Nova-67P and parallel equalizers explained
How do parallel equalizers work? The signal is passed through band-pass filters, gain applied and then the result is summed with the dry signal.
band-pass + dry signal = bell shape
low-pass + dry signal = low-shelf
high-pass + dry signal = high-shelf
What is so special about parallel equalizers in digital world? I like the way how bands interact with each other! Check the picture. There’s a typical serial equalizer on the left (SlickEQ GE). There’re 2 bands, 1 kHz and 2 kHz with +6 dB boost on both. In serial equalizers close bands tend to “stick” to each other and in parallel equalizers this effect is less prominent. The difference may be very subtle but for me a typical parallel equalizer provides greater bands separation especially in a busy midrange, which is very suitable for mixing tasks.
Parallel equalizers and cuts. Most parallel equalizers operate in a very special way when combining boosts and cuts. Why? Just an example. If you boost an input signal of 1 Volt by +6 dB you have the resulting signal of 2 Volts. So a parallel equalizer adds 1 Volt to the output. If you cut -6 dB from an input signal you have the resulting signal of 0.5 Volts. Thus a parallel equalizer subtracts 0.5 Volts from the output. Now if boost and cut bands are close together a boost band always tends to win because it affects the output more than a cut band. In our example 1 V + 1 V – 0.5 V = 1.5 V (+3.5 dB of total boost). I don’t like such unpredictable behavior! The solution is to connect boost stage and cut stage in series. Check the picture. For this type of connection +6 dB boost and -6 dB cut compensate each other.
Parallel equalizers and dynamic processing. Parallel equalizers are amazing for multiband dynamic processing because all necessary bands are already extracted from the signal! So it’s an easy trick to add multiband saturation or multiband compression here. Check the picture for the compression example. Now we have a parallel dynamic equalizer!
Each compression block returns gain reduction control signal (GR) to apply to the corresponding band. Is this dynamic EQ completed? No. We need external sidechain and it’s not bad to high-pass it!
Are we there yet? No. I want to control the gain of “dry” signal and to compress it too! Check the picture.
Now we have split-band path where each band is compressed independently and we have new full-band signal path. “Anti-filter” is a composition filter inverse to band-pass filters (series of notch filters for example) and it is used to remove the portion of a control signal already processed by split-band path from our full-band compressor. “Compensation” is a special signal to compensate gain change for the dry signal, which affects bands too. With this compensation the full-band compressor and split-band compressors don’t affect each other.
And in [Nova-67P] there’s also “emphasis” filter inside “Anti-filter” block. It allows full-band compressor to be more sensitive for some frequencies and less sensitive for another. Actually it’s one more parallel EQ hidden inside this block.
I hope this
short and easy description helps you to understand [Nova-67P] plugin better.