LFE = bass ???

Discussion in 'Archived Threads 2001-2004' started by umit, Jan 31, 2003.

  1. umit

    umit Extra

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    Just curious..

    what exactly frequance range contains LFE? 10-30 Hz? .. 10-40 hz?.. or 10-80 hz? (if crossover set 80). If so, can we say LFE means: all the bass??? (all the bass we get from a movie)

    I appreciate any info.. thanks
     
  2. Brett DiMichele

    Brett DiMichele Producer

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    LFE = Low Frequency Effects

    In a 5.1 Setup (or any .1 setup the .1 is the LFE Track)

    The fairly standard crossover (when running all mains and
    surrounds as small would be 80hz anything lower is directed
    to the LFE Channel)
     
  3. umit

    umit Extra

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    so we can name all the bass below 80 hz. as -LFE- .. right?
     
  4. umit

    umit Extra

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    ..if we set crossover 80 hz. of course..
     
  5. Dustin B

    Dustin B Producer

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    Depends on the unit doing the crossover I think. But for most I believe LFE is 120hz and down. This 120hz is a brick wall. They don't record any frequencies above 120hz on the .1 channel of a DD or DTS sound track. So unless your processor routes the LFE signal through your mains to the bass management crossover, LFE will be 120hz and down while all your other speakers set to samall will go through the bass management crossover which depending on the processor can be from 40hz to 200hz.
     
  6. Brett DiMichele

    Brett DiMichele Producer

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    Dustin is correct it depends on the Processor. Generaly
    anything THX Certified crosses at 8ohz and even some non
    THX units go with the 80HZ XO but then there are others
    that use 100Hz and 120Hz so it basicaly depends on the model.
     
  7. Dan Hine

    Dan Hine Screenwriter

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    Here is how I understand it...if someone knows better then feel free to correct me.

    As Dustin alluded to, the LFE channel is IT'S OWN track. There is information specifically recorded to this track which is generally 120hz and down (though that doesn't mean it HAS to have 120hz information, just that it can). So, if the LFE track has 120hz information on it, then to an extent it won't matter where the crossover on the processor is set. If the crossover is set to 80hz on the processor but the LFE track contains 120hz information then the sub will receive unfiltered non-sloped 120hz information since it is supposed to be there and no where else. LFE bass is different than re-routed bass in this respect. Bass that was mixed into the LCR channels that gets re-routed will be sloped around the crossover point since both/all speakers will be reproducing these frequencies.

    Did I make sense (yeah, it could probably be worded better)? Would it seem reasonable that I'm correct? :b
     
  8. Mike Sloan

    Mike Sloan Second Unit

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  9. Mike Sloan

    Mike Sloan Second Unit

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    actually...Dan said it better!
     
  10. Phil Iturralde

    Phil Iturralde Screenwriter

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    FYI: From Dolby Labs Technical Information website ... What is the LFE channel?
     
  11. Dan Hine

    Dan Hine Screenwriter

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    Thanks Mike! Yes, it is important to remember that the LFE track is the .1 in 5.1 (or 6.1, 2.1 etc..) Those fancy numbers refer to Discrete channels. Whatever is recorded on that track is the LFE, the bass being crossed over is just additional information (given to the sub, from the other channels).
     
  12. umit

    umit Extra

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    thanks for replies.. and thanks for the link phil..
     
  13. Edward J M

    Edward J M Cinematographer

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    In theory, the LFE channel can contain information up to 120 Hz.

    I would think bass at 120 would be fairly easy to locate in the room - giving away the position of the subwoofer. Also, the most common filter point for setting your speaks to "small" is 80 Hz per THX recommendations. It doesn't make much sense for the sub to be playing up to 120, while the rest of the speaks play down to 80.

    Theoretical possibilities aside, in practice would it be safe to assume the LFE channel generally contains no significant signal content above 80 Hz?

    Ed
     
  14. yung cheng

    yung cheng Extra

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    I have a question about LFE.

    In my case

    spec for my main______40hz~20khz(+-3db)
    rear______70hz~20khz(+-3db)
    center____100hz~20khz(+-3db)
    sub_______38hz~160hz(+-3db)

    receiver HK520 setup
    main____________large
    center__________small
    rear____________small
    sub_____________LFE
    sub xover_______60hz

    sub connection:receiver sub pre-out to sub LFE in

    If i play dolby prologic II(or logic 7 or dts neo), will it deliver all signals between 60hz and 100hz to LFE or individual channels(rear, center, etc)?
     
  15. Phil Iturralde

    Phil Iturralde Screenwriter

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  16. Lee Carbray

    Lee Carbray Second Unit

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  17. Mitch Stevens

    Mitch Stevens Supporting Actor

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    I have to agree with what Lee said about your Center and your crossover.

    Most centers out there go much lower than 100hz...I'm wondering if this thing is EXTREMELY tiny. Mine goes down to 50hz, and mine is kinda small, but large to the back.

    Also, your mains don't go low enough to be set to large. I think you should only set to large if your mains can go down to 20 hz. Hmm....maybe someone else will comment on this.
     
  18. Gabriel_Lam

    Gabriel_Lam Screenwriter

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    yung cheng: is there a setting for LFE + (L+R) for your sub on the AVR520? That might be a better choice for you than just LFE.
     
  19. yung cheng

    yung cheng Extra

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    If I set front speaker=large in HK 520, what is the difference between sub out=LFE and sub out=LFE+(L&R)?
    Do I still connect my sub Polk psw-350 with LFE in or with L&R in or connect all three (LFE, L & R line-in) together to HK sub out?
    thx for the reply
     

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