinetmaker of sorts and more into custom fabrication; Villchur was not and did not want to get into building specials, especially after production began to ramp up, causing the small company to be very busy in the late spring and summer of 1955.   

Insofar as the AR-1 was introduced to the public in October, 1954 at the New York Audio Fair, AR-1 production units didn’t begin shipping until March of 1955, and the factory began building around 50 speakers/month during the summer and fall of that year for a total of 450 or so AR-1s and AR-1Ws in 1955.  There were only six employees during the beginning of that first year, and production was limited to the confines of Kloss’ small loft (around 2000 sq. ft.) at 23 Auburn Street in Cambridge.  As production began to rapidly expand, employment ramped up to around 50 by the time the company moved from Mt. Auburn Street to the four-story building at 24 Thorndike Street in 1956.  Building custom cabinets just wasn’t even remotely practical.   

Also, the square shape of this cabinet was not considered as practical, attractive or convenient as the rectangular cabinet shape for placing on bookshelves, and the original AR prototype—which was also square at 19" x 19" x 11"—was not put into production because of the awkward square shape. 

—Tom Tyson


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Hello Tom,

I hadn’t thought about the KLH models with square cabinets. Those later designs support the notion that Henry may have been curious about building an AR system in a square cabinet.

I believe this speaker was built as an AR-1 simply because if it were built as an AR-1W they wouldn’t have had to place the woofer tight to a corner. They could’ve built a custom AR-1W to the same dimensions as the original prototype (19” x 19” x 11"), or some variant thereof, with the woofer centered. There’s a lot of latitude in a custom build if the box only holds a woofer.

The interesting thing about this speaker is that it is built to the minimum dimension needed to mount the two drivers diagonally on the front board, to make the smallest possible square. As you pointed out, the front board must be custom cut to allow for minimum spacing between the drivers, which necessitates that a portion of the 755A box sits below the woofer frame. This is shown in the pictures below, and it looks like they even took a rasp to knock down the corner of the upper portion of the 755A box. This is a tight fit to be sure, but due to the diagonal mounting, woofer removal is easy.

I believe your assumption is right, this is a one-off prototype or built for a specific customer. If it was built as a square cabinet prototype, it’s easy to see that it is unattractive compared to the rectangular AR cabinets meant to be used horizontally alongside books. One plus here is that the front trim with gold pin stripe matches the grill cloth (though I wouldn’t have chosen black paint for the cabinet finish).

Thanks for including pictures of SN: 0006. As with that speaker, this one also has a circular cutout for the woofer, pre-dating the later truncated cutouts. It’s also interesting to see the three hand wound resistors in the crossover, and the same use of a copper strap to hold the capacitor in place. And thanks also for your, as always, detailed and informative post!



AR Special 755A box 2.jpg

AR Special 755A box.jpg

AR Special 755A box 4.jpg

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