How do I test my home theater to see if it can do "Reference Level"?

Discussion in 'Archived Threads 2001-2004' started by Billy Gun, Nov 28, 2001.

  1. Billy Gun

    Billy Gun Stunt Coordinator

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    How do I test my home theater to see if it can do "Reference Level"?

    #1 What is reference level exactly?

    (And does "Bass" have a different Reference level? If so How do you test for it?)

    #2 How is it measured and what material is used to assure your theater is doing it?

    (I have a Radio shack analog meter, if that helps me?)

    #3 I also have a Video essentials DVD but I haven't opened it yet.....Does it have anything on it, other than just matching the speaker outputs?
     
  2. Brian Corr

    Brian Corr Supporting Actor

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    Use video essentials to calibrate your speakers to 75 db. If you are able, set your volume control to 0 or to the middle (depending on how it's labeled) when setting your speakers to 75 db with VE.

    VE is recorded 30 db below dolby reference, which is 105 db.

    If you get your speakers calibrated to 75 db using VE, and your volume level is set at 0, then when watching a movie with the volume set at 0, you will be listening at dolby reference or 105 db.

    Enjoy!
     
  3. Mike_T_

    Mike_T_ Stunt Coordinator

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    I recently set my speakers up using a Radio Shack sound meter. "Reference" is 85db, however, that is in an actual theater environment. At home, with much smaller rooms, people sometimes set it at a lower decibel rating. I have mine set to 75db and love it. You'll want to use the test tone provided by Video Essentials to calibrate your speakers. You just have the sound emmit from your front left and turn up the volume until it reads 75-85db or whatever you prefer, then go to each other speaker, including your subwoofer until they all match. I prefer to set my sub and surrounds slightly higher than other speakers. I also set my meter on a tripod equal distance from all main and surround speakers. If you stand too close to the meter, sound may bounce off you and disrupt the validity of the reading. Have fun!
     
  4. Bryan Acevedo

    Bryan Acevedo Second Unit

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    Mike_T - that is partially true about the 85db being reference vs. 75 db. It depends on what level the test tones are supposed to be playing at. Some calibration DVD's are set to calibrate to 85 db(Avia) and some internal test tones are set to calibrate to 75 db (my Denon internal test tones). But, with the volume level the same (reading 0) on my receiver, if I use Avia, I get an 85db signal, and my internal test tones give me 75db. Both are set at my "reference" level setting. I am just pointing out that 75 or 85 doesn't mean anything on its own - you have to know what level the signal is that is feeding it.

    Actually, I don't think this is what was asked. I could be wrong, but I think Billy is wondering what is reference level. Reference level in Dolby Digital terms is that your main speakers are capable of 105 db and the LFE channel is capable of 115db.

    If you adjust your levels as stated above, and watch a movie at those levels, then you are listening at the reference level for that movie. However, this doesn't mean you are listening at 105db. This is extremely loud, and you would not even be able to handle a few minutes of the movie actually being this loud. The 105 db comes into play during something like an explosion - where it gets really loud for a short period of time.

    The only way I know of to test for this, would be to get some test tones, and see if your system could play them at the required spl (105 db for the mains, 115 db for the sub). However, you would probably fry something trying to sustain these levels.

    So in reality, I have no idea if you can test that your system is truly capable of the SPL's. What most people do is take their receiver output in watts, with the sensitivity of their speakers, and do the math to see what their system is capable of on paper. I think with small mains, and a decent powered amp, you can easily reach reference level of 105 db. However, setting your speakers to small, now adds about another 6 db of bass that your sub needs to be able to play. So now your sub should be able to play at about 121 db. Almost no sub on earth can do this, flat to 20 Hz. I could be wrong, but I have never seen a sub able to produce 121 db at 20 hz. So you can rest assured that your sub probably won't be able to do this, as I don't think any of us can.

    What can happen though (with SVS) is get damn close with two of their subs. They can average output that meets the reference level, so you will be getting the required spl levels, but maybe not all the way down to 20 hz.

    I hope this helps, and didn't add more confusion.

    Bryan
     
  5. Jack Gilvey

    Jack Gilvey Producer

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  6. Greg_R

    Greg_R Screenwriter

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    With room gain I believe it's possible to reach full reference levels with a multi-driver woofer setup. However, not many people are willing to pay the premium (space and $$$) to get these large subs in their room...
     
  7. Billy Gun

    Billy Gun Stunt Coordinator

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    Is there a "Test movie scene" or something that I can play and check the level with my radio shack meter for 105 DB?

    (An action or loud scene?)
     
  8. Tom Vodhanel

    Tom Vodhanel Cinematographer

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    Billy Gun(is that a WWF name or what[​IMG]..?)
    What you would need to do is find a HT capable of reaching reference levels without measurable compression. Then measure it's output on various scenes at the seating positions....and compare that to the output you measure on yours at the same scenes. Remember, louder isn't always better.It's important to have all the channels balanced and capable of CLEAN output at the maximum levels you push the system too. I've sat in HTs that sounded like chalkboard scratches at reference level.But in a well balanced HT...reference levels can seem downright comfortable as long as the speakers can reproduce those levels without strain.
    I just put in TPM,with all speakers to small...and the subwoofer calibrated to the same level as the rest of the speakers...at reference level
    the THX trailer opening thunder hit 108dB on the RS meter.
    the ball explosion hit 107dB
    the jedi ship getting blown also hit 108dB on the RS meter.
    I think some of the highest SPL scenes I can remember off the top of my head are in BLADE,MATRIX,and LIS. But none of those had a real high amptitude under 25hz.
    TV
     
  9. Billy Gun

    Billy Gun Stunt Coordinator

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    Why yes, it is is a WWF name.....AND also, my first name and first 3 letters of my last name too! [​IMG]
    Wouldn't the THX scene be a better test since it is probably the full 20 HZ - 20 KHZ bandwidth?
    (I am assuming on this.)
    Commments.....
     

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