In order to determine the maximum peak Sound Pressure Level (SPL) of a speaker you will need to know the sensitivity of the speaker measured at 1W/1M, and the peak rating of the speaker. Given these specifictaions the following formula can be used to determine the maximum peak SPL:
ndB= 10 x log (P1 divided by P2)
Where
P1= Peak rating in watts
P2= Rating in watts at which sensitivity is specified. (Usually 1W)
This number should then be added to the Sensitivity rating to determine the maximun peak SPL.
EXAMPLE: A SW118IV has a sensitivity rating of 96 dB measured at 1W/1M, and a peak rating of 1000W.
ndB= 10 x log (1000W divided by 1W)
ndB= 10 x log 1000
ndB= 10 x 3
ndB= 30dB
By adding this number (30 dB) to the sensitivity (96 dB) we find that the maximum peak SPL of the SW118IV is 126 dB.
