A question about PEQ

[Bracumba]

I have a question about understanding what I am looking at in the PEQ screen. Lets say you boost around 200Hz 12 dB with Q set to a half. This Q means that the bandwih of the Bell form shown in the display has a width of 100 Hz at 6 dB. If I am right, ánd the working of a PEQ is symtrical, the Bell graphic would cross the 6 dB line at 150 and 250 Hz. That would show an a-symetrical figure since the horisontal distribution of frequenties is on a log scale. You see a perfect Bell Shape, crossing left at 150Hz by 6 dB, but to the right at 300Hz at 6 dB. What do I understand wrong ?
To make a musical mix on this wonderful machine, this is totally inrelevant. But I am just to anxious to understand . So please, If someone could explain to me, that would give me great pleasure.
Thank you 🤓🤗

[Bracumba]

A photo to make things more (un)clear 🤔

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[Wolfgang]

i think the graphic is rather meant to show the result more understandable. a scientific accuracy is not necessary at this point.
your left line is imho also a bit below 150Hz, you just can’t see it exactly. what’s important here is that you can see in which area you’re doing something.

[SteffenR]

Q factor 0.5 is as bandwith 2.54 octaves

[Bracumba]

I don’t understand. I thought the Q factor is the ratio between Centre Frequency and Bandwidth. I am still not getting it quite, though I am starting to see what mistake I made in the picture.

[andiabwaerts]

Q-factor for a bandwidth of a half octave is 2,871. the bandwidth is definded as the difference between the -3dB points higher and lower from the centerfrequency. The bandwidth for 200Hz @0,5Oct. is ~70Hz. F1 should be ~168Hz, F2 should be ~238Hz.

[Bracumba]

Hmm….my first mistake is that it is not Q what is displayed. It is bandwidth. Sorry for not Reading the Manual thouroghly. Still not everything is crystal clear for me. E.G why the graphic is symetrical… A work in Progress for my mind 🤔🤓

[Bracumba]

…..Q-factor for a bandwidth of a half octave is 2,871….
Can you explain me how to derive this number from knowing that the bandwidth is half an octave ?

[Bracumba]

Found an exact explenation on the internet. Sorry to have bothered you with my wish of better understanding what I am looking at in the PEQ screen. Thanks for the reactions. I will go study this Explanation
What remains is the question about the symetrical Bell form 🤓

[GCumbee]

I just can’t imagine WANTING to boost 200hz. That is what I’m pulling out of just about everywhere I work.

[Mfk0815]

What remains is the question about the symetrical Bell form 🤓

Take a ruler and measure the distance between 100 and 200 Hz (the octave below 200) and between 200 and 400 Hz (the octave above 200) on the screen. You will see that both distances are exact the same becaus of the logarithmic scale. And because the bandwidth ist defined per octave and not in Hz the bell have to be symmetrical.

[Bracumba]

Wow, that something seamingly so simple, took such a spin with my head. Thanks for your reply’s and putting up with me. No worries, when mixing I try to create as a musician, as an artist… It was the ‘science’ side of this endeaver that made me trip

[Bracumba]

@Mfk0815 Thanks so much. I understand now.

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[litti]

Sorry for the hi-jacking, but since we’re talking about PEQ: what bandwidth value on A&H digital desks equals a Q of 1.4 or 1.6 (as in many old analog consoles)?

thanks!

[Wolfgang]

A Q value of 1.414 results in a bandwidth of exactly 1
Q 1.6 results in 0.888, which would be about the 0.85

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