Has anyone actually done a frequency analysis of their 'hiss?'

I'm also a bit confused with the occurrence of hiss with high efficiency speakers. Shouldn't the efficiency just push the whole frequency sensitivity 'curve' up? - and the other non-hiss sounds around the 'hiss' frequency' increased in volume - leading to a simple 'wash.'

High efficiency horns shouldn't be selecting just the hiss - why isn't everything just remaining in the same RELATIVE distribution regardless of efficiency?

[This message has been edited by John Padova (edited November 25, 2002).]