In a very early Stereophile, Gordon Holt (a good recording engineer himself) showed a graphic equalizer as it was adjusted in a studio during a recording. He then showed the measured frequency response of the monitors in the studio. He pointed out that the equalizer settings were the exact inverse of the frequency response of the speakers---the engineer was using the equalizer to correct the frequency response of the speakers! The problem is, that equalization was applied to the tape, so when the recording was played on a speaker that didn’t require EQ’ing, the recording would sound like that inverse of the monitor speaker. In order to sound right, the recording HAD to be played on that studio monitor loudspeaker, and it alone! In many studios, since each speaker in the monitor booth makes a recording sound different, with no definitive reference to live sound, the engineer will adjust the EQ until the recording sounds about equally "good" (whatever that means to the engineer) on all the monitors. Oy!
