Why tone controls have 1kHz center freq ?

[Sebba]

I most bass/treble and also loudness controls frequences from 1kHz up and down are boosted or attenuated.
1kHz is neiter the center frequency nor the maximum sensitivity of human hearing (3kHz) In music, the "middle midle tone is 440Hz so why 1kHz ?
Here's a typical tone control with freq. response http://focus.ti.com/lit/an/sloa042/sloa042.pdf

 

[JRace]

Perhaps it is due to the fact that 1kHz is the easiest pure tone to heare, as well as the easiest tone to detect distortion or tonal changes.

At least that is why we ini the hearing tesing industry always start with 1kHz.

 

[PeteMcK]

unimaginative designers...

Rod E likes to move the turnover points away from 1Khz:

http://sound.westhost.com/dwopa2.htm