Tractrix Getting it right

[David R. Carlso]

Does anyone have access to the patents and any writings by P.G.A. Voight on the tractrix horn, the only thing that seems downloadable at this time from the varous sites maybe differnt from what Voight had layed out, possibly to compensate for the problem of not loading all of the way down to the design Fc. Or do we just take the Fc that we want and lower it by about 25% to reach our target freq.?

[tinitus]

I was once told to use at stick of a certain length .... and the flare comes by itself .... no, not a magic stick its true allright ... something about moving the stick in certain incrediments(?), crossing the previous point

[Scottmoose]

I've got Voigt's 1926 patent application ('Improvements in Horns for Acoustic Instruments') re the tractrix contour on my computer at the moment. It's a bit of a pain to read as it's in 4 separate pdf files. If you PM me, I'll send you over a copy.

FWIW, I don't like the tractrix contour for bass horns. Give me a good hyperbolic or hypex any day. It's fine for the midrange etc of course, and to be fair, a friend of mine built a superb pair of tractrix bass horns for his EX4s, so YMMV as ever.

Scott

[David R. Carlso]

Dinsdale gives an illustration of the of the graphical construction of the Tractrix, you can down load a copy of the articule from

http://www.volvotreter.de/dl-section.htm

[GM]

Greets!

Well, when I did it was closer to a half octave (0.707*Fc), but the problem is that the low throat distortion you use the tractrix for is now worse than if you'd used an expo with a tractrix-like mouth end correction. Then there's the much increased beaming issue..... Not many 'free lunches' in audio design.

GM

[David R. Carlso]

It's interesting that the .707*Fc comes close to what is stated in the HornClac Tractrix software documentation. There it is stated that "P.G.A. Voight can be claimed to calculate: Fc=c/(4*r)." If this is true then the horn is even larger then what you've come up with.

[Cloth Ears]

James Melhuishs' Tractrix Calculator.

[GM]

Originally posted by David R. Carlso
......."P.G.A. Voight can be claimed to calculate: Fc=c/(4*r)."

Interesting, never seen this before and according to it the horn I built should have been another ~5.83" long, which I know isn't true, so I have to wonder if it's just an approximation for patent/whatever purposes.

[Scottmoose]

I think it's more of an assumption on the part of the the author of the HornCalc software, although Voigt clearly generalised -reading p.2 of his patent, he didn't make quite such a specific claim; only that "...such that the sound is expanding as if the source was at the fixed distance which is at least a quarter wavelength of the lowest frequency at which full efficiency is required, away."