Altec 290E - modify?

Greetings all,

I have acquired several ALTEC 290E drivers, without the matching 15045A transformer and the rear cover. From research, the driver has the same motor assembly including the AlNiCo V magnet as the 288, but is fitted with a phenolic diaphragm, which is allegedly more weather resistant and can handle higher power, since the driver was intended for public access and outdoor usage. There downside is limited frequency range of operation. https://greatplainsaudio.com/wp-content/uploads/2016/06/290-Series_hfdriver_spec_sheet.pdf

I confirmed that the motor assembly, i.e., the phase plug and the gap, is the same as the 288 by trying an Al diaphragm from the 288, which fits - in a third world wort of way. The problem is that the metal and plastic rim of the phenolic diaphragm has larger outside diameter and the holes for bolting the diaphragm to the top plate are on a larger diameter, so that the Al diaphragm cannot be bolted.

I do not think that there will be much interest in it, since the matching 15045A transformer and the rear cover are missing. Consequently, I was thinking about modifying it to accept the Al diaphragm. There appear to be the following options:

(i) re-drill the top plate, which de-valuates the drivers even more;
(ii) machine a ring that will bolt into the original holes in the top plate and secure the Al diaphragm; and
(iii) machine a new top plate.

(ii) and (iii) are attractive in that the modification is reversible.

Any comments?

Kindest regards,

M
 

GM

Member
Joined 2003
Yeah, designed for 300 Hz horns for public address (PA) AKA 'Giant Voice', so only ~300 - 8 kHz IIRC. Guess it depends on the machine shop since we're dealing with needing a high degree accuracy and ideally with locating pins if one doesn't have the correct installation shims.
 

GM

Member
Joined 2003
Greets! Re-drill unless you want an adjustable cradle to allow some error and let a VLF signal center it, then tighten. Not knowing if the 290 is truly a 288 not just in design, but in quality construction..........i.e. IME I know it wasn't uncommon to use failed QA parts, (sub) assemblies to make other products that had less strenuous requirements, so assume Altec was no different, especially with such a high cost product.
 
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Hi VoxCelestial,

thank you for your reply.

I am afraid (i) that I will be unable to center the voice coil and (ii) to prevent the glue to seep into the gap.

I have disassembled the RCA driver mentioned in another post and they do it in a manner similar to what I proposed in (ii) in my post # 1, so that is what I am now contemplating.

Kindest regards,

M
 
I am noticing a trend that while glues are very popular in industry in general and loudspeaker production in particular, a lot of DIYers are averse to or afraid of them. Glues are great, people! There are dozens of them, and for most applications a perfectly suitable one can be found. They can be as controlled, secure and reversible as thread joint.
that I will be unable to center the voice coil
With some practice, it's quite easy. Apply a layer of glue to the top plate and diaphragm mounting ring, roughly center VC by hand, apply 300-400 Hz sine to the driver, gently move mounting ring from side to side until buzzing stops. Do not wait for glue to dry, center on viscous layer - it will damp movement, increasing ease and precision. Even if you fail to center, you can always clean parts with xylene, reapply glue and try again - or drop the idea and make adapter ring. Basically, glue costs nothing in terms of risk and money, and little in terms of labour, so it's a very reasonable first step.
to prevent the glue to seep into the gap
A non-concern, really. First, whole thing is kinda huge and you have a few mm tolerances from ring to gap, second, PU glue is viscous and doesn't spread by itself, third, even if you somehow screw up and drop a drop of glue right onto the gap, it will not leak inside - surface tension and viscosity are just too high. Any undesirable glue is easily cleaned with a xylene wetted q-tip or cardboard shim for narrow spaces. PU glue does not really stick to metal the way CA or epoxy do and can be easily removed with zero residue.
 
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Must take the opportunity to ask you experienced people if my CDs are a "Baltec 290/288 or similar product" or another model.

They where made by AGA/Baltic in Sweden from ca 1930-1975in different modells over the years, its 20 ohm and weight ca 10 kilo each.
Almost no information exist because most "knowers" are not with us anymore, and the internet doesen´t exist before the 90s

Aga had 70% of all the movie theater in Sweden in the 50s, 60s and early 70s
Sounds so realistic and are real hi end stuff

Advertising from their sound film division turned ten years old 1939
It was a large Swedish company!

In hole
https://www.filmsoundsweden.se/backspegel/aga_1929-39.html

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Hi VoxCelestial,

thank you for the reply.
There are dozens of them, and for most applications a perfectly suitable one can be found. They can be as controlled, secure and reversible as thread joint.
Based on your description, I am tempted to try it. Is there a glue that you would recommend? it needs to secure metal to metal.

Even if you fail to center, you can always clean parts with xylene, . . .
Will the xylene seep into the space between the top plate and the diaphragm ring?

Kindest regards,

M
 
Is there a glue that you would recommend?
Unfortunately I, not being in the US, cant give advice on particular brands, but any polyurethane or neoprene glue would do; vinyl acetate copolymer glues are even more convinient.

I checked Wallmart, and its really frustrating how manufacturers are not obliged by law to disclose ingridients/composition. How the f am I supposed to guess if this or that particular glue is compatible with a particular type of polymer, solvent, paint? Here in Russia I can glance over the "Composition" section on the back of a tube and immediately have a general idea of glue properties and applications, but what am I supposed to gain from "All Purpose Adhesive, Irritates Eyes And Skin"? I guess this lack of transparency is what holds back more widespread glue use.

Anyway, E6000 or E8000 butadiene rubber glue is widespread and will do the job OK.
https://www.walmart.com/ip/Eclectic...hesive-with-Precision-Tip-Clear-1-oz/52678045

Will the xylene seep into the space between the top plate and the diaphragm ring?
Yes. Or you can apply it through syringe needle directly into glue seam, but usually pouring some xylene around the ring, maybe covering driver with a stretch film to slow down evaporation is enough. After few minutes of exposure gently lift the ring with a thin knife blade, add some more solvent if it doesn't come off completely.
 
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AFAIK/TTBOMK/YMMV, etc., if not KlangFilm based, then it's W.E./Lansing based, which the ad clearly shows, ergo so are the drivers.

Hahaha, i had to use Google a while to understand all your abbreviations :) ( I'm bad at them)

Interesting info GM (y)

Swedish AGA/Baltic was founded by Gustaf Dalén and was from the beginning just AGA.
He was awarded the 1912 Nobel Prize in Physics for his development the AGA lighthouse, which now secured navigation in waterways around the world.
(the company AGA/Baltic) was founded in 1908, and started in 1928 with sound film products (In 1927, Warner Bros. released the first sound film, The Jazz Singer), so AGA/Baltic was early into the business.

They made lots of things like,radios, televisions, projectors, broadcast radio, sound systems, record players and tape recorders, round radios, transistor radio tube/electron tubes etc...And all electrical "things" for the Swedish army

Most of the AGA/Baltic was acquired by Siemens, AEG/KlangFilm & Philipps in the end, so i think all of them had spies and circumvented each other's patents.
 
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