Help make a tractrix horn for Altec 290-16K driver

[George Roland]

I just purchased a pair of Altec 290-16K drivers on e-Bay and I would like to try to build some 300Hz tractrix horns to attach to them since proper 300Hz Altec horns seem to be so rare and expensive.
If anyone has built such horns, I would be greatful for your help and advice.
I have seen Dr. Bruce Edgar's article on how to build such a horn for a cone driver, but I don't know how to calculate the dimensions needed or how to mount the horn to the rectangular end of the horn--kind of fitting a round driver to a rectangular mouth!
Thanks,

George

[taudo]

I got some nice 400 hz tractrix horns for my 802's from a group in Germany called

www.stereo-lab.de

It's a bit hard to get through the language barrier, but the folks there were quite helpful. Maybe the'd have what you want?

taudo

[jnorv]

I just ordered up a pair of their 1.4", 400 Hz horns. How long did it take for them to come?

Jim N

[jnorv]

$330 with shipping and currency conversion.

Jim

[GM]

Greets!

The 300 Hz multi-cells are true 300 Hz horns while a typical 300 Hz tractrix is actually a ~424 Hz horn, so for a true 300 Hz tractrix loading it will need to be a much larger ~212 Hz horn, so ~14.4" dia. x ~14.6" long Vs ~20.4" x ~24.2" plus its increased beaming/narrower 'sweet spot'. Really, it boils down to the desired XO point/slope as to what minimum size to buy/make.

If you make it a radial, then basically you make the throat 1.4" square and use wood putty or similar to blend it from round over several inches of length.

GM

[jnorv]

The 400 Hz German Tractrix horns are 300 mm dia x 280 mm long. When I run it thru my Tractrix calculator, Fc comes out to be 360 Hz which is just about right for a 500 Hz crossover.

Jim N

[GM]

Yeah, it's about the minimum size for a 500 Hz XO.

[jnorv]

That is one of the nice things about electronic crossovers. If it waont go to 500, just boost the xover frequency.

Jim

[George Roland]

How much did those horns costya?

George

[George Roland]

Jim,

Is your tractrix horn calculator someting computer-based and available to the public? Does it allow the user to calculate dimensions for rectangular as well as round tractrix horns? That'd be sweet!

George Roland