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THX setting and sub

Discussion in 'Subwoofers' started by EN, Oct 24, 2004.

  1. EN

    EN
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    There is something foggy about THX setting of sub.
    All five (seven) speakers must bu cut of at 80Hz. OK. All the bass goes to the sub.
    Sub must be set at 80Hz (THX) position. Am I right?
    But the LFE channel consist of more bass to the 120 Hz. Here is:

    From DOLBY.com:
    The sound information contained in each of the six available channels is distinct and independent. These six channels are described as a "5.1-channel" system, because there are five full-bandwidth channels with 3 Hz to 20 kHz frequency range for Front Left and Right, Center, and Surround, plus one "Low Frequency Effects" (LFE) subwoofer channel devoted to frequencies from 3 to 120 Hz.

    Where goes exra bass from LFE channel 80-120Hz?
    Or I'm getting something wrong.
     
  2. Arcangel

    Arcangel
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    It gets thrown away. Whether there is actually any 80-120hz content would depend on the sound mix itself. Most LFE content is below 80hz anyway.
     
  3. Jeff

    Jeff
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    I think it depends on the processor, some loose the upper LFE sounds and some keep it intact.
     
  4. EN

    EN
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    It doesn't matter what processor does, because you manualy set the sub to 80Hz cut off and the processor can't know what is your seting on sub.
     
  5. avanzato

    avanzato
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    The THX processor does the bass management and crossover, not the sub. On the sub the crossover is set at it's highest position or turned off completely if that option is available.
     
  6. EN

    EN
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    Avanzato,
    are you sure that THX setting (there is THX position on sub crossover switch) is not 80Hz?
    This meens no bypass, no higher frequency.
     
  7. avanzato

    avanzato
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    My sub has a THX mark on it for the level control and a THX mark on the crossover. The THX mark on the crossover is at the highest frequency on the dial.

    Download the D6 or D7 subwoofer manuals from the Jamo website to see how they're set up.
     
  8. Dr.Rock

    Dr.Rock
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    I always thought this cross-over frequency set on the amp, refers to the cut-off for mains/satellite speakers and not cut-off from LFE. ie, if you set this crossover to 80Hz, then anything below 80 Hz that's meant for the speaker channels will be directed to the subwoofer instead. But the whole LFE signal, on the other hand, whether if it's below or above your crossover frequency, is still directed to your subwoofer and therefore not affected at all by your x-over setting. Otherwise, we'll be missing out if any "above crossover" LFE is thrown away.

    Is that right?
     
  9. avanzato

    avanzato
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    Some processors/amps (sorry I don't know which) cut off the LFE channel at the same frequency as the crossover to the mains, when using small speakers. Others will spread the LFE between the sub and mains.
    It could be considered bad design but in reality the LFE channel is optional and the mains will already have all the bass that is needed.
     

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