SVS volume control and sub level

Discussion in 'Archived Threads 2001-2004' started by Jeff.bart, Jan 24, 2003.

  1. Jeff.bart

    Jeff.bart Stunt Coordinator

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    Using the Radioshack SPL meter, I ended up turning my SVS 25-31 sub volume level to slightly past the one-quarter mark, with the AVR channel level set to 0. Is that similar to the experience of other SVS users here?

    The SVS guide says to start with the sub turned up to 1/2 or 3/4 on the volume level. I thought it was odd I had to reduce it so much. (I used Avia).

    Also, if I set my full-range main speakers to work with the sub ('sub plus L+R' on my HK setup), do I measure sub output with the main speakers off or on?

    Naturally, I get different readings depending on how I do it. I even have to turn the volume level lower on the SVS -- below the 1/4 point -- when I measure with the mains on.

    I also find that output is vastly different when I compare the sub individually to the Left and right main speakers. I guess that's no surprise The left speaker is in a right-angle corner. The right speaker's back port empties partially into a more open part of the room that leads to a narrow hallway.
     
  2. Zack_R

    Zack_R Stunt Coordinator

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    Not sure on your volume control question but I can comment about my experience regarding..
     
  3. Jeff.bart

    Jeff.bart Stunt Coordinator

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    Good idea, Zack. I switched the 0-180 phase switch briefly but never actually measured output.
     
  4. Tim Hoover

    Tim Hoover Screenwriter

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  5. SVS-Ron

    SVS-Ron Screenwriter

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    Jeff,

    Given how sensitive the new ISD woofers are, and how powerful the BASH amps are, we're in the process of amending manuals and such to indicate 1/4th to 1/2 Gain on the PC amp is a good place to start calibrating.

    Again, the general rule of thumb is to run your sub Gain up relatively high, and the receiver's sub output level relatively low so as to keep the input distortion to a minimum. You do NOT want the receiver's sub output so low that you no longer have downward adjustment room still (using your remote for instance), nor do you want the level to be so low as to be insufficient to trigger the amp's "auto on" circuits, but the manual and this portion of our web site covers that pretty well.

    Ron
     
  6. Bill Kane

    Bill Kane Screenwriter

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    There are a coupla of issues here, and SVS Ron nicely weighs in on achieving a balance betw the sub amp control level and the receiver’s Bass/LFE level from the remote’s setup, where a midrange position is good. Too low on the AVR, you run the chance of not enough voltage to keep the Auto-On alive; too high, runs the risk of distortion-level voltage AND no room on the remote’s scale to adjust the Sub up/down3-6dB while seated.

    The other may be the oft-discussed issue of: “I’ve got full-range speakers and I don’t want to WASTE them by setting to small.”

    Brian Florian of “Secrets” steadfastly advocates adhering to the basic THX/DD protocol of ALWAYS setting all speakers to SMALL and directing all bass to the Sub, regardless of any “full-range” mains. More recently, he looks into the splitting of bass information betw the Sub Plus Mains, and recommends against this addition of up to 6dB of extra or overlapping bass HERE

    I think this mainly applies to DVD soundtracks, and I know it’s fun to experiment with other LARGE/SMALL combos with CD music, which is fine.

    For starters, I’d suggest using Avia and the SPL meter for baseline or standard calibration of the SVS Sub using all SMALL and all bass directed to the Sub (No L&R too). Listen to find out if your bass is smoothest in this configuration. You can always re-fiddle.

    A 3rd debate is where to match the sub’s dB output with the test Main using the RadioShack meter. When I first got my early-model SVS, I set it +4dB above the “reference” level (SVS Ron even suggested this). Today, I’m reading that the sub ought to match the main, 75 for 75 if that’s your reference, and because of meter “error” this actually sets the Sub 2-3dB too high. YMMV.

    bill
     
  7. SVS-Ron

    SVS-Ron Screenwriter

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    Bill,

    I still suggest that, since most folks don't come close to running their main system at reference level, it's a simple way to get a bit of a bass bump to compensate for the fact we are increasinly less able to hear bass as the volume goes down.

    The old "loudness" controls on stereo receivers worked the same way.

    Technically there's no doubt that 75dB for the sub (and more like 72dB as measured with a test disk and the Rat Shack meter) is correct.

    You'll never find my HT calibrated so low though ;^)

    Ron
     
  8. Zack_R

    Zack_R Stunt Coordinator

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    I don't disagree with Ron's point but I think (with movies anyway) that the sub would work perfect for human ears *if* the audio wizards that control the LFE would utilize the full peak output more often. For example AOTC, this movie plays fine and sounds great with my Ultra calibrated to technical specs. The LFE has a tremendous boost that compliments a well calibrated system. On the other hand there are many more movies that do not take advantage of the LFE benefit that has been put in place.

    So to go against tradition (in a perfect world), I am thinking that for movies you calibrate the sub flat and let the adudio engineer take care of the loss in low frequency info your ears hear by boosting the LFE 10db. For two channel music, I would say bump the sub bass approximately 2-3 db to compensate for the human ears reduced hearing of the lower frequencies. The music CDs don't have any type of boosting to compensate for the hearing loss of lower frequencyies the way DD has unlees they just record a bass producing instrumetn at a higher level.

    I run about 1-2 dbs hot and I use this setting for movies and music.
     
  9. Jeff.bart

    Jeff.bart Stunt Coordinator

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    Well, I read the SVS web site on sub levels. The way I read it, I am supposed to set the sub level on my HK 525 to –5 (it ranges from –10 to +10). Then turn up the sub volume control as close as I can get to 85 db on my Avia disk, and use the avr to make the final adjustment.

    However, the SVS site also says that most of the SVS people run their subs run a +2 to +6dB setting on the LFE channel.

    Does that mean my avr should end up with a sub level reading of +2 to +6 db? Or that my sub level should end up that many dbs above the avr settings for my speakers?
    If it’s the second scenario, what do I do if my speaker levels differ markedly?

    My mains, center and left surround all run 1-3 dbs above the 0 level on the avr at reference level. My right surround is at 5 db because it’s farther away due to room configuration. The sub is set to 0. At those settings, everything is at 85 db on Avia.

    Should the sub level run 2-6 dbs above my mains? And if the left main is on 1 and the right main is on 3, should I consider 2 the baseline figure for adjusting my sub?
     
  10. Christopher~O

    Christopher~O Stunt Coordinator

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    Hey Jeff, did you get any more info on this? I'm doing a simalar setup myself.

    Thanks,
    Chris
     
  11. Edward J M

    Edward J M Cinematographer

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    Jeff.bart:

    You are confusing the two terms here.

    The individual speaker settings on your receiver are relative, and are unitless.

    The sound pressure levels you are measuring with your meter are rated in dB.

    The reason you set your sub receiver setting to -5 (on a relative scale of -10 to +10) is to avoid signal compression and the associated voltage distortion problems.

    When calibrating with AVIA, set your sub receiver setting to -5 and all the remaining speakers to 0 as a starting point.

    The meter should be facing forward, tilted upwards at a 45 degree angle, set on C-Weighted Slow, and mounted on a tri-pod. Do not block the meter with your body when adjusting for the rear surround(s) if you have any.

    With the Master Volume set to 0, adjust the individual receiver speaker settings until all the speakers read 85 dB on the meter. Don't worry about what the final settings are - remember, they are simply relative to each other, and are not absolute numbers and do not represent any dB volume level, per se.

    Next, leave the sub receiver setting at -5, and adjust the SVS plate amp volume control until your SPL meter reads approximately 85 dB (it will fluctuate some so take an average).

    Your system is now properly calibrated. Since the RS meter reads about 2 dB low on the sub test tone, you are actually calibrated about 2 dB "hot" (i.e., 87 dB) on the sub channel at this point.

    Hope this helps.

    Ed
     

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