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Author Topic: Symetrical vs Asymetrical line array box design  (Read 3958 times)

Isaiah Haywood

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Re: Symetrical vs Asymetrical line array box design
« Reply #10 on: March 19, 2017, 07:40:12 am »

There is a bit of a "grey area".

1/4" is (should) be the design target.  If it is a little larger-then there will be more interference.

How much more?  It depends.  How much is tolerable?  it depends.

When some says "turn it down".  Is 1dB enough? You "turned it down-but not enough for them to notice.

 what about 10?  Would 3 do it, or maybe 5.

As I often say, there is no simple answer that is correct.

But you need a guideline.

Many people are simply not aware of the "patterns" they are creating by placing subs where they do.

Sometimes you have no choice.

Often times there is no "right for everybody" position.  It can be good for some people, but bad for others.

That is why it is ALWAYS best (no matter the manufacturer or product) to use a SINGLE sub and SINGLE full range cabinet.

As soon as you start to add more-you start to add problems.

But sometimes the end result is better than the problems it creates.

What IS important-is to understand how the interactions work, the penalties for doing so etc.

This way at least you have an educated idea of what to do and what might be the best compromise.

If you don't understand what if going to happen with various placements, then you are just "hoping" for something that may or may not happen.

VERY OFTEN, the result of adding more speakers is NOT AT ALL what most people think (or would like) will happen.

It is MUCH more science than voodoo.  An accurate model (that is taking phase into account) will show these interactions.

A simple "amplitude" model will not show this and "assumes" (wrongly) that everything is "playing nice" with each other.


I agree completely with the fundamentals you're referencing & trying to analogize--But aren't there circumstances where it's possible to place multiple cabinets in an array so that the combined performance would be  fully complimentary?   

Take, for instance, the EAW BH760 OR KF940 Bass horn cabinets:  They're 100% DESIGNED TO FUNCTION BEST in arrays of 4 or 8 pieces, stacked with the horn mouths adjacent & Coupling, effectively pieced together onsite to create a much larger single "bass Cabinet" which arguably acts better-behaved /is more directional than the generic common solutions available to those that  either throw longer distances & provide more  "tactile punch in the gut".

This Bass Horn Coupling I'm speaking of is much more noticeable & drastic than the much smaller benefits you'd reap attempting the same geometrical layout with "standard"Front-loaded Stadium Bass increase in in efficiency & low frequency linear extension by up to 10HZ or more

I also Design in-car Hi-Fi / High-End Custom Car audio systems that are designed with the intent of Getting Loud while Still sounding GREAT that Use similar principles--As a matter of fact, My current main Rear Subwoofer Temporary setup has three JBL Differential Drive W12GTI subs placed inside a large Enclosure to effectively create a single point-source via a large slot /round point for the Bass to emanate from, thus avoiding unwanted frequency cancellations & lack of in-phase cohesion.     





The port fires up, at a vertical but slightly non-parallel angle to the inward on the rear hatch glass & Creates a cohesive pressure wave thru-out the car that HITS SO FAST & HARD that I could do nothing but smile after putting them In that way!   


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Tom Danley

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Re: Symetrical vs Asymetrical line array box design
« Reply #11 on: March 19, 2017, 09:04:50 am »


I agree completely with the fundamentals you're referencing & trying to analogize--But aren't there circumstances where it's possible to place multiple cabinets in an array so that the combined performance would be  fully complimentary?   

Take, for instance, the EAW BH760 OR KF940 Bass horn cabinets:  They're 100% DESIGNED TO FUNCTION BEST in arrays of 4 or 8 pieces, stacked with the horn mouths adjacent & Coupling, effectively pieced together onsite to create a much larger single "bass Cabinet" which arguably acts better-behaved /is more directional than the generic common solutions available to those that  either throw longer distances & provide more  "tactile punch in the gut".

This Bass Horn Coupling I'm speaking of is much more noticeable & drastic than the much smaller benefits you'd reap attempting the same geometrical layout with "standard"Front-loaded Stadium Bass increase in in efficiency & low frequency linear extension by up to 10HZ or more

I also Design in-car Hi-Fi / High-End Custom Car audio systems that are designed with the intent of Getting Loud while Still sounding GREAT that Use similar principles--As a matter of fact, My current main Rear Subwoofer Temporary setup has three JBL Differential Drive W12GTI subs placed inside a large Enclosure to effectively create a single point-source via a large slot /round point for the Bass to emanate from, thus avoiding unwanted frequency cancellations & lack of in-phase cohesion.     

The port fires up, at a vertical but slightly non-parallel angle to the inward on the rear hatch glass & Creates a cohesive pressure wave thru-out the car that HITS SO FAST & HARD that I could do nothing but smile after putting them In that way!


Hi

“   But aren't there circumstances where it's possible to place multiple cabinets in an array so that the combined performance would be  fully complimentary? “

It’s a source spacing issue as illustrated in Peters graphic, consider that if one had two simple identical direct radiating sources and has a source to source spacing of about ½ wl or more, then one has two independently radiating sources which raises the total SPL 3dB compared to one, four of the same sources more than ½ wl apart gives you +6dB more sound.
Conversely a direct radiating subwoofer example, two close coupled (less than ¼ wl apart) gives your +6dB more sound and four of them gives you +12dB more sound. 

 Fwiw, WL in inches roughly 1130*12 / frequency.   

Bass horns fall in here too although they are not as straight forward as the direct radiating case as the horn gain stops increasing at the same rate.
While not serving the normal “sell the most boxes” goal, aside from the intelligibility considerations in the Hopkins Stryker equation and those that followed, there is a very strong acoustical reason to use the close coupled “coherent addition” approach so far as minimizing the total number of boxes / sources and cost, with enough sources acting as one acoustic source (with one source time arrival at any location) it is possible to provide “hifi” sound in large stadiums and outdoor venues with very few cabinets, in some cases one or two if you only have 30K-50K seats.

The technical problem doing this is our hearing spans a 1000:1 range of wavelengths so while it’s trivial to arrange a few subs to add fully but at 20KHz, the wavelength is only about 5/8 inch and for most uses, having directivity that is as constant as possible vs frequency is similarly challenging but also addressable.
How sound behaves depends strongly on the size of the physical objects compare to the wavelength of concern.

Best,
Tom
« Last Edit: March 19, 2017, 12:24:28 pm by Mac Kerr »
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Ivan Beaver

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Re: Symetrical vs Asymetrical line array box design
« Reply #12 on: March 19, 2017, 10:08:42 am »


I agree completely with the fundamentals you're referencing & trying to analogize--But aren't there circumstances where it's possible to place multiple cabinets in an array so that the combined performance would be  fully complimentary?   

Take, for instance, the EAW BH760 OR KF940 Bass horn cabinets:  They're 100% DESIGNED TO FUNCTION BEST in arrays of 4 or 8 pieces, stacked with the horn mouths adjacent & Coupling, effectively pieced together onsite to create a much larger single "bass Cabinet" which arguably acts better-behaved /is more directional than the generic common solutions available to those that  either throw longer distances & provide more  "tactile punch in the gut".


You MUST use your full real name to participate on this forum or threads will get locked or your posts removed

As Tom said-it all has to do with wavelength.

Everything I said holds true-once you start to think in terms of wavelength vs size.  Even for the cabinets you are talking about.

Actually the bass horns you mentioned were NOT designed to work together.

They were DESIGNED as smaller horns that could be transported easily.

Yes they will work together and in multiples they each help the impedance load of each other-so the end result is that they do couple.

A single larger horn would be a better "design", but then it becomes impractical to move around.
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Ivan Beaver
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Mac Kerr

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« Reply #13 on: March 19, 2017, 12:23:25 pm »

I agree completely with the fundamentals you're referencing

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

Mac
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Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #14 on: March 19, 2017, 07:13:31 pm »

You MUST use your full real name to participate on this forum or threads will get locked or your posts removed


Actually the bass horns you mentioned were NOT designed to work together.

They were DESIGNED as smaller horns that could be transported easily.

Yes they will work together and in multiples they each help the impedance load of each other-so the end result is that they do couple.

A single larger horn would be a better "design", but then it becomes impractical to move around.

Ivan, you may be thinking of the wrong box - these were all stadium sized horns designed to work in blocks of 4 or more for the best results - http://eaw.com/docs/2_Legacy_Products/Loudspeakers/BH/BH760/Spec_Sheets/BH760_SPECS_rev1.pdf
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Ivan Beaver

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Re: Symetrical vs Asymetrical line array box design
« Reply #15 on: March 19, 2017, 08:23:09 pm »

Ivan, you may be thinking of the wrong box - these were all stadium sized horns designed to work in blocks of 4 or more for the best results - http://eaw.com/docs/2_Legacy_Products/Loudspeakers/BH/BH760/Spec_Sheets/BH760_SPECS_rev1.pdf
I am aware of the cabinets.

I still say the "design" was a smaller cabinet that when combined with others, would smooth out the response.

If the "design" was a single large horn, to then be cut into smaller pieces, it would look different.
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Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #16 on: March 19, 2017, 09:21:46 pm »

I am aware of the cabinets.

I still say the "design" was a smaller cabinet that when combined with others, would smooth out the response.

If the "design" was a single large horn, to then be cut into smaller pieces, it would look different.

If 52” x 36"x 24” x 376 lbs (KF940) is a small sub with respect to this forum … you guys at Danley need to rethink your packaging  :D  :D

This is what the manufacture says – “Widely known as the SuperSub,the KF940 is engineered to be used in arrays of four or more to produce extremely high output sub bass response to the very bottom of the audible spectrum.”
« Last Edit: March 20, 2017, 03:06:57 am by Peter Morris »
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Isaiah Haywood

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Re: Symetrical vs Asymetrical line array box design
« Reply #17 on: March 19, 2017, 10:04:23 pm »

Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions in the Forum Announcements section, and on the registration page when you registered.

Mac
Got it--Thanks!
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Jean-Pierre Coetzee

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Re: Symetrical vs Asymetrical line array box design
« Reply #18 on: March 20, 2017, 05:23:01 am »


I agree completely with the fundamentals you're referencing & trying to analogize--But aren't there circumstances where it's possible to place multiple cabinets in an array so that the combined performance would be  fully complimentary?   


Yes at long wavelengths, that is what was discussed. The spacing between subs are pretty small related to the wavelengths, specially in the subs you are referencing and being stacked together. You still cannot create a large omni-directional source. What was mentioned and is still being mentioned is you need to decrease the distance to at least 1/4 wavelength. If you put a high enough frequency sine wave through even those subs and walk the room you will find that they start lobing just like was shown above because the spacing between the drivers are larger than the 1/4 wavelength requirement.

So no you cannot place multiple cabinets in an array so the combined performance would be fully complimentary across the entire frequency range unless the cabinets are infinitesimally small which needless to say is at present impossible.

I believe the original theory behind line array was an infinite length of infinitesimally small drivers. It works for subs and also in antenna arrays purely due to the wavelengths being reproduced but as the frequency gets higher you stop being able to use line array theory.

Most line array manufacturers use line array theory up to a point and then switch to manifolds or horns above that purely because it is a better compromise.
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Ivan Beaver

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Re: Symetrical vs Asymetrical line array box design
« Reply #19 on: March 20, 2017, 07:22:01 am »

If 52” x 36"x 24” x 376 lbs (KF940) is a small sub with respect to this forum … you guys at Danley need to rethink your packaging  :D  :D

This is what the manufacture says – “Widely known as the SuperSub,the KF940 is engineered to be used in arrays of four or more to produce extremely high output sub bass response to the very bottom of the audible spectrum.”
It just depends on how you look at what is called "design".
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

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