Re: Endfire sub array under a stage
Art, the cardioid array had the exact same frontal area and exhibited the exact same loss.
Art, the cardioid array had the exact same frontal area and exhibited the exact same loss.
Endfire sub array under a stage
- Thread starter Michael John
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Re: Endfire sub array under a stage
Hi Bennett,
Yes, I’m aware of that. The advantage of the end-fire array over the cardioid array is it loses less SPL and still has excellent sound quality, but the rear rejection is not as good.
One thing I have been curious about is the performance of things like end-fire slots or Dave Rat’s “Vortex” where all the cabinets are in close proximity for the reasons you mentioned. Does this minimize the SPL loss?
The other advantage of an end-fire or cardioid array is that you can design the array’s coverage to better match the venue and FOH. With less rear energy you have less reflection from the backwall and less lumps and bumps in the SPL coverage.
Hi Bennett,
Yes, I’m aware of that. The advantage of the end-fire array over the cardioid array is it loses less SPL and still has excellent sound quality, but the rear rejection is not as good.
One thing I have been curious about is the performance of things like end-fire slots or Dave Rat’s “Vortex” where all the cabinets are in close proximity for the reasons you mentioned. Does this minimize the SPL loss?
The other advantage of an end-fire or cardioid array is that you can design the array’s coverage to better match the venue and FOH. With less rear energy you have less reflection from the backwall and less lumps and bumps in the SPL coverage.
Re: Endfire sub array under a stage
As I pointed out earlier, ANY directional sub array requires open space around it in order to perform optimally. Introduce a stage or wall into the equation in close proximity, and the directional pattern is affected, often in an inconvenient manner, as was modeled and illustrated in the paper I quoted from. Unfortunately all currently available sound system modeling programs predicting low frequency coverage can only model under the assumption of a direct anechoic response. As Bennett correctly pointed out, you need to use boundary element method analysis to be able to take into account any boundary surfaces such as floors, walls, ceiling, stage, etc. Maybe in a few years BEM will be affordable and attainable for the masses as our computers become more powerful and the software made easier to use. Until then we need to acknowledge and understand the limitations of the tools we have currently at our disposal.
As I pointed out earlier, ANY directional sub array requires open space around it in order to perform optimally. Introduce a stage or wall into the equation in close proximity, and the directional pattern is affected, often in an inconvenient manner, as was modeled and illustrated in the paper I quoted from. Unfortunately all currently available sound system modeling programs predicting low frequency coverage can only model under the assumption of a direct anechoic response. As Bennett correctly pointed out, you need to use boundary element method analysis to be able to take into account any boundary surfaces such as floors, walls, ceiling, stage, etc. Maybe in a few years BEM will be affordable and attainable for the masses as our computers become more powerful and the software made easier to use. Until then we need to acknowledge and understand the limitations of the tools we have currently at our disposal.
Re: Endfire sub array under a stage
Hi Darren,
You may be interested in this picture (sorry its only the stage) – same venue as the end-fire array you described, but this time it’s Michael Jackson the Immortal World Tour (Adelaide 15 &16/10/2013).
FOH– Meyer Leo
Subsflown – 16 x HP700 Cardioid
Subs– end-fire 24 x 1100-LFC (?) under the stage!!
Hi Darren,
You may be interested in this picture (sorry its only the stage) – same venue as the end-fire array you described, but this time it’s Michael Jackson the Immortal World Tour (Adelaide 15 &16/10/2013).
FOH– Meyer Leo
Subsflown – 16 x HP700 Cardioid
Subs– end-fire 24 x 1100-LFC (?) under the stage!!
Attachments
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Re: Endfire sub array under a stage
Hey all, I'm a little late to jump in on this and I only scanned about half of the posts just to see if I was actually adding to the convo here.
I recently did a cardioid array of subs under a stage with 8 single-18 subs.
My goal was some rear rejection, but mostly to achieve uniform coverage for a diamond shaped room (with the stage being in a corner). I achieved very acceptable results by making essentially 2 cardioid arrays and placing them one in front of the other, then delaying the rears to the front and flipping their polarity to achieve maximum cancellation to the rear. This config was partially due to limited DSP outputs, so necessity was the mother of the invention. I placed 3 subs in front and 5 in the rear. (If you want to get technical, the rear array was more of a spaced-array, but I digress...)
It modeled pretty well in MAPP and behaved very well in the actual room. However, there was a considerable amount of energy at the front of the stage directly above the subs, which is to be expected. I'm sure I'm not the first to do this, but it was a decent solution and may be one that you can experiment with.
Hey all, I'm a little late to jump in on this and I only scanned about half of the posts just to see if I was actually adding to the convo here.
I recently did a cardioid array of subs under a stage with 8 single-18 subs.
My goal was some rear rejection, but mostly to achieve uniform coverage for a diamond shaped room (with the stage being in a corner). I achieved very acceptable results by making essentially 2 cardioid arrays and placing them one in front of the other, then delaying the rears to the front and flipping their polarity to achieve maximum cancellation to the rear. This config was partially due to limited DSP outputs, so necessity was the mother of the invention. I placed 3 subs in front and 5 in the rear. (If you want to get technical, the rear array was more of a spaced-array, but I digress...)
It modeled pretty well in MAPP and behaved very well in the actual room. However, there was a considerable amount of energy at the front of the stage directly above the subs, which is to be expected. I'm sure I'm not the first to do this, but it was a decent solution and may be one that you can experiment with.
Re: Endfire sub array under a stage
I recommend staying clear, within reason, of any boundaries (except for the ground floor) in general when it comes to subwoofer configurations that rely on level and time interaction.
Apparently there’s a preference for end-fired configurations over gradient or inverted stack configurations.
As was already mentioned, end-fire has less rear rejection than gradient or inverted stack.
It might be tempting to attenuate the rear speaker in gradient configurations for optimal cancellation at the microphone. This electronic offset however remains constant over distance, preventing the configuration from achieving maximum cancelation at greater distance. Without the electronic attenuation the difference in level caused by the physical displacement of the speakers becomes insignificant over distance, automatically increasing cancelation at greater distance when both levels become equal. The same can’t be said for end-fired.
I’ve attached examples of a 4 element end-fire and a (2 element) gradient configuration, both optimized for an upper bandwidth limit of 100 Hz. The spacing is 1,13 and 1,24 meters respectively. Point of observation is 15 meters.
The end-fire bandwidth is indicated by the yellow markers. The right marker resides at the frequency equal to 1/3 wavelength spacing. At this frequency nothing is gained or lost. The left marker is its counterpoint. The black marker indicates the first cancelation and the red marker the critical frequency where all speakers add regardless of the amount of speakers. At 15 meters the front-to-back ratio within the bandwidth is 16 dB.
The gradient bandwidth is in indicated by the yellow and red markers. The yellow markers reside at the minus 3 dB points and the red markers at the minus 6 dB or 1/3 wavelength or 120 degrees phase difference points. The green marker indicates maximum summation. At 15 meters the front-to-back ratio within the bandwidth is 25 dB.
For the sake of illustration, lets change the point of observation to 1 km. Now the front-to-back ratio for the same configurations becomes 14,5 dB and 63 dB for end-fire an gradient respectively.
I’d also like to point out that end-fired configurations lack uniform coverage over frequency in contrast to gradient. As can be seen in the polar plots.
End-fired configurations of 3 or more elements require more real estate than gradient or inverted stack. At 5 or more elements one could speak of diminishing returns?
When real estate is scarce gradient or inverted stack seems the lesser of two evils in contrast to putting the end-fired configuration under the stage.
If vertical coverage is of concern and equal resources are available pile your subwoofers in a gradient configuration.
And finally I’d like to point out that raising the level, for whatever reason, of an end-fired configuration over the mains comes “without” penalty. The same can’t be said of a gradient configuration.
Raising the level of a gradient configuration over the mains brings into play the cancelled frequencies beyond the bandwidth. No amount of equalizing can restore this energy and if you try, you might end up blowing up your speakers. You’ll most likely hear no change due to the cancelation but each speaker individually is affected. The common emphasis of the subwoofers levels might account for the lack of impact that’s often associated with this kind of configuration. If you require more sub use a low-shelf on your processor input or mixer.
Inverted stack is a poor derivative of gradient when real estate is an issue or flying is preferred because you hardly ever achieve true ¼ wavelength displacement.
These plots are modeled with infinite small speakers without any physical dimensions but the trends should be clear…
I recommend staying clear, within reason, of any boundaries (except for the ground floor) in general when it comes to subwoofer configurations that rely on level and time interaction.
Apparently there’s a preference for end-fired configurations over gradient or inverted stack configurations.
As was already mentioned, end-fire has less rear rejection than gradient or inverted stack.
It might be tempting to attenuate the rear speaker in gradient configurations for optimal cancellation at the microphone. This electronic offset however remains constant over distance, preventing the configuration from achieving maximum cancelation at greater distance. Without the electronic attenuation the difference in level caused by the physical displacement of the speakers becomes insignificant over distance, automatically increasing cancelation at greater distance when both levels become equal. The same can’t be said for end-fired.
I’ve attached examples of a 4 element end-fire and a (2 element) gradient configuration, both optimized for an upper bandwidth limit of 100 Hz. The spacing is 1,13 and 1,24 meters respectively. Point of observation is 15 meters.
The end-fire bandwidth is indicated by the yellow markers. The right marker resides at the frequency equal to 1/3 wavelength spacing. At this frequency nothing is gained or lost. The left marker is its counterpoint. The black marker indicates the first cancelation and the red marker the critical frequency where all speakers add regardless of the amount of speakers. At 15 meters the front-to-back ratio within the bandwidth is 16 dB.
The gradient bandwidth is in indicated by the yellow and red markers. The yellow markers reside at the minus 3 dB points and the red markers at the minus 6 dB or 1/3 wavelength or 120 degrees phase difference points. The green marker indicates maximum summation. At 15 meters the front-to-back ratio within the bandwidth is 25 dB.
For the sake of illustration, lets change the point of observation to 1 km. Now the front-to-back ratio for the same configurations becomes 14,5 dB and 63 dB for end-fire an gradient respectively.
I’d also like to point out that end-fired configurations lack uniform coverage over frequency in contrast to gradient. As can be seen in the polar plots.
End-fired configurations of 3 or more elements require more real estate than gradient or inverted stack. At 5 or more elements one could speak of diminishing returns?
When real estate is scarce gradient or inverted stack seems the lesser of two evils in contrast to putting the end-fired configuration under the stage.
If vertical coverage is of concern and equal resources are available pile your subwoofers in a gradient configuration.
And finally I’d like to point out that raising the level, for whatever reason, of an end-fired configuration over the mains comes “without” penalty. The same can’t be said of a gradient configuration.
Raising the level of a gradient configuration over the mains brings into play the cancelled frequencies beyond the bandwidth. No amount of equalizing can restore this energy and if you try, you might end up blowing up your speakers. You’ll most likely hear no change due to the cancelation but each speaker individually is affected. The common emphasis of the subwoofers levels might account for the lack of impact that’s often associated with this kind of configuration. If you require more sub use a low-shelf on your processor input or mixer.
Inverted stack is a poor derivative of gradient when real estate is an issue or flying is preferred because you hardly ever achieve true ¼ wavelength displacement.
These plots are modeled with infinite small speakers without any physical dimensions but the trends should be clear…
Re: Endfire sub array under a stage
Regarding level discrepancies between end-fire and regular stacked subwoofers. Besides increased radiating surface, the point of observation also matters. Relatively close (in relation to the length of the array) to the array, the level of each subwoofer at the position of the microphone isn’t identical due to the displacement (inverse square law). At greater distance these differences become insignificant and summation increases.
Also the parameters found in modeling programs often don’t account for the physical dimensions of the speakers. In real life often more delay is required to compensate for the increased path length caused by the obstruction of the closer speakers except for the closest speaker. Values between 0.5 and 1 ms of extra delay aren’t uncommon. All the more reason to always measure on site.
Regarding level discrepancies between end-fire and regular stacked subwoofers. Besides increased radiating surface, the point of observation also matters. Relatively close (in relation to the length of the array) to the array, the level of each subwoofer at the position of the microphone isn’t identical due to the displacement (inverse square law). At greater distance these differences become insignificant and summation increases.
Also the parameters found in modeling programs often don’t account for the physical dimensions of the speakers. In real life often more delay is required to compensate for the increased path length caused by the obstruction of the closer speakers except for the closest speaker. Values between 0.5 and 1 ms of extra delay aren’t uncommon. All the more reason to always measure on site.
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Re: Endfire sub array under a stage
So i did some measurements on a end fired config of 6 USW1p subs which were set-up in a trianglish sort of array
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-002.png
The mic in the back was very close due to lack of space so at larger distances in theory the cancels achieved should be deeper i think (do not know yet).
The problem when using delay as pointed out is that there are a few deep cancels but it's not a constant reduction al over the operating range of the sub's .
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0026.png
However when using all-pass filters you get a bit more control over the cancelation area in the back at a small reduction in frequency response in the higher frequencies of the operating range of the subs @ the front mic (past the 125Hz i have to cross them a bit high because i only have UPA1 and 2p's which have there x-over about 125Hz) . If i use the 1 and 2p together i can go to about 100Hz because of the coupling in the low end on the upa's
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0051.png
Again the mic at the back was close due to lack of space but if i given the chance and enough space i'll post some results when/if i have time .
(complete blog post :End fired sub array first with delay then with 2nd order all-pass filters | Timo's World all around the globe)
So i did some measurements on a end fired config of 6 USW1p subs which were set-up in a trianglish sort of array
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-002.png
The mic in the back was very close due to lack of space so at larger distances in theory the cancels achieved should be deeper i think (do not know yet).
The problem when using delay as pointed out is that there are a few deep cancels but it's not a constant reduction al over the operating range of the sub's .
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0026.png
However when using all-pass filters you get a bit more control over the cancelation area in the back at a small reduction in frequency response in the higher frequencies of the operating range of the subs @ the front mic (past the 125Hz i have to cross them a bit high because i only have UPA1 and 2p's which have there x-over about 125Hz) . If i use the 1 and 2p together i can go to about 100Hz because of the coupling in the low end on the upa's
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0051.png
Again the mic at the back was close due to lack of space but if i given the chance and enough space i'll post some results when/if i have time .
(complete blog post :End fired sub array first with delay then with 2nd order all-pass filters | Timo's World all around the globe)
Re: Endfire sub array under a stage
Hi Timo,
Very interesting and useful as usual. Very much appreciated.
Hi Timo,
Very interesting and useful as usual. Very much appreciated.
Re: Endfire sub array under a stage
You're welcome
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0027.png
Watch out with the use off allpass filters when doing this
You're welcome
http://timobeckmangeluid.files.wordpress.com/2013/09/end-fired-0027.png
Watch out with the use off allpass filters when doing this
Re: Endfire sub array under a stage
I did an endfire arrangement under a stage this summer which worked very well. It was three Bag End D18Elf speakers per side, laying on their sides underneath the PA hang bays, spaced 5' facing forward and delayed appropriately. The deck was just under 4' clearance to ground, and the stage sides were open all around. We half-assed stacked plywood behind the stage to try to cut the rear bleed even more, but of course that had minimal effect.
We tried doing a single array of all the subs, but felt the side coverage was lacking, and so went with two L-R arrays and lived with a power alley.
They were there the whole summer, and sounded the best I'd ever heard those subs sound, which was really good. We taped the seams in the deck so water didn't drip on them, and had them sitting on plywood on the ground.
They had been stacked in previous years three high on their sides on each side of the stage, which caused lots of complaints from behind the stage, and had no where near the throw that this configuration has.
It was a little noisy directly above them, but there were really no complaints from the artists who were over in the middle of the stage, largely; certainly stage spill was no more of an issue than it had been with the three-high stacks.
Thanks to another directional sub thread on this forum, which is where I got the idea. There were some posts in it that showed rows of subs facing each other and tightly packed; I could never get that to work, but what we wound up doing was easy and effective.
I did an endfire arrangement under a stage this summer which worked very well. It was three Bag End D18Elf speakers per side, laying on their sides underneath the PA hang bays, spaced 5' facing forward and delayed appropriately. The deck was just under 4' clearance to ground, and the stage sides were open all around. We half-assed stacked plywood behind the stage to try to cut the rear bleed even more, but of course that had minimal effect.
We tried doing a single array of all the subs, but felt the side coverage was lacking, and so went with two L-R arrays and lived with a power alley.
They were there the whole summer, and sounded the best I'd ever heard those subs sound, which was really good. We taped the seams in the deck so water didn't drip on them, and had them sitting on plywood on the ground.
They had been stacked in previous years three high on their sides on each side of the stage, which caused lots of complaints from behind the stage, and had no where near the throw that this configuration has.
It was a little noisy directly above them, but there were really no complaints from the artists who were over in the middle of the stage, largely; certainly stage spill was no more of an issue than it had been with the three-high stacks.
Thanks to another directional sub thread on this forum, which is where I got the idea. There were some posts in it that showed rows of subs facing each other and tightly packed; I could never get that to work, but what we wound up doing was easy and effective.
Re: Endfire sub array under a stage
Are you saying they were louder out front? If so-that goes against all of my (and others) testing with directional arrays.
Do you have any measurements to show that?
So what exactly do you mean by "throw"?
Are you saying they were louder out front? If so-that goes against all of my (and others) testing with directional arrays.
Do you have any measurements to show that?
Re: Endfire sub array under a stage
I mean that the sub impact at the back of the field was greater in this configuration than with the stacked boxes.
No, I did not measure that.
Yes, all of my crew, who have been present at this series for years, agreed that it was better in every way than our other arrays.
Edit: In remembering what I was thinking a couple months ago, what I decided was the reason it was sounding so much better was that all six of the boxes were on the ground and benefitting from the ground coupling, whereas only two were benefitting in the stacks, while four had varying degrees of distance from the ground.
We had tried a horizontal line of subs previously, in both a cardiod array (four front-firing and three rear- ) and with all forward facing, but found that the horizontal coverage (width) was nowhere near what we needed. The curving and delaying we were capable of helped, but was still not enough.
The vertical stack of three boxes gave the width coverage, but not only was it wide it was circular. Reversing and delaying one of the boxes in the vertical stack doesn't work so well with the Bag Ends; my theory is that because it's a sealed cabinet, the sides flex a bit from each in and out driver movement, generating some sound. I could be wrong, but the Bag Ends have more off-axis response than my Meyer ported subs and port vs. no port is the only thing I can think of to explain that difference.
I did mess around with MAPP predictions of doing the endfire, but only with all six subs grouped together in one cluster (three rows of two subs). The earlier thread talked about having a single cluster and it working fine, but I think their hangs had more low end than mine (Melodies), because it didn't work to have all the subs in the middle of the stage width or on one side. We on the spot divided them into two arrays of 3, and decided that worked fine and didn't worry about it again. All of the BE's were fine with the sub sound.
And I didn't pay any attention beforehand to whether or not the overall output was increased or decreased; the first priority was to decrease the rear throw without significantly decreasing the side coverage, and we did that, with the bonus of perceptually more even coverage front to back.
I mean that the sub impact at the back of the field was greater in this configuration than with the stacked boxes.
No, I did not measure that.
Yes, all of my crew, who have been present at this series for years, agreed that it was better in every way than our other arrays.
Edit: In remembering what I was thinking a couple months ago, what I decided was the reason it was sounding so much better was that all six of the boxes were on the ground and benefitting from the ground coupling, whereas only two were benefitting in the stacks, while four had varying degrees of distance from the ground.
We had tried a horizontal line of subs previously, in both a cardiod array (four front-firing and three rear- ) and with all forward facing, but found that the horizontal coverage (width) was nowhere near what we needed. The curving and delaying we were capable of helped, but was still not enough.
The vertical stack of three boxes gave the width coverage, but not only was it wide it was circular. Reversing and delaying one of the boxes in the vertical stack doesn't work so well with the Bag Ends; my theory is that because it's a sealed cabinet, the sides flex a bit from each in and out driver movement, generating some sound. I could be wrong, but the Bag Ends have more off-axis response than my Meyer ported subs and port vs. no port is the only thing I can think of to explain that difference.
I did mess around with MAPP predictions of doing the endfire, but only with all six subs grouped together in one cluster (three rows of two subs). The earlier thread talked about having a single cluster and it working fine, but I think their hangs had more low end than mine (Melodies), because it didn't work to have all the subs in the middle of the stage width or on one side. We on the spot divided them into two arrays of 3, and decided that worked fine and didn't worry about it again. All of the BE's were fine with the sub sound.
And I didn't pay any attention beforehand to whether or not the overall output was increased or decreased; the first priority was to decrease the rear throw without significantly decreasing the side coverage, and we did that, with the bonus of perceptually more even coverage front to back.
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Re: Endfire sub array under a stage
Just like any speaker system-the greater the direct sound-the cleaner it will be. Hence the reason for using large horns to keep the energy where it is supposed to be (on the people) and not where it isn't (walls-ceiling etc).
Wider ratios are welcome anywhere: direct to reverberant, Signal to noise, continuous vs peak. It is not the single component-but rather the ratio between them that makes the difference.
I have seen it several times where when the sound is all "muddy" people want to run the system harder-thinking it will sound clearer-when all it does is get worse.
With a cleaner/more direct sound-very often the levels will come down. When the levels come down-there is less distortion-less ear overload and so forth.
So the sound is better.
Unless it is the "crushing wall of sound" that one is looking for-then it really doesn't matter-just make everything louder than everything else.
More than likely what you were "experiencing" was simply less of "other sound" that comes from the subs spraying energy all over the place. So you heard more of the direct sound and less of the "reflected".
Just like any speaker system-the greater the direct sound-the cleaner it will be. Hence the reason for using large horns to keep the energy where it is supposed to be (on the people) and not where it isn't (walls-ceiling etc).
Wider ratios are welcome anywhere: direct to reverberant, Signal to noise, continuous vs peak. It is not the single component-but rather the ratio between them that makes the difference.
I have seen it several times where when the sound is all "muddy" people want to run the system harder-thinking it will sound clearer-when all it does is get worse.
With a cleaner/more direct sound-very often the levels will come down. When the levels come down-there is less distortion-less ear overload and so forth.
So the sound is better.
Unless it is the "crushing wall of sound" that one is looking for-then it really doesn't matter-just make everything louder than everything else.
Re: Endfire sub array under a stage
Maybe, but I don't think so. There's really nothing within a very long distance to give significant reflections from behind the stage. The reflecting surfaces that are present are in the path of the desired sound and so still in the equation.
Like I said, I think the improvement was due to effectively 24 drivers due to ground coupling vs. 16 with the vertical stacks.
Maybe, but I don't think so. There's really nothing within a very long distance to give significant reflections from behind the stage. The reflecting surfaces that are present are in the path of the desired sound and so still in the equation.
Like I said, I think the improvement was due to effectively 24 drivers due to ground coupling vs. 16 with the vertical stacks.
Re: Endfire sub array under a stage
There may have been other "things" at play than in the past, but I have never seen a directional array that has as good a freq response or output as the same number of cabinets all stacked together.
I would need some actual measurements to start to convince me.
There is always some degration in the sound quality due to the cancellation "effect". It is just part of the price you pay for the directivity.
It is good that you feel it is better-but I suspect something else is at play in the results you heard.
I still disagree. Even though a sub cabinet may not be on the ground-you will still get "ground coupling" at bass freq-up to a certain height. Or course it depends on the freq and the height of the cabinet.
There may have been other "things" at play than in the past, but I have never seen a directional array that has as good a freq response or output as the same number of cabinets all stacked together.
I would need some actual measurements to start to convince me.
There is always some degration in the sound quality due to the cancellation "effect". It is just part of the price you pay for the directivity.
It is good that you feel it is better-but I suspect something else is at play in the results you heard.
Re: Endfire sub array under a stage
In the interest of simply wanting to understand all this, is there a paper/website that talks about all the different array configurations and their pros/cons/uses?
In the interest of simply wanting to understand all this, is there a paper/website that talks about all the different array configurations and their pros/cons/uses?
Re: Endfire sub array under a stage
Jared,
I wrote two subwoofer articles for Live Sound mag back in 2010. They might be helpful to you
http://bennettprescott.com/downloads/SubwooferArraying.pdf
http://bennettprescott.com/downloads/AdvancedSubwooferArraying.pdf
Jared,
I wrote two subwoofer articles for Live Sound mag back in 2010. They might be helpful to you
http://bennettprescott.com/downloads/SubwooferArraying.pdf
http://bennettprescott.com/downloads/AdvancedSubwooferArraying.pdf
Re: Endfire sub array under a stage
Has it been that long already? Time keeps slipping away.
Has it been that long already? Time keeps slipping away.