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Calbiration questions

Discussion in 'Home Cinema Speakers' started by torrent, Jan 22, 2003.

  1. torrent

    torrent
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    Me again :rolleyes:

    I have a few questions regarding the calibrating of home theatre speakers. I have conducted a search in the forums and found a ton of information but it all seems to assume a certain level of knowledge, which sadly to say, I don't have. In case it helps, I am using a Nakamichi Soundspace 11.

    1) How do you know what the "frequency response" for your subwoofer is? How do you test for this?

    2) If you have two subwoofers (a left and a right), which I have, how do you conduct your SPL tests? Should I disconnect one and test the other, and then vice versa?

    3) Reading through the forums I see constant references to setting the amp's volume to 0dB as a "reference level". Then it says balance the volume to 75 - 85dB for each speaker. I am totally confused by this statement. How do I set the amp volume to 0dB, I don't appear to have an independant control for this and how does this differ from the main volume which then is set for each speaker?

    Is there a link anywhere on the Net with a real easy to understand, simple to follow, set of instructions? It's difficult trying to gleam all the information from multiple forums posts.

    Thanks. :)
     
  2. HotblackDesiato

    HotblackDesiato
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    1) Not quite sure what you mean here...subs generally work in the 20-120Hz range. Their upper limit usually being set by the user via the cut point control, and the subs volume being set by the "gain" control.

    2) Balancing two subs is a tricky buisness, i'm not sure a SPL will be much help go by what your ears tell you sounds right. You could always check with an SPL afterwards.

    3) Unless you're really hung up with reference level the absolute dB you use is arbitary. The idea is to get all your speakers set to the same "volume". You can accomplish this either via test tones on special DVDs or those your amp generates. Basically you sit where you plan to listen from, and using test tones then tweak the volume of each speaker until they all show the same dB figure on the SPL. I find it's easiest to start with front left and work to back left, in turn setting each speaker to the same dB as the front left. The SPL mic is generally pointed either up towards the celing, or at 45dgrees, towards the front speakers.
    The 75dB/85dB figures, i think, comes from the fact that most amps test tones and those on test disc are generated at 30dB and 20dB, respectively, less than dolby reference (105dB).

    Sorry if that's even more confusing...it's a hard thing to explain...as i only found out half way thru.

    spence
     
  3. Apocalypse

    Apocalypse
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    Reference level or 75Db equates to 105Db peak for the speakers and 115Db peak for the LFE channel. In other words if you set the speaker levels to read 75Db on the SPL during the test tones (on Video Essentials, 85Db on AVIA) you will get the peaks of 105 and 115 respectively during a DD movie, far too loud for most people.

    Basically as long as the channels are balanced ignore all that reference nonsense, set the sub's level by ear as it's the best judge for it.
     
  4. torrent

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    Thanks both.
     

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