Question- Subwoofer Volume setup

Discussion in 'Speakers' started by Bill Griffith, Nov 21, 2003.

  1. Bill Griffith

    Bill Griffith Supporting Actor

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    Start with a Sony - SA-WX700, it has 250W digital Amp, with Dual 10" Drivers, isobaric.

    This question is for subwoofers in general though.

    You have a volume knob on the Sub, and a individual volume adjustment for the sub preout from the reciever. What we have noticed is that if you Turn the Volumne on the sub 95% of max and turnt he Sub Volume preout on the reciever (yamaha HT5440) down to -12 (on a -20 to 0 scale, 0 being max). Doing this seemed to generate a crisper thump at the same volume level than having it set up (standard) with the Sub volume at 50% and the Reciever sub volume setting at 50%. This standard setup would create more a a slurred typ thump compared to the before mentioned setup.

    Is this hurting anything on the sub, as we don't hear anything outn of the ordinary (popping, or humming)? The bass response just seems to have gotten tighter.
     
  2. Gary Thomas

    Gary Thomas Second Unit

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    I'm not sure if there is any science behind this opinion, but I would think you'd want the full signal coming from your sub-pre out to your sub...then adjust the volume using the volume control on the sub itself.

    Either way, I can't imagine you hurting the sub in any way...you'd only hurt the sub if you were consistently bottoming it out with excessively high volume bass material.
     
  3. Bill Griffith

    Bill Griffith Supporting Actor

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    The way I see it,

    The signal from the reciever is merely information not power based. It sends the signal that the sub needs to generate the proper frequency and it send a signal for volume level adjustments.

    The sub Volume control is the amount of power you are allowing the sub to draw.

    Maybe some siganls require more power but if you are limiting the sub to only draw a certain amount of power then the sound will not be as crisp.

    Don't know if this is they way it works or not but thats kind of what I'm getting at with the question.
     
  4. PaulT

    PaulT Supporting Actor

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    Bill,

    The output of the receiver is 'Voltage' based (therefore in a round about way Power). LFE (Sub) outputs are voltage variable depending on how you set the output level on the receiver.

    According to the Owners Manual, in your case with the HTR5440, the Max Output Level of the Subwoofer out is 4.0V (see the Appendix Section of the Manual).

    As a general rule of thumb, you should set the receiver level to 0db, then using test tones and an SPL meter set the desired level on the Sub volume control. You can now fine tune the settings with your remote using the receivers levels. With some subs, setting the receiver output too low, the auto on/off function will not work due to it not sensing the low level signal.

    What you are also doing by sending a 'lower' signal level is making the sub amp work harder to attain the same output. On the other hand, sending too 'hot' a signal to the sub will allow it to clip more easily as you turn up the volume on the sub.

    Hope this makes sense.
     
  5. Edward J M

    Edward J M Cinematographer

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    The distortion of an AVR sub pre-out can approach several percent at the max setting.

    Keeping the AVR sub pre-out level low (into the negative range) typically keeps pre-out distortion below 1%.

    With the pre-out level set low, you are sending the subwoofer amp a cleaner signal and you might be able to hear the difference, all other things being equal.
     
  6. Bill Griffith

    Bill Griffith Supporting Actor

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    Paul - what do you mean by "Clip more easily"

    Does anyone else agree with Edward. I had never thought about that before on a pre-out. To be honest I really don't see how it could.

    I figured when you run a signal through a preout to the sub, your sub gets 2 signals. 1 signal for the frequency, the 2nd signal for the amount of volume to offset from a baseline, which is set by the main volume on the sub. Is this not they way they work?
     
  7. PaulT

    PaulT Supporting Actor

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    Bill,

    When I say 'clip' I mean a hot input to a power amp (your sub amplifier) will bring the sub to high distortion levels more quickly/easily when you turn up the volume on the sub amp.

    Your receiver Sub output is effectively a pre-amp for the amplifier in the Subwoofer. The adjustment of the receiver output sets the level of the signal (in Volts) being send out of the LFE connector. It is one signal only but above or below a baseline.

    You are right in your thinking except there is only 1 signal (the frequencies being sent of the source material), but it's reference level changes (adjusted by the level adjustment of the Receiver's output).
     
  8. Edward J M

    Edward J M Cinematographer

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  9. Bill Griffith

    Bill Griffith Supporting Actor

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    Intersting.

    Thanks a bunch for the help guys.
     
  10. MichaelOD

    MichaelOD Stunt Coordinator

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    quick question:

    example: my system is set to reference using avia and an spl, my sub amp is dialed low [2 out of a possible 10], and the lfe db on my receiver is set to 0 - what do i dial up if i want a hotter response from my sub? my sub, or the lfe on my avr?

    the equipment in question is a harman kardon avr330 and a 25-31 PCi SVS sub.

    thanks for any responses!
     
  11. PaulT

    PaulT Supporting Actor

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    In my opinion [​IMG] for a temporary boost in Bass, I would boost the receiver output from the comfort of my chair (with the remote). For a constant hot output I would crank the volume on the Sub.
     
  12. RichardH

    RichardH Supporting Actor

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    Another thing which may be factor with some subs is that the volume knob on a powered sub passes the signal through a potentiometer. The quality of the pot could have an effect on the sound quality depending on how much it is attenuating.
     
  13. DavidLW

    DavidLW Stunt Coordinator

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    Edward is correct in stating that a pre-amp will add distortion when approaching max. However, I think there's a little confusion here. I don't believe is correct to call the adjustment for the sub on the AVR a pre-amp. I don't think it's ampiflying the signal. It's only purpose is to passively reduce the gain from the master volume control so your subs can be balanced with your front speakers. Most ampiflied subs require less gain than the front speakers to sound balanced.

    The volume control on your sub on the other hand may be a pre-amp as it might be ampiflying the incoming signal. My feeling is that the control on your sub is not a pre-amp. Like the control on the AVR, it only reduces the incoming signal passively. Since both controls does the same thing passively, you should have one of them at "0" or "max" so you are effectively bypassing one of the pot and reducing signal degradation. The way you describe, the pot on the AVR is the better quality pot and should be the one you should be using to balance your sub. And the control on the sub should be on "max".

    Now, if the control on the sub is truly a pre-amp and does indeed amplify the signal. Then you would want to have the AVR control at "0" to effectively bypass that pot. But only if the control on the sub is set to at least 1/3 of it's range when you have it set at the volume you want. Having the sub control set too low is not good if it is ampiflying the signal.

    I may be completely off base on my assumptions as most of my experience with subs is form setting up music systems and not Home Theaters.
     
  14. Edward J M

    Edward J M Cinematographer

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    While it may be semantics and nomenclature, I always refer to anything with a functioning pre-out as a pre-amp.

    For example, my Denon AVR 3803 has pre-outs for all eight speaker channels (not just the ".1" subwoofer).

    One could certainly use an external 7 channel amplifier for all the speaker channels and bypass the internal 3803 amps. An AVR used in this fashion is usually referred to as a pre-amp.

    In any case, varying the sub level control (indeed any pre-out level control) in the AVR alters the strength of the signal (in millivolts) being delivered to the pre-out jack. Whether it is passively reducing the gain from the Master Volume, or actively amplifying the signal, I don't know.

    If it is passively reducing gain from the Master Volume, why does setting the level control to the maximum introduce more harmonic distortion into the signal?
     
  15. DavidLW

    DavidLW Stunt Coordinator

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  16. Edward J M

    Edward J M Cinematographer

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  17. DavidLW

    DavidLW Stunt Coordinator

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    I'm not familiar with the Yamaha AVR memtioned in the first post, but the way Bill described it, I envisioned him turning a small pot at the back of the AVR next to the sub out jack(s). These pots are nearly always passive as they do not offer any gain above the master volume control.

     
  18. MichaelOD

    MichaelOD Stunt Coordinator

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    hmmm...

    excellent information. the only catch is that, in regards to my original question, i'm a tad lost. i have an SVS 25-31 sub that is equipped with a 320watt BASH amp. the gain on this amp is set to 2 out of a possible 10, and my avr is set to 0. these settings are reference using avia and an analog spl. however, i find that my bass is lost, no longer as punchy as it once was...i'm looking for it to be a bit hotter if you will. so...how can i introduce the least amount of THD? or perhaps, what is the proper way to turn up my sub without it bottoming out? by turning the avr db down then turning the sub amp gain up? or leaving the avr @ its 0 db and just turning up the sub amp's gain?

    hopefully this clarifies...thanks in advance for all responses!
     
  19. Edward J M

    Edward J M Cinematographer

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    Avia tends to provide a somewhat weak sub calibration. Most users find running the sub 7-8 dB hot with Avia works well.

    The best way to increase the sub level is to run the AVR sub level at the 25% setting (e.g., -5 on a scale of -10 to +10) and increase the gain at the BASH amp until you obtain a satisfactory subwoofer output level.
     
  20. MichaelOD

    MichaelOD Stunt Coordinator

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    Edward J M,

    you da man! [​IMG]

    that's exactly what i was looking for...i had heard about that avia "issue", but was unsure if it was true.
     

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