Fader Levels and Channel Eq Relationship

When I open the channel EQ and lower the volume of certain frequencies, I see the decibels on the channel fader actually INCREASE rather than decrease. Can someone explain to me how this makes sense.

Also, what does the channel fader represent? Is it a peak or rms value? And does it just tell you the highest value for any given bit reading, or does it average the frequencies?

Yes, this is a counter-intuitive but real phenomenon, particularly when cutting low frequencies. Strange but true!

There are a few posts on this subject here, though you'll have to search for them (or perhaps someone will provide a link).

The fader is a volume control, plain and simple. It does not read out frequencies or bits. Just volume. Not sure if it's peak or RMS, someone else will have to chime in on that.

When I open the channel EQ and lower the volume of certain frequencies, I see the decibels on the channel fader actually INCREASE rather than decrease. Can someone explain to me how this makes sense.

as ski says, we discussed this a lot here, but I can't find any of those posts right now. But in a nutshell, anytime you apply a nonlinear phase filter, like the channel eq, you will have group delay. Meaning that low or high frequencies will be delayed with respect to each other and in some proportion depending on the severity of the filter. So.... If you had a high frequency transient event that was previously sitting at about the zero crossing of a low frequency signal, it may well now be sitting on the peak of that signal, thus giving you a much larger meter reading.

It can also happen if your filter q settings are extreme and your driving the filter into resonance. In any case, this is normal behavior.

Logics channel strip meters are peak reading.

In addition to what fader8 said, note that the issue is a natural one and would occur even if an ideal EQ wasn't delaying anything - in fact you can reproduce it with a linear phase EQ. It really is pure maths: subtract harmonics from a complex periodic signal and you can (sometimes) end up with a periodic signal of greater amplitude.

Here's a good thread on the topic: why does decreasing EQ increase the main meter level?

Here's the easiest (IMO) way to describe the phenomenon (from the same thread):

Ski, the animated picture below should explain better what I'm trying to explain. You can see that as you add the square wave harmonics to a sine wave, it slowly comes closer to being a perfect square wave with a lower amplitude (hence the lower peak level).

 

Nothing to do with phase shifting.

 

On the picture below, take the square wave and filter its harmonics, and you'll end up with the sine wave, which has a higher peak level. That's what you experience when you cut frequencies with an EQ and see the peak level rise.

 

http://upload.wikimedia.org/wikipedia/commons/0/0a/Synthesis_square.gif

 

Source: viewtopic.php?p=25663#p25663

You can record this and watch the peak climb as the low end gets filtered.

(Limiters are a blessing, eh?)