Wooden tractrix horn question

[gaspr]

All of the home built mid horns that I have seen, have the two sides curved, and the top and bottom panels are flat. Has any one tried to design or build one where the top and bottom panels are the curved ones and the side panels are flat? Seems to me that if this were possible, that it might well improve the horizontal polar patterns of these horns, although the verticals may be squeezed... Floyd Toole teaches us that good dispersion at all frequencies, is a common denominator of all good speakers...seems that if the room reflections contain the same spectra as the direct sound, that they are not perceived as separate or distinct and therefore contribute to the overall spaciousness of the total sound...Any thoughts??

[Al Klappenberger]

Gaspar,

I did look into doing that. As it turns out, a horn with a given mouth size will have a lower Fc when the top and bottom (the longer dimension) is the curved side than the shorter dimension, BUT, it becomes very difficult to make. I think Bruce Edgar does make some of them that way. The salad bowl horn is the end result of your thinking though.

A horn with a mouth size of 20 X 7 inch will have an Fc of 264 Hz with the top and bottom curved, but will be 309 Hz the normal way.

Al K.

[Guest David H]

I suppose it is possible, but the horizontal expansion would grow so rapidly you would have to squeeze the throat of a one inch driver down to a half an inch around the one inch marker, then start your expansion. I think this would be much more difficult to build.

Dave.

[Al Klappenberger]

Dave,

You have my Trachorn computer program. Just input the mouth dimensions into the program in the opposite order. It will give you the taper.

Al K.

[Chris A]

Floyd Toole teaches us that good dispersion at all frequencies, is a common denominator of all good speakers...seems that if the room reflections contain the same spectra as the direct sound, that they are not perceived as separate or distinct and therefore contribute to the overall spaciousness of the total sound...Any thoughts??

If good sound is your measure of merit (as opposed to "looks" or "buildability"), then I'd look at this for 1" diameter throat drivers, and this for 2" drivers. I think that you will find that hybrid conical/tractrix sections might sound best at midrange/tweeter frequencies, exponential horns work best at lf. This is an opinion that is shared by a few folks here.

Chris

[Guest David H]

Dave,

You have my Trachorn computer program. Just input the mouth dimensions into the program in the opposite order. It will give you the taper.

Al K.

Yes, I did that AL. I may try to build a horn in this fashion, to see how difficult it would be, I imagine the flair would be a very tight radious.

We'll see how it goes. This horn would look like a trumpet from the sides, however if this is a feasable build it would solve some size contraint issues.

Dave.

[Chris A]

Rationale for the conical horn discussion here.

A quote:

"Since conical horns have no curvature, the ever emerging wave is not deformed as it moves from the throat to the mouth. This means that there is a linear pressure change throughout the horn.

When this condition is met, the horn will have very low 'air column' distortion, or distortion cause by squeezing the air at the throat. Conical horn also have good phase response, due to the reason stated above.

In short, the conical horn amplifies the sound, with the least disruption to the sound wave.

The sound of a conical horn system has very little trace of the 'honky' sound usually associated with horn. Because the horn has good phase response it can be crossed over with another horn or direct radiator very smoothly."

Now I don't necessarily adhere to the comments shown above, but I hear many good things about this guy from folks whose opinions I really respect.

[seti]

Rationale for the conical horn discussion here.

A quote:

"Since conical horns have no curvature, the ever emerging wave is not deformed as it moves from the throat to the mouth. This means that there is a linear pressure change throughout the horn.

When this condition is met, the horn will have very low 'air column' distortion, or distortion cause by squeezing the air at the throat. Conical horn also have good phase response, due to the reason stated above.

In short, the conical horn amplifies the sound, with the least disruption to the sound wave.

The sound of a conical horn system has very little trace of the 'honky' sound usually associated with horn. Because the horn has good phase response it can be crossed over with another horn or direct radiator very smoothly."

Now I don't necessarily adhere to the comments shown above, but I hear many good things about this guy from folks whose opinions I really respect.

Bill Woods of acoustic horn is very interesting. I'd love to hear his horns especially the AH!500.

[Al Klappenberger]

Dave,

I think the problem building it will be making that complex cut to the flat pieces that must be done on a band saw. It's going to take some sort of imaginative jig to do them one at a time. It may also require several support pieces across the front of the horn similar to with Altec used in the 511 and 811 VOT horns. When I made the very first Trachorn, I had to make the flat pieces by hand, using a file because I have no band saw! GOOD LUCK!

Al K.

[Guest David H]

When I made the very first Trachorn, I had to make the flat pieces by hand, using a file because I have no band saw!

AL, that is dedication, and we are all glad you tried it. I dont have a bandsaw either, I usually use a CNC router for my master templates, then replicate.

Here is a pic of the router from when I had an unsucessful business building and selling model airplanes.

[bluesboy]

I've been thinking about turning some round horns on my lathe for a while now. Can any of you guys come up with a plot for a 400hz round horn?

[gaspr]

Has anyone tried rotating the trachorn or the fastrac horn 90 degrees to see if the were more or less beamy (horizontally) with the higher frequencies?

[Chris A]

Can any of you guys come up with a plot for a 400hz round horn?

Here is a tractrix calculator, and here is the technique of building round tractrix horns. My guess is that you need something with a mouth diameter of about 800mm to have enough performance to crossover at 400 Hz (see the AH-204 here and its performance using a couple of drivers) and still have good performance in the crossover region.

[Marvel]

Here is a calculator,...

Erik's rectangular tractrix horn has the curves on the top and bottom as the defaults, with the flats for the sidesl, as you can see on his spreadsheet and in the pics of his tractrix midbass horns.

Bruce

[Chris A]

Eric's rectangular horn has the curves on the top and bottom as the defaults, with the flats for the sidesl, as you can see on his spreadsheet and in the pics of his tractrix midbass horns.

Marvel,

Yes, but I think bluesboy asked for a round horn design...Did I misunderstand?

Chris

[bluesboy]

Eric's rectangular horn has the curves on the top and bottom as the defaults, with the flats for the sidesl, as you can see on his spreadsheet and in the pics of his tractrix midbass horns.

Marvel,

Yes, but I think bluesboy asked for a round horn design...Did I misunderstand?

Chris

That's right. I'm looking for a round design that can be turned on a lathe.

[Chris A]

This is what I was looking for earlier, but I just couldn't put my finger on it. It is the technique of stacking MDF and turning it on a homemade lathe.

Chris

[Marvel]

Marvel,

Yes, but I think bluesboy asked for a round horn design...Did I misunderstand?

Chris

The original poster (gaspr) was asking about turning the horn vertically. I understand that Bluesboy asked about the round horns.

Turning that mdf will sure make a lot of dust and dull the bits pretty quickly. I think Erik did some of his smaller horns with stacked mdf.