Modifying horn flare/cutting a horn's mouth

[Andy_P]

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

 

[Robh3606]

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

 

[Andy_P]

Xover is 4th order LR at 840 Hz, i.e. 2342 won't make me happy...
2426 drivers are swapped for B&C DE500.

 

[Robh3606]

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

 

[Andy_P]

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?

 

[Robh3606]

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

 

[gedlee]

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.

 

[Andy_P]

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).

 

[Andy_P]

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?

 

[Pano]

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.

 

[badman]

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

An externally hosted image should be here but it was not working when we last tested it.

I applied foam to the entire mouth. Inside the throat is reticulated foam, the periphery is regular open cell foam, cut by hand with a hot knife. The periphery foam smoothed ripple at the bottom end (cutoff) of the horn by as much as 2dB. Doesn't sound like much but it's quite a bit of ripple to eliminate.