Receiver output setting for subwoofer

Discussion in 'Speakers & Subwoofers' started by George Pappas, May 5, 2003.

  1. George Pappas

    George Pappas Auditioning

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    Hello HT forumers.

    I have a question.

    A audio/video dealer where I live suggested that the sub setting on the receiver should be set to the highest db output and from there adjust the subwoofer's output accordingly. The idea is that since the receiver's sub-out connection is only a signal boost and does not affect it's amplifiers, then this is okay. Setting the receiver's sub-out signal to max will require the sub-out setting on the back of the sub to be lower so the sub's amplifier does not work as hard or as hot.

    For example: My Onkyo TX-SR600's sub-out setting is maxed out at +12db and I lowered my Klipsch KSW-10 sub's rear output setting from 9.5 (11 being maximum) to 7.5 to get the same power output thus enabling the sub's 225 watt Mosfet amplifier to run cooler or not as hard.

    Just for your information all my speakers are set to small, my sub's frequency knob is set to max (120 hz) and my receiver's subwoofer setting is crossed over at 80 hz.

    Does this type of sub/receiver output setting, as this dealer suggested, make sense or am I missing anything here?
    I'm fairly new to home theatre.

    Thanks people
    GP
     
  2. StephenL

    StephenL Second Unit

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    Setting your receiver's subwoofer trim level to the highest output is not a good idea. Using worst-case test signals, Sound & Vision magazine has measured high distortion at the subwoofer output on some receivers with the subwoofer trim level set to 0 dB. For such receivers, Sound & Vision now specifies the subwoofer trim level necessary to avoid distortion. So, depending on your receiver, you may have to set the subwoofer level below 0 dB to avoid distortion. I wouldn't exceed 0 dB in any case. You can adjust the subwoofer's amplifier level instead of the receiver's subwoofer trim level to obtain the proper sound pressure level when calibrating your system. The subwoofer amplifier is designed for high power output; the receiver's subwoofer output is not.
     
  3. ColinM

    ColinM Cinematographer

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    Like Stephen said...

    The AVR's sub-out can clip if driven hard, sending a clipped signal to the sub, which amplifies it.

    Set the AVR's level to 1/4 (-5 if the range is -10 to +10) and let the gain (volume) knob on the sub go where it needs to be. It will work just as hard as the other way, just with a cleaner signal.
     
  4. George Pappas

    George Pappas Auditioning

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    Thanks a lot Stephen and Colin.

    I really appreciate your definitive answers to my question. You gave me a great senario. I didn't know this about the receiver's sub setting being capable of adding distortion. I will go back to at least the 0db setting and experiment downward to -5db from there and raise the sub setting back up to my 9.5 or 9.75 setting. Now I know why the opening explosion scene on AOTC sounded a bit different and more forward. It was probably this added distortion.

    Thanks again and thanks in advance to any other responders as well.
     
  5. JeremyFr

    JeremyFr Supporting Actor

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    I know I had a kind of similar issue but mines different in that my sub has a direct input that bypasses the level and filter on the sub and allows a straight unprocessed signal to the amp. With mine I had originally had it running the other way but found that since my reciever cross's off at 90hz I ran the sub out to the direct in and now use the Sub adjustment on my reciever and find that I'm quite happy with the reciever level set at -14 to -10db. it sounds 100 times better than it did before using the built in filter/level on the sub.
     
  6. David Preston

    David Preston Supporting Actor

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    This helps me too. I had my sub set at +5db. I can't test right now because everyone is sleeping. Even the next door neigbors.(haha) I went ahead and switched it to 0db. I plan on getting a calibration soon so it will get fixed then for sure.
     

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