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Making a Square Tractrix Horn
Making a Square Tractrix Horn
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Old 2nd November 2018, 07:14 AM   #31
kokoriantz is offline kokoriantz  Lebanon
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With Rhino you can easily ply the horn in a desired pattern defined by an independent curve ,so that waves that are already propagating at the troth reach the mouth reflected , hence avoid cavernous sound and of course more compact horn . See ex. Of WE and several Japanese realizations. Most popular material used is mazonite. It can easily get formed by steam iron , temporary wooden structures holding than fiberglassed. The first 1/8th wave length is transformed externally into cylindrical so that the fiber glass fiber is wound around. This avoids the low frequencies be attenuated . Internally the mazonite can be painted with Elastomer of
Desired color used to waterproof house decks.
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Old 12th November 2018, 04:46 PM   #32
midrange is offline midrange  United Kingdom
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Making a Square Tractrix Horn
Quote:
Originally Posted by David McBean View Post
You are making heavy work out of what can be reduced to a very simple exercise using Hornresp :-).

Given that the intended mouth size is 3' x 3', what are the proposed throat size (W x H), and tractrix horn length (or horn cutoff frequency)? If you care to post this information I will provide you with the details you are seeking - and you won't even have to learn how to use Hornresp!
Thank you for this kind offer which I now wish to accept.

The throat size is 4" x 4".The mouth size is 3ft x 3ft. A full tractrix is what my friend is seeking (as I interpreted the example spreadsheet you provided)

I am very grateful not to have to learn how to use Hornresp.

Do any of the numbers supply the tractrix curve that the four petals construct into. (Just wondering for ease of making supports for the petals)

With thanks.
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Old 13th November 2018, 07:30 AM   #33
David McBean is offline David McBean  Australia
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Hi midrange,

Quote:
Originally Posted by midrange View Post
The throat size is 4" x 4".The mouth size is 3ft x 3ft. A full tractrix is what my friend is seeking (as I interpreted the example spreadsheet you provided).
The tractrix horn meeting the above specification has a throat area of 103.23 cm^2, a mouth area of 8361.27 cm^2, an axial length of 97.69 cm and a flare cutoff frequency of 106.12 Hz.

Plot 'Side Len' against 'Width /2' to obtain the cutting pattern for one half of a flat uncurved petal. The full flat uncurved petal should look like the one shown in Attachment 1.

Quote:
Originally Posted by midrange View Post
Do any of the numbers supply the tractrix curve that the four petals construct into. (Just wondering for ease of making supports for the petals).
Plot 'Length' against 'Inradius' to obtain the profile for the petal supports. The petal support profile (for both the width and height supports) should look like the one shown in Attachment 2.

Kind regards,

David
Attached Images
File Type: png Attach_1.png (39.4 KB, 217 views)
File Type: png Attach_2.png (40.2 KB, 217 views)
Attached Files
File Type: txt Tractrix.txt (6.2 KB, 22 views)
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Old 13th November 2018, 09:23 AM   #34
midrange is offline midrange  United Kingdom
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Making a Square Tractrix Horn
Fantastic. Thank you so much.
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Old 14th November 2018, 06:16 AM   #35
David McBean is offline David McBean  Australia
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Quote:
Originally Posted by midrange View Post
Fantastic. Thank you so much.
Not a problem :-).
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Old 16th November 2018, 12:04 AM   #36
xrk971 is offline xrk971  United States
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Making a Square Tractrix Horn
This is a very handy feature to make flat plan profiles. Cool!
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Old 16th November 2018, 11:15 AM   #37
midrange is offline midrange  United Kingdom
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Making a Square Tractrix Horn
I note that in #27 I was asked for three variables: throat size, mouth size, and horn length, and that horn length would affect the cutoff frequency. So if the horn was longer, the cutoff frequency would be lower, at the expense of ripples in the bass due to the mouth no longer being optimal? Would the ripples begin below where the mouth is too small?

If this is the case it seems that it could be a viable compromise (within limits) in that in a normal living room bass response is fairly non linear anyway.
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Old 16th November 2018, 10:07 PM   #38
DonVK is offline DonVK  Canada
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I've made a few smaller petal horns using hornresp.

If you make the horn longer, with the same mouth and throat area, it will not be fully formed (exit <90deg) but will go lower with ripples (see pic). I don't think the exit angle matters at these low freq but the size (3m long) will surely roll some eyes. I attached a sample graph from hornresp.

There is also the possibility of using more petals (than 4) to get the side width smaller to make to wood easier to bend and easier to dampen.
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File Type: jpg midranges tractrix xtralong.jpg (69.3 KB, 87 views)
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Old 16th November 2018, 10:53 PM   #39
tapestryofsound is offline tapestryofsound  Scotland
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Quote:
Originally Posted by DonVK View Post
There is also the possibility of using more petals (than 4) to get the side width smaller to make to wood easier to bend and easier to dampen.
Yep, second that. With 4 petals, depending on the thickness of the material, there will be quite a lot of tension around the mouth. Might need to be attached to a support frame to stop the panels from bowing. But then again, the bowing can look really nice .......

8 petals is a lot easier to work with. 16 petals would be a doddle - virtually a round circular mouth exit. OK, its four times the work, but as you know, building horns is just crazy anyway.

If you do go with four petals, you can work with either Masonite or MDF that is pregrooved on one side to make a somewhat easier bend without too much effort.
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Old 17th November 2018, 01:50 AM   #40
DonVK is offline DonVK  Canada
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@tapestryofsound : I prefer odd number of petals to avoid symmetry. I believe your past horns have been in this size range.

@midrange : if you want I can run a few hornresp models for you as well, if you let me know what changes you need. It would also help to have the driver you intend to use so it could be included in the sim.
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