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Author Topic: Calculating and interpreting manufacturer published SPL data for speakers  (Read 2595 times)

Danijel Foler

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hello...
Help me, educate me...I am little confused about speaker SPL capabilities from manufacturers data.
Example, no name two way speaker with two 15" bass driver and one 2" compression horn, 2000W RMS, 100db/1w-1m, crossover 1.2khz. Calculated, this box can make 133dB continuous. But, compression driver have 100W, 110dB 1w/1m from 1000-4000Hz and after 4khz sensitivity drop to 106dB/8khz and 100db/1w/1m/15khz. Calculated, this driver can make 130db 1000-4000hz and 126db/8khz and 120db/15khz. So no close to 133dB continuous in entire freq range.
Here is picture for that driver (this is only for example for topic)
rcf nd3030


If I simply calculate spl from data power/sensitivity this nd3030 driver cant make 133dB SPL from 1khz-20khz. Why manufacturer write 133dB continuous for this speaker example if individual components (drivers) cant make this SPL in entire range?

Do I make mistake in reading/interpreting data???

edit:
example 2:
http://www.voidaudio.com/product_detail.asp?id=81
http://www.voidaudio.com/pdf/plots/Stasys%203%20mk2%20Plot.pdf

driver have 80W and 108db 1w/1m..Box have declared 135dB continuous. How this compression driver can make 135dB cont???

thanks
« Last Edit: October 29, 2012, 10:29:43 am by Danijel Foler »
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Mike Pyle

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I can't attest to the accuracy of Void's specs, but if you mount any raw driver to a horn you will get much higher output than the driver can produce in free air.
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Charlie Hughes

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Hi Danijel,
You seem to be confusing the SPL capabilities of the HF driver at a single frequency (based on the sensitivity curve and the power handling spec) with the broad band SPL capabilities of the entire loudspeaker system.  This is a fairly common.

One must remember that the broad band SPL that manufacturers reference in spec sheets is not for a single frequency but instead over the entire spectrum.  Typically, the maximum SPL spec does not use a white spectrum (equal energy at all frequencies), as the sensitivity curve measurement does.  Instead the max SPL for a loudspeaker system typically uses a specially shaped noise that more closely resemble the spectral content on music.  This inherently has less HF content, so less energy goes to the HF driver.
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