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Author Topic: "Multi cellular array" vs "Single Source array"  (Read 25876 times)

Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #50 on: July 23, 2016, 11:04:06 pm »

Like I said, I don't have access right now to the info. 
I do know that there have been many concerts done with less than the full compliment of 24 boxes per side (typically 18 or 19 MLA and a single MLA-D) with coverage out to 250 meters and drop off created at 300 meters to avoid noise complaints.

I will try to find the info that I have on the other coverage.  It was between 700' and 900' if I am remembering correctly although my memory is not what it used to be. :-)

Lee

Just following up on this.  Since I was going by memory before.

I can't find the write up that I was thinking of (seems to me it was in Japan and was 2 - 24 box hangs at something over 700', I just can't come up with it) but I have found others referencing 200 and 250 meter coverage for specific events with MLA and MLD.  The 200 meter mark seems to be the typical maximum before most people want to add delays.

There are no specific published measurements in the write ups so I did my own Display file with very little playing to smooth things out or try different array heights, starting distances, etc. 
In a quickly created file I can keep response to approximately +/- 6dB from 100Hz to 10kHz, 20' in front of the array to 650' in front of the array (approximately 200 meters).  This is only with standard configuration (splay and EEQ calculations) and not any system equalization factored into zones of the array.  This is a single array of 23 MLA and 1 MLD.

Display predictions vs real world results have been shown to be accurate to +/- 0.5 dB/SPL.

There are 72 - 1" HF devices in a 24 box MLA array.

There could be MASSIVE differences in the result depending on humidity.  High humidity areas could get away with this while arid areas could not. 



Lee
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Robert Lunceford

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Re: "Multi cellular array" vs "Single Source array"
« Reply #51 on: July 24, 2016, 01:05:46 am »

5 date=1469
Quote from: Lee Buckalew link=topic=160077.msg1470975#msg147097292593
I do know that there have been many concerts done with less than the full compliment of 24 boxes per side ....

Something else to consider,
MLA nominal power consumption is 900 watts X 48 boxes = 43,200 watts
MLA weight is 193 lbs X 48 boxes = 9,264 lbs
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Ivan Beaver

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Re: "Multi cellular array" vs "Single Source array"
« Reply #52 on: July 24, 2016, 05:55:54 am »

Just following up on this.  Since I was going by memory before.

I can't find the write up that I was thinking of (seems to me it was in Japan and was 2 - 24 box hangs at something over 700', I just can't come up with it) but I have found others referencing 200 and 250 meter coverage for specific events with MLA and MLD.  The 200 meter mark seems to be the typical maximum before most people want to add delays.

There are no specific published measurements in the write ups so I did my own Display file with very little playing to smooth things out or try different array heights, starting distances, etc. 
In a quickly created file I can keep response to approximately +/- 6dB from 100Hz to 10kHz, 20' in front of the array to 650' in front of the array (approximately 200 meters).  This is only with standard configuration (splay and EEQ calculations) and not any system equalization factored into zones of the array.  This is a single array of 23 MLA and 1 MLD.

Display predictions vs real world results have been shown to be accurate to +/- 0.5 dB/SPL.

There are 72 - 1" HF devices in a 24 box MLA array.

There could be MASSIVE differences in the result depending on humidity.  High humidity areas could get away with this while arid areas could not. 



Lee
IS that with air absorption turned on?

It makes a HUGE difference.

The numbers I gave are based on actual measurements in a venue-NOT predictions.

Every bodies predictions are much better with air absorption turned off
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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #53 on: July 24, 2016, 07:04:08 am »

IS that with air absorption turned on?

It makes a HUGE difference.

The numbers I gave are based on actual measurements in a venue-NOT predictions.

Every bodies predictions are much better with air absorption turned off

Yes,  air absorption is on.

Lee
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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #54 on: July 24, 2016, 07:23:39 am »

5 date=1469
Something else to consider,
MLA nominal power consumption is 900 watts X 48 boxes = 43,200 watts
MLA weight is 193 lbs X 48 boxes = 9,264 lbs

Yes, although I would not use the nominal power rating, since peak is 6000 watt capability.  They are 100, 120, or 208/240 volt capable. 

JBL VerTec VT4889ADPDA is 205 lbs per cabinet with a similar power draw and universal voltage capability.  As a line array it lacks the coherence capability for extremely long "throws" of HF. 

Meyer LEO is 265 lbs per cabinet and capable of 208/240 only (no 100, 120 volt ability).  Also a standard line array. 

All of the other manufacturers fall right around this same weight, size, power, and per cabinet output specification.  Mid-sized boxes is where the size, weight, power, and output per cabinet specs start to vary more significantly.

MLA falls right into the weight and power consumption, per box, of similar sized concert PA cabinets.  It has higher output than others of similar size due to its greater coherence. 

Other threads here have hashed out the portability, reconfigurability, etc. concerns of the touring and portable PA folks.

Lee
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Hayden J. Nebus

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Re: "Multi cellular array" vs "Single Source array"
« Reply #55 on: July 25, 2016, 04:10:25 pm »

D&B is doing very little in the technology department compared to either EAW or Martin and are really still just a line array with some FIR applied (up to 6 max per cabinet if my information is correct) across the full range cabinet as I am understanding it. 

Lee

I will vouch that there's a serious amount of maths happening with d&b array processing. The crux of their approach looks to be a whole lot of vector summing.

I've literally just gotten the chance yesterday to point a mic at a d&b rig with array processing. 8x Y series on 30D amps, set to front/back -0dB SPL drop (smaller venue) , with Glory@11. Here's what I've gleaned on how it works. Just the facts (and some postulations) .

It appears to me that each cabinet gets its own linear magnitude (phase only) FIR filter, a parametric-allpass, if you will. AP adds 6.5ms throughput latency on the 30D. latency = N-1 / 2*fs, so it's likely to be 625 tap filters at 48kHz. There's enough ripple to the filters that 1/6 octave phase smoothing was required to make the trace human-legible, so IMO 1250 taps @ 96kHz, which I would expect to look a lot smoother, isn't likely.  On this rig, d&b applies the AP filters from roughly 1k-20k.

Array calc reckons multiple data points of raw response curves along the vertical axis of the array. In "glory", each cabinet's mid-hi band phase response is adjusted such that the resultant frequency response is as similar as possible at each of the reckoned data points.

The result is interesting. The magnitude response is very consistent everywhere. A coherence-weighted average of multiple transfer functions looks a lot like just another data point. As a result, the rig is very responsive to EQ, and it responds to EQ the same way everywhere, much unlike most vertical arrays.

The resulting phase response at each seat falls somewhere within +/-45° of "normal" at the nyquist frequency, which nets a 90° distribution. I did not get to measure each box on/off axis to see what the AP is actually doing per box, but rather looked at the whole rig from multiple locations.

I can post some traces later, or open a new thread on the measurement forum if Doug or Mac would prefer. 
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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #56 on: July 25, 2016, 06:32:52 pm »

I will vouch that there's a serious amount of maths happening with d&b array processing. The crux of their approach looks to be a whole lot of vector summing.

I've literally just gotten the chance yesterday to point a mic at a d&b rig with array processing. 8x Y series on 30D amps, set to front/back -0dB SPL drop (smaller venue) , with Glory@11. Here's what I've gleaned on how it works. Just the facts (and some postulations) .

It appears to me that each cabinet gets its own linear magnitude (phase only) FIR filter, a parametric-allpass, if you will. AP adds 6.5ms throughput latency on the 30D. latency = N-1 / 2*fs, so it's likely to be 625 tap filters at 48kHz. There's enough ripple to the filters that 1/6 octave phase smoothing was required to make the trace human-legible, so IMO 1250 taps @ 96kHz, which I would expect to look a lot smoother, isn't likely.  On this rig, d&b applies the AP filters from roughly 1k-20k.

Array calc reckons multiple data points of raw response curves along the vertical axis of the array. In "glory", each cabinet's mid-hi band phase response is adjusted such that the resultant frequency response is as similar as possible at each of the reckoned data points.

The result is interesting. The magnitude response is very consistent everywhere. A coherence-weighted average of multiple transfer functions looks a lot like just another data point. As a result, the rig is very responsive to EQ, and it responds to EQ the same way everywhere, much unlike most vertical arrays.

The resulting phase response at each seat falls somewhere within +/-45° of "normal" at the nyquist frequency, which nets a 90° distribution. I did not get to measure each box on/off axis to see what the AP is actually doing per box, but rather looked at the whole rig from multiple locations.

I can post some traces later, or open a new thread on the measurement forum if Doug or Mac would prefer.

First, I know, I write too much. :-)
Second, I may seem to be arguing but, for those who know me, they will attest that I am not.  I am merely explaining differences and also hearing and understanding different approaches and different technologies. 

I will be very interested to see/hear how D&B's ArrayCalc compares ultimately.  Thus far it has been utilized for a demo of D&B in a room which has also demoed K2, KARA, Nexo, Lyon, and MLA-C (I may be forgetting 1 or 2).  Measurement and listening comparisons have been interesting.


I was not meaning to suggest that there is not "a lot" of math being done to produce the results that D&B is now getting, just that there is significantly more math occurring in Display. 
The raw number of filters able to be utilized by MLA is many times that of D&B's ArrayCalc.  Given 10 years of refinement to MLA technology and 3 complete speaker lines all utilizing MLA's patented numerical optimization process I expect MLA to be the front-runner that everyone is chasing and comparing themselves to.  Understanding what is being done with it and how and why it was developed has really helped me to have a greater understanding of applied acoustical principals.

My understanding is that D&B are doing something similar to what Clair is doing and what VUE is doing in terms of applying array processing.  As I understand it it is full range cabinet processing, not driver by driver, and I think it is limited to 6 filter points per cabinet.  This certainly helps to significantly smooth overall response. 
On the other hand, MLA is providing driver by driver processing with up to 6000 filter points per array.  This should equate to 250 filter points per cabinet since each box contains all of the processing that it utilizes.  This is 41 filter points (and change) per drive section, per cabinet but I do not know how the filter point distribution is within the 6 independently powered and processed driver sections.

Martin Display analyzes multiple data points as well, I do not know how many data points are being calculated in D&B's calculations nor how many virtual test points they are using but, I believe that Martin Display is utilizing 1,800,000 per virtual measurement microphone for a full array of full size MLA (1,200,000 and 1,800,000 are both in my mind and I do not recall which is correct).  So a 100 meter deep audience area would have 540,000,000 calculations for just the audience plane (if I am doing my math correctly), add to that the height of the walls, length of the ceiling, height of the backstage wall, etc. and you get an idea for how much math is being done here.

In Display virtual measurement mics are placed every 1/3 meter in the listening plane of the audience area and every 1 meter in the non-audience area, on-axis.  Calculations are based on a combination of positional, flanked, and isolated cabinet data.  This is because it was found that utilizing isolated cabinet data alone (which is what was used by all that I am aware of when MLA was in development) resulted in errors of as much as 8dB.  The requirement for accuracy for modeling was found to be 1dB (+/- 0.5dB) which could not be obtained by utilizing isolated data.  MLA utilizes balloon data generated with a combination of positional, flanked, and isolated data and confirmed to be accurate to +/- 0.5dB with a resolution of 1 degree through 360 degrees both vertically and horizontally. 

This is utilized to create for an 8 box array for example, 5 unique balloons plus three mirror image balloons.
When all array angle calculations and elemental EQ are complete in Display the resulting balloon data is utilized to create a single complex directional point source balloon.  This CDPS can be utilized in EASE for room modeling where EASE is the preferred method.

Here is a link to an indoor measured hang of 12 boxes MLA from 2009.  http://forums.prosoundweb.com/index.php/topic,159272.msg1463372.html#msg1463372

Since it is now a patented approach it will be interesting to see what other developments happen to avoid infringement yet allow for the flexibility and resolution that MLA has introduced. 

Lee
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Mark Wilkinson

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Re: "Multi cellular array" vs "Single Source array"
« Reply #57 on: July 25, 2016, 07:54:29 pm »



The resulting phase response at each seat falls somewhere within +/-45° of "normal" at the nyquist frequency, which nets a 90° distribution. I did not get to measure each box on/off axis to see what the AP is actually doing per box, but rather looked at the whole rig from multiple locations.


Hi, need help......my understanding is that nyquist frequency is 1/2 sampling rate...so 24Khz for a 48Khz dsp....?
What freq are you referring to 'within +/- 45 degree of "normal" '?
Thx,  mark
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Roland Clarke

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Re: "Multi cellular array" vs "Single Source array"
« Reply #58 on: July 26, 2016, 08:01:35 am »

First, I know, I write too much. :-)
Second, I may seem to be arguing but, for those who know me, they will attest that I am not.  I am merely explaining differences and also hearing and understanding different approaches and different technologies. 

I will be very interested to see/hear how D&B's ArrayCalc compares ultimately.  Thus far it has been utilized for a demo of D&B in a room which has also demoed K2, KARA, Nexo, Lyon, and MLA-C (I may be forgetting 1 or 2).  Measurement and listening comparisons have been interesting.


I was not meaning to suggest that there is not "a lot" of math being done to produce the results that D&B is now getting, just that there is significantly more math occurring in Display. 
The raw number of filters able to be utilized by MLA is many times that of D&B's ArrayCalc.  Given 10 years of refinement to MLA technology and 3 complete speaker lines all utilizing MLA's patented numerical optimization process I expect MLA to be the front-runner that everyone is chasing and comparing themselves to.  Understanding what is being done with it and how and why it was developed has really helped me to have a greater understanding of applied acoustical principals.

My understanding is that D&B are doing something similar to what Clair is doing and what VUE is doing in terms of applying array processing.  As I understand it it is full range cabinet processing, not driver by driver, and I think it is limited to 6 filter points per cabinet.  This certainly helps to significantly smooth overall response. 
On the other hand, MLA is providing driver by driver processing with up to 6000 filter points per array.  This should equate to 250 filter points per cabinet since each box contains all of the processing that it utilizes.  This is 41 filter points (and change) per drive section, per cabinet but I do not know how the filter point distribution is within the 6 independently powered and processed driver sections.

Martin Display analyzes multiple data points as well, I do not know how many data points are being calculated in D&B's calculations nor how many virtual test points they are using but, I believe that Martin Display is utilizing 1,800,000 per virtual measurement microphone for a full array of full size MLA (1,200,000 and 1,800,000 are both in my mind and I do not recall which is correct).  So a 100 meter deep audience area would have 540,000,000 calculations for just the audience plane (if I am doing my math correctly), add to that the height of the walls, length of the ceiling, height of the backstage wall, etc. and you get an idea for how much math is being done here.

In Display virtual measurement mics are placed every 1/3 meter in the listening plane of the audience area and every 1 meter in the non-audience area, on-axis.  Calculations are based on a combination of positional, flanked, and isolated cabinet data.  This is because it was found that utilizing isolated cabinet data alone (which is what was used by all that I am aware of when MLA was in development) resulted in errors of as much as 8dB.  The requirement for accuracy for modeling was found to be 1dB (+/- 0.5dB) which could not be obtained by utilizing isolated data.  MLA utilizes balloon data generated with a combination of positional, flanked, and isolated data and confirmed to be accurate to +/- 0.5dB with a resolution of 1 degree through 360 degrees both vertically and horizontally. 

This is utilized to create for an 8 box array for example, 5 unique balloons plus three mirror image balloons.
When all array angle calculations and elemental EQ are complete in Display the resulting balloon data is utilized to create a single complex directional point source balloon.  This CDPS can be utilized in EASE for room modeling where EASE is the preferred method.

Here is a link to an indoor measured hang of 12 boxes MLA from 2009.  http://forums.prosoundweb.com/index.php/topic,159272.msg1463372.html#msg1463372

Since it is now a patented approach it will be interesting to see what other developments happen to avoid infringement yet allow for the flexibility and resolution that MLA has introduced. 

Lee

Hi Lee,

I just took a quick look at the plots posted in the link you provided and though coverage looked relatively even, it appears that (according to the scale provided), hf is significantly down at about 14khz, some 20db and nosedives above that, pretty much in line with what Ivan was talking about earlier.  Whilst I have had a subjectively good experience hearing MLA, it still looks like there are many of the issues that all systems suffer from due to interaction from multiple drivers in multiple boxes, though I would concede these would be likely much worse without the processing power MLA offers.
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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #59 on: July 26, 2016, 08:29:21 am »

Hi Lee,

I just took a quick look at the plots posted in the link you provided and though coverage looked relatively even, it appears that (according to the scale provided), hf is significantly down at about 14khz, some 20db and nosedives above that, pretty much in line with what Ivan was talking about earlier.  Whilst I have had a subjectively good experience hearing MLA, it still looks like there are many of the issues that all systems suffer from due to interaction from multiple drivers in multiple boxes, though I would concede these would be likely much worse without the processing power MLA offers.

With MLA it is all based on configuration provided by the processing and numerical optimization.  Up to the limits of air absorption you can make it give you what you want.  Often that means tapering HF to limit reflective bounce from floor to wall, etc. 
It is all based on choices for the particular space, is there a need for a large area of Hard Avoid on the stage, does the back wall or the floor create unwanted reflections that limit intelligibility.  All of this is configurable within Display and the results can be modeled very, very accurately although it does not account for room modes or other significant acoustic room interactions only the simple boundary reflections as far as I am aware.

The point of the plots that I linked to was to show the impulse response in a highly reverberant space and the overall consistency of frequency response front to rear.  At 75 meters there is no issue with HF roll-off if you don't want it there.

This thread started as a discussion about what each of the various newer processed systems are doing and how they compare.  I would choose to compare their technical capabilities since " how do they sound" has significant variables that are far beyond the ability to type a few paragraphs on an online forum.

Cellular Drive is the only technology that starts with the listeners ear and allows the designer/system tech the ability to create the result they want to achieve (at the listener) and translate that into requirements for each individual speaker element in order to achieve that goal.  All others also attempt to achieve a particular result but the focus of the processing is to create that result at the speaker system and project that created field out into the listening area.  Cellular Drive does not care what is happening at the speaker system (it is also not limited to the current form factor).

Below is a quote from Martin's product specialist, Jim Jorgensen from a recent email discussion that we were having about various systems for a project that we have upcoming.  The discussion was based around what is being done with the various approaches of different manufacturers and how do they differ.  The most basic is, what problem do they seek to solve?

From Jim,
“To compare different points of sound propagation takes a bit more than a paragraph, and is even more often a theory than an application. What happens when we simply place a full range point source on top of another full range point source? What happens when you put one next to the other? Why would there be any difference (and there is) if they are both truly point sources? The true difference with “cellular technology” is not about source propagation. It is giving each driver or set of drivers its own information with-in any type of array in order to meet a predetermined set of goals. What and how that information is derived is now protected by a patent and the current form factor is only available in the MLA family of products. “

Lee
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Lee Buckalew
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Re: "Multi cellular array" vs "Single Source array"
« Reply #59 on: July 26, 2016, 08:29:21 am »


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