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2" tractrix horn, any interest?

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SouthwestCNC View Drop Down
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    Posted: 28 February 2017 at 12:00am
Hi There.

I'm getting a few 2" throat tractrix horns made up by a boat builders next door to us. The current quote is £100ea 6mm walls, gel and 8x reinforcing ribs which I feel is a bit steep. But then again I watch these guys build 200ft fiberglass catamaran's and know their quality of work is high and the horn is quite large at extremities of the mouth not including surround measures 585 x 428 & 368mm deep.

response looks good 106 db @ 300hz , directivity good also 50/40.

Thinking if anyone else is interested at cost price might be able do get that price down somewhat in a larger order. Message me if you're interested.

As I'm cnc'ing the mold there is room for customisation of the mouth surround and throat plate, and gel colour all within reason.

TIA

Image and comsol sims.



Horizontal


Vertical








Edited by SouthwestCNC - 28 February 2017 at 12:32am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 7:25am
My only comment is that if you're going to the effort, I would pay more attention to the mouth termination to reduce any possible diffraction effects.  Check out the mouth on the 18Sound XT1464.

The other issue you might have is the width.  The 'magic number' for the width of cabs for standard truck packs is 580-600mm.  Ideally you'd want to be able to keep the horn, plus 15/18mm of wood either side within that.  If you don't care about truck packs then it's not a problem.

I don't have any need for any I'm afraid but I'll be interested to see how they come out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 9:15am
Thanks for your comment. The mouth termination of the xt1465 only appears to be a larger roundover because it has added thickness on the four corners of the front surround but only on the 4 corners. The roundover at its centres is infact only 10mm in radius. Adding thickness to the corners is fine in a small injection molded horn like the xt1464 not so practical with a large glass one. And the sims are not showing any diffraction (that is a 20mm roundover so scale for scale it is infact larger than the xt1465 along its centre planes )

To make it smaller is going to shorten the horn an raise the response & Cant make it more round without a negative effect on directivity. Got to be compromises if you're looking for a 300hz horn and it sounds like that could be one of them unless of course you were to put it inside an eliptical shape fiber glass casing. It would then fit inside the truck pack at an angle.



Edited by SouthwestCNC - 28 February 2017 at 9:16am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 9:16am
I think £100 each for a decent horn of this type is actually pretty cheap. To minimise discontinuity you also want to make sure that ideally the slope angle at the start of the horn is the same as the exit angle of your compression driver. You may have to dismantle one and measure it to find out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 9:21am
It really wasn't that much trouble, it is infact just an enlarged xt1464 with the same angles. That's good that you see the price as agreeable, I'm not looking to make anything on them as the horn is borrowed geometry, well what horns are not, Just to serve a purpose where there is nothing else in 2" this size on the market that's appropriate.

Edited by SouthwestCNC - 28 February 2017 at 9:48am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 12:02pm
I don't think anyone is going to to be able to copyright or trademark a particular type of horn expansion, there is too much prior art out there. Unless you were making inverse moulds of an existing product and copying the manufacturer's colour etc you'll be fine, especially if you can back up your design process with data and simulation to prove it was not a straight copy. Not that you want to find yourself in court doing that regardless.

Also I agree with what Chris says, you want a radius on the mouth to minimise diffraction at that discontinuity.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 12:35pm
The roundover is there and at 20mm in size. The xt1465 I believe the large round over on the corners to just be ascetics unless they were only seeing diffraction in the corners as the extremities of the mouth just have a 10mm roundover, the 2" has 20mm so above scale and cant see anything untoward in the sims.




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Post Options Post Options   Thanks (1) Thanks(1)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 1:33pm
From the sim results i myself was actually pretty astounded that it performed so good.
Below some GIFs from the solution to the Comsol model.
What you see are the stationary solutions to time harmonic exciation at a specific frequency (listed on top) as it scrolls through all the frequencies. To the left is the horizontal cross section, to the right the vertical cross section. No real signs of diffraction apparent.

100Hz-6k in 1/24th octave spacing
6k-10k in 1/12th octave spacing
10k-20k in 1/12th octave spacing (I know, the mesh is a bit on the big side but you have to do something to get up to 20k)
Best regards,
Teun.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 2:11pm
The goal was to have as constant dispersion as possible in a nice continuous horn that is ''reasonably'' sized and can reach down low.  Diffraction throat is a no go so the limited directivity up high is to be expected.

Regardless it being 2'', it is still 26 degrees -6dB at 20k. At 10k you are looking at about 38 degrees and below that it is pretty constant 60 degrees between 800Hz and 5k.
Should be perfectly arrayable 2 per side with even fairly chunky 2'' drivers attached to them in a nice trapezoidal shaped box.


Edited by Teunos - 28 February 2017 at 2:15pm
Best regards,
Teun.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 2:42pm
Give you an idea how big these things are:

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 2:44pm
please do not suggest to stack them this way..
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Post Options Post Options   Thanks (1) Thanks(1)   Quote SouthwestCNC Quote  Post ReplyReply Direct Link To This Post Posted: 28 February 2017 at 3:19pm
Stack them however you want.just an example of size.. should be arrayed. Jesus cant even give things away :P


Edited by SouthwestCNC - 28 February 2017 at 3:27pm
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