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[Jeff Bankston]

Can someone post an image of what the sound waves look like with four 40x40 horns side by side straight ahead and the sides touching each other in a stage stack ? Would there be any comb filtering with those narrow patterns ? crossover point is 1.2K 24DB L-R crossover.

Horn 1>
Horn 2>
Horn 3>
Horn 4>
   

[Mark McFarlane]

Even with 1 degree, done theoretically perfectly, there will be comb filtering at some distance.  Still, no horn falls off to 0 db outside it's stated pattern, and the rate of falloff is frequency dependent, so your question cannot be answered without measurements of the specific horn design.

[Jeff Bankston]

Even with 1 degree, done theoretically perfectly, there will be comb filtering at some distance.  Still, no horn falls off to 0 db outside it's stated pattern, and the rate of falloff is frequency dependent, so your question cannot be answered without measurements of the specific horn design.

i posted the crossover info.

[Ray Aberle]

i posted the crossover info.

So you want to know about the falloff at 1.2khz then? Or a different frequency?

… do you have these, and can just set them up and try them, or do you need it visualized to show someone else?

[Jeff Bankston]

So you want to know about the falloff at 1.2khz then? Or a different frequency?

… do you have these, and can just set them up and try them, or do you need it visualized to show someone else?

i was wondering if there would be a lot of comb filtering from 1.2K-16K

[Ivan Beaver]

Can someone post an image of what the sound waves look like with four 40x40 horns side by side straight ahead and the sides touching each other in a stage stack ? Would there be any comb filtering with those narrow patterns ? crossover point is 1.2K 24DB L-R crossover.

Horn 1>
Horn 2>
Horn 3>
Horn 4>
 

The answer will vary depending on the physical size of the horn and the distance away.

Each distance will have a different set of "combfilters" because the distance from each device will vary depending on the listening distance.  The physical size of the horn will dictate how far the drivers are away from each other.

The answer is yes there will be lots of combfiltering.  Anytime 2 devices arrive at the listener at different times there WILL be comfiltering.

The freq of the notches and humps will change with distance.

The closer in level the 2 sources are the deeper the notch. 

The physical size of the horn will help to dictate how much one source interferes with another.  If the horns are large-then up close the combfiltering will be less-since the levels from the other horns will not be as much.  But as you move further away-you will be in the pattern of 1 or more of the horns-so the combfiltering will be greater in depth.

The basic math is the first notch will be the freq that is 1/2 of the arrival time.  The "humps (gain) will be at the freq of the arrival time.

They will be all spaced at the freq (NOT ratio) of the arrival time.  So if you look at it on a linear (not log) scale-it will look like the teeth of a comb.

[Merlijn van Veen]

Can someone post an image of what the sound waves look like with four 40x40 horns side by side straight ahead and the sides touching each other in a stage stack ? Would there be any comb filtering with those narrow patterns ? crossover point is 1.2K 24DB L-R crossover.

Horn 1>
Horn 2>
Horn 3>
Horn 4>
 

Hi Jeff,


Took the liberty of making you an image. Used a Meyer Sound MSL-4 (40° speaker) under your conditions.

With no splay you have a 4 to 1 speaker advantage or 12 dB but also 100% overlap or 100% comb filtering. With 100% splay, where unity splay is equal to the coverage angle of a single speaker (40°), you'll have no SPL advantage, 0% overlap ergo minimal comb filtering and 4 x 40° = 160° degrees of coverage (symmetrical coupled point source).

For the frequency which wavelength equals line length (2.16 m - 160 Hz) the combined coverage angle is 72° (Harry Olson). Twice that frequency is 36° and 4 times that frequency is 18°. But now the displacement between the speakers equals 1 wavelength and lateral summation occurs because the sound of the speakers arrives in phase, be it 1 through 3 cycles apart respectively in this case.

The high frequencies are saturated with comb filtering due to the absence of splay. The combined coverage angle for this frequency range is 4 times the Forward Aspect Ratio of a single speaker (2,92) so 4 x 2,92 = 11,7 or approx 10°.

The approach you're referring to, is known as the "coupled line source" as you're undoubtedly aware and inherently lacks homogenous constant coverage, varying from 72° to 10° in this case, but it will go LOUD.


Hope it helps,


Merlijn

[Jeff Bankston]

Hi Jeff,


Took the liberty of making you an image. Used a Meyer Sound MSL-4 (40° speaker) under your conditions.

With no splay you have a 4 to 1 speaker advantage or 12 dB but also 100% overlap or 100% comb filtering. With 100% splay, where unity splay is equal to the coverage angle of a single speaker (40°), you'll have no SPL advantage, 0% overlap ergo minimal comb filtering and 4 x 40° = 160° degrees of coverage (symmetrical coupled point source).

For the frequency which wavelength equals line length (2.16 m - 160 Hz) the combined coverage angle is 72° (Harry Olson). Twice that frequency is 36° and 4 times that frequency is 18°. But now the displacement between the speakers equals 1 wavelength and lateral summation occurs because the sound of the speakers arrives in phase, be it 1 through 3 cycles apart respectively in this case.

The high frequencies are saturated with comb filtering due to the absence of splay. The combined coverage angle for this frequency range is 4 times the Forward Aspect Ratio of a single speaker (2,92) so 4 x 2,92 = 11,7 or approx 10°.

The approach you're referring to, is known as the "coupled line source" as you're undoubtedly aware and inherently lacks homogenous constant coverage, varying from 72° to 10° in this case, but it will go LOUD.


Hope it helps,


Merlijn

Thank you , this is what i was looking for.

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