Sound and Video and SPL meter

Discussion in 'Home Theater Projects' started by Cesar*P, Jan 19, 2004.

  1. Cesar*P

    Cesar*P Extra

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    Does S&V have test tones that can be used with an SPL meter?

    *Sound and Vision
     
  2. Rick Faldo

    Rick Faldo Stunt Coordinator

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    I assume you are speaking of the S&V Home Theater Tune Up DVD? If that is the case, yes they do. There are two parts to the disk, one for audio, the other for video.
    Use your spl meter to balance the sound from all speakers.
    Good luck
    R
     
  3. John Gido

    John Gido Second Unit

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    FYI, I received this response from Ovation Software in reference to a question about test tones:

    The tones on S&V are just like Avia. Now, if you set with our tones using Avia and 85 and then play back Video Essentials at 75, they should be the same. VE encodes the tones at -10 dB, we encode at 0 dB. This is why we are 85 dB and VE is 75 dB.

    S&V also contains DTS test tones.

    If you compare DD to DTS, DTS will be 4dB louder. This is because our disc is encoded -4dB on DD. This is called Dialog Normalization and it is set to -27. (-31 is 0 offset.) This is done because the majority of DVD movies are also encoded at -27.


    Hope this is helpful.
     
  4. Cesar*P

    Cesar*P Extra

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    Thanks for the replies. The reason why I ask is because I ordered the S&V DVD which should come at the end of the week. I'm also thinking about buying the SPL meter from Radio Shack.
     
  5. Rick Faldo

    Rick Faldo Stunt Coordinator

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    Money well spent
     
  6. Zen Butler

    Zen Butler Producer

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    Thanks John, that is helpful.
     
  7. Cesar*P

    Cesar*P Extra

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    Quote above is from Vince Maskeeper regarding test tones on what I assume from the DVE disc and Avia. Does anyone know the db reading I should reach on the SPL meter if I'm using the Sound & Vision test tones? Also, do I still set the dial on the SPL meter to 70?
     
  8. douglas-b

    douglas-b Stunt Coordinator

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    There is more than one way you can do this. I chose to play the test tones on the disk with my receiver turned up to "00". I had the SPL meter on the "80" setting and adjusted my individual speaker levels until the SPL meter hit the 85db mark on every speaker.

    My reference level is now "00" so if I watch a movie at "-17" on my receiver I know I'm 17 below reference level.
     
  9. Jeff Gatie

    Jeff Gatie Lead Actor

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    Sound and Vision is similar to Avia in that the tones are attenuated to 85dB, not 75dB. You should set the dial to 80 and calibrate to 85dB for reference.

    Like douglas-b, I also use the "put receiver on '00' and calibrate to 85dB" method on my Denon 3801. For some receivers this may be too loud of a starting point, but it works fine for me.
     
  10. Cesar*P

    Cesar*P Extra

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    OK, when you say you put the receiver on '00' is that the master volume? If I were to put the volume on my receiver to 00 then that would result in very loud test tones. My receiver's volume level increases as the number decreases.
    The range on my receiver starts at -96db for being the lowest and then -1db being the highest or loudest.
    Also, the reason why I asked if I should set the SPL meter to 70 is because that's what the S&V presentation for the SPL meter calibration setup recommends.
     
  11. Jeff Gatie

    Jeff Gatie Lead Actor

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    I could have sworn I have read the S&V tones are attenuated to 85dB, which would make sense because it is produced by the same company as Avia. Can anyone confirm this (I own VE and Avia, but no S&V).

    Cesar, the tones are supposed to be loud (75dB is moderate, 85dB is pretty loud). If the '00' mark on the master volume is too loud for the target SPL level, just start with the left front speaker gain (the individual speaker adjustment) at '0', increase the master volume until the tone from the left front equals your target SPL level (75 or 85dB), then proceed to adjust the other speakers (using the individual gains) to the same level. After you are done, make note of your master volume level - this is now your reference volume.
     
  12. Guy Kuo

    Guy Kuo Supporting Actor

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    S&V tones are at 85 dB when the system is calibrated to reference state. The instructions have you target 75 dB because 10 dB below reference is typical for most home theater listening. If you want reference level, target 85 dB.
     
  13. Jeff Gatie

    Jeff Gatie Lead Actor

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    Thanks Guy. I didn't expect an answer straight from the horse's mouth, but there it is!

    Cesar, you can call Guy's answer definitive on the matter, just look at his sig!

    Edited to add:

    Cesar, reference is very, very loud. Just because you calibrate to reference does not mean you have to listen to your system at this level. It simply gives you a "reference" point to compare with other systems. It basically gives you a way to come on the HTF and say "Boy, I was listening to SPR at 10 below reference and my dog wet himself all over my new carpet during the D-Day invasion" and everyone will know just how loud to go if we want to experience the same nirvana.
     
  14. Cesar*P

    Cesar*P Extra

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    Alright, so let me get this straight. The procedure is to set the receiver's volume level at it's loudest setting (-1 db in my receiver's case) and then decrease or lower the volume until the db level on the meter reaches 85 db while running the test tones?
     
  15. Guy Kuo

    Guy Kuo Supporting Actor

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    Reference level is a term which really seems to confuse a lot of people.

    It boils down to this....

    By convention, max peak sound level during playback of the audio system as measured at the listening position is 105 dB SPL when the system has its volume set to "reference level." At that same volume setting, a signal which is 20 dB softer than max peak would measure (drum roll.....) 85 dB. A signal which is 30 dB softer than max peak would measure 75 dB.

    It really isn't a fixed dB level of 65, 68.343, 75 or 85 dB which is "reference level" but the setting of the system such that the measured volume at the listening position equals that of another system which is also at "reference level." This is usually accomplished by playing back test signals that have a known SPL level when played back on a system which is at "reference." You adjust your system so the SPL level is that same level and YOUR system is then at "reference level." This allows us to standardize what we mean when talking about how loud our systems are set during playback. In other words the same recording played back on different systems will have the same loudness (at the listening position) if all systems are set to the same setting relative to "reference level."

    So Joe can set his master volume to 10 dB below reference and tell Hank to also set his system to 10 dB below reference. If both of them play the same recording, they'll hear the same loudness level.

    "Reference Level" is commonly used to refer to the master volume setting on your system which placed it in such a state that its playback matches the loudness of other systems which are also set to be at "reference level"

    Most consumer test tones for setting SPL level produce 75 dB SPL if the system is at reference level. AVIA test tones are 10 dB louder, matching pro equipment practice, and consequently should measure 85 dB SPL if your system is at reference. Sound and Vision Home Theater Tuneup also follows this convention.

    Notice that this doesn't mean that all systems at reference level are generating the same amount of sonic energy. This is sonic energy measured at the listening position, not total sonic energy. If the venue is larger, greater wattage is needed to reach reference level.

    When calibrating your sound levels you are doing several things:

    1. Equalizing the relative sound levels of your various speakers so the channels are balanced relative to each other.

    2. Finding the master volume setting on your amplifier which sets your system to reference level.

    3. Recalibrating the master volume setting such that its dB markers read correctly relative to reference level. (This goal is not possible on many receivers)

    If you keep in mind those three goals and know what the dB level is of the test tones you are using, it is pretty easy to understand what seems to confuse a lot of beginners.

    Most receivers have channel level controls for the speakers. Those are used to get the channels balanced with respect to each other. You can also alter the overall volume of a system by moving all the channels up or down together. That gives you some ability to alter which master volume setting yields reference state.

    On simple receivers, set the channel levels to midrange, then use the master volume control to make one of the main front speakers read 85 dB SPL (assuming you are using Avia or SV HTT). This should set the main volume to a something at which you can go through each channel and have enough range to get all the channels to read 85 dB. Once all channels are balanced, mark or memorize the master volume setting. That setting now sets your system to reference level. If you want to hear your system at 10 dB below reference, you just decrease the master volume 10 dB. Notice that you can alter the setting at which the system is at reference level by tweaking the channels up or down together. This can sometimes let you make the number easier to remember. One caveat, not all low cost receivers have their master volume controls marked in dB. You might need to use your SPL meter to find how far down you need to turn the master volume to read 75 db SPL. Probably a good idea to check anyway.

    On more advanced receivers, the master volume and channel balancing acts in a more independent manner. For instance, going to channel balancing automatically presets the master volume to 0 dB attenuation. That automatically makes 0 dB on the master volume be reference level once all channels have been set to read 85 dB SPL. Other systems will even let you adjust the number readout of the master volume control independent of the volume setting. That lets you zero the number at reference level for our system.

    Because receivers differ in their implementation, you'll have to think about how the controls interact and work out how you can attain the first two goals. The third goal is not always possible.

    At any rate, once done you can listen to something at reference level and hear the same intensities as someone else using another system at reference level. This makes discussion of what you hear much more meaningful. Reference level IS quite loud. Indeed 10 dB below reference is also loud. Typically, I use my system at 17 to 15 dB below reference during films for comfortable hearing. You are not required to keep your system at reference level, but it is good to know where you are relative to reference so your comments about loudness and audibility have some basis for comparison.

    As I previously mentioned, the SVHTT disc has you target 75 dB SPL even though that actually sets your volume to 10 dB below reference. Remember it's a consumer disc so the instructions are simplified to match average consumer needs. You now now too much to simply follow those on disc instructions.
     
  16. Jeff Gatie

    Jeff Gatie Lead Actor

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    Ladies and gentlemen, I think we have an entry for the FAQ! Thanks Guy, I have tried to ecplain it before, but now I just have to include a link. Excellent job!
     
  17. Cesar*P

    Cesar*P Extra

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    Thank you very much for the detailed response, Guy. I'll review and work with it next time I calibrate my system. [​IMG]
     

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