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Cardioid Sub Array, Subwoofer Steering, HOW TO DO IT?

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Justin Sumrall:
Hey Guys and Gals,

    I have been reading up on the contreversal topic of Cardiod Sub Arrays and bass steering. I get the jist that the whole point is to capture the energy that is being wasted under the stage and elsewhere in the plane and shooting it twards the audience. What I don't get is the physics behind it. I know that Dave Rat has written about this several times but I need a down to the basics explanation of how it is done and the theory behind it. If anyone has a good explanation or has and artical that you could share I would appreciate it. Thanks!

HarryBrillJr.:
A simplistic way to look at it but a good way to get started.


http://www.tigeraudioinc.com/endfire2.jpg

Better rejection of more frequencies in the rear, and better overall control, less impact.


http://www.tigeraudioinc.com/endfire.jpg

Better impact, but less control.


Some prefer to pick a higher frequency to work with.  The choice is yours.


In real life you won't get exactly 6dB gain in front compared to 1 speaker.


If you want to deploy what d&b calls a CSA array, you can simply do this.....

http://www.rationalacoustics.com/forums/showpost.php?p=1726&postcount=2


Here's a shot of that in MAPP.....

http://www.tigeraudioinc.com/csa.jpg


The LINES coming from the speakers indicate the direction that speaker is facing.

Edit: link repairs

Bennett Prescott:
What's controversial about it? If you understand phase, it is a simple concept. If you don't, great, I need to pay my bills.

The basic question is, are you willing to sacrifice a few dB of forward output for directionality? That can be very important. Having the pattern of your sub array match your mains array is uncommon. Some of us spend a lot of time on that sort of thing.

Tim McCulloch:
For a different take on using delay and arraying:


http://www.jblpro.com/catalog/support/getfile.aspx?docid=234&doctype=3


Then taking the concept a bit further:


http://www.jblpro.com/catalog/support/getfile.aspx?docid=272&doctype=3


Harry's 'quick and dirty' shows you what to do.  The JBL docs give you a bit more of the 'how'.


If you own an advanced calculator and know what the buttons do, try Chapter 12 of "Sound System Engineering", 3rd, D. Davis & E. Patronis, Jr. Focal Press.  Hell, just buy the book.  And get a copy of Bob McCarthy's "Sound Systems: Design and Optimization" while you're investing in your education. 


The more I learn, the less I know.  I'm still figuring out how big a dunce I can be.  <img src="images/smiley_icons/icon_rolleyes.gif" border=0 alt="Rolling Eyes">


Have fun, good luck.


Tim Mc

Edit: link repairs

Dave Sturzenbecher:
Bob McCarthy states on his blog that the second edition of his book goes into this topic a little more then the first.  I haven't seen this edition though.

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