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LPF of LFE?

Discussion in 'AV Receivers' started by Linksys 845c, May 18, 2008.

  1. Linksys 845c

    Linksys 845c Well-Known Member

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    There is a "Low Pass Filter" for the LFE channel setting on my Onkyo 605's speaker setup menu...the selections are 80, 100 and 120Hz...I have been told to keep this at 120 so that the entire spectrum of LFE is passed to the sub...is this correct? What should this setting be on?
     
  2. Linksys 845c

    Linksys 845c Well-Known Member

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    Can anyone possibly assist with this question? I'm just wondering if the Low Pass Filter for LFE setting on the Onkyo 605 should be set to "120Hz" for optimum subwoofer output...
     
  3. thrca

    thrca Well-Known Member

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    I would think that this would entirely depend on the speakers you are using with the system.

    If you have a high quality set of mids, I would recommend setting the subs LPF a little lower, as using 120Hz may make a great sub sound a little loose and sloppy.

    I personally use 80Hz for my 500W 15" subs on my Acoustic Research AR1s and they sound great.. When I changed to 120, it seemed slightly louder, but at the cost of being more sloppy and less controlled. (explosions dragged out beyond where they should, etc.)
     
  4. Linksys 845c

    Linksys 845c Well-Known Member

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    Thanks so much Jim...

    My speakers are bookshelf-sized Polks, the mains a larger set from their "R" series, the R20s, and the rears smaller R15s...

    Interesting that you suggest going a little lower on the LPF; sometimes it does seem like the bottom end is a bit too boomy out of my Polk PSW-10, but I was originally told, on a different site, that this "LPF" setting in the receiver is really for if you can "identify" where a sub is located in a room, and adjusting for that -- and then it was suggested just setting this to 120 so the "full spectrum of LFE" comes through that channel...

    Based on the type of speakers I have, what setting would you recommend? My sub is up against a side wall of my theater, tucked next to the couch.
     
  5. Brent_S

    Brent_S Well-Known Member

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    120hz should be the correct setting.

    Jim is talking about the main speakers to subwoofer crossover...those should be based on the lowend response of your mains. This is different from the LPF of the LFE.

    The LPF of the LFE seems to be a user option unique to Onkyo, or at least it's very unusual. The LFE (.1 in 5.1/7.1) is brick walled in the encoder (at least, in DD) at 120hz. According to Onkyo, you may get a hum in the LFE channel when set that high...it's unclear if this is a possible artifact of the LFE encoding process or maybe an induced harmonic of the 60hz AC voltage, or something else entirely. I personally haven't had any problems running my 805 with the LPF of LFE at 120hz...all regular crossovers are at 80hz. I also don't recall seeing anyone else mention it as a problem in the 450+ page thread dedicated to the 805 over at AVS.

    -Brent
     
  6. Linksys 845c

    Linksys 845c Well-Known Member

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    Thank you for clearing that up, Brent. I suppose I will leave it at 120Hz.

    You say Jim is talking about the speaker crossover; he says this, though, about the "LPF":

    "If you have a high quality set of mids, I would recommend setting the subs LPF a little lower, as using 120Hz may make a great sub sound a little loose and sloppy."

    ...so it seemed like it was suggesting I should use something UNDER 120Hz on the LPF setting of the Onkyo...
     
  7. Brent_S

    Brent_S Well-Known Member

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    Since you started with "low pass filter"', it's a typical response to assume someone is talking about the main-sub crossover point for redirected bass when they have a question that includes LPF and a question about setting it. Only someone who's used a recent Onkyo and run into the "LPF of LFE" option (or read some of the posts and confusion it has generated at various forums) will recognize that your post is not the normal "where do I set my crossover" question.

    The LPF of LFE has been discussed at length in the 705/805 threads at AVS. One of the principals at Audyssey tried to get Onkyo not to even give the user the LPF of LFE option because they recognized the confusion it would generate. Of course, they also tried to get Onkyo not to set speakers as full range just because their -3dB point was below 80hz, but that didn't work either.

    To add insult to injury, Onkyo defaults the LPF of LFE to 80hz (and includes the THX logo with that choice on the 805 suggesting some official endorsement). While I'vre read that audio mixers *generally* limit the LFE channel to
     
  8. Linksys 845c

    Linksys 845c Well-Known Member

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    Thank you, Brent; so, essentially the bottom line is use 120 for that setting, yes?
     
  9. Brent_S

    Brent_S Well-Known Member

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    Unless you hear the "humming" noise that Onkyoe suggests might happen with going higher than 80hz.
     
  10. Linksys 845c

    Linksys 845c Well-Known Member

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    Thanks so much...because of all you guys making this much clearer, I think I understand the whole issue of the Low Pass Filter Onkyo included on these receivers...

    It's basically a way to filter out a hum that may occur above 80 Hz -- but otherwise, the setting SHOULD be 120 to brickwall all the LFE to that channel...did I get it right?

    Thanks everyone for your help. [​IMG]
     
  11. thrca

    thrca Well-Known Member

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    Heh, Im not very quotable.. I in fact was referring to the crossover frequency between the mains and the sub. I don't recall seeing an LFE specific setting for this, and it maybe to clear up LFE artifacts as Brent said.

    In my specific situation, I have acoustically measured my mids and they seem to perform well all the way to the crossover point (and beyond maybe) so I prefer to trim my subs at 80Hz because it seems to sound more controlled to me.

    I would say that if you can tolerate watching a single scene over and over a few times, to try it with the same scene at the same volume setting using the same seating position in a portion of a feature with a decent LFE track. While there is Mfg recommended settings, only *your* ears will decide what works best for you.

    Good luck, and keep us posted what you find to be the best for your tastes.
     
  12. Linksys 845c

    Linksys 845c Well-Known Member

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    Jim,

    Actually there was just some confusion, apparently, on what you had replied on regarding my original question, and what I actually meant -- no harm done whatsoever...

    My original question had to do with ONKYO'S particular menu setting for this "Low Pass Filter of LFE" selection the TX-SR605 receiver asks you to make under the speaker setup...apparently, this circuit is to filter out a hum that may occur if the LFE's level is above 80Hz -- at any rate, I believe, from the information I gathered here, that this setting should be at 120Hz unless there's a hum present when bass is pounding your sub...[​IMG]
     

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