"RBJ" PEQs vs "Legacy" PEQs vs "Symmetrical Constant" PEQs

[Chuck Gerlach]

Based upon what I have read, it appears that both REW and Multi-Sub-Optimizer make use of "RBJ" PEQs. And MSO also provides the option to use "Legacy" PEQs. I will be using a Trinnov to implement the PEQ filters generated bby MSO and I was told that the Trinnov uses "Symmetrical Constant PEQs" and was provided the following explanation:

"The terminology used to describe the various ways of implementing PEQ vary somewhat depending on whose white paper you are reading. But it looks like the best description is “Symmetrical Constant Q.”

With Proportional Q, the affected bandwidth varies as you change amplitude while leaving everything else the same.
With some implementations of Constant Q, a notch is not that same shape as a peak with the same values.
With what we have (and what Ed gave us), the bandwidth remains the same as amplitude changes; also, two filters of the same values for Frequency and Q, but opposite amplitude (eg, +6 dB and –6 dB) will yield a perfectly flat electrical response.

So, as far as any documentation goes, our PEQ implementation is “Symmetrical Constant Q.”

So given the choice of using RBJ or Legacy, which option do I select?

 

[John Mulcahy]

RBJ