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Recognizing Subwoofer Distortion...

Discussion in 'Subwoofers' started by darkdune, Feb 27, 2005.

  1. darkdune

    darkdune
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    Hi,

    I'm looking to tighten up the response of our Home Theater powered/slave subwoofer system. I have been experimenting with the settings on the VSX-37TX Pioneer Elite receiver we have, and found that setting the Bass Peak Level to -48dB seems to minimize distortion and tighten up the subwoofer response.

    My questions below are about how to really recognize distortion, but here is some more background...

    The instructions for the Pioneer Elite VSX-37TX tell you to "gradually increase the level of the LFE channel until the test tone begins to distort. Then go back and leave the level setting at a point just before that." The range goes from -80dB to 0dB (0dB is louder). I notice that setting it to -48dB gives no rumble to the room during the test tone, but seems to keep playback of TV and DVDs tight.

    When I say tight, I mean that when watching a movie like "The Village" and something shocking or scary zips by, the Bass hits you with a quick jolt, but doesn't boom. You know?

    Also, when I say tight, I mean that the subwoofer keeps the Bass Peak at a level that allows TV shows like "Angel" (which I don't like, but I've noticed the actors have deep voices) to reproduce a Bass'ey element when people talk.

    Here are my questions:

    Does setting the Bass Peak level to a point where I can barely hear the test tone make sense?

    Does the "rumble" in the room during a Bass Peak test tone indicate distortion? Or is distortion simply evident if it sounds too loud?

    I am looking for an answer on how I can recognize distortion. Is a test tone rumble an indicator of it?

    Thanks in advance!

    Darkdune
     
  2. Ilkka R

    Ilkka R
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    You should not use any bass peak limiters etc. Just calibrate your system using for example AVIA. 85dB for mains and others and 82-83dB for subwoofer.

    You don't need to recognize distortion and it's very difficult to hear by ear (low THD). You need microphone and special software for measuring THD.
     
  3. elcid

    elcid
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    You would immediately know if your sub was distorting (a distorting sub sounds ugly! :eek: ).

    Distorting subs (or any other component in the audio chain for that matter) also means users most likely are overdriving their electro-mechanical limits.
    That's why I use several subs to eliminate or lessen potential distortion components and dynamic compression, while still been able to "crank" sound pressure levels without having to be concerned about doing so.
    Of course, the use of several subs entails higher cost, system complexity, and allocation of a lot of the HT room's real state... :(

    -THTS

    "...hi, my name is Frank...and am an SVS bassaholic..."
     
  4. Ilkka R

    Ilkka R
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    Frank, I bet you can't hear 1% THD... :) Most people have difficulties to recognize even 10% THD.
     
  5. Ian J

    Ian J
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    I'm not sure that's true for many people as they have nothing to compare it with. The difference between a poor rumbly subwoofer and a good distortion free sub is quite profound but people that have never heard one will not know the differences.

    Much of the rumble in the background on films is actually sub induced distortion as a good sub will produce tight, crisp notes with the same snap as further up the frequency scale.

    The SVS website contains examples of good bass tester tracks and they aren't just explosions etc but shorter pieces containing snappy bass notes.

    One of my favourites is the beginning of Ice Age when the glacier snaps sending Scrat and his acorn tumbling.
     

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