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January 9th, 2010, 09:20 AM
I was wondering what exactly I have to do processing wise to create a cardioid sub array. I'm using three subs per side vertically and the center one is flipped since it is off the ground.
Side Note for Harry: I was paying attention, I just forgot. :D
January 9th, 2010, 01:06 PM
There are several ways to create cardioid subwoofer, but basically if you use 3 subs per side my 2 ways I can think of.
1 .- Sub cardioid: 2 subs facing forward and one looking backward, for this you need 2-channel processing, one for subs looking forward and one for looking backward, not that you use subs, because the running for this arrangement is to delay and reverse the polarity of the sub that looks backward, and I have data for some models subwoofer.
But the way I use to determine the delay for the sub looking backward is to place the micro measuring approximately 4 meters in front of the rear sub, turn off the rear sub and turn on the front sub, get the response and phase transfer, turn off the sub forward, turn the sub back and equalize the phase response of the sub rear with rear sub stored measurements using the delay, and once the phases coincide reverse the polarity of the sub back. This will create a zone of cancellation of 180 degrees on stage.
2 .- End fired: placing the subwoofer in line back & front between them separated 1 meter. (The distance between subs can be changed about 1 / 4 T, the frequency you prefer to have higher termination), and you need 3 channels of processing, one for each subwoofer, you must delay the 2nd subwoofer 1 meter and the 3rd subwoofer 2 meter, this will create a cancellation area behind the speaker and conduct the sum of the three subs forward.
In both cases after adjustment arrangement, this will behave like a single speaker, so you need a delay for the entire array to produce then the alignment with the main array.
While the first option is the one that produces more cancellation in the back, is somewhat more complicated by the alignment with the main array, by using an inverted subwoofer produces a small change in the phase response of the array.
End Fired The arrangement results in less cancellation on the back, but produces a little more pressure on the front, and is easier to align.
I hope this helps.
January 10th, 2010, 10:55 AM
But the way I use to determine the delay for the sub looking backward is to place the micro measuring approximately 4 meters in front of the rear sub
Is "in front of" referring to the upstage side or down stage side of each sub array?
equalize the phase response of the sub rear with rear sub stored measurements using the delay
Did you mean to say "equalize the phase response of the sub rear with front sub stored measurements", or did I miss something completely?
January 10th, 2010, 12:08 PM
Sorry for my English, but this is not my language and sometimes it's harder for me to explain in English that align a system.:o
1 .- I mean take the transfer phase response and the speaker looks forward, placing the microphone 4 meters in front of the speaker facing backwards (I measure the response at the rear of the array with the speaker backward direction turn off.)
2 .- you are right, front speaker is off and turn on the rear sub, use the delay to match the phase and reverse polarity.
A relationship that I use is:
1 .- If the level difference at the point of measurement is between 0 dB - 2 dB the ratio is 1:1 speakers
2 .- If the level difference at the point of measurement is between 3-4 dB the ratio between speakers is: 3 to forward 2 backwards.
3 .- if the level difference at the point of measurement is between 5 to 7 dB the ratio between speakers is: 2 forward, 1 reverse.
January 10th, 2010, 01:31 PM
Thank you Pepe. I think I got it this time.
Do you have any tips for aligning the sub array to the main array...will the cardioid sub array behave differently than a non-cardioid sub array when aligning to the main array?
January 10th, 2010, 02:28 PM
Basically, the procedure for the alignment of the cardioid sub against PA is the same as if this were not cardioid. Once set the subwoofer under this behaves like a single speaker and therefore the procedure for adjusting the PA is the same.
With regard to the construction of sub cardioid 2:1, once you've found the time delay for the rear sub, this time will be the same for all your productions.
A tip that I got to line up a cardioid subwoofer under 2:1 against PA main switch off the sub is looking backward, producing an alignment with the PA primary and once this is completed turn on the sub also looking back and verify the answer.
In this thread Rational people gave me great advice:http://www.rationalacoustics.com/forums/showthread.php?t=203
January 10th, 2010, 02:46 PM
Thank you for your time, Pepe
January 11th, 2010, 10:11 AM
Thanks! I forgot how easy it was. It ended up working great.
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