Thank you so much for starting this thread and setting the tone for this discussion! I know it’s been a long time coming.
Let me add a few details and I’ll have my colleagues add their two cents as well:
We normally set the Q value to 0.7 for broad boosts or cuts to any given frequency (Fc [Frequency Center] value). This is widely considered to be one of the most musical Q values for digital equalizers. By the way, the amazing audio coding you hear has been done by the the industry recognized masters at Z-Sys.
A Q value of 1.4 is good for affecting less broad ranges but still sounds musical.
A Q value of 3.0 is good for getting rid of harsh or honky sounding resonant frequencies inherent to specific speakers.
Here are some useful frequencies to consider:
50 Hz = The “chesty” thump of a bass drum.
100Hz = The lowest elements of a bass guitar.
150Hz = The “throaty notes” elements of a bass guitar.
250Hz = The “thwack” of a snare drum.
300Hz = The lower part of the human voice. This is usually attenuated (lowered volume) in pop music but it’s still there.
450Hz = Not the prettiest frequency but necessary for good guitar, piano or other midrange instruments.
600Hz = If you like electric guitars you like this frequency.
700-900Hz = Important for overall vocal level within a mix.
1000Hz = 1kHz = Almost all speakers can represent this frequency accurately. It is the test tone frequency you hear when curse words get “bleeped” out. It’s also an industry standard test tone.
2-5kHz = This ranges represents the frequencies our ears are most sensitive to. This range has everything to do with the perceived loudness of a recording.
6-8kHz = I consider these to be “presence” frequencies. That’s a personal statement. The upper elements of strings and horns lives here as well as the lower elements of cymbals.
9-16kHz = “Air”. Depending on the playback system this range may not be represented accurately. When it is, the mix and open up and sound very pretty.
17-20kHz = Your dog has something to say about these frequencies.