PS

When I started to 'conflict' with the horn comments here - I was reacting to the 'efficiency' aspect of horns and got myself waylaid there.

I had forgotten about the directivity.

But maybe there was some good in my getting 'off-track' - it seems like there were more than a few here that thought of the efficiency characteristic of horns to be the reason for 'hiss sensitivity' - it was (is) instead the increased higher frequency response because of the wider dispersion due to the higher directivity-feature of 'horns.'

The use of the word 'directivity' in this connection is itself a bit of a paradox - because 'directivity' is the reason 'normal' speaker elements disperse high frequencies 'badly.' A horn that is exponentially curved (correctly) to allow frequencies to be widely dispersed at many angles is what is behind this - the horn is 'widening' the spectrum which would normally be restricted by the principle of directivity which says that the higher the frequency the more it will only be directed in a straight line from its point of emission.

Back to Fletcher and Munson's for a bite of steak (sans ketchup or 'steak sauce')!