Rek O Kut Tips

....vintage studio equipment in a scene from "The courtship of Eddie's Father", starring Glenn Ford..

Not much information can be found in cyberspace about the original Rek-O-Kut company based in NYC. But the company was a highly regarded manufacturer of turntables, tonearms and cutting lathes during the golden age of Hi-Fi. A lot of these idler driven turntables found duty in radio stations due to their quick start up time, stable speed and simple yet well executed engineering. My 1961 Lafayette catalog lists several idler models starting with the entry level 2-speed 4 pole induction motor driven Rondine Jr. L-34 [33 and 45] and L-37 [33 and 78], 3 speed Rondine B12 with same 4 pole motor as the L-34/L37, Rondine Deluxe B12GH which uses the Papst "flywheel" hysteresis motor and the the top of the line B12H which uses the HUGE hysteresis motor [see picture below]. By 1963 the L-34/37 Rondine Jr. series was replaced by the N33/34H belt drive which usually was fitted with the Papst motor. I have no experience with these models or motor but they have a good following.

All the Rek-O-Kut turntables are a model of engineering simplicity [no pitch control or eddy current brake] making the Garrard 301/401 and Thorens TD124 look over engineered. The motor and idler wheel arm assembly are individually isolated through rubber grommet mounts to prevent extraneous vibration from reaching the platter. The control switch physically moves the isolated motor with stepped capstan to engage the idler wheel at a chosen speed. Surprisingly the budget Rondine Jr. model employs dual idler wheels, the compromise being a simpler idler wheel arm assembly that does not need to be moved up or down to engage the capstan. Building a massive plinth for this model is very easy since it only requires a rectangular cut out to accomodate the motor unit. Due to the simple design the condition of the idler wheel[s] and rubber isolators as well as the few lubrication points have to be addressed to insure optimum operation.

---

The spindle is approximately 5/8" in diameter and comparable to those found in a TD124 or 301/401. The platter is a precision lathe turned aluminum weighing about 5-6 lbs. depending on the vintage [earlier models were lighter].

Pull out the platter and then remove [3 screws] the bearing well from the motor board. The inner rim of the platter and spindle should be cleaned and the bearing well should be flushed with lighter fluid or denatured alcohol. There should be a small ball bearing inside the bearing well. Inspect the condition of the ball bearing and if it shows signs of corrosion, replace it with a 1/4" or 5/16" ball bearing available from a bicycle shop. A brand new shiny ball bearing insures a smooth and silent turning platter. I am not sure what the original diameter of the ball bearing was but find that a 1/4" seems to turn a bit quieter than the 5/16" and the platter rests quite low on the top chassis which looks just like in the original brochures.

The motor assembly can be removed from the top chassis by unscrewing the switch knob [1] and the 3/8" hex nut on the opposite side [2]. Now is the time to check the condition of the rubber mounts [1& 2 below and two more on the other side not visible] 4 of these are used to isolate the motor. If they are pliable and free from cracks just clean up all the grease and accumulated gunk. Replacement rubber grommet mounts are still available from Lord Corporation in Erie, PA although I have yet to encounter cracked or glazed rubber mounts.

After years of storage the top and bottom motor bearings' lubricant may have gummed up. Spray Electric Motor Cleaner and compressed air into the oiling turrets [marked with arrows]. Once the bearings are turning without significant resistance, light oil can be added. 

To clean the idler wheel bearing remove the E-clip and flush the stud [1], brass bearing [2] and washers with lighter fluid. For reassembly the sequence [from bottom to top] is - thick washer, thin washer, idler wheel, thin washer, thick washer then E-clip. I use thin gun oil to lubricate the stud and brass bearing.

Idler wheel condition is very critical for a quiet running ROK. Minute flat spot[s] in the idler wheel will definitely be heard as loud rumble. It has been suggested in the Vinyl Asylum that cleaning the rubber with lacquer thinner can rejuvenate a "not so tired" idler. With the platter off, turn on the motor and engage the idler while brushing the rubber wheel with a small paint brush dipped in lacquer thinner. Sometimes this trick will work but if the rubber hardens and becomes noisy when it dries up, it needs to be refurbished. It didn't work on this particular idler wheel set. 

Worn out idler wheel - the rubber is glazed and hardened, it also measures 1/32" less than 2.5"

Refurbished idler wheel is exactly 2.5" in diameter

The turntable is now almost as quiet as my Garrard 301. Mechanical noise should not be audible 4 feet away from any idler driven deck in a quiet room. Another way to determine a worn out or glazed idler wheel is to try grabbing the platter and if it stops easily or does not offer much resistance the rubber is slipping.

According to the manual SAE 20 motor oil is the recommended viscosity for the main bearing. I use non-detergent SAE 30 and you only need to pour in enough oil to cover the top of the ball bearing and then rubbing some to the spindle before inserting the platter into the bearing well. As pictured the tip of the 1/4" bearing I used is not quite submerged in oil and needs a couple more drops.

This picture shows the position of the set screws with rebuilt idlers installed and speed calibrated. Although there is no pitch control in most ROK models, speed can be fine tuned by moving the set screw along the arrow marked directions. The motor should have been running for at least 15 minutes before adjustments are made. In general it would be prudent to keep the idler to rim tension at a minimum [closer to the knob] to prevent premature idler wear. Too much tension with good idlers slow down the speed and generate more noise. Proper tension is obtained when the platter locks in to speed within a couple of minutes. I use a neon pilot lamp from Radio Shack soldered/heatshrink wrapped to a long AC cord to view the stroboscope markings.

---

Other Models

Rondine Jr. L-37 and LP743 - 3 speed

These are very similar in design but the earlier LP743 has rather innovative features - the same idler is used for 33 and 45 and the mechanical switch to the extreme right changes the height of the idler to match the 33 or 45 rpm capstans of the motor. The idler on the left is exclusively a driving wheel to spin [no contact with the motor capstan] the platter at 78 rpm. However the idler arm on the LP 473 is directly attached to the top plate so the idler is rigidly in contact with the inner rim on start up whereas the L-34/37's idler arm is mounted on a substructure isolated by 3 rubber grommets contributing to less mechanical noise but a tad less kick on start up.

The bottom idler wheel [marked with an arrow] is driven by the bottom capstan [78 rpm] in the motor shaft which then transfers the motion to the top idler wheel to turn the platter. This pair of idler wheels for 78 rpm are mounted using set screws instead of an E-clip. The platter on the LP743 is slightly smaller and a bit lighter but the main bearing dimension and quality are identical. Earlier versions of the Rondine Jr. L-34 or L-37 also used this square type motor.

Idler wheels are not interchangeable between the B12H, LP473 and L-34/37.

Rondine Deluxe B12H fitted with a ROK S220 Gyropoise tonearm. This is the top of the line 3 speed model using a single idler wheel. Notice the tool kit under the platter?

The tools are provided to fine tune the speed and idler tension - the Allen wrench is used to remove the big control knob and the hex wrench to loosen the hex nut to fine tune the speed. As you slide towards 2 there is greater tension. Apply the same adjustment procedure as noted in the Rondine Jr.

Top motor is the hysteresis unit found in top of the line ROK machines, the bottom motor is from an L-37.

B12H stock plinth

Rek-O-Kut Rondine deluxe B12H after restoration and idler wheel rebuild. Tonearms CW from left: Pickering 190, Argonne AR600 and Velvet Touch.

Rek O Kut L34 Rondine Jr. + SME 3012 + Excel ES801
DIY Plinth

For more information and discussion of Rek-O-Kut turntables visit the Vinyl Asylum Archives.

Idler Wheel rebuilders:

Terry's Rubber Rollers

The Voice of Music

WE/Altec 755 Part 2 (2 cf box)

As many of you know I am an open baffle advocate and have used the 755A and 755C in this concuction for years. However, I recently attended a radio show event after a few years of hiatus and saw my friend Chong Ong. He handed me these ~ 2 cubic foot "homebrew" sealed boxes designed for use with the 8" WE/Altec 755 speakers. According to him these cabinets were acquired from a retired WE engineer which encouraged me to give the sealed box enclosure another chance.

In the past I have experimented with two types of slanted 2 cu. ft. enclosures - an original Altec 618 and custom built 622 using 1/2" plywood - and always ended up with mixed results. The above cabinets look like the 618 and the dimensions are - 22"H x 17"W x 10 1/2" top depth x 13 1/2" bottom depth - using 5/8" plywood instead of the 1/2" used in the original Altec 618 Utility cabinet. The panels are lined with ancient type of damping material known as "Kimsul", which reminds me of crepe paper. I have seen this material inside Western Electric 753 and 757 loudspeaker systems and even as wrapping material in old tube boxes.

Altec 618

Custom Altec 622 with Altec 408A

The first driver I tried was the 755C but these observations were also validated when I installed the 755A and 755E. Compared to the open baffle, this cabinet gives an impression of quicker transients and dynamic nuances which Joe Roberts call "snap" which I could never achieve from dabbling with the 618 and 622. My main frustration when I experimented with the aforementioned cabinets was, both sounded slow in spite of the many tricks I tried - walls lightly damped with pillow stuffing [Dacron], bare "lacquered and resonant" panels and etc.

Anyway, along with the "snap" comes a more forward soundstage presentation. There is a bit of a midbass hump in the 90-120 hz region reminiscent of an LS 3/5A, most evident with the 755C and 755E because they extend lower in the bass. Bass aficionados will probably prefer this cabinet over an open baffle because of this sonic illusion. But remember that even with open baffles, there is not much solid bass below 60 hz on any of these drivers. For that matter I never heard a modern high-end speaker with an 8" woofer that can go down flat to 50 hz and still possess a lucid midrange like these vintage units. The midbass bloom is less obvious with the 755A and overall this was the best sound I got from this box.

Even if the pancakes are claimed to go up to 15khz, they sound like the highs begin to drop slowly around 9khz whereas the 755A still has some energy past its 13khz limit. This may be a psychoacoustic phenomenon given that the pancakes have been redesigned to extend almost an octave lower and lost the "exotic" cone chemistry of the 755A which brings out the even more glorious midrange and silky highs. As many of you already know specs really do not mean much in real world conditions.

The lack of high frequency extension in the "pancakes" is more apparent in the 2 cu. ft. box and I was compelled to use a super tweeter. The Altec 3000 is a natural choice but since this is hard to find and pricey I found the Fostex FT-17H as an excellent and modestly priced [$70/pr.] alternative. I use a 1uf oil filled capacitor and an 8 ohm attenuator to hook up either tweeters to fill-in the drooping response above 10 khz on these drivers. With the 755A, I did not deem it necessary to use a super tweeter. Even the "ribbon-like" Altec 3000 can diminish the purity of the high frequency abilities of the 755A if not attenuated and crossed over properly. If you insist on extending the 755A's, I can only recommend using the 3000 with a .5uf oil cap and attenuated judiciously.

When I designed the JEL SE300Bdx, my only reference speakers were the 755As and 755Cs in open baffles. The 755As can tend to sound peaky if driven by a brighter sounding amplifier or source component while the 755C and 755E are more forgiving. In terms of "apparent" sensitivity/efficiency, the 755C has a slight edge over the "A" and "E". I need SE300B power to enjoy large scale symphonic music with the 755A and 755E. With the 755C I can get by with an SE2A3 amp. However this does not prevent me from using microwatt SE71A for listening to small scale music on any of these drivers.

Like I said in my SP17 homebrewer article, the 755/OB combination reminds me of the Quad ESL57 with greater dynamic range and sensitivity. This 2 cubic foot box is like an LS 3/5A with a larger soundstage presentation, greater dynamic contrasts and SPLs without the "bextrene" coloration in the mids. If you like planar speakers, the open baffle will yield flatter bass response, even bigger soundstage, provide more depth and airy spaciousness at the expense of "snap". But if space is at a premium, you can achieve an "SE amp" friendly speaker system with BBC nearfield monitor quality from this 2 cu. ft. enclosure with the 755A and the 755C/755E with an Altec 3000 or Fostex FT-17H super tweeter.

Below is a sketch of this enclosure's external dimensions:

Building tips:

·        Use 5/8" cheap plywood, the more resonant the better, 1/2" slows down the sound from my experience

·        Do not use MDF, this was not a known cabinet material to the designers of the 755 and other vintage drivers, anyway it is a sure fire recipe for disaster when using any vintage driver

·        Front mounting will probably lessen the midbass bump and the darker mid-range tonality of the "C" and "E" but make sure that the driver is "routed in" so that the front of the speaker frame is flush with the baffle which will provide enough space at the rear for sound to exit through the small holes at the back of the speaker frame

·        If the driver is front mounted, it is no longer necessary to have a "screw on" front or back panel, this way the cabinet will be tightly sealed

·        I have no source for Kimsul but reckon that Dacron polyester fill will be a decent substitute, just line the walls with 1- 2" of this stuff and it should be fine.

Back to Part 1

Visit Joe Robert's Junkyard Jukebox for great WE755A information!

Another site I just discovered with good information on WE/Altec 755s.

WE/Altec 755 Part 1

From Western Electric to Altec

The original Western Electric 8" 755A driver along with the 10" 756A and 12" 728B and 754A were marketed a couple of years after World War II. According to Walt Bender, former publisher of Audiomart and a leading authority and expert on vintage American audio components, the transition from WECO [Western Electric Corporation] towards Altec [All Technical Services division of WECO/AT&T] was not completed until the early 1950s. This was due to a 1930s anti-trust lawsuit filed against the giant telephone company whose business ventures, amongst other interests, included providing sound systems for movie theatres during the booming Hollywood film industry of the pre-WWII era.

Below is an email I received from Steve Schell, manufacturer of Cogent True-to Life Loundspeakers and whose research on vintage American classic speaker components I truly respect. This is probably the most comprehensive and easily grasped explanation of the transition from WE to Altec as well as establishing the [James B.] Lansing connection. Many thanks to Steve for allowing me to upload this information!

May 26, 2006

Hello Joseph,

I just read your 755 pages, after following a link from the Audio Asylum High Efficiency Speakers forum. I recall running across your site several years ago, as well as reading your fine contributions to my well worn and valued copies of the Angela Instruments print catalogs.

There is a little history I can add to the story of the 755. What follows is not authoritative, but based on the reading I have done. Altec Lansing was formed in 1941, after All Technical Services bought Jim Lansing's struggling Lansing Manufacturing Company in Los Angeles. All Technical had been the theatre service branch of Western Electric, which maintained service contracts with several thousand theatres that were equipped with Western Electric sound systems. When the U.S. Government forced W.E. to divest itself of its U.S. theatre sound operations in September 1937, the All Technical branch was purchased for a token amount by several of its managers. They continued to maintain the theatre contracts, though they began running low on replacement parts. Part of the reason for their purchase of Lansing's company was to give them facilities to manufacture the needed parts. They also acquired the designs and production capability of Lansing's theatre systems, regarded by many as being the best at the time. The Lansing product line continued in production, and formed the basis of many of Altec's later sound products.

Western Electric continued to manufacture sound products for numerous applications, but not for domestic motion picture theatre use due to the 1937 consent decree. In about 1940 they began making the 750A, which looks to me like the ancestor of the 755A. It was a 10" driver with an aluminum cone and 4" edgewound aluminum voice coil- please see attached pictures. The 750A is very scarce, and sells for $5000 or more in Japan.

After WWII they introduced their postwar line of speakers, including the 755A, 756A, 728B, 754A, and several phenolic cone variants. W.E. made a huge effort to design the best speakers possible, and to market them effectively through Graybar. In 1949 the U.S. Government intruded on them again and insisted that they cease manufacture of these products. W.E. signed another consent decree at this time. In late 1949 a full page ad in Audio Engineering magazine announced that W.E. was discontinuing manufacture of several of their speaker and microphone models, and that these products would be henceforth be manufactured by Altec Lansing. W.E. had apparently made a deal with their former associates at Altec to manufacture these products and provide W.E. with a portion of them as an OEM. This apparently satisfied the gov't. and allowed W.E. to continue to offer products such as their monitor systems, which contained the Altec-produced components, now labeled with "KS" numbers.

One funny story... I have seen at least two Altec hi fi speaker cabinets from about 1950-1952 on ebay that used shiny perforated metal discs to hold their fiberglass lining in place. Looking closely, I realized that these discs were identical to the metal rear plates on a W.E. 756A. Altec must have received a box of these along with all the other stuff from W.E. and found a use for them.

Altec continued to produce several of the W.E. drivers, horns and microphones through the 1950s. Most of them eventually left the catalog, but a few W.E. designs like the 755 continued to be produced through the 1970s and 1980s.

Apparently the government had good reason to go after W.E. in the 1930s, as they held a majority of market share in the theatre sound business and often acted as a tyrannical monopoly. I'm not sure why they hounded W.E. in 1949, except possibly to try and contain W.E's endeavors to the communications industry for national defense purposes. I have often wondered, though, if the awful performance of most current consumer loudspeakers would have been better if the government hadn't repeatedly driven W.E. out of the business. I suppose we'll never know the answer, but at least we can enjoy some of the surviving W.E. products. I got to hear a pair of 753C monitors recently and they were really something.

Best regards,

Steve Schell

Long Beach, CA

Co-founder, Lansing Heritage web site www.audioheritage.org

---

Altec 755C, Altec 755A and Altec 755E [left to right]

This 8" full range driver has achieved "cult status" amongst audio aficionados. The most desirable version are the ones branded with the Western Electric logo with the frame in smooth silver or textured charcoal greyish brown finish. The mounting gasket always had 5 - 8 quality control stamps showing the tight tolerance procedures excercised in their manufacture. The later Altec branded 755As only had 1 or 2 stamps but essentially looked the same and came finished in either textured charcoal greyish brown or silver hammertone. A lot of silver Altec 755As served as the midrange/tweeter unit in Edgar Vilchur's AR-1 speaker.

Aside from those quality control procedures and alnico magnet, what sets the 755A apart from the later 755C and 755E is the chemistry of the cone material. The procedure was very intensive according to Walt Bender, involving a "vacuum formed" process to produce a cone that contained silk and cotton components. This cone material is also found in original examples of WE/Altec 756A, 754A and 728B. Perhaps this contributes to that beguiling and lifelike midrange quality of a 755A that eludes the later "pancake" versions.

I have seen 755As without the WE or Altec logo but with a KS14703 decal. KS = Kearny Specification, a New Jersey subsidiary which supplied replacement parts for WE. These units may have been represented the final transition period from WECO to Altec. But take note that there are ferrite magnet "pancake type" with KS14703 logos finished in Altec green. These units are really 755Cs and should be identified as such.

Altec 755A

early to mid 50s

[alnico magnet]

Frequency Response: 70-13,000

Sensitivity: 81.5dB/8W/9M

SPL graph courtesy of Steve Schell

Nominal impedance 4 ohms

Impedance graph courtesy of Steve Schell

Typical prices asked for a mint matched pair of WE755s are in the stratosphere, about $3,000/pr. while the Altec 755A go for about 50% less. I never owned a pair of WE nor heard them in the context of my system. But I have heard them in familiar systems and honestly cannot hear much difference between the WE and Altec. Although my impression might change if I start splitting hairs....but I do not want to get into that, through the years I learned that if I can't afford it, I would not think about it.

Altec 755C

Introduced ca. 1961

[ferrite magnet]

Frequency Response: 40-15,000, Impedance: 8 ohms, Sensitivity: 95.5dB/1W/1.2M

In 1961, the "Altec green finish" 755C "pancake" was introduced and the alnico magnet was replaced by ceramic/ferrite. Although the cone looked familiar, the material is diferrent, indicating a move towards 'cost effectiveness'. An additional roll or two was also added to the suspension surround [more compliant] to extend bass response.

This unit was later replaced around 1969 by the slightly less efficient but still SE amp friendly 755E, also with ferrite magnet but the frame is now finished in white and blueish grey combination. The 755C usually came with the surrounds heavily doped, even running and staining the cone itself, whereas the 755E is typically doped sparingly.

Altec 755E

Replaced the 755C around 1969

[ferrite magnet]

Frequency Response: 40-15,000, Impedance: 8 ohms, Sensitivity: 92dB/1W/1.2M

These later versions should not be overlooked because they sound good. Supply is drying up but nice clean units with intact cones show up ocassionally at eBay - 755Cs normally trading from $700-$900/pr. and the 755Es for $500/pr.

I have not come across a modern 8" full range driver that sonically comes close, so they are still worth it in my opinion. Amongst the classics, the only 8" FR drivers I've heard that compare favorably are the rare and hard to find Japanese Pioneer PIM8L OEM for the Lafayette SK98.

The most important consideration when purchasing any of these drivers is to make sure that the drivers are matched! Since they were used in various applications, they may have been electrically damaged or physically abused. Typical problems include partially damaged voice coils. This usually shows up when tested with a DVM, for example the DC resistance reading on my Altec 755A is 2.2 and 2.3 ohms and 6.8 ohms for both 755Cs and 755Es.

At a reasonable price, slight cracks or splits in the cone material can easily be repaired with careful application of Elmers glue and will not significantly impair the sound, if the voice coil is intact. Unfortunately I am not aware of NOS replacement cones for the 755A. There may still be replacement cones available for the "C" and "E" but the availability of original voice coils for these models is also unconfirmed, I have a pair of 755Cs with damaged cones waiting for this procedure.

Here are some 755 sonic impressions from esteemed hobbyists collected from Sound Practices list archive:

Joe Roberts: "Well the 'C' is pretty good. A little bit less high frequency energy than the 755A but good nontheless. More tilted towards the lower mids and a little less crisp than the 'A'.

jc morrison: "by the way, i would also like to add that the later 755s are, in my not always respected opinion, much better than the early ones, which are too peaky for my taste [especially joe's favorite, the really dry cones...] i have heard a lot of 755s. i like the c's and e's crossed over to a tweeter (yegads) in a tapered pipe. these are some of the nicest direct radiating midrange speakers of all times. make a nice pipe drea with a 755C or E, add a focal titanium tweeter: nice, in my book anyway...."

Koji's [of EIFL] translation of Stereo Sound "Tube Kingdom" No. 3 comparison:

Altec 755A - "...reproduces musical sources as it is. The presence of musical instruments is excellent..."

755C - ".....sounds modest but sonic qualities very amplifier dependent. Very good for monitoring the sonic characteristics of amplifiers."

755E - "....also sounds modest, calm, thick and beautiful. Very good for a real audiophile."

WE 755A - "....you feel as if you were embraced with music. Sounds open and brilliant."

Sources and references:

• Stereo Sound Special Issue Volume 1 featuring vintage American speakers.
• Stereo Sound "Tube Kingdom", No. 3 and No. 26
• Walt Bender's "Ask Walt" essays in Audiomart and article on "Olden Goldies" published by The Absolute Sound in the '80s

Go to Part 2 (2 cf box)

Visit Joe Robert's Junkyard Jukebox for great WE 755A information!

Another site I just discovered with good information on WE/Altec 755s.

JE Labs Plinth

Any idler driven turntable should be free from vibration or rumble before building a plinth since a heavy plinth is not a cure for a worn out idler wheel or mal adjustment. 

I used my TD124 for several years on a stock box type plinth and my 301 spent months on a single layer of 3/4" plywood while I made sure it was working up to factory specifications. 

Turntable restoration sites:

Thorens TD124

JD's Garrard 301

Lenco Heaven

JE Labs Rek O Kut Tips

Only then did I avail of the benefits of a heavy plinth which in my experience serve to dampen the last vestiges of vibration from the heavy duty motors employed in idler drive design.

My choice of using layered plywood evolved from my open baffle project wherein I purposely avoided the damped everything approach. Besides I got used to working with the material. ;) I decided to make the plinth 20-30% heavier than the turntable assembly, not very scientific either. ;)

Construction is very simple, it is a sandwich layering [anywhere between 5-7 layers] of 3/4" Birch or Fir plywood boards clamped overnight using hide glue which is the preferred adhesive of violin makers. Using a jigsaw, I cut the first two or three layers based on the mounting template of the turntable and once the proper clearance [depth] is attained I usually leave the two bottom layers solid except at the arm mounting positions which should be pre-determined along with the motor board cutout. 

Fortunately my local lumber yard cut the boards evenly so that the sides square up nicely and only a touch up with a hand plane and sander is necessary to smooth things out.

My 301 plinth 24"W x 24"L x 7 layers of 3/4: plywood

Pictures of 301 plinths built by my SETUP buddies.

Living proof wood veneered MDF also works.

A custom base for a TD124 built using scrap pieces of Philippine Mahogany and other indigenous hard wood glued together. 

Some people claim the best material to build a plinth is using different types of hard wood glued together which is supposedly the Shindo approach in building his plinth. 

Have fun and happy listening!