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250-4k horn

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JulianDA View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JulianDA Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2021 at 4:35pm
Originally posted by Augusts Augusts wrote:

Julian, do you mean the sharp edge of the perimeter at the very end of the mouth or the not so sharp corners towards the end of the mouth?

I simulated the horn in hornresp, as far as it could be simulated. Have not got my head around akabak



Yes i mean the perimeter on the hornmouth. You have to keep in mind that all sudden changes in acoustical impedance (i.e. flarerate) will produce diffraction effects which can be interpreted as new point-like "sound-sources" which then will radiate omnidirectional and therefore also back into your horn, causing resonances.
Another thing to keep in mind is the big spike in groupdelay on the tuning frequency of a horn. In an optimal world you dont want to have this spike in the used range of the horn. At lower bass frequencies the groupdelay is less noticeable, but in the mid-range it can be problematic. So a really good midrange horn should be tuned ~1 Octave lower than the desired crossover frequency. But this leads to really big horns...there is a compromise to be found somewhere inbetween big enough and to small 

But on another note: you can listen to the advice of citizensc, he knows his stuff regarding horns and akabak ;)

 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2021 at 5:56pm
Thank you for the insights

I am now learning Akabak

Do you know why it could be that tha phase plug is absent in the BEM section but visible in the General- Mesh section?





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2021 at 6:16pm
This is what I got without the phase plug. First try




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JulianDA View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JulianDA Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2021 at 8:26pm
Originally posted by Augusts Augusts wrote:

Thank you for the insights

I am now learning Akabak

Do you know why it could be that tha phase plug is absent in the BEM section but visible in the General- Mesh section?

Sorry i cant answer that question on the fly since i am not that deep into akabak at the moment (there is alot of other stuff to be done in my life :D ), but maybe citizensc has encountered a similar problem?


But your directivity plots dont look to bad :) For easier comparison of plots i would advise you to normalize your plots. There should be the option "normalize to x-axis" in VACS-Viewer under "processing" (or "postprocessing"). After that you can choose your dB-steps as indicated by the different colours to show the -6dB Point better. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 23 March 2021 at 9:01pm
Take a look here for tips on BEM simulation for horns. They’re using ABEC3 but it’s very similar to the new AKABAK, so the same concepts apply.

https://sphericalhorns.net/2019/10/20/bem-simulation-for-a-freestanding-horn/
https://sphericalhorns.net/2019/10/22/drba-calculator-and-bem-simulation/
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Post Options Post Options   Thanks (0) Thanks(0)   Quote citizensc Quote  Post ReplyReply Direct Link To This Post Posted: 24 March 2021 at 9:17am
Good work getting up and running with AKABAK 3 so quickly! it is not the most intuative program when you first start using it.

Can you please post a top down view like this and include the horn itsself 

https://www.facebook.com/voyager.system

@voyager_soundsystem
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 24 March 2021 at 10:48am
I found a very good guide on youtube on how to use AKABAK, without it I would not be able to work my way this far.

I do not know how to do a simulation like that with the horn. Could you give me some keywords?LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doller Quote  Post ReplyReply Direct Link To This Post Posted: 25 March 2021 at 9:08am
Have a look at the fane speaker book page 50 w type bass bin. They claim 60 to 4500hz. There is a plot included. Just saying. I have made some and they are surprisingly OK psy trance sounds just sweet through them. I struggle to get them to 1.8hz with a pd 121. 
That said look at the pm 60 90 streach the fane design a bit and squeeze it a bit to fit that 18 sound horn and two drivers. Quite similar. Not saying that is was the inspiration for the pm in anyway shape or form. But fane say in the book stick a comp in the middle. If you want.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote citizensc Quote  Post ReplyReply Direct Link To This Post Posted: 25 March 2021 at 12:19pm
Originally posted by Augusts Augusts wrote:

I do not know how to do a simulation like that with the horn. Could you give me some keywords?LOL


In the general tab define a new node with 4 points eg. x=2y=2, x=2y=-2, x=-2y=-2, x=-2y=2 ,this example is for a 4x4m square but you can make it any dimensions you like. - This step defines the plane you want the measurement to be taken from and displayed. 

Then go to the observation tab, create a 'fields (nodes)' then under planes tab inside the 'fields (nodes)' add the node you just created. From memory, it should just work now if you re run the simulation. If not, PM me!
https://www.facebook.com/voyager.system

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Danny Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2021 at 8:30pm
Hello,

For a 3-way, 15"+8"+CD I'm thinking of using the Oberton 8NMB250v4,
the specs look very good.
If you have purchased them, how do you judge them ?

Regards,
Danny

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Augusts Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2021 at 8:39am
Hi

They are excellent drivers, the response is smooth up to 5kHz, I would compare them to BMS.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Danny Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2021 at 9:50am
Thanks,
I will put them in my basket :-)
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