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Author Topic: When is it a line-array?  (Read 10922 times)

mark lonow

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Re: When is it a line-array?
« Reply #20 on: July 28, 2014, 07:18:22 pm »


thanx kevin nice posts

too some of the others...
how come line arrays need to be 6 foot?
but  its ok for point source/ trap arrays  to have no 250hz  directivity?
another random stab....
and its ok for trap arrays to be non 1/4 spacing?

its all about $$$$$$ and directivity in audio is high dollar
a dash is just another compromise in a imperfect world on a budget
pick ur evil





« Last Edit: July 28, 2014, 07:22:04 pm by mark lonow »
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Mac Kerr

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Re: When is it a line-array?
« Reply #21 on: July 28, 2014, 07:26:10 pm »

how come line arrays need to be 6 foot?
but  its ok for point source/ trap arrays  to have no 250hz  directivity?
another random stab....
and its ok for trap arrays to be non 1/4 spacing?

Point source can have directivity at low frequencies if they're big enough, just like line arrays. The length of the line determines the low frequency corner for pattern control. Six feet gets it down to a useful number.

Many line array elements also rely on the positive summation of the low frequency drivers to have enough low end, so short lines may be low end deficient.

Many point source speakers do not sound good used in multiples.

Mac
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Peter Morris

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Re: When is it a line-array?
« Reply #22 on: July 28, 2014, 07:51:48 pm »

I am quite sure that the experts are tired of repeating this information but there is so much FUD concerning arrays that these conversations (especially with the same participants) have tremendous value to the community.

I touched on the Vue AL-4 and others mentioned compact and ultra-compact have a place.  Vue claims that they can alter the phase to each driver within a narrow range of frequencies and be able to control the pattern via software and physical alignment.

Is this an accurate claim?  If you went into one of these null zones would the energy still be there just canceled out?

http://firmaker.afmg.eu/

http://www.youtube.com/watch?v=PA2fKdbeDT8
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mark lonow

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Re: When is it a line-array?
« Reply #23 on: July 28, 2014, 08:43:11 pm »

thanx mac
if u cant do 6 feet of line array(for what ever reason)
u probably  cant do 6 feet of point source ither
or 6 feet   trap array
or pay for cardioid low mid

or a extra low box+amp 75-150hz or what ever

performance cost what it costs








« Last Edit: July 28, 2014, 08:47:23 pm by mark lonow »
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Lee Buckalew

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Re: When is it a line-array?
« Reply #24 on: July 28, 2014, 11:28:22 pm »


Martin and EAW are already doing it to great effect with MLA and Anya respectively. And their advantage is that you're not trying to do all the work, the trial and error of manually changing delay times and seeing what effect it has, change again and test, change again and test......  With their software you just tell it the coverage you want, where you want it to start and end and where/if you want 'holes' in the coverage to miss balconies and things, and then the software does all the hard work to calculate what processing all of the drivers need to get it done.


k

These are two very different systems.  Anya is beam steering but, as far as I am aware it uses no FIR filters.  MLA on the other hand is all FIR filters and does not beam steer at all.  It creates a phase and frequency coherent summation at the audience plane and it creates cancelation in the non audience and the hard avoid areas.  It does not steer sound away from those areas but merely reduces the level.

Lee
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Scott Holtzman

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Re: When is it a line-array?
« Reply #25 on: July 28, 2014, 11:52:13 pm »

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Peter Morris

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Re: When is it a line-array?
« Reply #26 on: July 29, 2014, 02:06:15 am »

These are two very different systems.  Anya is beam steering but, as far as I am aware it uses no FIR filters.  MLA on the other hand is all FIR filters and does not beam steer at all.  It creates a phase and frequency coherent summation at the audience plane and it creates cancelation in the non audience and the hard avoid areas.   It does not steer sound away from those areas but merely reduces the level.

Lee

Exactly - while the MLA is not a beam steered array, and you could even argue its not a line array,  it will however steer, just a little  ;).

I would be surprised if Anyaís processing didnít use some FIR filters.  While EAW does not mention FIR filters they do say itís "focused", and AFAIK that requires some FIR magic.


http://www.youtube.com/watch?v=th1VqW2dD4w
http://www.youtube.com/watch?v=e8OgtU29M8k
http://www.youtube.com/watch?v=GTEK3v2oMDk
« Last Edit: July 29, 2014, 02:25:28 am by Peter Morris »
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Kevin McDonough

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Re: When is it a line-array?
« Reply #27 on: July 29, 2014, 04:19:06 am »

Exactly - while the MLA is not a beam steered array, and you could even argue its not a line array,  it will however steer, just a little  ;).

I would be surprised if Anyaís processing didnít use some FIR filters.  While EAW does not mention FIR filters they do say itís "focused", and AFAIK that requires some FIR magic.


http://www.youtube.com/watch?v=th1VqW2dD4w
http://www.youtube.com/watch?v=e8OgtU29M8k
http://www.youtube.com/watch?v=GTEK3v2oMDk

Hey

Yeah I've read all Martin's papers etc on MLA, and am aware of the technical jargon they use. I'd still argue that it was beam steering though, even if they use a slightly different method to get there.

There are many very successful reports of them having hard avoid areas at say 50 or 75 metres from the stage, then suddenly using the processing to extend it out to 100m. Or suddenly adding a notch in the coverage to miss an area, changing the start of the coverage to add in or miss out a pit area.

Sounds like beam steering to me...  ;)

Lol, no seriously, they way their software works (which I'm sure you know) is by repeated testing of processor settings. What the human would have to do only the computer can do it far faster. It uses a very accurate model of the cab's dispersion both as a single cab and how it behaves in lines, and plots thousands of different graphs of coverage. By trial and error it works out which one is closest to what you have told it is your ideal coverage pattern for this job.

How it achieves this coverage would be open to debate. While yes Martin does say phase coherence at the audience etc, it's pretty hard to get the kind of changes in coverage the system is capable of just by creating a phase relationship at a single point in space. Mostly because cancellation is very frequency and wavelength dependent and that single point you were cancelling at would only hold true for a fairly narrow band of frequencies, the other frequencies with different wavelengths would still be full volume at that point and so it wouldn't be very 'cancelled'.

I feel as if there would have to be a significant amount of what you would think of as traditional beam steering in there too, deliberately creating 'lobes' in the coverage for given areas to cancel the sound out.

But technical details aside, as I said both cabinets use arrays of multiple, independently processed and amplified drivers, to be able to achieve changes in coverage using software and processing alone. Even if there are some technical differences they're both still beam steering to me.

K
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Lee Buckalew

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Re: When is it a line-array?
« Reply #28 on: July 29, 2014, 06:27:17 am »

Exactly - while the MLA is not a beam steered array, and you could even argue its not a line array,  it will however steer, just a little  ;).

I would be surprised if Anyaís processing didnít use some FIR filters.  While EAW does not mention FIR filters they do say itís "focused", and AFAIK that requires some FIR magic.


http://www.youtube.com/watch?v=th1VqW2dD4w
http://www.youtube.com/watch?v=e8OgtU29M8k
http://www.youtube.com/watch?v=GTEK3v2oMDk

It does not steer at all.  It covers the entire area that is available based upon the array inter cabinet angles.  From there the top and bottom apertures, as they call it, are affected by either being available to be heard or by being canceled.  Same goes for exclusion zones.  This is all budgeted into the processing ahead of time so that there is enough DSP processing available to allow for the required cancellation or addition.  There is no steering occurring.  When steering is done every time you change where a beam is pointed you change the frequency response adjacent to that beam.  From a physics standpoint what MLA does is very different from beam steering.

Lee
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Lee Buckalew
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Lee Buckalew

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Re: When is it a line-array?
« Reply #29 on: July 29, 2014, 07:19:43 am »

Hey

There are many very successful reports of them having hard avoid areas at say 50 or 75 metres from the stage, then suddenly using the processing to extend it out to 100m. Or suddenly adding a notch in the coverage to miss an area, changing the start of the coverage to add in or miss out a pit area.

Sounds like beam steering to me...  ;)
But it's not.  Since each driver can only produce a given amount of energy MLA pre calculates how that coverage will happen for the entire potential coverage of the array based upon the inter cabinet angles and it calculates these inter cabinet angles based upon what your anticipated start and stop coverage needs will be and where you have indicated you will need audience vs. non-audience vs. exclusion areas.  This coverage already includes the areas that you indicate as "suddenly using processing to extend...".  The change in processing is not steering, it is making the area that is already being covered able to be heard.  No change in energy inside the already existing coverage area occurs, they just make the energy that is already covering the "new" area able to be heard.  They do not redirect the energy.
In a beam steered example, since there is only a given amount of energy available from each driver, when you process the beams differently you redirect where that energy is focused.  This takes energy away from areas that were being covered creating a change in the frequency response, SPL, and phase interaction both inside and outside of the "new" coverage area.


Lol, no seriously, they way their software works (which I'm sure you know) is by repeated testing of processor settings. What the human would have to do only the computer can do it far faster. It uses a very accurate model of the cab's dispersion both as a single cab and how it behaves in lines, and plots thousands of different graphs of coverage. By trial and error it works out which one is closest to what you have told it is your ideal coverage pattern for this job.

It is hundreds of thousands of calculations.  Something along the lines of 180,000 per virtual measurement position.  In 1/32 octave resolution for frequency response.  Compare that to EASE resolution.
It does not work out the one solution as there is not a single available solution.  Each time you run a new calculation a different solution may be obtained to create the result that you want because there is a range of combinations that can create the solution to the problems presented.
The important point is that the entire potential coverage area, including the possible "aperture" areas at the top and bottom of coverage and any exclusion zones, have been calculated into the processing ends and are being covered with acoustic energy all of the time.  Sometimes that energy is audible such as when you open up a top or bottom aperture or choose not to exclude a balcony face and sometimes it is inaudible such as when you don't extend an aperture or you exclude the balcony face.  The energy coverage is not changing, only canceling or not in given areas. 


How it achieves this coverage would be open to debate. While yes Martin does say phase coherence at the audience etc, it's pretty hard to get the kind of changes in coverage the system is capable of just by creating a phase relationship at a single point in space. Mostly because cancellation is very frequency and wavelength dependent and that single point you were cancelling at would only hold true for a fairly narrow band of frequencies, the other frequencies with different wavelengths would still be full volume at that point and so it wouldn't be very 'cancelled'.

MLA creates cancellation on purpose across the entire band and it does not change the focus of the energy outside of the exclusion area to achieve this.  Beam steering refocuses energy in order to create a shift in the coverage pattern.  It actively takes energy away from certain areas in order to focus it elsewhere.  It does not create a continuous and even coverage of energy and only change the ability to hear or not hear certain areas of that energy it instead actively changes the focus of the energy.  This in turn changes the sound throughout the coverage area as it changes all of the acoustical interactions.


I feel as if there would have to be a significant amount of what you would think of as traditional beam steering in there too, deliberately creating 'lobes' in the coverage for given areas to cancel the sound out.

But technical details aside, as I said both cabinets use arrays of multiple, independently processed and amplified drivers, to be able to achieve changes in coverage using software and processing alone. Even if there are some technical differences they're both still beam steering to me.

K

When MLA first came out I looked at it simply as another version of beam steering just with much higher resolution.  As I studied further what was going on I realized that it was actually a wholly different process occurring as there are significant differences in the physics applied. 

Both jet engines and propellers are used on aircraft.  Aircraft with either can fly.  If we applied the same physics to both we would not be able to understand how each works so differently from the other.  We don't just say that both help to make the plane fly so they are both the same.  They are significantly different from each other.

Lee
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Lee Buckalew
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Re: When is it a line-array?
¬ę Reply #29 on: July 29, 2014, 07:19:43 am ¬Ľ


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