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What db to calibrate sub to?

Discussion in 'Speakers' started by ChristopherW, May 24, 2003.

  1. ChristopherW

    ChristopherW Agent

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    HI,

    I'm using the Sound snd Vision dvd to calibrate my system. I've calibrated all the speakers to 85db. I also have calibrated the sub to 85 db. It seems a little lacking though. Any hints?
     
  2. Michael R Price

    Michael R Price Screenwriter

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    Chris, the questions that first come to mind is: are your main speakers set to "large" and where are they placed? If they are set to small, where is the subwoofer and what kind is it? What volume setting do you listen at?

    If everything is set up right, you might be used to, or prefer, more bass than is supposedly "correct"... so just kick it up a couple notches. There are some variations in the way movies are mixed anyway, so there's nothing wrong with adjusting the level a few decibels on either side of your calibration point.
     
  3. MikeKaz

    MikeKaz Stunt Coordinator

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    A common practice is to have your sub about 6 db louder than the rest of your speakers. Try that out.
     
  4. Mitch Stevens

    Mitch Stevens Supporting Actor

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  5. SVS-Ron

    SVS-Ron Screenwriter

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    Mitch,

    Really it depends on the subwoofer in use, if it's in a good corner location (for maximum room gain), how large the room is, if it's sealed or open to other rooms.

    And most importantly if you ARE running all your speakers as "small" or not... and what are your master playback levels???

    It should be noted that if you measure 6dB "hot" on your sub with a Sound and Vision-like test disk your actual calibration is more like 8 or 9dB hot.

    Again, with the right room with moderate playback levels and a very good subwoofer this isn't really that outrageous at all.

    That's not to say running 6dB hot is the audiophile's solution for critical two channel music playback, but for home theater it can be a riot with the above caveats.

    Ron
     
  6. ChristopherW

    ChristopherW Agent

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    Thanks for all the info guys. As far as my setup is concerned I have GR Research AV1+s for the Mains and Center speakers. I have B&W 602s2 in the rear. My subwoofer is a Stryke AV12 with 2 15" PRs in a 2 cubic ft enclosure. It is powered by a 350 watt plate amp.

    Like I mentioned before I am using the Sound and Vision disc to calibrate my system. I've calibrated everything to 85 db, sub and speakers. 85db is equal to -16 on the preamp. My preamp/ amp combo is the Sherwood Newcastle AVP9080/ AM9080. My speakers are set at small.

    The sub is corner placed. The room is fairly small 15x13x10.5. It open up to a small kitchen area. I live in an apartment.

    I hope this information clarifies some of the questions you guys need.

    One other question I have. What level should I have the subwoofer set on the PREAMP? Should I set it low on the PREAMP and use the gain on the AMP to adjust to reference levels? Or vice versa- have the level high on the PREAMP and lower on the AMP?

    I've seen on the forum that people reccommend different ways, and its kind of confusing. The one thing that concerns me is that if the level is low on the PREAMP, then the signal going to the plate amp will be so low that the sub will be constantly turning on and off during time of little input.

    Thanks again for all your input !!
     
  7. Donnie Eldridge

    Donnie Eldridge Supporting Actor

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    On your Sub have the gain set between 1/2 and 3/4. Then use your Preamp to adjust to reference level.
     
  8. Brian Bunge

    Brian Bunge Producer

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    Chris,

    I'm going to disagree with Donnie on this one. Most of the plate amps I've used I've ended up setting the sub amp's gain somewhere around 1/4 to 1/3 up and then set the preamp's output from there. Since you've got a Newcastle unit you should be good to go with this route. The 250W version of your sub amp can't even be set above 1/3 of the way up and still allow you to calibrate the sub properly. Even with the sub out set at minimum the sub was running very hot. I'd expect the same from the 350W amp that you have.

    Anyway, feel free to set the sub out so that you're running about 3dB hot on the SPL meter. That should give you a good starting point to get the sound you're looking for. I prefer this method most of the time for a HT setup. Just listen out for distortion from bass heavy scenes.
     
  9. Donnie Eldridge

    Donnie Eldridge Supporting Actor

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    Brian is correct. I just go thru checking the gain on my sub and 1/4 to 1/3 seems more appropriate.
     
  10. Edward J M

    Edward J M Cinematographer

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    I like to set the pre-amp sub level between 1/4 and 1/2 of the total range (i.e, between -5 and 0 if the control range is -10 to +10) in order to to minimize pre-out distortion.

    A few studies a while back on sub pre-out levels showed distortion up creeping up into the 1-2% range when the control level was cranked up into the positive range.

    As for the actual sub calibration level, for HT and the speaks set to small, +3 to +4 (i.e., 88-89 dB for S&V and Avia) works pretty well for me. For music, I prefer a "flat" calibration.

    You have to remember, the S&V and Avia are true DD soundtracks, so the sub test tone is NOT discrete, and the corresponding surround speaker will still contribute quite a bit of the total sub tone volume, even when set to small, particularly if you are using an 80 Hz or lower high pass.

    If you don't believe me, run the sub test tone for a given surround channel and power off the sub - you will be getting anywhere from 78-82 dB contribution from the surround speaker if you have an 85 dB overall calibration level with the sub running. This phenomenon can lead to "undercalibrating" the sub, as compared to the AVR internal test tones, which are discrete in comparison.

    So don't be afraid to go a bit hotter than you might suspect is prudent if you are doing sub calibration with Avia / S&V.

    Regards,

    Ed
     
  11. ChristopherW

    ChristopherW Agent

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    Thanks for all the input everyone. I think I got it figured out.

    One more question. When does someone have to worry about doing damage to a subwoofer? I know this may be hard to answer.

    For example, say I have a small room that provides lots of gain. Thus my output on the receiver and subwoofer amp are lower when compared to the same sub placed in a much larger room without ideal room acoustics. Given this example, wouldn't the second setup, in the larger room, be much more prone to "blowing up" the subwoofer?

    I don't know if I'm oversimplifying stuff. Thanks agian for your time

    chris
     
  12. Michael R Price

    Michael R Price Screenwriter

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    Chris, you're right... in a smaller room you'll have more output potential before damaging anything. Since your plate amp can't deliver enough power to thermally damage the sub, your only concern is over-excursion. If you hear any noticeable distortion in the bass you should be very careful with the level. If the sub bottoms, you may want to set a peak limiter (if you have one) to just below that point... or just turn the sub level down a little. I think you won't have any problem though, an AV12 should be good for pretty impressive output in that room.
     

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