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Author Topic: Long vs short throw boxes  (Read 5358 times)

Brad Weber

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Re: Long vs short throw boxes
« Reply #10 on: March 26, 2011, 10:10:31 am »

Thanks for that guys. So from what I understand throw is a product of directivity. A narrower dispersion focuses the energy into a smaller area and results in a greater distance travelled before the energy is dissipated?
Perhaps it's easiest to think of it this way, if you had to cover a certain number of people where everyone was within a or 'short' distance you'd probably want a wider pattern device in order to provide good coverage of all of the listeners.  If you moved those people further away from the speaker, a 'long' distance away, then you would likely want a narrower pattern device.

If that is the case, then is there an ideal distance to have a listener from a loudspeaker? For a singer woofer and a horn, is there a point where you can be too close? I'm thinking that the directivity at certain frequencies may result in an imbalance in the frequency spectrum up close?
You can get into more tchnical aspects such as near field versus far field, but the primary thing is probably simply whether the speaker provides the desired levels and response over the desired listener area.  "Too close" might be asociated with varying levels at the edges of listener area.
 
What explains my observations about intelligibility and stability in the drum fill? I've also noticed this when listening to program material when sitting in the drummers stool compared with listening from a couple of meters back. While the level is lower further away, the balance is dramatically better.
Think of the angular relationship as well as the distance.  The output of speakers tends to drop off as you move off-axis and often falls off differently for different frequencies.  Some speaker exhibit a nice smooth drop of for most frequencies right up to the pattern cut off, others may have some frequencies that drop off dramatically while other frequencies drop off very little.  As you move closer or further away from a speaker is that movement along the speaker's axis or does the movement result in how far you are off axis also changing?  It could be that moving further awway simply puts you more into the coverage of the speaker at all frequencies and thus provides a better frequency response.
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David Parker

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Re: Long vs short throw boxes
« Reply #11 on: March 27, 2011, 04:58:08 pm »

What facet of speaker design contributes to the long/short throw charateristics of a loudspeaker?

I've always hated using powered boxes like eons and srm450 for monitors and had put that down to their "throw". I'm always amazed at how good the drum fill sounds from monitor op position, but then just falls apart on the riser.

A church I attended years ago  hired a consultant to spec a system. The church was a 208' diameter concrete dome. The consultant spec'd a system that absolutely did not work. There were 20 horns total, all huge with JBL 2445 drivers. 10 of the horns were "long throw", about 4' long, intended to "develop" at 300'-400'. As noted, the back was was less than 200' from the horns. As expected, there were hot spots and cold spots with regards to sound. At the back of the room, the horns had not spread out enough to meet each other's coverage. At the front, where the shorter "throw" horns were aimed, it was equally spotty, since those horns were still too narrow in coverage for the distance they covered.
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Ivan Beaver

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Re: Long vs short throw boxes
« Reply #12 on: March 27, 2011, 05:34:50 pm »

A church I attended years ago  hired a consultant to spec a system. The church was a 208' diameter concrete dome. The consultant spec'd a system that absolutely did not work. There were 20 horns total, all huge with JBL 2445 drivers. 10 of the horns were "long throw", about 4' long, intended to "develop" at 300'-400'. As noted, the back was was less than 200' from the horns. As expected, there were hot spots and cold spots with regards to sound. At the back of the room, the horns had not spread out enough to meet each other's coverage. At the front, where the shorter "throw" horns were aimed, it was equally spotty, since those horns were still too narrow in coverage for the distance they covered.
I ran into the same sort of thing a number of years ago when the consultant spec JBL PD horns for a traditional Baptist church.  The reason was that the narrow pattern would not energize the room as much.  OK, But you have to use enough of them to adequately cover the audience or else you end up with hot spots and dead spots-like they did.

Nothing against the product, but it was the wrong tool for the job at hand.
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Ivan Beaver
Danley Sound Labs

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Mac Kerr

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Re: Long vs short throw boxes???
« Reply #13 on: March 27, 2011, 05:39:23 pm »

A church I attended years ago  hired a consultant to spec a system. The church was a 208' diameter concrete dome. The consultant spec'd a system that absolutely did not work. There were 20 horns total, all huge with JBL 2445 drivers. 10 of the horns were "long throw", about 4' long, intended to "develop" at 300'-400'. As noted, the back was was less than 200' from the horns. As expected, there were hot spots and cold spots with regards to sound. At the back of the room, the horns had not spread out enough to meet each other's coverage. At the front, where the shorter "throw" horns were aimed, it was equally spotty, since those horns were still too narrow in coverage for the distance they covered.

What kind a system fixed the problem? In an acoustic disaster area like a concrete dome I don't think those horns were a bad idea. There is no such thing as a horn intended to "develop" at 300'-400', there are only horns with different coverage angles. AFAIK the narrowest coverage horns JBL made were 40Hx30V. If these were arrayed 5 wide by 2 high, with 5 of overlap, the 10 horns would have a coverage pattern of about 180Hx55V, without significant gaps in coverage, at any reasonable distance. In a concrete dome, it is certainly possible, even probable that reflections off the ceiling and walls were causing those dead spots. Those big horns were used to try to reduce those reflections by keeping sound off the ceiling and walls. Maybe it was not possible to have a good sound in that room at that time, but it wasn't because the horns didn't have enough coverage.

Mac
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Mac Kerr

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Re: Long vs short throw boxes
« Reply #14 on: March 27, 2011, 05:43:32 pm »

I ran into the same sort of thing a number of years ago when the consultant spec JBL PD horns for a traditional Baptist church.  The reason was that the narrow pattern would not energize the room as much.  OK, But you have to use enough of them to adequately cover the audience or else you end up with hot spots and dead spots-like they did.

Ivan, with 10 of the narrowest horns JBL made, and 10 somewhat wider pattern horns there was probably enough to cover the room, even if it was in the round. Ten 40 horns in a circle should cover 360.

That doesn't make the design a good one, but it seems unlikely the dead spots were completely due to horns being too narrow. It would help to know about the actual design and implementation.

Mac
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Jeff Harrell

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Re: Long vs short throw boxes
« Reply #15 on: March 27, 2011, 06:43:29 pm »

these cabnets were considered "short throw" but got out to over 200,000 people and could be heard past the 1/2 mile point. when you build a wall off sound it will get out especially when indoors. "IF i remember right" the 15" woofs in these cabnets were rated to handle 150 watts each. this was the CalJam74 pa system. check out the amp racks next to the speakers.
« Last Edit: March 27, 2011, 06:49:52 pm by Jeff Harrell »
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Ivan Beaver

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Re: Long vs short throw boxes
« Reply #16 on: March 27, 2011, 06:55:49 pm »

Ivan, with 10 of the narrowest horns JBL made, and 10 somewhat wider pattern horns there was probably enough to cover the room, even if it was in the round. Ten 40 horns in a circle should cover 360.

That doesn't make the design a good one, but it seems unlikely the dead spots were completely due to horns being too narrow. It would help to know about the actual design and implementation.

Mac
In my particular case there were only 2 horns used for the balcony and 2 for the main floor.

It was just a case of a poor overall system design-not the tools that were used.

But as the contractor, we had no say in the design (I tried to point it out-but the customer would not listen to me), we were hired to put it in as designed.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

David Parker

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Re: Long vs short throw boxes???
« Reply #17 on: March 27, 2011, 08:50:16 pm »

What kind a system fixed the problem? In an acoustic disaster area like a concrete dome I don't think those horns were a bad idea. There is no such thing as a horn intended to "develop" at 300'-400', there are only horns with different coverage angles. AFAIK the narrowest coverage horns JBL made were 40Hx30V. If these were arrayed 5 wide by 2 high, with 5 of overlap, the 10 horns would have a coverage pattern of about 180Hx55V, without significant gaps in coverage, at any reasonable distance. In a concrete dome, it is certainly possible, even probable that reflections off the ceiling and walls were causing those dead spots. Those big horns were used to try to reduce those reflections by keeping sound off the ceiling and walls. Maybe it was not possible to have a good sound in that room at that time, but it wasn't because the horns didn't have enough coverage.

Mac

some of the horns were intentionally aimed at the walls, to counteract whatever.  That didn't work at all. I took four of the shorter horns and aimed them down into the audience and turned the rest of them off. The longer horns were stadium horns, they were huge. 31" square at the end, 54" long. They had no place in that room.  Shortly after that the Astrodome in Houston put in a new sound system. I recognized the horns in that setup distinctly, they were the same as the ones in the church. That system MIGHT have worked had all the horns been pointed into the seats and properly aimed and levels properly set, but that is not the way it was installed. I didn't have the wherewithal to set all of them up that way. This was 20 years ago. I was just learning about live audio. What I did improved it immensely, but had I had some horns with wider dispersion, it would have been even better. Here are the horns in question, JBL2366a.http://www.jblpro.com/pub/obsolete/23606566.pdf
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Mac Kerr

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Re: Long vs short throw boxes???
« Reply #18 on: March 27, 2011, 09:14:33 pm »

some of the horns were intentionally aimed at the walls, to counteract whatever.  That didn't work at all. I took four of the shorter horns and aimed them down into the audience and turned the rest of them off. The longer horns were stadium horns, they were huge. 31" square at the end, 54" long. They had no place in that room.  Shortly after that the Astrodome in Houston put in a new sound system. I recognized the horns in that setup distinctly, they were the same as the ones in the church. That system MIGHT have worked had all the horns been pointed into the seats and properly aimed and levels properly set, but that is not the way it was installed. I didn't have the wherewithal to set all of them up that way. This was 20 years ago. I was just learning about live audio. What I did improved it immensely, but had I had some horns with wider dispersion, it would have been even better. Here are the horns in question, JBL2366a.http://www.jblpro.com/pub/obsolete/23606566.pdf

More evidence that the problem wasn't the fact that long throw, narrow coverage pattern, horns were used in what may have been the right room, but that it was a bad design or installation. No sound system in the world will work in the face of bad design and installation.

Mac
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David Parker

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Re: Long vs short throw boxes???
« Reply #19 on: March 27, 2011, 10:27:43 pm »

More evidence that the problem wasn't the fact that long throw, narrow coverage pattern, horns were used in what may have been the right room, but that it was a bad design or installation. No sound system in the world will work in the face of bad design and installation.

Mac
My original point for the original poster was that if the pattern was too tight and the targets too close, there would be hot and cold spots. Unless there are adequate tight coverage horns to be aimed to cover the targets. The install in question was a disaster, and a very expensive one. As I recall, the install was $140,000 about 1987. I don't remember the name of the contractor, but they were highly recommended for church installs at the time. This was their first shot at a concrete dome, and it didn't work. They had a couple of the shorter horns in that series aimed down at the stage for monitors. That also did not work at all.
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