why would all my speakers be trying to play a 20Hz signal

Discussion in 'Archived Threads 2001-2004' started by David_Stein, Mar 6, 2003.

  1. David_Stein

    David_Stein Second Unit

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    i got a new sub today, and have been playing with it all day.

    i used a tone generator and made pure sine waves at 20hz, 19hz, 18hz, 17hz, and 16hz, and then burnt it onto a cd from the .wav file.

    i put it in my dvd player (its also the cd player at the moment) and played the first track (20Hz). to my suprise there was a signifigant amount of noise from all five speakers plus the sub. obviously, the stuff coming out of the bookshelf speakers was just distortion, but it confused and disturbed me.

    my reciver is an onkyo 575x, the speakers are jbl n24s, n26s, and ncenter. i checked immediately after to make sure the speakers were set up and they were (subwoofer on, all speakers set to small). i dont know for sure what the onkyo crossover is, but i think its 80hz.

    does anyone have any idea why this is happening?
     
  2. Edward J M

    Edward J M Cinematographer

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    Just a guess - is your bass management circuit bypassed with an analog signal?
     
  3. David_Stein

    David_Stein Second Unit

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    i really doubt that my reciever has something like that, as its a fairly lowend reciever, but even if it did the dvd player is connected using a coaxial digital connection.
     
  4. Geno

    Geno Supporting Actor

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    david, do a test. record nothing on a cd. i mean it could just be noise from your dvd player to the receiver amplified.
    can you record silence onto a cd then test it?
    you got me?
     
  5. David_Stein

    David_Stein Second Unit

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    yeah, that should be pretty easy. im on it.
     
  6. David_Stein

    David_Stein Second Unit

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    alright, update:
    i made a cd of silence by unplugging the mic and recording in sound recorder and then burnign the wav file on cd.

    in the center, two surround speakers, and the sub there is a hum (it can not be heard in the main speakers). in retrospect this could have just been something that was picked up out of the input of the soundcard even without a mic.

    it seems to be of a constant volume, no matter the volume setting on the receiver, except when you turn the reciever all the way down as far as it will go, then the sound goes away. it does not play when changed into stereo mode (not using the center or surrounds, i should note that all other testing is done using "5channel stereo").

    when i press stop on the disc the hum remains, however when i eject the disc the hum stops.
     
  7. Geno

    Geno Supporting Actor

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    i wouldnt worry
     
  8. Brian Bunge

    Brian Bunge Producer

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    David,

    Are you using the digital or analog connections (or both) between your DVD player and receiver? Have you set the subwoofer to YES and all the other speakers to SMALL? Check these things first. If your speakers are set to LARGE then you are feeding them a full range signal.
     
  9. Brian Bunge

    Brian Bunge Producer

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    Oops! I re-read your first post and noticed it already said you have the speakers set to small. Sorry about that.
     
  10. Sebastian

    Sebastian Second Unit

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    I had a similar problem with my Onkyo 484 but it was mostly the center channel at it was at 16Hz.
    Here is link that I originally posted:
    Onkyo 484 whacked?
    Anyway the links in the thread do not work anymore, deleted the pics.

    Are you running it in 5 or 6 channel stereo? If you are just try 2Ch and see what happens. Anytime I plot my freq in 5 Ch it gets all hosed up(weird readings), but when I am in 2 channel stereo everything works.
     
  11. Guy Usher

    Guy Usher Supporting Actor

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    If you can achieve silence on a CD on a 400 dollar receiver, I want to know where I can buy a truck load of them. . . .
    Most all audio gear has some strange sounds if you really listen, all you can do is try to pin it down and fix it, if you cant you may have to live with this noise providing everything is working properly. . . .
     
  12. Brett DiMichele

    Brett DiMichele Producer

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    I must be the exception then, not the rule..

    Granted I don't have a $400.00 Receiver but I don't have
    anything near high end either.

    I run basic cables, nothing fancy, some are bought and some
    are even home made...

    I go from my DVD Player into a Behringer Tube Ultra-Q out
    from the Tube Q into my Onkyo TX-DS787 out of my 787 into
    my Onkyo M-282 Power Amp and then out to my speakers.

    I get absolutely no white noise untill 60+ on the main
    volume with no media playing.. 60+ is well over 100Db when
    there is music playing.

    I guess I am lucky I don't have some of the noise issues
    some people have.
     
  13. David_Stein

    David_Stein Second Unit

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    the hum really wasnt the problem, the problem was that when running a 20Hz sine wave through the system (in 5 channel stereo), a signal that purely should have been cut out of all the main speakers and routed to the sub with the bass management, i was getting badly distorted sound from my speakers (save for the sub, that sounded good). i could literally hear the poor midranges on the surrounds (n24s) flapping trying to play something.

    i suppose the 5channel stereo DSP could be creating some sort of harmonics that i was hearing, but it was still a bit disconcerting. next time i have the balls to try those test tones ill make sure i do it in regular stereo and see if things are better.
     
  14. BrianWoerndle

    BrianWoerndle Supporting Actor

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    I had a cheap old JVC receiver that did not implement a crossover in stereo. It would send a full range signal to all mains no matter if you had a sub and speakers set to small. It would only crossover in Dolby Prologic, DD5.1, and DTS. The manual even said that.

    So it is possible that your receiver is not using the crossover, or it could be bass doubling.
     
  15. David_Stein

    David_Stein Second Unit

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    woah, ill have to look into that.
     

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