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Old 3rd July 2006, 05:22 AM   #1
exuviae is offline exuviae  United States
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Default Calculate SPL

Ok i am a bit slow, is there some calculation given an amount of watts and sensitivty that tells you a theoretical max spl? For example I have SoundStream Tarantual series T4-15 with a 91db at 1 watt at 1 meter, and will be pushing those with a 2000 watt rm Picasso PCA200D amp also from soundstream. Without sitting there figuring out exponents (2, 4, 8, 16, 32, 64, 128,256,512,1024,2048) i know this because of computer programming lol. By my faulty calculations i would only hit around 124db. I think that is right, 11 doubles in power, 3db gain for a total gain of 33db added to a sensitivity of 91db = 124. However on 1000 watts and 2 10" in a ported box i hit 138.9 on a term lab meter (official meter of db drags) and the box was to small for the speakers, and the starting sensitivity was only 82. Something just don't add up, with 2 15"'s seeing 2000 watts i should be in the 145-150 on the term-lab meters.

anyone know how to figure out what the theoretical SPL should be. I use winisd and it says the same 124db, and only like 110db on my 10's.
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Old 3rd July 2006, 01:54 PM   #2
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In house and car there are room and cabin gain, these increase spl tenfold up an extra 10 - 30 db, for reasons I cant fully explain, but I know is right
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Old 5th July 2006, 07:45 AM   #3
Nanook is offline Nanook  Canada
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Default ah.. a dB question ...

the formula for sound pressure level increase ,not power is db=20*log(p2/p1)so for example. if p2=say 100 watts, p1=1 watt, log of 100/1 is the same as log 100(essentially)=2, then 20 * 2 is 40, therefore total accoustical db =91+40=133
similarly 1000watts=:136 dBfor power db the formula is dB=10*10log(p2/p1)
this is with the assuption that Z=2 ohms total..not 1/2 ohm of course.

Q?: what does SS use for spl, 91 is posted but is that 2 Ohms (voice coils in series) or 1/2 ohm (VC in ll)?

also in house there may be as much as 9db "room gain" and upto 12 or 15 db "car gain"..as previously stated.
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Old 5th July 2006, 07:51 AM   #4
Nanook is offline Nanook  Canada
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Default db

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