AR-1 Anomalies

[Guest rotor]

I recently acquired a pair of Acoustic Research AR-1 speakers. Would appreciate any info regarding the following, please see attached pictures:

1. Based on my research, the AR-1's have the Western Electric 755-A mid/tweet. The pictures I've seen of the 755-A all have a black cone/dust cap. My AR-1's both have light brown cones/caps that physically look like the black ones. Were any 755-A's made with light brown cones? Can I definitively determine if they are 755-A's without tearing anything apart?

2. What is the procedure for removing the drivers/crossover? All I've done so far is pulled back most of the grille cloth. There is a front panel which appears to be firmly glued preventing access to the drivers.

3. Although both cabinets have stickers that say AR-1, they are different from each other. What's odd is that both have the round cutouts on the back; however, one has a pot with three terminal connectors, the other has no pot and has seven terminal connectors. Are there several versions of the AR-1?

4. The pictures I've seen of other AR-1's have a cream-colored grille cloth. Mine have a multicolor weave-type cloth. Would these be an original variation or replacements?

[johnieo]

>1. Based on my research, the AR-1's have the Western Electric

>755-A mid/tweet. The pictures I've seen of the 755-A all have

>a black cone/dust cap. My AR-1's both have light brown

>cones/caps that physically look like the black ones. Were any

>755-A's made with light brown cones? Can I definitively

>determine if they are 755-A's without tearing anything apart?

ar_pro kindly posted a link to an excellent description of the three Altec-Lansing 755 versions used in the AR-1. The link is:

http://members.myactv.net/~je245/755survey.htm

Perhaps this will help in differentating between versions. The 755 is mounted in its own small enclosure, which is not part of the main air-sealed cabinet. You may easily (but carefully!) remove the four screws holding the 755 in place; its version number will be printed on its side.

>2. What is the procedure for removing the drivers/crossover?

>All I've done so far is pulled back most of the grille cloth.

>There is a front panel which appears to be firmly glued

>preventing access to the drivers.

It is my understanding that all AR-1 filler panels were not assembled in the same manner. This panel must be removed to access the mounting screws. On my AR-1, it was held in place with about 7 dolups of glue and small nails. Try carefully inserting a small putty knife under the edge of the filler panel adjacent to the driver holes, and twisting it gently. Please be careful, should you attempt to insert a flat blade near the outside of the panel near the finished wood trim, else you gouge it! If that is necessary, then use a wide, thin blade between the finished wood and your removal tool. Try first to work from the inside out; you may find that the dried glue separates easily, once the nails are removed.

Likely, you will want to remove the woofer and examine the capacitors. If the large 150 uF capacitor (or dual capacitor) is housed in a wax paper box, it is by now leaky (high equivalent series resistance) and should be replaced. If the 150 uF capacitor is contained in a gray, steel can, you can be pretty confident that it has retained its low dissipation factor. The PCB dielectric liquid used in those surplus capacitors made an excellent dielectric and the metal can prevented leakage. PCB is no longer used in capacitors, as it is a carcinogen; keeping this cap in your home, or replacing it with a polypropylene, metal-film capacitor is your decision. Tom Tyson gave suggestions in other posts for spraying the cloth surrounds with armorall to retain their compliance, and for recoating with butyl rubber--should one leak.

[tysontom]

>

>1. Based on my research, the AR-1's have the Western Electric

>755-A mid/tweet. The pictures I've seen of the 755-A all have

>a black cone/dust cap. My AR-1's both have light brown

>cones/caps that physically look like the black ones. Were any

>755-A's made with light brown cones? Can I definitively

>determine if they are 755-A's without tearing anything apart?

>

AR-1s always came with the Altec Lansing version of the 755A. Altec Lansing had absorbed Western Electric's licensed speaker-building business by the time the first AR-1; the Altec Lansing and Western Electric 755As are identical except that the WE version had more inspection stamps on the mounting ring. The brown color for all of the 755As was entirely normal. I have two or three AR-1s -- including one with serial number 0006 -- and each has the brown cone. I believe the later versions of this driver might have had the darker cone. You do not need to remove the speaker to determine its namesake; you can easily tell it is a 755A by the unique design of the dust cap and the slight corrugation in the cone to allow the inner portion of the diaphram to decouple at the highest frequencies. The entire diaphram couples in its lower operating range. Another (more pronounced) iteration of this construction was the "whizzer cone" used on earlier Electo-Voice and University woofers.

>2. What is the procedure for removing the drivers/crossover?

>All I've done so far is pulled back most of the grille cloth.

>There is a front panel which appears to be firmly glued

>preventing access to the drivers.

You have to access everything from the woofer hole, and you must remove the masonite grill panel (glued and sometimes stapled) from the front baffle board. Gently pry it little-by-little inside the woofer hole until it begins to break loose, but be careful not to snap it. You can then remove the eight machine screws that hold the woofer. The mortite that holds the AR-1 woofer in place will be hardened by now, and removing the woofer is not easy, particarly since the baffle is 1-1/8-inches thick and difficult to get under the woofer frame. Unless you are having trouble, or unless you are going to strip the speaker of its Altec Lansing 755A (a speaker with cult following for no known reason), you are better off leaving the speaker alone.

>

>3. Although both cabinets have stickers that say AR-1, they

>are different from each other. What's odd is that both have

>the round cutouts on the back; however, one has a pot with

>three terminal connectors, the other has no pot and has seven

>terminal connectors. Are there several versions of the AR-1?

>

The first production AR-1s, beginning around December 1954 to January 1955, had straps on the back to select the output level of the 755A tweeter. Subsequently this changed to a level control (not the familiar Aetna-Pollock used in the later AR speakers), so you simply have two AR-1s with serial numbers a little bit apart. Both should sound the same. All early AR-1s had oil-filled capacitors in the crossover, and these components were used well into the late 1950s. There is little reason to believe that they have failed or are failing unless the speaker had been subjected to abnormally large amounts of amplifier power, and other components would have been damaged. The level controls on the early AR-1s don't usually give as much trouble -- that is, oxidize -- as easily the later Pollock versions. I don't believe that the Chicago Industrial plastic-impregnated (not wax as reported previously) paper caps were introduced until around 1963 or so in AR speakers. Also note that the earliest AR-1s used an impregnated-cloth pleated surround (shown in your picture of one of your AR-1s), which was AR co-founder Henry Kloss' design. Pleated-cloth surrounds were an industry standard beginning in the early 1950s, but shortly into 1955 this changed to Ed Villchur's half-round surround, the familiar design now in universal use throughout the speaker world. Villchur's patent also shows the half-round design. To be sure, Acoustic Research decided to test each surround to determine which was better, and the half-round had smoother response and lower distortion, and it was adopted thereafter. This is another good reason for using objective testing to determine the right course of action. One advantage of the pleated surround, however, is that it does not change in time. It does not develop air leaks particularly, since the pleats hold the glycerol-like treatment better than the half-round.

>4. The pictures I've seen of other AR-1's have a

>cream-colored grille cloth. Mine have a multicolor weave-type

>cloth. Would these be an original variation or replacements?

>

The multiweave brown cloth grills were standard on all early ARs, and the earliest had the randomly interweaved circular gold thread. In about 1957 or 1958 AR began to use the ivory-colored grills like the AR-3.

--Tom Tyson

[Guest soundlove]

Hi Idid find an old AR-1 pair of walnut speakers.

Grill is intact& in pretty good shape .Sound is terrible crackling

distorted sound Idid not try to go any further -not to damage my Receiver,The guy who will fix those speakers is pretty good guy

He repairs all speakers commercially.He does not know how to get inside.

Thanks to this wonderful forum wee did learn -front is the only way.What type caps

Wee should choose to replace those old caps? Any advice what to look for?

I will take pictures of those speakers.I would like to preserve those speakers and try to keep original parts as much as possible.I had almost all AR speakers in past-except LST. I have 2 pair AR11s, 1 speaker AR3a ,1AR5, also pair of AR3a-improved.I love those speakers.Also I have pair of big ESS AMt- and pair of ESS-Tempest.Excellent speakers.But in long run I love more Ar-11s .This is fantastic forum .To bad Iam not technically inclined.Thank you for any advice. I am collector and trying to preserve those AR speakers.Iam using BOSE Spatial Receiver 90W-per side excellent FM /also Luxman Receiver FQ 900 driving those 4 ESS.Very nice sound .soundlove

[tysontom]

>Hi Idid find an old AR-1 pair of walnut speakers.

>Grill is intact& in pretty good shape .Sound is terrible

>crackling

>distorted sound Idid not try to go any further -not to damage

>my Receiver,The guy who will fix those speakers is pretty good

>guy

>He repairs all speakers commercially.He does not know how to

>get inside.

>Thanks to this wonderful forum wee did learn -front is the

>only way.What type caps

>Wee should choose to replace those old caps? Any advice what

>to look for?

>I will take pictures of those speakers.I would like to

>preserve those speakers and try to keep original parts as much

>as possible.

Just a small bit of advice: beware of speaker-repair experts, especially commercial ones, that don't know "how to get inside." Repairing an old AR-1 requires a thorough knowledge and understanding of this highly specialized design. Most speaker-repair people want to get in there and get it "fixed," without too much regard to whether it is original or correct or not. Removing and replacing an old Altec Lansing 604E cone and voice coil is not what you are doing here. This is more like repairing an antique, and it requires knowledge of the piece of furniture.

Some might consider this to be over-reacting; but in order to preserve the old AR-1, you need to treat it in a special fashion. Go back through the AR-1 posts of many of the people on this site and you can get a better insight to what is required to repair these special speakers.

--Tom Tyson

[Guest soundlove]

Thank you Tom

I did study all previous postings . Myself &AllReimer speaker an old guy print all helping notes from all your members.and thank you all .Iam very lucky to find this forum and learning.Iam not worry about All Reimer repairing Altec speakers.This guy is an old musician base player brilliant cabinet maker and he did design equipment -like bass box for some of top groups.He does repair most of altec repairs and old equipment.He fix my Altec-mod 19, But this is the first time for him to do my AR-1.s/ Another friend of mine is super good guy-very humble person.He was shortly in early days sound man for Grateful dead.He produced &design amps for PA systems -also does recording studio work.He is humble electronic scientist and poor business man!!.His amps Rolling stones &Emerson Lake &Palmer were using on concerts through Canada and other well known groups. -lightweight has 2 amps in one unit.(notice Iam not electronically smart to describe functions)-Iam O.K with sound-Iam former average musician).He almost -most musicians saying yes -duplicated tube sound with those amps.He is now designing guitar amps for some of top musicians in his spare time.Iam so lucky to know this humble guy who does not like to publish his name.He fix all my Marantz 2325,&Tandberg H.K -Lux &Bose gear.I have nice sounding old Blaupunkt integr.amp- this amp producing fantastic sound to bad it is only about 25w per side.Made in Germany.Tuner sound is something else.All Reimer has some precious old Vintage speakers for sale .Iam not making sales pitch here.All &Myself wee love good old stuff gear and he loves to keep them in original condition. .Thank you again for your input. TOM you are an expert electronic&speaker jewel .Soundlove.