compression driver throat adapter length for synergy horn - diyAudio
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Old 1st August 2014, 08:39 PM   #1
bqc is offline bqc  United States
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Default compression driver throat adapter length for synergy horn

I need to mount a JBL 2426 compression driver to a synergy horn. This requires that I mount the JBL to a 3/4 in plate. Then mount that plate to another plate that is glued to the throat of the synergy. This will add 1.5 in distance to the distance from the compression exit to the synergy horn throat exit. My question is , would that distance negatively affect the response of the JBL and if so how would I simulate it with hornresp

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Old 1st August 2014, 11:34 PM   #2
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Originally Posted by bqc View Post
My question is , would that distance negatively affect the response of the JBL and if so how would I simulate it with hornresp
Assuming your Synergy horn is "normal", the expansion is simulated as Con(ical) in Hornresp. A nice smooth round to square (or rectangular) transition is required for smooth response.

Adding the pieces in may increase the distance where the mid drivers enter, ideally the mid exits should be within 1/4 wavelength of the crossover frequency.
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Old 1st August 2014, 11:54 PM   #3
bqc is offline bqc  United States
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Originally Posted by weltersys View Post
Assuming your Synergy horn is "normal", the expansion is simulated as Con(ical) in Hornresp. A nice smooth round to square (or rectangular) transition is required for smooth response.

Adding the pieces in may increase the distance where the mid drivers enter, ideally the mid exits should be within 1/4 wavelength of the crossover frequency.
Thanks for responding, so you are saying it will increase the value of L12 as used by hornresp to indicate distance between the throat of horn and mid port ?
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Old 2nd August 2014, 08:12 AM   #4
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Yep sure will. Try an adapter out of alumium plate, 3mm. Adding 1.5inches will make it even harder to get the ports where you need them witout killing the hf reaponse of the mids.
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Old 2nd August 2014, 07:29 PM   #5
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It is equally important that the adapter provide a smooth as possible transition between the slope of the compression driver throat and that of the adjoining horn. Use an OS horn neck profile for this purpose and keep the adapter cross section circular. For a preferred transition between the a circular and rectangular sections use fillets of declining radii inside the horn body. See references [1] & [2] for details. Recommend use of separate power amplifiers and a DSP front end to optimize horn output. Here you may introduce delay as necessary to compensate for path length differences between driver diaphragms as well as the required c/o filters, equalization and output level matching.

Regards,

WHG

References:

[1] Mike Seddon's Synergy Horn Design Website
mike.seddon.ca - Horn Design

[2] Fillet Image
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Last edited by whgeiger; 2nd August 2014 at 07:36 PM.
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Old 2nd August 2014, 08:05 PM   #6
bwaslo is offline bwaslo  United States
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Watch out, though. The delay of a DSP won't help the 1/4 wave reflective notch (midrange port to tweeter and back) frequency. The further the mid ports get from the tweeter's diaphram, the lower you'll have to crossover to keep the notch out of the midrange. Taper, but avoid lengthening the throat transition unnecessarily.
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Old 2nd August 2014, 08:08 PM   #7
bwaslo is offline bwaslo  United States
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whgeiger,

Thanks for the Seddon link, BTW. I hadn't seen that.
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Old 2nd August 2014, 09:16 PM   #8
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Quote:
Originally Posted by bwaslo View Post
Watch out, though. The delay of a DSP won't help the 1/4 wave reflective notch (midrange port to tweeter and back) frequency. The further the mid ports get from the tweeter's diaphram, the lower you'll have to crossover to keep the notch out of the midrange. Taper, but avoid lengthening the throat transition unnecessarily.
I would still press the trade envelope towards adapter smoothness to keep HOM's under control. I would also pick a throat-less compression driver for this application like the TAD TD4002.

Regards,

WHG

Last edited by whgeiger; 2nd August 2014 at 09:21 PM.
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