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Author Topic: Mouths  (Read 5439 times)

Jason Phair

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Mouths
« on: August 15, 2011, 07:17:05 pm »

So my knowledge of the finer details of horn loaded subs is spottier than it should be.  I blame this on my just not using them very much (and I've never liked the sound of them as compared to direct radiators).  So, a few questions, because unfortunately I'm forced to use them sometimes.


I understand coupling the mouths to get lower and more efficient.  If you put them mouth down (say in a line across the stage), does the boundary loading of the mouth treat it as coupling it to another, as with a front-loaded box?

Next, with the driver at the top of the box, and the mouth at the bottom, again in a single line across the stage, do they tend to rear-lobe more than front-loaded boxes?  That seems to be my anecdotal experience, but I've never measured it at all, and there may be other factors in play at those particular venues.

Okay, so I guess just two questions for now then.
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Art Welter

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Re: Mouths
« Reply #1 on: August 23, 2011, 10:16:29 am »

I understand coupling the mouths to get lower and more efficient.  If you put them mouth down (say in a line across the stage), does the boundary loading of the mouth treat it as coupling it to another, as with a front-loaded box?

Next, with the driver at the top of the box, and the mouth at the bottom, again in a single line across the stage, do they tend to rear-lobe more than front-loaded boxes? 
Front loaded horns have mouths much smaller than the diameter of a full wavelength, so will roll off down low. Stacking the horns so the mouths all couple in a square or rectangle will increase the low frequency level, when the mouth is large enough, frequency response will tend to flatten out.

Placing the horns in a line across the front of the stage will be less effective in correcting the "too small" mouth problem, and will narrow the horizontal dispersion, just as in a line of front loaded cabinets.
A horn cabinet generally has  more directivity in the upper bass range than a front loaded cabinet, so further narrowing the pattern up high makes the omnidirectional low frequency even more apparent, perhaps accounting for the "rear-lobe" you have encountered.
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Connif Boudoin

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Re: Mouths
« Reply #2 on: August 24, 2011, 08:09:08 am »

Front loaded horns have mouths much smaller than the diameter of a full wavelength, so will roll off down low. Stacking the horns so the mouths all couple in a square or rectangle will increase the low frequency level, when the mouth is large enough, frequency response will tend to flatten out.

Placing the horns in a line across the front of the stage will be less effective in correcting the "too small" mouth problem, and will narrow the horizontal dispersion, just as in a line of front loaded cabinets.
A horn cabinet generally has  more directivity in the upper bass range than a front loaded cabinet, so further narrowing the pattern up high makes the omnidirectional low frequency even more apparent, perhaps accounting for the "rear-lobe" you have encountered.

Hey Art do you have any suggestions when using horns in a larger system? We have Ten that we deploy for larger Festivals and we have tried separating, Well you know what that does. Nulls in the front usually about the middle of the stack then a power alley then back to a null then you tend to get it back when moving further to the outside. Moving stacks in or out usually changes where that null is and how bad. We have also tried stacking them all in the center but then we get really directional horizontally. If you are standing under the stacks for FOH you basicially have no low end. When I was at monitor world it felt weird because there didn't seem to be any low end there like I was used to. We arched the subs and it increased the low end in the middle of the stage which was expected. Since then we have gone back to separating them. I rather deal with the nulls then no low end at the outer edges of the stage. It sucks. Several large shows I have seen have the same problems with some really nice systems.
Later
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Art Welter

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Re: Mouths
« Reply #3 on: August 24, 2011, 12:28:24 pm »

Front loaded horns have mouths much smaller than the diameter of a full wavelength, so will roll off down low. Stacking the horns so the mouths all couple in a square or rectangle will increase the low frequency level, when the mouth is large enough, frequency response will tend to flatten out.

Placing the horns in a line across the front of the stage will be less effective in correcting the "too small" mouth problem, and will narrow the horizontal dispersion, just as in a line of front loaded cabinets.
A horn cabinet generally has  more directivity in the upper bass range than a front loaded cabinet, so further narrowing the pattern up high makes the omnidirectional low frequency even more apparent, perhaps accounting for the "rear-lobe" you have encountered.

Hey Art do you have any suggestions when using horns in a larger system? We have Ten that we deploy for larger Festivals and we have tried separating, Well you know what that does. Nulls in the front usually about the middle of the stack then a power alley then back to a null then you tend to get it back when moving further to the outside. Moving stacks in or out usually changes where that null is and how bad.
There is  always a compromise in sub placement, a small center sub cluster can have even dispersion, but will cause off axis nulls with the L/R mains in the crossover region, sapping "punch".

For that reason, in general, I prefer the subs to be beneath the mains.
Without knowing what "Ten" you have, or what your mains are, whether ground stacked or flown, and stage width,  I can't give any useful suggestions .
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Ivan Beaver

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Re: Mouths
« Reply #4 on: August 24, 2011, 12:54:43 pm »

Hey Art do you have any suggestions when using horns in a larger system? We have Ten that we deploy for larger Festivals and we have tried separating, Well you know what that does. Nulls in the front usually about the middle of the stack then a power alley then back to a null then you tend to get it back when moving further to the outside. Moving stacks in or out usually changes where that null is and how bad. We have also tried stacking them all in the center but then we get really directional horizontally. If you are standing under the stacks for FOH you basicially have no low end. When I was at monitor world it felt weird because there didn't seem to be any low end there like I was used to. We arched the subs and it increased the low end in the middle of the stage which was expected. Since then we have gone back to separating them. I rather deal with the nulls then no low end at the outer edges of the stage. It sucks. Several large shows I have seen have the same problems with some really nice systems.
Later
Give this a try. Put the subs on either side as "normal".  Now turn down one side by a couple of dB-maybe 3.

If the sound man is in the middle-then it doesn't matter which one you turn down.

If he is one side, then turn down the other side (typically).

Yes the subs will be louder on one side than the other, but they are pretty omni in pattern and until you are pretty close to the "low" side, you won't realize it.

Now also depends on how high you run them to the crossover point.  I am assuming 90Hz or less.  Running them higher in freq and this idea does not work as well.  The lower the crossover point the better this works.

Of course that also brings in a whole new set of "problems".  If you mains are going very low, and don't have good pattern control (most modern speaker systems don't have horizontal pattern control down that low), the you will have the same problem-due to the spacing and the freq involved. 

Maybe roll off the low end of one side a little more than the other.
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Ivan Beaver
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drew gandy

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Re: Mouths
« Reply #5 on: August 29, 2011, 03:18:53 pm »

Next, with the driver at the top of the box, and the mouth at the bottom,

Are you referring to speakers like this?  Classic scoops?


-drew
« Last Edit: August 29, 2011, 03:20:29 pm by drew gandy »
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Jason Phair

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Re: Mouths
« Reply #6 on: September 08, 2011, 09:31:17 pm »

So I got busy and totally forgot I posed this question.  Thanks for the replies!

Subs in question are WSX - not a terrible sounding box, but I'd still take a lot of front-loaded double-18's if I had a choice.

I use them on smaller gigs (usually 6-8), and I have never liked them split, but with one particular venue, I've got a WIDE area I've gotta cover.  Think kinda V-shaped, as FOH is pretty close, but the audience tends to spill out into the V's (it's an intersection of sorts).  Splitting the subs puts the nulls right along those two legs of the V, and bounces a whole lotta energy off the nearby building located right behind FOH.  Putting them in the center centralizes the low end a little more, but really hits the deck hard, and still doesn't cover the V's, due to its narrowed horizontal dispersion.  I ended up putting them in a line across the front of the deck, but spread out about 4 feet, center to center, and this not only widened coverage, but decreased the "rear-lobing" (though I'm not sure why, and no I haven't modelled it yet).

Anyway, thanks for the input, guys (Art, your knowledge of horn-loaded systems is always invaluable!)
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