Speaker sensitivity and power requirements

Discussion in 'Speakers & Subwoofers' started by John H, Apr 30, 2003.

1. John H Second Unit

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What is the formula for calculating the SPL db output of different sensitivity rated speakers with the same power input.

Is there an online chart availble for reference.

John

2. Myo K Stunt Coordinator

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are referring to the whole speaker spl+3 decibles everytime the wattage is doubled?

3. Phil Iturralde Screenwriter

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Using a JBL S26 (87 dB) & JBL S36 (90 dB) Sensitivity Ratings as an example:

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.......87.........90
2.......90.........93
4.......93.........96
8.......96.........99
16......99.........102
32......102........105
64......105........108
128.....108........111
=========================
NOTE: Incorporating an Powered Sub-woofer will remove the AMP/REC requirements & strain.

So, w/64 watts, the S26 = 105 dB (very loud) and the S36 = 108 dB (very, very loud!)

To get an little more accurate SPL vs. 5 (or 6) Speakers vs. Room, use C.M.Collins excellent SPL CALCULATOR

Phil

4. John H Second Unit

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So theoretically a loud speaker that is rated at

Sensitivity: 103 dB SPL, 1 Watt @ 1 meter
Power Handling: 800w continuous

with 512w applied should output 130dB @ 1 meter?

John

5. John Kotches Cinematographer

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John,

Yes.

However, at the seats is another issue altogether.

Degradation of SPL is (for most speakers) an inverse square law, which means that for each doubling of distance your output drops by a factor of 2^2 (in other words 4). This correlates to 6dB of drop for each doubling of distance.

This is great if you're in an anechoic chamber, and few of us are

There is room reinforcement, which is typically 3-4 dB when all is said and done.

Regards,

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