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Phase extraction!!!
Phase extraction!!!
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Old 18th October 2011, 01:19 AM   #1
frecklestbone is offline frecklestbone  United States
diyAudio Member
Join Date: Oct 2011
Smile Phase extraction!!!

I'm wondering if I can extract certain phase of audio with a circuit of some kind? For example, what if I want to extract 40 to 50 degrees right of center and only hear that section of the stereo field. I know my surround sound system some how separates out the front three speakers into different phase sections and the same in the back ( I understand the back "phase cancellation) but I wonder how they do it in the front? A circuit would be greatly appreciated!?!?!?!?
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Old 18th October 2011, 06:36 PM   #2
lcsaszar is offline lcsaszar  Hungary
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Join Date: Mar 2004
Location: Budapest, Hungary
An all-pass filter could be designed to do constant phase shift of a wideband audio signal. Perhaps such circuit can be used here.
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Old 18th October 2011, 06:52 PM   #3
sreten is offline sreten  United Kingdom
Join Date: Nov 2003
Location: Brighton UK

Simply I don't understand the question or the purpose, as all phase is relative.

In 2 channel encoding delays and adding or subtracting the L+R with or without
delays are used to derive separate channels, the reverse to encode them.

90 degree shifts are used, that reinforce or cancel on addition or subtraction.

I have no idea what you mean by 45 degree signals, AFAIK they don't exist.

rgds, sreten.
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Old 18th October 2011, 07:03 PM   #4
lcsaszar is offline lcsaszar  Hungary
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Join Date: Mar 2004
Location: Budapest, Hungary
If you connect the L and R signals to the X and Y input of an oscilloscope, then you get a Lissajous pattern. If the phase between L and R is 0, then it is a right slanted degrees straight line. At 180 degree it is a left slanted straight line. At 90 degrees it is a circle. You can shift L by 90 degrees to R, then the originally 90 degrees difference will give a straight line. Then you can do some substraction between the phase shifted L, R, and the original L, R, and you get what you want. It can be done with other phase shift, as well.
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Old 18th October 2011, 07:15 PM   #5
DF96 is offline DF96  England
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Join Date: May 2007
I think the OP is asking about direction, not phase. I think the quick answer is that it can't be done, although some very rough approximation might be possible with wideband phase shifters.
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