Understanding Sub, Bass, & LFE

Discussion in 'Archived Threads 2001-2004' started by Jason Wolters, Dec 19, 2001.

  1. Jason Wolters

    Jason Wolters Stunt Coordinator

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    I have spent hours trying to get a good concept of how a receiver handles bass and LFE. Does anyone know of a good link that explains this or can you help me here? If my receiver has a crossover frequency of 100hz what does that mean? Also if the crossover of my sub is set to 60hz than all frequencies above 60 are directed back to the mains? (even with the mains set to large?) Isn't the LFE lower than 60 hz? I have good sized floor speakers with 12" woofers. Should I set the mains to large? My sub is a little 8" Aiwa with a 60 watt amp. Is there a use for this in my setup? Or should I use it for a door prop?
    [​IMG]
     
  2. Bob_M

    Bob_M Stunt Coordinator

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    I can help with a little

    >If my receiver has a crossover frequency of 100hz what does that mean?<

    Everything about 100Hz will be directed to speaker in question it it's set to small and everything below 100Hz will be directed to the sub. Note: this is no a brick wall and your will have a roll off both ways. Meaning your speakers will get some material below 100Hz and your sub will get some material above 100 HZ.

    >Also if the crossover of my sub is set to 60hz than all frequencies above 60 are directed back to the mains? (even with the mains set to large?)<

    This depends how you have your sub set up. If your just using (most common) the low level sub out on your receiver then the Xover on the sub will not send anything back to the mains. In this case you should set it as high as possible in in order to get it out of the way.

    If your using High level or speaker level inputs (not common anymore) into the sub and your mains are connected to the output of the sub then the xover in the sub would work in the same manor as the xover in your receiver. In this case you would want your speakers set to large and LFE directed to your mains.

    >Isn't the LFE lower than 60 Hz? <

    It's like 20-200 or so Hz. I don’t know the exact number but it higher than you would think. I also believe this is a brick wall.

    >I have good sized floor speakers with 12" woofers. Should I set the mains to large? My sub is a little 8" Aiwa with a 60 watt amp. <

    Your will have to experiment and see what works best.

    the above is my understanding and i am not an expert.

    Hope this helps,

    Bob
     
  3. BruceD

    BruceD Screenwriter

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    Not sure what you have for a receiver or how you have your sub hooked up, but here's a stab at explaining:
    Say your receiver has a 100Hz xover for bass redirection.
    You DO NOT want to also have your sub's 60Hz xover engaged. The sub's xover should be turned OFF.
    Bass Management essentially means bass redirection
    bass redirection = bass < 100Hz taken from any speaker (set to small) that is sent to the Sub-out (RCA connection) on your receiver which then goes by cable to a powered sub.
    The thing to remember about crossovers is that they work and look like ski slopes not rock cliffs, i.e. gradual reduction not abrupt reduction.
    Actually this means any speaker defined as small will still be producing output below the 100Hz crossover, but the output level (SPL) gradually reduces in volume as the frequency sent to them goes below 100Hz (SPL levels will typically be down -12dB to -24dB at 50Hz for example). You can probably hear a -3dB reduction easily.
    Two examples for you:
    Example #1
    mains set to Large
    center set to small
    surround set to small
    sub = Yes
    Here the bass actually being produced by the sub originates from three sources
    1. LFE from DVD source
    2. Any DVD source bass redirected from center
     
  4. Pete Mazz

    Pete Mazz Supporting Actor

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    Doorstop.

    Pete
     
  5. greg_t

    greg_t Screenwriter

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