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Old 4th May 2010, 10:19 PM   #1
Andy_P is offline Andy_P  Germany
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Default Modifying horn flare/cutting a horn's mouth

Hi all,

I wonder if anybody here has experiences about changing an existing horns flare to achieve smaller dimensions without sacrificing sound.

In detail:
I'm using DIY boxes similar to JBL4825, using JBL2344 horns. They sound very nice, even better after replacing the drivers, but their look isn't quite modern. I'd like to cut down the cheeks up to about 1-1.5 inch, in order to cover the whole front with a decent grill.

This might invent additional horn reflections and directivity changes. Has anybody tried this before? How about replacing the very edge with some absorbing material?

Regards,
Andreas
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Old 4th May 2010, 11:37 PM   #2
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I would not cut them down. How about you look at a 2342?? You don't say where your crossover is? If you have 2426's you can screw off the 3 hole horn mounting plate and expose the threaded snout to use with the 2342.

Rob
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Old 5th May 2010, 12:00 AM   #3
Andy_P is offline Andy_P  Germany
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Xover is 4th order LR at 840 Hz, i.e. 2342 won't make me happy...
2426 drivers are swapped for B&C DE500.
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Old 5th May 2010, 12:42 AM   #4
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840 hz, that won't work with a 2342. Cutting them makes them yours for good though. I am out of JBL options the PT Waveguides don't load well enough to crossover that low. Here take a look at this in case you have not seen it. Food for thought if you decide to cut them.

Good Luck Rob
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File Type: jpg 2344 Horn Exp.jpg (41.3 KB, 134 views)
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Old 5th May 2010, 01:04 AM   #5
Andy_P is offline Andy_P  Germany
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Interesting picture, very helpful, thanks!
Though the horizontal dimension of the 2344 actually is 320mm. My idea was to replace the cutout partially by absorbing stuff to smoothen the edge rolloff/avoid reflections. Do you have hints towards this technique?
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Old 5th May 2010, 01:46 AM   #6
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Quote:
Though the horizontal dimension of the 2344 actually is 320mm.
320mm??? Mine don't, they measure 11 1/4 or about 280mm across the flare, you are an 1" and change too big across the flares. Top to bottom they measure 12.5 or 320mm where the mounting skirts are. Once you cut them you are going to shorten the distance and loose some directivity control in the lower portion of the horns range compared to a stock horn. If you are not worried about that then cut away. I don't know what the effect of the dampening material would be as it relates to changing the horns size.

Rob
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Old 5th May 2010, 03:56 AM   #7
gedlee is offline gedlee  United States
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I would expect your proposal to cause major problems with a horn that already has problems. I had a pair of those for probably ten years or more. There were very harsh. cutting them down will only make this problem worse. Things have moved on quite a lot since those horns were designed. A cheap waveguide from Parts Express will work better than those will. Time to upgrade you horns.
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Old 5th May 2010, 12:49 PM   #8
Andy_P is offline Andy_P  Germany
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Quote:
Originally Posted by Robh3606 View Post
320mm??? Mine don't, they measure 11 1/4 or about 280mm across the flare, you are an 1" and change too big across the flares. Top to bottom they measure 12.5 or 320mm where the mounting skirts are.
Rob
I checked all my 2344; apparently they all measure differently. I've got 3 old 2344 (separatable) measuring between 318 and 322mm across the flares, the latter exposing >90 flare (having 90 at about 310mm), with a mere 18mm mouth opening, and two 2344A with 315mm and the said 19.6mm mouth (All have the original JBL tags on them). I tried to measure the curve, apparently the older ones flare more rapidly than the diagram suggests (which fits the 2344A).
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Old 5th May 2010, 01:00 PM   #9
Andy_P is offline Andy_P  Germany
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Quote:
Originally Posted by gedlee View Post
I would expect your proposal to cause major problems with a horn that already has problems. I had a pair of those for probably ten years or more. There were very harsh. cutting them down will only make this problem worse. Things have moved on quite a lot since those horns were designed. A cheap waveguide from Parts Express will work better than those will. Time to upgrade you horns.
Well which horn doesn't expose major problems... I checked into waveguides for replacement, but none meets my requirement to have some 100 directivity from below 1kHz with reasonable dimensions. The boxes are for PA, not for home usage. And "very harsh" is too harsh a judgement; the driver/horn combination sounds sweet compared to what I use to hear in PA boxes.

Apparently my cut-down plan would reduce the horn size just a little under the design size (280mm design, 265-270mm target). I might loose a little (hopefully acceptable) direction control at the low end, will acoustical damping at the edges help avoiding (more) reflections? What material would you suggest?
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Old 5th May 2010, 03:24 PM   #10
Pano is offline Pano  United States
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100% Wool felt. Cover it with 100% wool cloth if it needs to be dressed up and protected.
Blends aren't bad if you can't get pure wool.
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