Multicell construction

[bfish]

Do any of y'all happen to have any info to share regarding the sheet-metal construction details of Altec multicells? I've never owned any, or even had a chance to study any up close. I'm assuming each cell is simply 2 sets of four identical pieces, or maybe 2 pair, with leaded joints, tar potting in the voids, and all joined to a "header"/throat. I'm also prepared for that assumption to do what assumptions do...

More than once, a (fleeting) curiousity along these lines has made me consider an attempt at building some multicells, as I still have access to a well-equipped metal shop. There's even a CAD plasma cutter to make quick and efficient cutout of bulk parts, plus all the requisite brakes, shears, etc.

A template sure would be handy.......s'pose I could buy a pair to study, but then I'd have no reason to build any......

I've too many unfinished projects to start anything seriously yet, but I thought I'd just shake the branches a little and see what falls out.

[Steve Schell]

Below is a link to a picture of the multicellular horn building bench at Lansing Manufacturing Company. This picture was probably taken at about the time of the formation of Altec Lansing in 1941.

To the best of my knowledge, an individual cell was constructed of four stamped sheet metal pieces. Two of them were shaped like the interior of the cell, and the other two had additional widths on both sides that were bent over to provide a seam for soldering. Once the cells were soldered, they were assembled into a cluster and soldered together. Small pieces were soldered on to finish off the cell joints in front, and the assembly was installed into an outer sheet metal casing. The brass throat flange was soldered in place, then the whole shebang was filled with molten tar through a hole in the casing. The hole was covered up with a soldered patch, then the horn was painted.

There is an article by C.G.McProud in an early issue of Audio Engineering magazine that describes this process in detail. The article is included in Audio Anthology Volume one, which is available in reprint form from Old Colony.

[Steve Schell]

Oops, here's the link:

http://www.audioheritage.org/html/hi...nsing/lmco.htm

[GM]

Greets!
Back in the '60s I made a mold of a tar filled 1803 that had its driver off for repair and found that it would only ~fit some of the cells, and not knowing diddly at the time why they wouldn't be all the same and didn't have it available long enough to go through the hassle of potentially making a bunch of different plugs, etc., I didn't pursue cloning it, though this tidbit of knowledge ultimately gave me a keener insight into the basics of pattern control, not to mention the early designer's attention to detail and the 'bean counter's' $nightmare$ the early multi-cells must have been.

Anyway, it had different horizontal and vertical dims, though it calc'd as an expo flare by area, so how you allocate it will dictate its pattern control, though the tricky part is the common throat that unless you can make a mold of one for the desired cell layout would probably be a very time consuming R&D 'adventure'.

If I haven't 'rained on your parade' enough to dampen your spirits, experiment with a M = 1 (expo) flare factor 6.375" square mouth/0.75" square throat x 16" long. This yields a ~288 Hz flare frequency, 600 - 5100 Hz cell that when eight are ganged together yields a 300/500 Hz horn with low/high power handling - IF you can get them properly combined acoustically to present a uniform load over such a wide BW to the driver. If nothing else the R&D will garner you enough practical theory to design some bodacious performing intake/exhaust plumbing for a big block driven bass boat.

GM

[Steve Schell]

Hi GM,

Here's some minutia and speculation; you may have had one of the earliest multicellular horns produced by Lansing Manufacturing Company. For the first couple of years their horns had details similar to Edward Wente's original multicellular horns as illustrated in his U.S. Patent #1,992,268.

In Wente's horns (used in the Bell Labs Fletcher Horn System), the earliest Lansing and RCA horns and presumably in the Shearer prototype horns, the cells begin as nearly parallel in the throat, then curve to find their individual axes. In Wente's compression driver, the circumferential phasing plug and internal throat section were designed to create plane waves. The horn begins with a short adapter followed by the cells which begin in a plane. Another feature of these horns is that the cell mouths are brought tightly together; they had not yet begun to use the vertical spacers that allow each cell to remain square at the mouth. The cells, especially the outer ones, are forced into parallelograms. The mouth of an early Lansing 805 horn can be seen here:

http://www.audioheritage.org/html/pe...ives/found.htm

In about 1937 Western Electric informed Lansing that he was violating their patent by using the circumferential phasing plug. His driver was modified to have a radial slit phasing plug. This is also about the time his horns were changed to have straight cells that clustered into a spherical section in the throat. I have suspected that patent issues may have been involved here as well, or maybe it was just the adoption of a simpler method of construction. I think that all Lansing and Altec Lansing horns had identical shaped cells after about 1938. You can see them stacked in the picture of the Lansing factory. The RCA multicellulars, which retained the cell dimensions of the Shearer horns (as did the Lansings), had the curved cells at first, but changed to straight cells at about the same time as the Lansings. Lansing may have built RCA's early curved cell horns, but I've never been able to pin this down.

[bfish]

Steve,
Thanks! Your description of the process is pretty close to what I suspected. Back when this kind of thing was done the hard way, tinbending was quite an art. My old HVAC instructor was old enough to have been there, and the things he could do with a hammer were just plain amazing.

I'll look for McProud's article, it sounds like just what I needed (except maybe a 3D wireframe and a detailed cutsheet!).

I hadn't considered the wavefront from the driver in relation to the header arrangement. Wouldn't tangerine-laden drivers deliver a spherical front? It seems that equal-length straight cells would naturally terminate in a psuedo-sphere.

GM,
It wouldn't take more than a heavy dew to rain on this parade, it's just another of those things I've pondered over. In my mind's eye, I'm seeing brass and silver solder....something tells me any flaws in the solder work would buzz in a big way, and brass would be the best for a good solder base. Creating the cut sheets for precision assembly of the first run is the hard part for me, I'd have to cut up a lot of cardboard to get it right.

You gave me enough to start with, though. Next time I'm snowed in I may give it a whirl.

[Todd W. White]

The cells come to a point around an imaginary sphere in the throat - they're also razor-sharp where the cells meet, one of the reasons why plastic versions (like the prototype Altec made that I have) didn't work - they could get the cell geometry, which is NOT identical, to work, but they couldn't get the place where the cells met sharp enough to prevent reflections going back up the throat to the driver and making it sound bad.

[Steve Schell]

Bfish, the early Lansing horns were made from a thin sheet steel that came from the manufacturer with a thin coating of lead on both sides. This made soldering easy, but I doubt if we could find this material these days. The soldering joints were made by sliding a big ol' soldering iron along the joint while feeding solder. The irons weren't electric, but the tips were placed in a fire when not being used. Those guys were good as the workmanship is impeccable, especially on the earliest horns.

Todd, the workmanship is indeed beautiful on the horns where the cells begin in a plane. Both the Western Electric and earliest Lansing multicellulars were made this way, with the cell edges in the throat filed to knife edges.

[GM]

Originally posted by Steve Schell:
Hi GM,

Here's some minutia and speculation.....

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

Thanks for the history 'lesson'! Truth be told, I called it an 1803 since it resembled later ones I've been around and didn't feel like typing in a bunch of irrelevant info in answering BF's Qs, but since you mention details.......

This one was owned by a crusty old EE that was a pardner at the first engineering firm I worked at. He claimed it was an all WE system from his time at Bell Labs in the '30s. At the time I had pretty much zero interest in 'ancient' audio history though, so any of his ramblings other than what passed for technical answers to my horn design theory Qs 'went in one ear and out the other without slowing down' and by the time I did get interested, he was gone and no one I asked had a clue what had happened to it. Considering the consumer and prosound business 'climate' here at the time of death in the early '70s, it more than likely was s c r a p p e d.

For sure it didn't have axially curved cells, but they were longer than any labeled JBL/Altec's I've seen and transitioned to ~round at the throat, which were all tapered and soldered together with a flange that bolted to a short pipe adapter that the driver mounted to. Never having seen any other really early WE/JBL/Altec multi-cells AFAIK, I just assumed that they were all like his. Sonically, I preferred my brand new A7 cloned bassbins to his huge OB, but that horn made my 511s sound like anemic tweeters and why I was interested in trying to clone his, which had what we now call a small format driver also. Several years later I was able to score several late '50s 210 cabs and 288/805s, but I wasn't nearly as impressed with them and ultimately went back to my (by then) much modded 511s. Today would be a different story though now that we have the option of BW limiting them and electronically aligning a super tweeter relatively cheaply.

Anyway, between Wente's patent drawing, your info, and what I recall, maybe his claim that it was a 's c r a p p e d' prototype was true.

GM

[GM]

Originally posted by bfish:
In my mind's eye, I'm seeing brass and silver solder....something tells me any flaws in the solder work would buzz in a big way, and brass would be the best for a good solder base.

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

Well, if tar filled, it won't be an issue, but if just undercoated or similar, then it could be, so yeah, if made from metal I'd use brass too. Better yet, use lead sheeting if it's still available. This would allow you to easily morph them from square to round at the throat. FWIW I had planned to use paper-mache, at least for the proof-of-concept.

GM