Western Electric KS12046

[tomt]

These speakers couldn't have been that expensive to make - since they were only selling for $30 each when new.

back when these were made,

federal minimum wage was 75 cents an hour. (1955)

by 1965, $1.25.

dollars then vs. dollars now ...

The ferrite 755C,
but it is also nothing special.

i'd have to disagree about that.

(though i suspect the 'A's to have more/better resolution)

i had 4 per channel, on an open baffle.

6.5 or 7 feet high, two feet wide.

lo powered 6L6 tube amps.

j-fet pre-amp.

except for the beaming,

they sounded much like the 1989/90

martin-logan cls.

--------------------------------------

i'd left a space for tweeters, as i have still several of these -




this is the Polydax / Audax HD13D34H.

these have an acceleration factor of more than 7500 meters per second.


if your amp/electronics can keep up ...

[wws944]

I found some specs on the 755A. Looks like it has 1.3 lbs of Alnico:

http://www.lansingheritage.org/image...755A/page1.jpg

and:

http://www.lansingheritage.org/image...755A/page2.jpg

Googling around, here are some modern full-range drivers that make many of the same claims. He has a choice of ferrite, Alnico, and neo magnets. A big difference is that they use whizzer cones w/phase plugs instead of biflex cones. He is asking $500/pr for the 8" Alnico model:

CommonSense Audio

Did the 755A (or C or E) have the traditional Altec edge-wound voice coil?

[bowtie427ss]

i'd left a space for tweeters, as i have still several of these -




this is the Polydax / Audax HD13D34H.

these have an acceleration factor of more than 7500 meters per second.


if your amp/electronics can keep up ...

An exceptional tweeter. Westlake used them in my BBSM-10's as well as a couple other models.

The Westlakes have a removable metal bug/dust screen that is held in place by the magnet. Do you know if the bug screen is a product of Westlake Audio or Polydax/Audax?

[Geekstar]

I saw those Altec 755A data sheets and I don't think the 1.3 lb figure for magnet weight is correct. 3.1 pounds is more like it.

The speaker is heavy @ 5 lbs. The magnet is very large and solid AlNico except for a groove on the bottom (against the frame) for a charging coil. The rest is made of thin stamped sheet metal. It seems obvious to me, holding one in my hand, that the magnet constitutes most of the weight of the driver.

I know the donut magnet in the 12" 728B weighs 10 pounds but i can't find any WE data on the magnet weight in the 755A.

In any case, it would be a very expensive magnet to manufacture today. The end product would have to sell for at least $500-600 each to make any sense, and that is before factoring in tooling and minimum orders for the cones.

I know somebody who has special mix hot press paper cones made. He pays a few dollars each but has to order 10000 units at a time and he had to pay around $15000 to have the mold made--and that was a simple curvilinear woofer cone, not a complex structure like the 755A "diacone" construction.

except for the beaming, they sounded much like the 1989/90 martin-logan cls.

Does that make them special?

The 755C is a very decent 8" for sure but there are many other good 8" cones, new and old.

Nothing else sounds like a 755A though...that's what I am calling special.

[Alien_Shore]

Sparkling, astounding triumph.

[Geekstar]

Yeah I know I sound like a broken record... but the WE/Altec Alnico cones are the only speakers that, 25 years after I first started using them, I sit and listen amazed with a stupid grin on my face the whole time.

They don't do this to everybody, but the 755A really gets inside my head.

I owned and heard a lot of speakers but the 755/756/728/754 based setups are really special to me.

Astounding triumph, indeed!

[wws944]

Someone must have seen the last pair on ebay, and now wants to cash in on his. Asking $9500/pr - very used and no original boxes: RARE Pair Western Electric KS 14703 755A Speakers Original Cabinets w KS12048 | eBay

Rereading Badmaieffs biflex patent (Patent US2834424 - SOUND-REPRODUCING DEVICE - Google Patents), he documents a frequency response dip when the inner and outer areas of the cone are out of phase with each other. He resolves this by applying a 'viscous damping fluid' both at the corrugated area between the two cone portions, and also at the edge of the cone.

Looking at photos of a 755A, as I have never seen one in person, it seems there is 'goop' around the edge of the cone - as is common with a lot of Altec drivers. However, there doesn't seem to be any mid-cone. So do the 755A and friends have a problem with the response dip that Badmaieff documents? Or perhaps damping the outside edge of the cone was sufficient?

I might add that it is interesting reading through some of the early (1930s, 1940s) patents on these types of cones. The Stevens patent the Badmaieff patent refers to, 2549139, refers to quite a few of these. (My father used to tell me that I should have become a patent attorney...)

[Geekstar]

The WE speaker line which featured the 755A was introduced in 1947-1948.
I have not found any WE patents relating to this cone design.

I vaguely recall a few lines in old articles about these cones but those brain cells responsible for that data storage drifted away some time ago.

You can read the 1947 WE Oscillator article on these speakers in the article linked below.

http://silbatoneacoustics.com/images...oudspeaker.pdf

I 'm seeing the cone in light of the 10 year later Altec design but there might be differences between the two in intent and implementation that we'll never know about.

The point I made above about the variable thickness cone came from somebody who measured it.

The USPTOs image reader is crashing my browser when I try to read the Altec patent but I'll try a few other approaches. Thanks for the link!

[wws944]

No problems here reading those patents, using either firefox or chrome (on linux).

The 1947 article is really good. Thanks for sharing it. I briefly tried searching for some relevent WE patents as well, but so far have come up empty handed. Wonder if they were ever documented in the BSTJ?

I have a really good book on the Bell System ("Engineering and Operations in the Bell System", 2nd edition). It is a 800+ page tome with lots of cool techie info. The book was compiled in the early 1980s and documents the Bell System just before it was all broken up. Looking through it, there is no technical detail about the audio/theater stuff that was spun off in the late '40s. Just some descriptions of the various regulatory and court actions.

[Geekstar]

Western Electric's accomplishments in theater sound are largely forgotten by most, although rediscovered by the hobby audio world over the past two decades, and even more so the studio and PA electronics of the mid-late 1940s.

All of this equipment and technology is very sparsely documented. I have have a collection of copies from various Bell publications I made at engineering libraries and the library of Congress but they are currently in storage. Who reads books in this Google age?

One thing to note about the 755A is that the advertising mentions "Presence." The speaker was designed for high intelligibility and peaks are engineered into the response. With a proper amp, and I can't quantify that, the 755A takes on a lively exciting character. With the wrong amp, it will take your head off. You will find user reports swinging both ways. A lot of people tried 755as and couldn't get rid of them fast enough! Tricky sucker!

I read somewhere that the 755A was based on fundamental hearing research in a number of ways, one being the balance of the high and low cutoff, note the speakers that go lower cut off in HF sooner, and another being the intelligibility research done as part of Bell's concern with transfer characteristics for phone transmission.

Mention was made to empirical research in hearing performed with tens of thousands of subjects at the World's Fair playing a role in the voicing of that speaker. by the standards of that study, the HF response of the 755a was way extended. I think they talked about 8kc as the goal for full frequency response.

My sense is that the 755A cone characteristics and that molded in compliance are part of the response shaping rather than decoupling strategy we see in most "diacone" approaches. Also, marketing play was made of the flat profile of the 700 series speakers for installs. Later, the 755C was called the "pancake" in Altec lit. A 12" Jensen is twice as deep as a 728B.


Here, have a look at the 1947 WE loudspeaker catalog. These are all really really good parts.

http://silbatoneacoustics.com/images...speakers47.pdf

I like this stuff more than the legendary field coil theater gear in a lot of ways. At one time I had a good collection of this gear. Now I can't find it and couldn't afford most of it if I did.

I have a pair of Altec 756Bs and working on getting a pr of Altec 755As boxed up and playing. I get to hear 757As, L-8, L-9s. etc. though my connection with the Silbatone collection and took them to a few hi-fi shows for educational outreach.

On the one hand, I believe that knowing the sounds and having a catalog of the sound in my head is more important than owing tons of rare gear, which takes a lot of dedication and space...on the other hand, I want a pair of 757As!

--------------------------

Indeed, if you look up Hopkins 1946s WE patent US2549091 (cited in Badmaieff 1956) and go though the prior art Hopkins cites, you will have a good idea of the technical space WE was working in with these cone speaker designs.