Hi guys, sorry for the simple question but sometimes i have paranoia of this. i wanna understand how much the value of it affects the frequencies of the band. Meaning how can i be sure which frequencies i am affecting. The Q is not the same amount for the low frequency or for the high frequency.
Is there a simple formula to know which target i am taking (freq.). also i thing this depending on the type of band (bell, high shelf, ecc.). For example the bell one has most of the effect to the centre of his shape and then decreases the amount of effect at the edges.
thank you all.

 

Maybe this will help u @ Min 2:50

 

If you want to calculate Q from bandwidth or the other way around, Wikipedia -> Q-Factor has got you covered.

Section: Relationship between Q and bandwidth.

Note that in audio, bandwidth is described as the relationship of the centre frequency's gain to the gain of the octave around it - in other words: it's not linear.

Also: some developers do their own thing and normalise the Q value to their own scale.

 

Which EQ are you currently using? Please stop apologizing. There are no stupid questions here, only stupid answers.

With graphic equalizers like the FabFilter Pro-Q4 you always see exactly what you are doing, work by ear rather than with fixed values. You should hear every change you make. Take your time, everyone starts small and practice makes perfect.

Graphic and parametric equalizers work with peak bands that resemble bell-shaped curves. The shape of the bell is characterized by the parameters gain, frequency and bandwidth. Depending on the type of equalizer, not all of these parameters can be adjusted by the user.

The bandwidth is defined as the width of the bell curve at the point where the gain is 3 dB below the maximum value.
The bandwidth is specified in Hertz. The Q-factor is calculated as the quotient “center frequency by bandwidth”.

As a pure ratio, the Q-factor is a number without dimension.
The higher it is, the narrower the frequency band, a Q-factor of 5 is a narrow one.

Boost or Cut

20 Hz to 250 Hz = Positive -> Foundation | Negative --> Drone
250 Hz to 500 Hz = Positive -> Warmth | Negative -> Mud
500 Hz to 2 kHz = Positive -> Definition | Negative -> Telephone sound
2kHz to 8 kHz = Positive -> Presence | Negative -> Cutting
8 kHz to 20 kHz = Positive -> Transparency, Brilliance | Negative -> Sibilance

Remember that you can not only boost frequencies but also cut them. If bass and treble frequencies need to be boosted considerably, lowering the mids instead often achieves the same goal, but without the risk of clipping and usually also sounds cleaner. Unwanted signal components are also removed by attenuation. These include, for example, the male vocal formant between 2.5 and 3 kHz or mains hum at 50 Hz.

 

The rule of the thumb is ye olde rule:
Cut sharp and boost wide

 

2 important values easy to remember: Q 1.4 (1.414) - 1 octave wide, Q 0.7 (0.707) - 2 octaves wide.
Usually 1 oct Q for cutting and 2 oct Q for boosting. 0.7 (0.707) is useful for setting high and low pass filter's Q, too.

 

Didn't know this. I exclusively use 0.21 so almost 4 octaves.

 

If someone wants to derive the exact Q values:

1/sqrt(0.5) = 1.414...
1/sqrt(2) = 0.707...
1/sqrt(3) = 0.577...

1/sqrt(3) is of particular interest because it's the basis for a Bessel filter, which is as flat in terms of delay/phase as IIR filters can be.

 

i don't get the formula.
ex:
1 / sqrt (0.5) = 1.414...

what is 1
what is sqrt (0.5)
what is 1.414...

 

some eq's use an evolving Q, which the shape will change depending on how far you boost or cut. Some dont. Its really about just doing whats right for your song, as many eq's will have different q shapes etc. What i like to do i just start boosting or cutting with the default q, i'll make a significant move, so that i can hear what im doing, say 7-10db. From there i will adjust the q until it sounds like what i want, and then back off the amount of boosting or cut, and sort of flipflop this process until it works for my current need.

 

It's a division. "sqrt" means square root.
https://www.google.com/search?q=1+/+sqrt(0.5)

 

This ACMT EQ has a really nice EQ mode called "asymmetric" (Neve consoles made it famous) and I use this one most of the time. Here's how 1 octave (Q 1.4) 9dB boost with 1/3 octave (Q 4.0) -9dB cut looks like.

 

Last edited: Mar 6, 2025 at 6:43 AM

this depends on EQ design,
it can be same,
it also depends how you approach frequency spectrum (for ex. bandwidth between 100-110Hz can be considered "equal" as bandwidth between 1000-1100Hz)