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Author Topic: Symetrical vs Asymetrical line array box design  (Read 3017 times)

Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #20 on: March 20, 2017, 08:54:58 am »

It just depends on how you look at what is called "design".

Hmmmm ...

"The design was based on a block of four, but they work fine one at a time or two at a time.  Using fewer than four does not change the shape of the response, so the same processor settings will work no matter how you stack them.

Dave Gunness
(designer of BH760)"

http://forums.prosoundweb.com/index.php?topic=2376.10
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Art Welter

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Re: Symetrical vs Asymetrical line array box design
« Reply #21 on: March 20, 2017, 04:26:33 pm »

Hmmmm ...

"The design was based on a block of four, but they work fine one at a time or two at a time.  Using fewer than four does not change the shape of the response, so the same processor settings will work no matter how you stack them.

Dave Gunness
(designer of BH760)"

http://forums.prosoundweb.com/index.php?topic=2376.10
Peter,
As you know, Dave also designed an asymetrical "line array" the EV MT4 system.
Anyone that has deployed those systems, or the more current EV asymetrical line arrays,
knows, or should know  ::) if not set up "mirror image", you will be stuck with a response that sounds quite different
from one end of a centered mix riser to the other.
Greg Huber was experiencing that problem at the Minneapolis First Avenue night club,
the installers had not mirror imaged the cabinets, he dropped and re-hung, instant "success",
the system now has the same different sound on either side of dead center ;^).

Art
« Last Edit: March 20, 2017, 04:29:34 pm by Art Welter »
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Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #22 on: March 21, 2017, 12:07:53 am »

Peter,
As you know, Dave also designed an asymetrical "line array" the EV MT4 system.
Anyone that has deployed those systems, or the more current EV asymetrical line arrays,
knows, or should know  ::) if not set up "mirror image", you will be stuck with a response that sounds quite different
from one end of a centered mix riser to the other.
Greg Huber was experiencing that problem at the Minneapolis First Avenue night club,
the installers had not mirror imaged the cabinets, he dropped and re-hung, instant "success",
the system now has the same different sound on either side of dead center ;^).

Art

Art you make an interesting point - here is the frequency response plots of the T12 I mentioned above. You can see the results of the asymmetric design.  The T12 is actually an excellent design. It should be noted that there are also big problems trying to produce good horizontal patterns with a symmetric design.  Often the drivers are spaced too far apart either side of the HF horn to achieve good summation and horizontal pattern control.
« Last Edit: March 25, 2017, 03:54:34 am by Peter Morris »
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Art Welter

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Re: Symetrical vs Asymetrical line array box design
« Reply #23 on: March 21, 2017, 07:19:45 pm »

Art you make an interesting point - here is the frequency response plots of the T12 I mentioned above. You can see the results of the asymmetric design.  The T12 is actually an excellent design. It should be noted that there are big problems trying to produce good horizontal patterns with a symmetric design.  Often the drivers are spaced too far apart either side of the HF horn to achieve good summation and horizontal pattern control.
Peter,
Excellent design other than the 8 to 10 dB off-axis suck-out at 2000 Hz ;^).
I had the same problem with my year 2000 line array, except the crossover was lower.
The off axis suck-out in the crossover region with "side by side" layout is a problem with no solution, which is why we prefer multi way virtual point sources using shared horns for mid/high or low-mid/mid/high.

Art
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Sean Thomas

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Re: Symetrical vs Asymetrical line array box design
« Reply #24 on: March 22, 2017, 12:22:07 am »

Excellent design other than the 8 to 10 dB off-axis suck-out at 2000 Hz ;^)

Peter and Art,

What would be cuasing the 10dB cut at 2k?  Is that calculation
model accurate?  It looks like your Listener Position is no where near the 100˙ pattern edge.
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Ivan Beaver

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Re: Symetrical vs Asymetrical line array box design
« Reply #25 on: March 22, 2017, 07:29:20 am »

Peter and Art,

What would be cuasing the 10dB cut at 2k?  Is that calculation
model accurate?  It looks like your Listener Position is no where near the 100˙ pattern edge.
Yes.  Because the signals at that freq are coming out of 2 different drivers-which are in two different positions in space, the different time arrivals will cause combfiltering.

As you move (and change the difference in signal arrivals)-that notch will change freq.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #26 on: March 22, 2017, 08:05:08 am »

Peter and Art,

What would be cuasing the 10dB cut at 2k?  Is that calculation
model accurate?  It looks like your Listener Position is no where near the 100˙ pattern edge.

The T12 uses LR filters between the Mid and HF – because of the spacing between the MF and HF there is a parallax time error that causes cancellation off axis as Ivan said. This happens with most “standard” designs.

If you could run the HF crossover down to 1000Hz the problem would be almost gone, but that causes a different set of performance problems.

Another solution is to use synergy horns like Danley does, this however is not without design challenges
.
http://www.rane.com/note160.html
« Last Edit: March 22, 2017, 08:09:36 am by Peter Morris »
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Sean Thomas

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Re: Symetrical vs Asymetrical line array box design
« Reply #27 on: March 24, 2017, 07:28:43 pm »

The T12 uses LR filters between the Mid and HF – because of the spacing between the MF and HF there is a parallax time error that causes cancellation off axis as Ivan said. This happens with most “standard” designs.

Peter - would FIR filters (steeper slope) fix most of this issue at the xover point?
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Art Welter

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Re: Symetrical vs Asymetrical line array box design
« Reply #28 on: March 24, 2017, 09:42:02 pm »

Peter - would FIR filters (steeper slope) fix most of this issue at the xover point?
A steeper slope narrows the bandwidth of the "hole", but won't change the cabinet layout, there will always be an off axis dip if the spacing of drivers is not within 1/4 wavelength at the crossover frequency.
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Peter Morris

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Re: Symetrical vs Asymetrical line array box design
« Reply #29 on: March 25, 2017, 03:32:54 am »

A steeper slope narrows the bandwidth of the "hole", but won't change the cabinet layout, there will always be an off axis dip if the spacing of drivers is not within 1/4 wavelength at the crossover frequency.

Hi Art,

FWIW here is a graphical representation of what you described -

http://www.felusch.com/ton/Lake/004_Tech_Papers/Lake_Technology_-_Linear_Phase_Brick_Wall_Crossover.pdf
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