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Old 26th August 2002, 04:15 PM   #1
sapito is offline sapito
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Question Surround decoder


I've this question:
How can I cancel the surround and center signal in the L and R output?

The circuit I have made is from Rod Elliot (http://sound.westhost.com/project18.htm)

Or anyone have a more efficient design?


Pedro Martins
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Old 26th August 2002, 04:19 PM   #2
tiroth is offline tiroth  United States
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There is not much point in trying to remove the S channel from the front channels as it should already be pretty far down despite mismatching.

I discussed something like the above with Rod and he seemed to think it was perhaps not worth the effort, considering the extra electronics in the signal path. (his original design leaves the R,L channels unaltered) I've never got around to trying it out though.
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Old 24th May 2004, 10:24 AM   #3
red is offline red  Romania
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Well I tryed it.
I wroks pretty fine.Of course it doesn't compare to a digital decoder but I liked it. I didn't see the need for a center loudspeaker because I was satisfied with my main speakers.
On the rear channel I used some rather old, but very good car speakers. The sound is pretty surprising but I think the delay unit would make it even better.
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Old 24th May 2004, 06:43 PM   #4
leadbelly is online now leadbelly  Canada
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Surround decoder
Default Re: Surround decoder

Originally posted by sapito
How can I cancel the surround and center signal in the L and R output?

The circuit I have made is from Rod Elliot (http://sound.westhost.com/project18.htm)

Or anyone have a more efficient design?
I don't know what your measure of efficiency is, so I can't answer that.

There are other techniques for simplistic surround decoding:


One technique is to build "wide" circuits for the L and R.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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Old 24th May 2004, 07:19 PM   #5
purplepeople is offline purplepeople  Canada
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Do not waste your time removing any of the encoded signals.

Left surround and right surround are encoded 90deg out of phase, which is why there is no need to remove them for stereo.

Center is supposed to be mixed evenly into left and right at -3dB so that when they are added, they are not louder than either front channel. Also, since it is also the mono mix, removing it will probably also remove most of the movie dialogue.

You are correct about adding delay. It is used to fool the brain into believing that a sound is coming from behind the head.

How have you positioned the speakers?

Those who claim to be making history are often the same ones repeating it.
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Old 30th May 2004, 02:48 AM   #6
Daniel-A is offline Daniel-A  Canada
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if your speaker image well, why in the hell should you put a mono signal in front and switching to half mono-stereo left and half mono-stereo right. I use fantom on my lexicon and everything is great.

Try your surround without center and get back to stereo front.
After all your always in the sweet spot and except when your room is so large that people sit far outside your speaker they don't need center speaker.

You can have real surround with full stereo front or they can have center speaker. it's your choice: them or you!

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