Fostex FE83En

I was doing a little bit of research on this driver, mainly because I think it’s the main driver used in Vaughn speakers.  In the specifications (see link below), I believe the ‘sound pressure level’ is the efficiency, 88 dB/W(m).  

http://www.fostexinternational.com/docs/speaker_components/pdf/FE83En.pdf

So with these drivers rated at 88dB, I’m wondering how the overall efficiency of the speakers could be rated at 96dB+.  

http://www.vaughnloudspeakers.com/products

I am convinced I am missing something here…

Dave

Thanks Lin.

Below is the response from John K, which is the best explanation...

http://www.diyaudio.com/forums/multi-way/158611-acoustic-summation-multiple-driv...

"When discussing multiple drivers systems it is important to separate out the differences between efficiency and radiated SPL. For a multiple driver system where the drivers are acoustically close (much less than a wave length), assuming that each driver individually radiates the same SPL as if it were isolated, then the SPL is just the vector sum of the SPL form each driver. Being acoustically close means all drivers operate in phase so the SPL would increase by 6dB for two driver, 9.5dB for 3 drivers and 12dB for 4 drivers. This assumes also that the multiple driver system, is also small in dimensions compared to the wave length. (In other words, the radiation pattern remains spherical)."

"When looking at efficiency it is a simple matter of summing the input power. To keep the radiated SPL of each individual driver constant at the single driver level, the power delivered into the 2 driver system increases by 3dB, the three driver system by 4.77 dB and the 4 driver system by 6 dB. The the efficiency of the 2, 3 and 4 driver system increase by 3, 4.77 and 6dB as well. Or you cam look at it as the two driver system produces the same SPL as the single driver with 3 dB less power. The 3 driver system, the same SPL with 4.77dB less power and the 4 driver system the same SPL with 6dB less power."