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8" MID HORN (development thread)

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luthier View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 11 February 2019 at 9:30pm
Originally posted by ceharden ceharden wrote:

14:1 ratio is practical in any shape or form.  Even HF drivers with complex phase plugs don't go that high.

For a cone driver I would say 3:1 is probably a realistic maximum.

You have to also take into account path length matching.  All areas of the cone need to have a similar path length to the exit of the horn and a small circular throat is probably about the worst for that.  It would also be very hard to avoid a large front chamber without a phase plug.




Right, that's matches up to what I've been reading.

Interestingly I've been on that website quite a lot recently, I'll have to take another look.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 12 February 2019 at 10:24am
This should be fun, there was a warning on the last tutorial saying ' if you are not an expert in this field you should not be using this software as you will not understand what you are doing'. Hopefully in the process of learning the software I can begin to understand what I'm doing, it might be a steep learning curve.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote sgarfa Quote  Post ReplyReply Direct Link To This Post Posted: 12 February 2019 at 4:23pm



this is the model (1/4 to speed up the calculations) for a mid with b&C 8mbx ,I wanted to study the behavior of the phase plug in comsol 
was fine with the complete parallel with  inventor, anyway  I became crazy,
 in the end I made a quick script with akabak..simulated..make de 3d drawing.. milled the mold ... stop..I think I'm not smart enough to comsol
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 12 February 2019 at 7:40pm
[QUOTE=sgarfa

this is the model (1/4 to speed up the calculations) for a mid with b&C 8mbx ,I wanted to study the behavior of the phase plug in comsol 
was fine with the complete parallel with  inventor, anyway  I became crazy,
 in the end I made a quick script with akabak..simulated..make de 3d drawing.. milled the mold ... stop..I think I'm not smart enough to comsol
[/QUOTE=

 

Glad it's not just me finding it tricky!


Edited by luthier - 12 February 2019 at 7:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2019 at 9:14pm
So with a little more time playing on Hornresp and thanks to all the input I have recieved on here I've managed to get this.

When moddeled as one horn off Axis I gain massive sensitivity over 450hz + 10db in places so I'm just focusing on the most useable frequency range.  






Edited by luthier - 17 February 2019 at 9:17pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2019 at 9:24pm
I've also been practing modeling horns in Solidworks as I can export the CAD file to COMSOl when I manage to learn to use the bastard thing. 

Here's a few pictures, they're just experiments really, I'm not planning on using any of the files. I'm just trying to get the hang of using the more complicated equation driven curves. 

Here's a Hyperbolic horn equation:



Here's what I made with the hperbolic horn equation:




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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 17 February 2019 at 9:32pm
What I've gathered so far is:
 
- I need a small VTC under 100cc

- s1 needs to be at least 72 in order to stay at/below 3:1 compression ratio 

- a slow flare rate at the begingng of the horn smooths out the graph 

- a large mouth is important to increase linearity  

- displacement is 1mm over the 1mm xmax at 300hz which hopefully won't be an issue 

- Lining the rear chamber is very important to stop waves reflecting 

Also installing a virtual machine to sim in Akabak is a right pain! 




Edited by luthier - 17 February 2019 at 9:33pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sgarfa Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2019 at 10:23am
really a good job,what angle of the dispersion you want? ... if I were you I would make a different dipersion between horizontal and vericale..in any case you could also use a mid with closed back ... so as to simplify a little the thing

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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2019 at 7:04pm
Originally posted by sgarfa sgarfa wrote:

really a good job,what angle of the dispersion you want? ... if I were you I would make a different dipersion between horizontal and vericale..in any case you could also use a mid with closed back ... so as to simplify a little the thing



Thank you! I'm aiming for a 60 x 40 dispersion, although I've not been very successful in measuring the current dispersion. I'm modelling the horn as one segment and looking at the directivity: Polar map, beam width and dispersion pattern.

A closed back mid would certainly make things easier, if I can find one with suitable T/S parameters I'll go for it.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2019 at 7:55pm
Originally posted by luthier luthier wrote:



A closed back mid would certainly make things easier, if I can find one with suitable T/S parameters I'll go for it.


https://www.bcspeakers.com/en/products/lf-driver/8-0/8/8NSM64-8

It's good enough for the d&b GSL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2019 at 8:30pm
For the mid and high sections it may well be worth thinking of them as wave guides as opposed to horns, in this case where horns primary goal would be to present a load to the driver and a wave guide to control directivity.
All but the conical horn will have uneven dispersion versus frequency.
The type of cabinet your working on I think dispersion over it's working range is critical to a good outcome, especially as you looking to use them in arrays.



https://www.diyaudio.com/forums/multi-way/103872-geddes-waveguides.html

http://mariobon.com/Articoli_storici/Horns_measurements_ETF2010d.pdf

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.536.5361&rep=rep1&type=pdf

http://www.gedlee.com/Papers/paper.aspx

PS finally getting somewhere with 'Inventor'Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote luthier Quote  Post ReplyReply Direct Link To This Post Posted: 18 February 2019 at 9:43pm
Originally posted by toastyghost toastyghost wrote:

Originally posted by luthier luthier wrote:



A closed back mid would certainly make things easier, if I can find one with suitable T/S parameters I'll go for it.


https://www.bcspeakers.com/en/products/lf-driver/8-0/8/8NSM64-8

It's good enough for the d&b GSL


Very glad you mentioned this driver I simmed it a few weeks ago on a previous horn I was modelling and it didn't look great. Now though, different story.

With the 1.5L chamber a larger S1 and reduced compression ratio I managed to get this:








Group delay and Xmax limit me to a hpf around 330hz which isn't a problem, think I found my driver!

Edited by luthier - 18 February 2019 at 9:46pm
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