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Author Topic: "Multi cellular array" vs "Single Source array"  (Read 25875 times)

Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #30 on: July 22, 2016, 12:46:22 pm »

...  a proprietary and patented way of doing something that is an improvement over existing, similar things.  That gives them a virtually unlimited ability to be in an internet comparison as there is nobody else doing what they do the way they do it.

MLA is also in this category.  The processing and/or its application is patented.


I'm certainly interested in hearing less fan-boy and more input regarding other technologies that are raising the bar of both sound quality and touring practicality.

I could not agree more! 
Actual users with data and quantifiable results and also information on the various pluses and minuses. 
How does it rig, how does it travel, what aspects work well/don't work well in given situations, reliability, service, etc., etc.



Lee
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Lee Buckalew
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Doug Fowler

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Re: "Multi cellular array" vs "Single Source array"
« Reply #31 on: July 22, 2016, 02:15:25 pm »

Probably deleted as we're 'not allowed to discuss Danley in this thread' lol

That's why I deleted it.  I don't want another "Danley vs the world" thread via thread drift.
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eric lenasbunt

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Re: "Multi cellular array" vs "Single Source array"
« Reply #32 on: July 22, 2016, 05:36:52 pm »


In the hands of owner-operators I'm fairly sure that there isn't much out there that can equal what D.S.L. does for either size or price point, but I've heard (and measured and evaluated) a couple of installations that used Danley products exclusively and they don't sound good.  That's out of Tom, Mike and Ivan's hands - and I don't assess blame to them or DSL for the result - I offer these observations to point out that whatever 'secret sauce' is used, the positive results of that can be instantly and permanently negated by a problematic design or FUBAR installation provisions by the general contractor, or errors by the installing dealer... or misapplication by end users.



Tim is spot on as always. Besides poor installation or implementation there is also just the basic problem that some mix engineers suck at their job. We install in a lot of churches with volunteer sound teams. While some are great, others obviously aren't absorbing the training and in some cases have made our very flat, VERY good sounding installs sound quite horrible. There are a few churches around that I am proud of our install work but not proud to tell people it is our install, as the operators make it sound horrible.

Even the nicest car can be crashed into a tree by a driver who doesn't know what they are doing.
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David Sturzenbecher

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"Multi cellular array" vs "Single Source array"
« Reply #33 on: July 22, 2016, 05:43:49 pm »

That's why I deleted it.  I don't want another "Danley vs the world" thread via thread drift.

The picture was essentially a Danley line array. Not sure what else you would call 4 boxes stacked in a vertical line at 0 degree splay...What do you call it??? Just google "LSU Danley Jericho" in an image search and it will come up on the first page.  It's odd that the post with the picture gets deleted, but not Ivan's post. Without context it's meaningless, and not germane to the topic. This thread is surely beyond simple elementary electro-acoustics.
« Last Edit: July 22, 2016, 06:48:33 pm by David Sturzenbecher »
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Ivan Beaver

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Re: "Multi cellular array" vs "Single Source array"
« Reply #34 on: July 22, 2016, 09:53:34 pm »

The picture was essentially a Danley line array. Not sure what else you would call 4 boxes stacked in a vertical line at 0 degree splay...What do you call it??? Just google "LSU Danley Jericho" in an image search and it will come up on the first page.  It's odd that the post with the picture gets deleted, but not Ivan's post. Without context it's meaningless, and not germane to the topic. This thread is surely beyond simple elementary electro-acoustics.
Yes it is 4 J3-64 cabinets stacked on top of each other.

HOWEVER-it is important to understand some of the theory and design intent behind it.

Most large stadiums use  a single J1 for the far seats.

But because LSU is known for being loud (they set off the seismic detectors in the earthquake lab during a play at one game) the consultant wanted "a bit more" in the system. (there is a different solution available now that was not available when the install was done)

It is not the physical distance between the elements that causes comb filtering.  But rather the distance in time between the elements that the listener hears.

Since the closest listener for these cabinets is around 700' away, the signal arrival time difference are very small.

At that distance, the air absorption pretty much kills anything above 4Khz-unless it is REALLY loud (that is where the "tweeter cabinets" come into play).

So where the differences in arrival would be causing interference in freq response, the air is killing those freq anyway.  So it is actually minimal interaction.  Up closer it would be a different story-but there are no listeners there.

It is important to consider how a particular system is used and the intended outcome.

I could go into more details, but should probably stop now.



 
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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #35 on: July 23, 2016, 12:09:52 am »

Yes it is 4 J3-64 cabinets stacked on top of each other.

HOWEVER-it is important to understand some of the theory and design intent behind it.

Most large stadiums use  a single J1 for the far seats.

But because LSU is known for being loud (they set off the seismic detectors in the earthquake lab during a play at one game) the consultant wanted "a bit more" in the system. (there is a different solution available now that was not available when the install was done)

It is not the physical distance between the elements that causes comb filtering.  But rather the distance in time between the elements that the listener hears.

Since the closest listener for these cabinets is around 700' away, the signal arrival time difference are very small.

At that distance, the air absorption pretty much kills anything above 4Khz-unless it is REALLY loud (that is where the "tweeter cabinets" come into play).

So where the differences in arrival would be causing interference in freq response, the air is killing those freq anyway.  So it is actually minimal interaction.  Up closer it would be a different story-but there are no listeners there.

It is important to consider how a particular system is used and the intended outcome.

I could go into more details, but should probably stop now.

For those following along who do not routinely deal in comb-filters and time offsets here is an equivalent for a comb-filter with the first null at 4kHz.
1.685" distance offset = 0.125 ms offset = 1st null at 4kHz and 1st peak at 8kHz for the comb-filter.

Lee
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Steve Anderson

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Re: "Multi cellular array" vs "Single Source array"
« Reply #36 on: July 23, 2016, 02:00:33 am »

For those following along who do not routinely deal in comb-filters and time offsets here is an equivalent for a comb-filter with the first null at 4kHz.
1.685" distance offset = 0.125 ms offset = 1st null at 4kHz and 1st peak at 8kHz for the comb-filter.

Lee
And at 700' on axis the distance delta between middle and end of array is about 0.55" so first null would be at 12.4kHz which is well and truly above the HF air loss freq Ivan referred to.

Not to say that entire audience is on axis at that distance, but at least for the ones that are, this "chosen compromise" design decision stands up to scrutiny.
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David Sturzenbecher

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Re: "Multi cellular array" vs "Single Source array"
« Reply #37 on: July 23, 2016, 03:09:03 am »

And at 700' on axis the distance delta between middle and end of array is about 0.55" so first null would be at 12.4kHz which is well and truly above the HF air loss freq Ivan referred to.

Not to say that entire audience is on axis at that distance, but at least for the ones that are, this "chosen compromise" design decision stands up to scrutiny.

This is also the same "design" that goes into the HF and MF section of every line array on the planet, worth its salt of course.


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Lee Buckalew

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Re: "Multi cellular array" vs "Single Source array"
« Reply #38 on: July 23, 2016, 09:04:14 am »

And at 700' on axis the distance delta between middle and end of array is about 0.55" so first null would be at 12.4kHz which is well and truly above the HF air loss freq Ivan referred to.

Not to say that entire audience is on axis at that distance, but at least for the ones that are, this "chosen compromise" design decision stands up to scrutiny.

I was merely providing the distance and time delay required for a first null for the 4kHz frequency that Ivan mentioned.  I made no suggestion that the design would not "stand up to scrutiny". 

Since this thread is ultimately about how cabinets interact let's look at this specific compromise, understanding that it is representative of a common compromise that is necessary in many designs, not just for the now removed photo but for all separately mounted speaker cabinets and most individual cabinets with separate components.
In this case it is one compromise to utilize a secondary enclosure to gain additional HF because it creates a distance between the primary enclosure and the secondary.  If air absorption is creating an acoustic crossover at 4kHz from the main cabinet and the additional HF cabinet is augmenting that beggining at 4kHz then those cabinets would need to be within 1.685" vector delta centerline of HF to centerline of HF in order to avoid comb-filtering.
If the vector delta is great enough they would also require very steep crossover slopes or the effective beggining of the comb-filter would be at a lower frequency.

A second common compromise is utilizing separate enclosures to cover a wider horizontal area.  When two cabinets are used, or in the case of MLA two arrays, to cover adjacent areas there will be an area of overlap that does, at some frequencies and dependant on the vector delta between band-pass center lines, produce comb-filtering.  That is usually preferable to leaving a hole in the coverage. 

Physical design changes in cabinets or in array layouts can only accommodate the physics involved up to a certain point before other factors become more important.  Things like size, weight, SPL capability, etc. 

Most of us use lip fills in a large deployment.  They all produce comb-filtering.  There is no way to arrange multiple speakers along the face of the stage so that you transition from one coverage area to the next with no overlap.  The same holds true for out fills.  This is one of those areas that can be minimized but not eliminated once we begin to choose our compromises for real world coverage. 

Lee
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Ivan Beaver

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Re: "Multi cellular array" vs "Single Source array"
« Reply #39 on: July 23, 2016, 09:30:45 am »

This is also the same "design" that goes into the HF and MF section of every line array on the planet, worth its salt of course.


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Except that with line arrays, the audiences are MUCH closer to the cabinets, making the difference in distances MUCH larger-lowering the null point

In this case the cabinets are well above peoples heads and the horns are larger and wider coverage angles-so the pattern control extends MUCH lower.

The horns on line arrays are very small and narrow.

So they lose pattern control up high.

A 12" tall horn that has a 10 degree coverage pattern (typical for many line arrays) will lose pattern control around 8Khz

So below that freq the horn will simply be "spraying" sound everwhere.

As the pattern gets narrower-the horn MUST get larger to have the same control to the same freq.

Or for a given size-a wider coverage horn will control to a lower freq

So when you are closer- you will hear the different arrivals.

This is VERY EASILY measured when looking at and ETC or impulse response of a line array.  Especially when looking at the higher freq.
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Re: "Multi cellular array" vs "Single Source array"
« Reply #39 on: July 23, 2016, 09:30:45 am »


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