When would you use the LFE only channel?

Discussion in 'Speakers' started by GeorgeGA, Oct 27, 2004.

  1. GeorgeGA

    GeorgeGA Auditioning

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    My Meridian 568 has the option of directing the discrete .1 LFE channel exclusively to the subwoofer, i.e., no bass from the other channels is mixed into the .1 channel.

    When would you ever use this option?

    Part of the Meridian controls include an LFE low pass filter so it is not necessary to send the full 125hz to the sub.
     
  2. aaron campbell

    aaron campbell Second Unit

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    If your speakers could be set to large.
     
  3. GeorgeGA

    GeorgeGA Auditioning

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    But why would you want to divide up the bass in this manner? You would have some 80hz and lower (for example) coming from the sub and some from the L and/or R for no particular improvement that I see.

    I guess a corollary to my question is: how do they decide what LF goes into the the .1 channel and what LF goes into the rest of the speakers?
     
  4. SteveCallas

    SteveCallas Second Unit

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  5. ScottCHI

    ScottCHI Screenwriter

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    questions?
     
  6. GeorgeGA

    GeorgeGA Auditioning

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    Thanks for the link. According to the article you should never send LFE only to the sub, even if your speakers are full range. See quotes below. So why would Meridian and a few other processors give you this option?


    To quote Miller & Kreisel, bosses of bass, “never send only the LFE to your subwoofer”.

    So, on some soundtracks, sending only the LFE to your subwoofer could leave it with nothing to do while your mains struggle.

    Therefore, the subwoofer jack can contain only LFE (not recommended), a mixture of LFE and bass from the main 5 channels, or nothing at all.
     
  7. SteveCallas

    SteveCallas Second Unit

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    Well I disagree that you should never send only the LFE to a subwoofer. If you have capable speakers, playing them all full range with a sub handling the LFE is the way the movie was intended to be heard. Having 5 or 7 full range speakers is probably going cost quite a bit, and your room would have to be pretty decent sized to get the benefits of having each speaker go down low when needed. However, you have other options.

    Let's say you crossover all your speakers at 60hz. On most processors, you'll be cutting off everything above 60hz from your LFE, which is not what was intended. Having a sub out for the redirected bass and another for the LFE would solve this.

    Another option is to have multiple subs, with one or more only handling the redirected bass, and another one or more only handling the LFE. This will lesson the load on each sub and allow you to experiment with things such as stereo subs (a sub on the right handles all redirected bass from the right main, right surrounds, and center, and vice versa for the left).

    In other words, if I had this option I would be happy.
     
  8. Hartwig Hanser

    Hartwig Hanser Second Unit

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    I can only say that I have played around with the different options and I am most satisfied with the sound when I have all speakers full range and send only the LFE to my Sub. One possible reason may be, that I do not like the LFE too loud, so I am inclined to turn down the sub. If I mix all lower frequencies with the LFE, I will turn them down, too. My way I only turn down the LFE, which is in many modern movies exaggerated IMO.
    LFE only to sub simply gives me the fullest sound.

    I have B&W 7NTs front, B&W CNT center, MJAcoustic REF1 sub and B&W Matrix 1/II surround.
     
  9. RyanSoares

    RyanSoares Stunt Coordinator

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    oh i'm confused, i have all my speakers set to small on my receiver and the sub out on the reciever to LFE in on the back of my sub.... now my fronts are jbl e 30's and my rears are the jbl n24's are you saying i should set those to large?
     
  10. aaron campbell

    aaron campbell Second Unit

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    Ryan, your settings are fine.
     
  11. SteveCallas

    SteveCallas Second Unit

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    No, you should definitely not set JBL E30s to large. I was just saying that your processor gives you more options with bass managemnet than most do, and if you ever decide to get full range speakers or intend to use multiple subs, you will be happy that you can send the LFE only through its own output.
     
  12. LanceJ

    LanceJ Producer

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    Maybe I am missing something here but whenever you set a Dolby or DTS processor to "large" for all the satellite channels, when it is programmed for "yes subwoofer" the LFE signal is still sent to the subwoofer.

    And why would the sound people place extreme low frequencies (< 30Hz) in the satellite channels anyway? That's what the LFE channel was specifically designed for.

    So.......

    Here's a riddle for the bass experts about something I mentioned in a thread recently concerning surround music:

    Phase cancellation is brought up a lot as a major potential problem when discussing using "large" on all channels but AFAIK phase problems can only occur when identical (but reversed) waves are involved. But do movie and music sound mixers put IDENTICAL bass sound/frequencies in all five channels all at the same time? I think that would be rather dumb to be honest.
     
  13. ScottCHI

    ScottCHI Screenwriter

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    "sound people" engineer the sound for truly full-range speakers and an independent LFE channel; not crossed-over "satellites".

    the bass management in our home theater receivers is a CHEAT.
     
  14. Mark Hedges

    Mark Hedges Second Unit

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    I understood that on most better engineered soundtracks, there is little or no bass content below 70 hz or so sent to the surrounds. I have heard of people setting up a sub in front of their surround and then finding it to be a waste since there is no deep bass content anyway.
     
  15. Brian L

    Brian L Cinematographer

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    Without any supporting evidence, I would say probably thats true with most films, but a good example of surround channel bass would be U571.

    My rears are crossed at 80Hz, but you will believe that they are blasting out much lower than that during the "Depth Charged" chapter. And that was when the sub was still in the front of the room!

    BGL
     
  16. LanceJ

    LanceJ Producer

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    Whew! Someone else read what I read!

    Ever since the Dolby & DTS 5.1 formats came out, I thought that because most people would not purchase five 100lb floorstanders for their living room (or even tolerate them if they could afford them), for home playback soundtracks would be designed to have all the extreme low bass effects in one channel. And that channel would be played back by a speaker that is easily accomodated into most living rooms i.e. a subwoofer.

    In most shots of movie sound studios that I have seen, I see bookshelf-sized monitors with 8" to 12" woofers. But then when I was poking around B&W's site last week, I saw this:

    "George Lucas Studio, Skywalker Sound Uses B&W"

    The N802s go down to "only" 39Hz (on a +/-2dB scale) but still, that's getting very close to full range (and they are -6dB at 27Hz).

    And check out what this surround mastering (including sacd & dvd-audio) studio uses.....again!

    Abbey Road Studios

    Now I'm getting confused.....
     
  17. ScottCHI

    ScottCHI Screenwriter

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  18. LanceJ

    LanceJ Producer

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    I'll go along with that Scott.

    Though I'm stretching the definition of full-range here, with my own system the front & rear channels are set to large; all four speakers have 8" woofers and make it to the low 40s. In my small room this works out fine. The center is just too small to effectively run it that way but I'm working on that (i.e. a different speaker).

    Like I've said before, IMO bass management was designed to accomodate the people who don't want five large speakers in their room & not just to make things easier for the driving amp or the loudspeakers.

    And the purist in me is bothered a little by all those crossovers that are employed in a bm'ed system.

    Maybe this will encourage others to adopt Big Speakers [​IMG] again (JBL E30s, Boston VRBs, and larger) & get away from those sexy but thin-sounding little boxes that can nearly get knocked over when a housefly lands on them.
     

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