Sensitivity (2.83V @ 1m): 92dB?

Discussion in 'Speakers' started by BrianHo, May 13, 2003.

  1. BrianHo

    BrianHo Agent

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    Is this good? What does it mean in performance?

    Brian
     
  2. Geoff L

    Geoff L Screenwriter

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    I give, you win....[​IMG] [​IMG] [​IMG] [​IMG] [​IMG]
     
  3. AlbertA

    AlbertA Stunt Coordinator

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    It means that with 1 watt of power at a distance of 1 m you will get 92 dB of sound pressure level.

    For every 3dB of SPL increase you will need twice the power. For example, if you want 95dB SPL you'll need 2 Watts. for 98dB, 4 Watts, 101 dB 16 Watts, 104dB 32 Watts and so on.

    So, the higher the sensitivity the better, since you don't need to use a lot of power to drive your speakers and leaves headroom for those reference level peaks.
     
  4. Michael R Price

    Michael R Price Screenwriter

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    It might be deceiving, especially if that's an "in room" sensitivity spec or the speakers are lower than 8 ohms, since calculating levels from that spec means you assume your amplifier is a perfect voltage source. What speakers in particular are you describing?

    Otherwise, higher is better (and 92db is not bad at all). I think most conventional speakers are 83-90db, but some horns can be 100db and higher.
     
  5. Danny Tse

    Danny Tse Producer

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    The sensitivity doesn't mean anything in terms of performance. But it does give you an idea on what kind of power is needed to power them correctly. There are excellent speakers with high sensitivity, and there are excellent speakers with low sensitivity. Just remember a lot of things go into making a "system" sound good.
     
  6. John Kotches

    John Kotches Cinematographer

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    AlbertA said:

     
  7. Dan Hine

    Dan Hine Screenwriter

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  8. BrianHo

    BrianHo Agent

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    I'm refering to JBL s312II speakers.

    Thanks for the info even though it really confused me.

    Brian
     
  9. John Kotches

    John Kotches Cinematographer

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    Dan,

    I was taught that there are two germane (and relatively simple) equations for these calculations:

    Ohm's law says V (Voltage) = I(Current)*R(Resistance(Impedance for our purposes)).

    Power = V(Voltage) * I(Current)

    Voltage(2.83v) is constant for our examples.

    Solving to determine current with Ohm's law:

    2.83 = x * 8

    2.83/8 = x

    x ~= .35A.

    Then calculating power usage:

    x = 2.83 * .35

    x = 1 (watts)

    When we talk about a 4 ohm speaker, we have

    2.83 = x * 4

    2.83/4 = x

    x ~=.7A

    Power usage in this case:

    x = 2.83 * .7

    x = 2 (watts)

    The 3dB difference would directly equate to the difference in power applied, assuming the speakers rated impedance is 4 ohms.

    There is no one spec to look at in this case which is more correct than another. Both xxdB/1w/1m and yydB/2.83v/1m describe the sensitivity. The first example is a little more straightforward.

    I could be wrong, it's been way too long since I took the appropriate course.

    Regards,
     
  10. Phil Iturralde

    Phil Iturralde Screenwriter

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    STUDIO™ SERIES – S312II / 3-Way, 12-Inch Floorstanding Speaker
    • Impedance: 8 Ohms
    • Sensitivity (2.83V @ 1m): 92dB - Measurement Standard used by the Speaker Manufactures for comparison of efficiency w/1 Power Watt vs. SPL (Sound-Pressure Level)
    Excluding powered sub-woofers, speaker sensitivity ratings is your quick** starting point in determining how loud SPL vs. watts can deliver.
    First the basic rules: (SPL = Sound Pressure Level)
    1: It takes at least 3 dB of SPL for the human hearing to perceive an increase of loudness.
    2: In terms of Power output vs. SPL, to achieve 3 dB increase of acoustic SPL requires doubling (x2) the REC/AMP Power.
    =============================
    Watts--SPL (dB)------SPL (dB)
    1------86------------92
    2------89------------95
    4------92------------98
    8------95------------101
    16-----98------------104
    32-----101-----------107
    64-----104-----------110
    128----107-----------113
    =========================
    Using 2 examples:
    Column 1 = 86 dB sensitivity rated speakers using 1watt @ 1 meter
    Column 2 = 92 dB sensitivity rated speakers using 1watt @ 1 meter
    Based on 86 dB sensitivity, ... 64 watt output, you can achieve 104 dB SPL! (very loud!)
    Based on 92 dB sensitivity, ... 64 watt output, you can achieve 110 dB SPL! (ear bleeding levels)
    NOTE: Incorporating an Powered Sub-woofer will remove the AMP/REC requirements & strain.
    -----
    **To get an little more accurate SPL vs. 5 Speakers vs. Room, use C.M.Collins excellent SPL CALCULATOR
    The JBL S312-II will be an easy load for just about any AV REC/AMP that you might want to use! Hope your neighbors aren't too close to your HT setup!!!
    Phil
     
  11. Michael R Price

    Michael R Price Screenwriter

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    Brian,

    Be careful though, because I remember James Johnson posting a review of the S312s saying they were fatiguing when played loud; they might be somewhat brighter speakers, like Klipsch. They'll go loud for sure, but it would help to listen to those speakers before buying them, so you're sure you like the sound.
     
  12. John Kotches

    John Kotches Cinematographer

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    Phil,

    I don't know many people that listen in the nearfield at 1m.

    Don't forget to adjust the SPLs for distance (and make an allowance for room reinforcement).

    Regards,
     
  13. Phil Iturralde

    Phil Iturralde Screenwriter

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  14. hdnrs

    hdnrs New User

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    Real Name:
    Mike
    Hi,This thread has helped explain quite a bit about SPL, and I was hoping to get a little more info about how to use SPL. I am trying to create a portable sound system for various applications (battery powered, transportable via subway). I am concerned with size, weight, quality and throw (I hope that is the correct term). I have a variety of speaker / amp / battery solutions currently I am working on my subwoofer.Since sound level is measured at a reference point and SPL is measured at the source I wanted to try and work out power consumption vs. relative sound levels in order to approximate how my power source (i.e. battery) requirements and volume levels. Currently I am focused on using this outdoors.Here is what I suppose to be the relevant pieces of dataSub SPL: (2.83v/1m): 85.6 dbAmp: 200 Watt RMS (Class D ~86% efficiency)

    Here is the logic used

    Input power (power draw @ battery) = output (amp) power / 86%
    -Output Power should be ~86% of the input power

    db (@ source (i.e. 1m) ) increases 3 db for every 2 watts (output power) over SPL
    -For the data below I used an increase of 9 db for every 6 watts

    DB @ distance = (DB@source - (20 * log(distanceFromSource/1m)))
    As taken from http://www.sengpielaudio.com/calculator-distancelaw.htm

    Is this correct ? Thanks

    Input Power Output Power db (@source) @2m @3m @4m(Watts) Watts (86% eff)1 1 85.6 79.6 76.1 73.68 7 94.6 88.6 85.1 82.615 13 103.6 97.6 94.1 91.622 19 112.6 106.6 103.1 100.629 25 121.6 115.6 112.1 109.636 31 130.6 124.6 121.1 118.643 37 139.6 133.6 130.1 127.650 43 148.6 142.6 139.1 136.657 49 157.6 151.6 148.1 145.664 55 166.6 160.6 157.1 154.671 61 175.6 169.6 166.1 163.678 67 184.6 178.6 175.1 172.685 73 193.6 187.6 184.1 181.692 79 202.6 196.6 193.1 190.699 85 211.6 205.6 202.1 199.6106 91 220.6 214.6 211.1 208.6113 97 229.6 223.6 220.1 217.6120 103 238.6 232.6 229.1 226.6127 109 247.6 241.6 238.1 235.6134 115 256.6 250.6 247.1 244.6141 121 265.6 259.6 256.1 253.6148 127 274.6 268.6 265.1 262.6155 133 283.6 277.6 274.1 271.6162 139 292.6 286.6 283.1 280.6169 145 301.6 295.6 292.1 289.6176 151 310.6 304.6 301.1 298.6183 157 319.6 313.6 310.1 307.6190 163 328.6 322.6 319.1 316.6
     

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