Speaker Sensitivity Question/Concern

Discussion in 'Archived Threads 2001-2004' started by MikeDierbeck, Aug 14, 2002.

  1. MikeDierbeck

    MikeDierbeck Agent

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    t drop a line here and let me know how far you sit back from your main speakers.

    Mike
     
  2. MikeDierbeck

    MikeDierbeck Agent

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    Weird, they only posted my last sentence on here. Let me try this again.

    I keep reading about speaker sensitivity and I think I understand the concept. The JBL S38's have sensitivity at 89dB and the S-Center is at 91dB. Should I use these sensitivity numbers to decide how far back I should sit to get the best sound possible? Right now, I sit 16 feet away from all of the main speakers. Should I sit closer? My 64 inch Mits looks great at 16 feet away, but I think I could get away with moving a couple feet closer. Should I arrange my viewing/listening distance according to the sensitivity numbers?

    Also, like my abbreviated post said before this, can you let me know how far you sit back?

    Mike
     
  3. John Garcia

    John Garcia Executive Producer

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    I am about 8-9ft from my main speakers. Sensitivity doesn't matter, what matters is the actual volume (dB) at the listening position. To set this properly, you need to use test tones and an SPL meter. Do a search on calibration and/or SPL meter.
     
  4. Dustin B

    Dustin B Producer

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    Like John said, the sensitivity spec just tells you how much power you need to reach a certain volume. All receivers and processors have individual level controls for each channel. This will allow you to compensate for differences in volume to the listener that result from distance and sensitivity. Just don't try and do it by ear, get a Ratshack SPL meter and calibration disc (Avia or Video Essentials).
    You may find this little post I wrote for the HTF Primer useful in helping you understand what is going on.
    http://www.hometheaterforum.com/htfo...124#post517124
     
  5. Phil Iturralde

    Phil Iturralde Screenwriter

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    Phil
     
  6. Hanwook_K

    Hanwook_K Stunt Coordinator

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    Different Center Speaker Sensitivities
    Ah. I would presume that this is not a good thing. As you increase the volume, the center channel will get louder faster than the lefts and rights. But my assumption is that a 2db rating and the amount you HT amp puts out is probably not significant to make a difference. BUT it is a word of caution.
    I would use the SPL from RS and use a DB at your usual listen volume vs. the 70db - try it out and see what happens...
    Do most same brand center channels have different sensitivities?
     
  7. Mark Austin

    Mark Austin Supporting Actor

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  8. Paul_Dunlop

    Paul_Dunlop Second Unit

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    Hi
    This is why everyone recommends calibrating all your speakers to 75 dB (or 85 dB) - this is not only to adjust for the different distances you are from each speaker, it's also to ensure that the different sensitivities of your speakers are not an issue.

    Hope this helps
     
  9. Hanwook_K

    Hanwook_K Stunt Coordinator

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    After more thought, this is actually an interesting question.
    Too much thinking
    If we assume that we send equal power to the front three channels, the center will be slightly louder. So to compensate you have to put the center channel further back than the front left and right, but then you have to deal with timing of the sound if its placed further back outside the radial distance of the left and rights. In this model above you would have to delay the left and right channels the distance you put the center channel.
    Easy answer
    Much easier to use the HT receiver to lower the volume of the center.
    Timing Delay
    Also be mindful of the center channel delay. If the HT receiver has a delay reduce the center channel by an the necessary amount if the center channel is in the same line as the left and rights(typically 1ms = 1 feet). Most modern HT receivers that have delay are converting to the distance between the speaker and listener to adjust the delay vs. milliseconds.
     

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