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3rd July 2006, 06:22 AM  #1 
diyAudio Member
Join Date: Jul 2006

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 T415 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 145150 on the termlab 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. 
3rd July 2006, 02:54 PM  #2 
diyAudio Member

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

5th July 2006, 08:45 AM  #3 
diyAudio Member
Join Date: Feb 2004
Location: Chinook Country.Alberta

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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5th July 2006, 08:51 AM  #4 
diyAudio Member
Join Date: Feb 2004
Location: Chinook Country.Alberta

db
nt
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stew ☮ "A sane man in an insane world appears insane." 
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