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Author Topic: 12 Lab's in a horizontal row -- Sugestions for settings?  (Read 7504 times)

Jeremy Bridge

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12 Lab's in a horizontal row -- Sugestions for settings?
« on: July 22, 2004, 01:21:13 pm »

I have a show comming up here in two weeks were we will be using 12 labs in a horizontal cluster.

I recal hearing about some issues with response and directionality when using groups this large.

Do anyone here have any sugestions on what to look out for / setup?   Ie delay, Eq, etc.
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Tim Padrick

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #1 on: July 22, 2004, 11:07:55 pm »

With the Canadian Flexline system, the subs are spread across the entire stage width (as opposed to stacking them in clusters), and they say it works very well.  http://www.verityaudio.com/VDGroup/Pictures.htm

Too Tall (Curtis H. List)

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #2 on: July 23, 2004, 11:20:39 am »

Jeremy Bridge wrote on Thu, 22 July 2004 13:21

I have a show comming up here in two weeks were we will be using 12 labs in a horizontal horizontal cluster.

I recal hearing about some issues with response and directionality when using groups this large.

Do anyone here have any sugestions on what to look out for / setup?   Ie delay, Eq, etc.



Hi Jeremy,
   I sorry, but I don't know what a "horizontal horizontal" cluster is. I'm guessing it is a typo. Wink
   For the sake of argument lets say you mean putting them next to each other 12 wide across the center of the stage. You could stand them all up so that they are 45" high in which case the horizontal array is 22.5 feet wide.
   If you lay them all down the array is 45 feet wide. I'm guessing you are standing them up.
   Al did four laying down across the center (about 15 feet wide) and reported the bass response was as not much wider then the array when he walked the audience area. So you set up will have even less horizontal dispersion at even lower frequencies.

The solution is delaying the outer boxes. The center boxes gets no delay. As you move toward the outer boxes the delay becomes more and more. Imagine you are making an arch with the outer boxes being pushed back toward the back of the stage.
   You would also like to set the high pass frequency lower on the outer boxes. That way at 80Hz only the center boxes are working so the "array width" is smaller as you go up in frequency.
   Of course delaying the boxes in pairs you would need a DSP with six outputs just for the subs. If you don't have access to that I would steal a garden-variety reverb/digital delay from the effects rack and use it on the outer six cabinets. If you have a spare EQ roll off around 65Hz to 80Hz or so on those outer boxes too.
   I have never done this so I won't give you specifics on delay time or high pass frequencies. If I had to do it I would start with a short delay of about 2ms and walk the audience area as I added more and more delay.
   Tako Tamas has actually done some of this so he would be a better source for specifics.
   Too Tall

PS- Tako, if you read this I hope I got it all right.  Smile
   

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Mark Seaton

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #3 on: July 23, 2004, 02:31:15 pm »

Too Tall wrote on Fri, 23 July 2004 10:20

Jeremy Bridge wrote on Thu, 22 July 2004 13:21

I have a show comming up here in two weeks were we will be using 12 labs in a horizontal horizontal cluster.

I recal hearing about some issues with response and directionality when using groups this large.

Do anyone here have any sugestions on what to look out for / setup?   Ie delay, Eq, etc.



   Al did four laying down across the center (about 15 feet wide) and reported the bass response was as not much wider then the array when he walked the audience area. So you set up will have even less horizontal dispersion at even lower frequencies.

The solution is delaying the outer boxes. The center boxes gets no delay. As you move toward the outer boxes the delay becomes more and more. Imagine you are making an arch with the outer boxes being pushed back toward the back of the stage.
   You would also like to set the high pass frequency lower on the outer boxes. That way at 80Hz only the center boxes are working so the "array width" is smaller as you go up in frequency.
   Of course delaying the boxes in pairs you would need a DSP with six outputs just for the subs. If you don't have access to that I would steal a garden-variety reverb/digital delay from the effects rack and use it on the outer six cabinets. If you have a spare EQ roll off around 65Hz to 80Hz or so on those outer boxes too.
   I have never done this so I won't give you specifics on delay time or high pass frequencies. If I had to do it I would start with a short delay of about 2ms and walk the audience area as I added more and more delay.



Having modeled and played with this in different fashions, in my oppinion, it is best to approach this as simple as possible.  Delay is a PITA to get dialed in, and will have some odd effects out of the intended bandwidth.  I went through this a couple times here on the LAB when Al posted his impression of what 4 wide on their side had given him, so it might be worth searching my name and LAB sub for the old posts.

Most users forget that almost any low pass incurrs group delay.  This source of delay is no more or less valuable than a straight delay block in a DSP at a given frequency.  I would first ask to consider if you can stack 4 sets of 3 high on their side rather than 12 standing upright?  Either way, you will need to shade the outer boxes.  The simplest way which can even be done in the analog world is to take a mono sub feed through a 4th order(24dB/oct) low pass, where you then take two outputs from the filter.  One goes to the center cluster of subwoofers, chosen to be small enough to have wide enough coverage over the intended area.  The second output goes to another low pass filter, where I like the effects of a 2nd order (12dB/Oct) low pass which feeds the outer subs on either side of the center block.  This gives you 3 blocks total.  If your length gets really long and you want to go relatively high in frequency, you may find you need 3 filter sets, and 5 blocks.  So far as setting the filters, for most cases it appears the best results are had when staggering the two filters about the effective crossover, or setting the 4th order filter at your desired crossover if you plan to have the bass ramped up a good bit from the main passband.  Since the filter adds delay while attenuating the high frequency energy, the 2nd order filter for the outer boxes doesn't have to be much lower than the primary crossover.  I recommend this 2nd filter to be a Butterworth or Bessel, where 3rd order (18dB/0ct) can also work depending on the setup.  Subjectively, what you end up hearing with the filters engaged vs. just all commonly fed is that the level in the center "hot spot" will drop to match that of the off axis level, while the off axis level comes up slightly.  EQ wise you may find the need to boost slightly at or just below the crossover frequency, where I would apply any EQ BEFORE all filters, to the mono signal.  Doing otherwise will screw up what you just worked to fix.

That should be a good guideline/starting point.  Taking measurements at two distant locations, one on and one off axis should allow for easy verification.

Good luck,
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Phillip_Graham

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #4 on: July 23, 2004, 03:12:52 pm »

Jeremy Bridge wrote on Thu, 22 July 2004 13:21

I have a show comming up here in two weeks were we will be using 12 labs in a horizontal horizontal cluster.

I recal hearing about some issues with response and directionality when using groups this large.

Do anyone here have any sugestions on what to look out for / setup?   Ie delay, Eq, etc.



If you can do this with the subs traversing the venue from wall to wall, it's quite a powerful effect, and gives even coverage across the whole horizontal range.  If you have to cover off axis, the suggestions of the others are good ones.
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Rob Burgess

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #5 on: July 26, 2004, 01:19:19 pm »

Hey Mark,

Mark Seaton wrote on Fri, 23 July 2004 14:31


So far as setting the filters, for most cases it appears the best results are had when staggering the two filters about the effective crossover, or setting the 4th order filter at your desired crossover if you plan to have the bass ramped up a good bit from the main passband.  Since the filter adds delay while attenuating the high frequency energy, the 2nd order filter for the outer boxes doesn't have to be much lower than the primary crossover.


    I'm trying to wrap my head around this Smile  In a system where the subs are high passed at 30Hz and crossed over at, say, 100Hz - you'd recommend the outer stacks be low passed at ~90Hz?  Am I reading you right?

--
Rob

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Phillip_Graham

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #6 on: July 26, 2004, 02:10:54 pm »

Dwarf wrote on Mon, 26 July 2004 13:19

Hey Mark,

Mark Seaton wrote on Fri, 23 July 2004 14:31


So far as setting the filters, for most cases it appears the best results are had when staggering the two filters about the effective crossover, or setting the 4th order filter at your desired crossover if you plan to have the bass ramped up a good bit from the main passband.  Since the filter adds delay while attenuating the high frequency energy, the 2nd order filter for the outer boxes doesn't have to be much lower than the primary crossover.


    I'm trying to wrap my head around this Smile  In a system where the subs are high passed at 30Hz and crossed over at, say, 100Hz - you'd recommend the outer stacks be low passed at ~90Hz?  Am I reading you right?

--
Rob




Yeah, Rob, you understand Mark correctly.  Low passing the outer boxes lower does two things.  First it provides amplitude shading by causing their output to tail off sooner, widenening the coverage zone.

Second it provides delay shading.  By lowering the crossover frequency, you are incurring more group delay at the crossover point than at a higher frequency.  If you have 180 degrees phase shift at the xo point (i.e. 4th order Linkwitz Riley lowpass), then at a 100hz xo that 180 degrees is approximately 5ms of delay, but that same 180 degrees at 50hz resuslts in a group delay of 10ms, b/c the 50hz tone has 2x the period as the 100hz tone.

Hope that clears it up.
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Rob Burgess

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #7 on: July 26, 2004, 03:50:21 pm »

Hi Phil,

gtphill wrote on Mon, 26 July 2004 14:10


Hope that clears it up.


Thanks, yeah it helps a lot.  

--
Rob
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Doug Fowler

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #8 on: July 28, 2004, 08:28:47 am »

Hi Mark -

Interesting approach, using low pass and group delay.  I wrestled with a 16 wide of d&b B2s back in March, modeled with Arrayshow.  You are indeed correct about strange things happening at higher frequencies as you add delay incrementally to the outside.  I managed to get it so that the weirdness was far enough outside the low pass for the B2s, and was down in level enough it didn't matter in the end.

This was 16 standing on end, next to each other.  I ended with 21 msec. of delay on the outer pair.  It seems a wider block of course requires more delay on the outside, which lowers the frequency at which the weird things start to happen.  In the end I was good up to around 60 Hz, which was fine for the application (B2s in infra mode).  Walking the amphitheater the level was pretty much equal out to maybe 140 degrees, with no hot spot and no nulls created by interference by separated sources.

One thing that comes with this is the loss of apparent punch, or whatever you choose to call it.  I attributed it to spreading an acoustic source out to 140 degrees or so, vs. 20 degrees.  16 B2s in a row obviously sets up a killer power alley  Shocked  

What got all this started was a client request for even subbass throughout the venue for a rave (Ultra Music Festival 2004 in Miami) without the power alley.  The previous year, there was no type of delay scheme for a similar setup.  This thing really worked well.  However, I did spend quite a few hours modeling it.

Do you have examples of the implementation by low pass, rather than "regular" delay?

Thanks, this is interesting stuff IMO......

The attached photo is a view of part of the amphitheater.  You can just barely see some of the subs in the lower left hand corner, against the curved rail.  Interestingly, the radius of the railing factored into the equation and had to be taken into account when modeling.  

-doug
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Phillip_Graham

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #9 on: July 29, 2004, 11:41:12 am »

Doug Fowler wrote on Wed, 28 July 2004 08:28

Hi Mark -

One thing that comes with this is the loss of apparent punch, or whatever you choose to call it.  I attributed it to spreading an acoustic source out to 140 degrees or so, vs. 20 degrees.  16 B2s in a row obviously sets up a killer power alley  Shocked  

However, I did spend quite a few hours modeling it.

Do you have examples of the implementation by low pass, rather than "regular" delay?

Thanks, this is interesting stuff IMO......

-doug


Doug, doing the low pass shading modeling is difficult in arrayshow, because you have to calculate the amplitude attenuation and the group delay by hand, and then enter them in for each point source.  Monte said at Infocomm that a new version of arrayshow, that works with XP, should be up on the website by now.  I have yet to check.

The RACE software for the DX38 allows you to apply actual filters to the devices in your setup, making this easier to model.  There is a pretty good tutorial on this with the program.  The display is almost like a virtual SMAART window.  The visualization is not the same as arrayshow.  It's been a while since I've played with it (not much audio recently), so my memory is a bit foggy.

The intellivox people have a couple good papers on doing these sort of tapered arrays floating around out there.  I have even read some sonar array papers, they do some even more creative stuff.
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Phillip_Graham

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Re: 12 Lab's in a horizontal row -- Sugestions for settings?
« Reply #10 on: July 29, 2004, 11:47:32 am »

Doug Fowler wrote on Wed, 28 July 2004 08:28



The attached photo is a view of part of the amphitheater.  You can just barely see some of the subs in the lower left hand corner, against the curved rail.  Interestingly, the radius of the railing factored into the equation and had to be taken into account when modeling.  

-doug


One more thing, Doug.  Are you system teching the 311 tour?  If so, please drop me a PM.  Your profile won't accept PM's...
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Doug Fowler

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« Reply #11 on: July 30, 2004, 02:30:35 pm »

Philligator -

I changed my profile.  But no, I'm not on 311.

thanks for the insight....

-doug
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