Pro Logic bass

Discussion in 'Archived Threads 2001-2004' started by Hugh Scrivener, Sep 29, 2002.

  1. Hugh Scrivener

    Hugh Scrivener Stunt Coordinator

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    While of course DTS or DD is the preferred format Many of my 'digital' cable channels broadcast a Dolby 2.0 signal, which I use traditional Pro Logic to decode into surround. I know the center channel is culled from the two front channels by taking the shared information from each channel and matrix's it into the center, leaving the uncommon info to each respective front. And I know the rear channels are derived from the fronts through some out of phase voodoo that I'm not sure I completely understand. But where does the bass track(sub-woofer) come from? I'm sure its a set crossover in the decoding that sends low freqs to the woof, but what is that freq?
    With the cheap sub I have...won't mention any names(mainly from embarrassment), it rhymes with yolk...oops..I slipped, Ican't really handle some of the lower freqs found in DTS or DD without turning the woofer WAY down..of course losing the original impact of the flick. But with music and Pro Logic decoding its not so bad. I figured if I could set the x-over as close to the PL standard as possible I might get better over-all response from the shoe box in the corner.
    Or am I totally whacked in the head? I'd still, just for curiosities sake, like to know.
     
  2. Chris Brown

    Chris Brown Stunt Coordinator

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    Standard Pro-Logic provides for four channel reproduction (4.0). This includes Right Front, Left Front, Center, and Rear Surround (although 2 speakers are often used, they are producing the same sound). There is no dedicated LFE/Bass channel.
    Pro-Logic II provides for 6 channel reproduction (5.1). This includes Right Front, Right Left, Center, Right surround, Left surround, LFE (Bass)
    If you are using the regular Pro-Logic, there is no bass separation done in the decoding, however your receiver may still be able to send bass to your subwoofer via your crossover. (When you have your speakers set to small and it redirects the bass to the subwoofer). On my old Pro-Logic receiver I simply had the sub getting the signal from my mains and then using the onboard crossover to filter the signal.
     
  3. NickSo

    NickSo Producer

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    Yeah, the bass on ProLogic1 was horrible... I got a makeshift fix by adding a car subwoofer crossover that had a bassboost. I rigged it so it got power off a 12v AC/DC adaptor rather than from the car. Whenever i wanted more bass, i just flick the switch for bassboost, and i got it. Not the most elegant way, but it works...
     
  4. Lewis Besze

    Lewis Besze Producer

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    Hugh,
    Dolby Surround goes like this in a simplistic way:
    Center= L+R [mono sum]
    Surround= L-R,then reversed to out of phase[kinda like Hafler "surround"]
    There is no "LFE" as others ponted out,the bass is in the full range mains as well,however the surrounds are limited by design from 100hz-7khz.
     
  5. Hugh Scrivener

    Hugh Scrivener Stunt Coordinator

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  6. Lewis Besze

    Lewis Besze Producer

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