Uber nerd question about EQ center frequencies

ThingsWithStrings · April 12, 2021 at 8:36 PM

Hi everyone,

Just wanting to know a couple of things about the Bass - Middle - Treble EQs (on all settings - Amp, Output, Monitor, etc). Not the EFX EQs.

I'm curious if anyone else has done measurements on what the center frequency is for each band and their respective Q. Are the Qs broader for the output EQs (as I would assume) or the same like in the Amp section? And finally, if they are linear when summed.

I can find out really easily using a frequency analyzer, but was curious if anyone had the answer. For example, if you add 3.5dB of Treble at the amp stage, and then again at Output stage (I know it's global here), and both EQs share the same center frequency - like 5.5kHz, then you are adding a total of 7dB boost to 5.5kHz to that particular rig (and of course 3.5dB of 5.5kHz to ALL rigs).

It may seem innocuous, but this is important to know especially if you're using the Output EQ for home monitoring and looking to dial in a sweet spot using multiple monitors for recording/mixing, and for FOH and Monitor engineers playing live.

Thanks in advance,

Bryan

Wheresthedug · April 13, 2021 at 9:20 AM

ckemper posted the centre frequencies in a thread a while back but you would need to do some searching to try and find which one.

karlic · April 13, 2021 at 11:13 AM

Maurizio70 Did some analysis years ago if I remember correctly. I did download his results, but can't find them now.

Wheresthedug · April 13, 2021 at 11:20 AM

I think that was the same thread and Christoph chipped in with the definitive answer.

lightbox · April 13, 2021 at 11:22 AM

I posted graphs and values 2 years ago:

4 Main EQ Knobs - Question

karlic · April 13, 2021 at 11:43 AM

Thanks lightbox. Here is the other thread, but the links no longer work:

AMP EQ Curve Characteristics Information

Maurizio70 · April 14, 2021 at 11:36 PM

I found in my old test and researches something similar to these...

EQ OUTPUT --> Correct frequencies of the output EQ: Bass Shelf 150 Hz (steep); Mid Peak 600 Hz

Treble Shelf 2400 Hz; Presence Shelf 10000 Hz; all go from -12db to +12db; Q wide < 0,7.

EQ AMP --> Bass EQ (range -5+5 ; -12+4 dB @ 80 Hz); Mid EQ (-5+5; -7+5 dB @600 Hz)

Treble EQ (-5+5; -12+4 dB over 10kHz); Pres EQ (-5+5; -12+12 dB @20kHz)

But ... the Tonestack (EQ in the Stack) is different and softer. There is interaction between the controls,

so there are no perfect frequencies that can be announced.

ThingsWithStrings · April 15, 2021 at 5:07 PM

Thanks everyone! Much appreciated!