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-   -   Acoustic Horn Design The Easy Way (Ath4) (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4.html)

mabat 15th October 2019 06:47 AM

Quote:

Originally Posted by Ro808 (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post5943194.html#post5943194)
Behind the rather straightforward waveguide of this JBL 2-way cinema speaker, the same 2409H is mounted as used in the 7-series.

This is surprising to me, that's a two-way with a 15" woofer. According to datasheet the (horizontal) beamwdith is around 100 degrees nominal, which would mean the crossover won't be higher than about 1 kHz, rather even lower. Must be a fantastic driver (or they compromised the midrange seriously - I believe they didn't).

https://www.jblpro.com/ProductAttach...Sheet_8_18.pdf

jzagaja 15th October 2019 07:30 AM

1 Attachment(s)
Marcel - any chance include variable intensity (asymmetric) waveguide in your soft? For ceiling cinema speakers - corners and center. Example - Danley SH-DFA.

mabat 15th October 2019 08:05 AM

1 Attachment(s)
Yes, in principle this is the kind of thing you will be able to create. There are like seven design parameters to be specified and each of them can be an arbitrary function of the rotational angle (see the waveguide formula). So to achieve that you just have to find the respective functions of these parameters. In this case you would change mostly the length and coverage angle (and maybe the s and q). I could also implement this as an import from a text file in a form of a table. All of this should be possible to evaluate based on the WG formula and the shape requested, for example the 3D mouth curve coordinates.

- BTW, is this an OSWG profile? It looks like that.

Also some fancy looking unbaffled horns will be possible. Or an elliptical with a circular mouth, etc...

jzagaja 15th October 2019 09:22 AM

1 Attachment(s)
I've created this drawing using your equation in CAD. Ellipse cross section.

mabat 15th October 2019 09:24 AM

Indeed it looks familiar. I thought it's from some Danley datasheet :)
So you have it already... Brilliant.

jzagaja 15th October 2019 09:26 AM

Danley writes SH-DFA is add on to SH50. I don't quite understand this.

mabat 15th October 2019 10:23 AM

Neither do I.

- When I think about how to imlement this specifically, I would let the user simply to select a mouth curve, distance from a throat and an inclination of the mouth plane. Could be this easy without the need of calculating it all externally. This could be one of the ways how to set the input parameters.

Ro808 15th October 2019 05:23 PM

The SH-DFA is a separate 'add-on' 2-way downfill synergy horn with asymmetrical mouth.
There's a 1" comp. + 10" cone inside.

https://www.danleysoundlabs.com/wp-c...4860729555.png


This part is particularly interesting:
"Please note! The front grille is cosmetic only! The horn is the bottom of the unit."

Who would have expected anyone would care about cosmetics at Danley.

Ro808 16th October 2019 06:02 AM

Quote:

Originally Posted by mabat (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post5944697.html#post5944697)
This is surprising to me, that's a two-way with a 15" woofer. According to datasheet the (horizontal) beamwdith is around 100 degrees nominal, which would mean the crossover won't be higher than about 1 kHz, rather even lower. Must be a fantastic driver (or they compromised the midrange seriously - I believe they didn't).

Yes they did ;)

The woofer in the C211 is JBL's run-of-mill M115-8A.
Basically a mid-woofer that was used in many entry level 2-way cabs, like the JRX series.
The 2409H isn't suited to low crossover points. Therefore JBL decided to let the M115-8A play all the way up to 1800Hz (the XO-point),
just like they did with the portable cabs in the past.

I think this driver is far more interesting than the 2409H, because it was specifically designed for 1kHz crossovers.

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.



It seems BMS have finally decided to improve the (finish)quality of the parts that are exposed to air.

mabat 16th October 2019 06:29 AM

Are you sure about the crossover point? If you take a look in the datasheet, the horizontal beamwidth of 100 degrees is relatively constant from 1 kHz - I can't quite imagine how they achieved that with a 15" woofer crossed at 1.8 kHz. Is it possible?


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