Variable-Q EQ info

clarky

clarky

Axe-Master
I'd like to know a little more about this so that I know if it's something I'd like to use or not.

could some please explain a few things:
- what is the triggering source to make the Q variable? as in, is it the signal level within a given freq range?
- how does it behave upon being triggered? does the Q widen or reduce the band's freq range?
- what am I listening for when goofing around with this??
 
Traditionally variable Q circuits would narrow the Q as the gain is raised or lowered.

So small boosts and cuts would have a broad Q and large boosts and cuts would have a narrow Q.
 
clarky said:
I'd like to know a little more about this so that I know if it's something I'd like to use or not.

could some please explain a few things:
- what is the triggering source to make the Q variable? as in, is it the signal level within a given freq range?
- how does it behave upon being triggered? does the Q widen or reduce the band's freq range?
- what am I listening for when goofing around with this??
Click to expand...

There is no "triggering". It's not a dynamic Q, it's a variable Q. The Q varies with slider position. In a constant-Q equalizer the Q is independent of slider position. If you set the Q to 0.7 it's 0.7 whether the resonant gain is 1 dB or 10 dB. In a variable-Q equalizer the Q would be 0.7 at a gain of 12 dB and decreases as you reduce the gain.

Classic stomp-box graphic equalizers are/were variable Q as it's simply easier to make a variable Q filter. You can make an 8-band variable-Q graphic equalizer with three chips and a few dozen passive components.
 
thanks guys....
so if I'm understanding this correctly, when the slider is closer to 0dB, the freq range is wider, and when further from 0dB [for + and - values], the freq range of that band is narrower??
 
Great stuff guys.
Out of curiosity, is there a "triggered" / dynamic EQ? I think the "Character" parameter might do something like that but I'm not sure...
 
Wolfenstein98k said:
Great stuff guys.
Out of curiosity, is there a "triggered" / dynamic EQ? I think the "Character" parameter might do something like that but I'm not sure...
Click to expand...

In the Filter block you can attach a modifier to Gain. Using an envelope modifier will make the filter's gain dynamic and triggered by your playing (like an Envelope Filter pedal but you get to pick & configure the filter). If you watch the display on the Axe, not in Axe Edit, you can see the filter react to your playing.
 
MaxTwang said:
In the Filter block you can attach a modifier to Gain. Using an envelope modifier will make the filter's gain dynamic and triggered by your playing (like an Envelope Filter pedal but you get to pick & configure the filter). If you watch the display on the Axe, not in Axe Edit, you can see the filter react to your playing.
Click to expand...

Awesome, thanks! I'll have to play around with it.
 
Note that variable Q has artifacts that mean that the overall frequency response is not as close to the graphic representation of the sliders compared to constant Q.

For me, variable Q gives a more natural response (ie an "expected response") when using a single slider, but when you're shaping an overall EQ curve, constant Q is far more accurate.

There's plenty of good info on the web on this. Here's just one:

http://www.sound-better.net/Tech%20Papers/Tech%20Paper%20106.pdf
 
Q, amplitude and freq are generally independent. eg. parametric eq variable controls.
Q and bandwidth are terms that have been used as synonyms but actually are different..
I believe there is a diagram in our manual , listed under eq types
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom