I was reading a forum thread about an unnamed speaker manufacturer that still uses a TEF analyzer and thought I would read about the device.
Unfortunately I can’t find a wiki article on TEF but here is some basic information:
TEF stands for “Time / Energy / Frequency Analysis”.
“TEF is the invention of Richard C Heyser, TEF was brought out of Richard’s lab and into the world by Don Davis of Altec and our friends at Crown Audio.
Richards brilliance was brought into the audio world in 1967? when a paper submitted by him on a new (his) audio measurement method was discovered in a trash can of the AES by none other than Harry F Olsen.”
It just so happens that there is one for sale on eBay right now which provides an opportunity to see what one looks like.
The only modern TEF system I can find is produced by Gold Line:
gold-line.com TEF webpage