EQ parameter ranges (parametric equalizer)

[reverbel]

Hello,

Many audio enthusiasts use REW (https://www.roomeqwizard.com/) to generate parametric EQ presets optimized for their listening environments. However, REW-generated filters have

• gain parameters in the range from -20 to 20
• Q parameters in the range from 0 to 20.

Moreover, for low frequency (below 200 Hz) filters, REW-generated frequency parameters may take fractional values. Please see the attached file for an example.

Since Poweramp started supporting parametric EQ, I have been using it with REW-generated EQ presets and am very pleased with the results. However, due to the different parameter ranges accepted by Poweramp EQ (which are smaller than the ranges above), manual changes to the optimized presets are needed.

In order to circumvent the smaller gain range (from -15 to 15) accepted by Poweramp EQ, I replace each filter with gain parameter greater than 15 or less than -15 by a pair of filters with identical frequency and Q parameters, and whose overall gain (i.e., the sum of their gain parameters) is the needed gain.

In order to circunvent the smaller Q range acccept by Poweramp EQ, I replace each filter with Q parameter greater than 10 by a filter with Q = 10, then ask REW to re-optimize the remaining filter parameters. I do something similar to deal with low-frequency filters with fractional frequencies.

Would it be possible to change the accepted parameter ranges of the Poweramp parametric EQ so that is takes gain parameters from -20 to 20 and Q parameters up to 20?

@maxmp: Thanks for the great player! 
 

rew-generated-file.txt

Edited June 29, 2022 by reverbel
Fixing typos

[maxmp]

@reverbel while dB range can be extended (though you’ll need a lot of headroom to handle this), increasing Q may lead to unstable filters. I guess some optional ultra advanced mode should be possible, for example, for manually entered values or imported presets.
As a side node, currently you may need to enable cascade mode for the overlapping bands and also disable reducing max band gain (see Settings / Equalizer advanced options).

Thanks for the request.

[reverbel]

Thanks for your response, @maxmp!

The idea of an optional advanced mode sounds great.

I think it would be sufficient to allow extended parameter ranges in imported presets. REW-generated presets may have quite a few filters (10 or more filters in a preset are common), so it is not very convenient to enter them via the Poweramp UI anyway. It is much more practical to create a json file with the preset and import it into Poweramp. I use a Python script that reads a csv file whose lines are triples <freq, gain, Q> and generates a json file in the format accepted by Poweramp.

Extended gain ranges require a lot of headroom indeed. In some of my presets with high-gain filters (implemented with the "filter pair" trick), the preamp gain is set to a large negative dB value. (One of these presets has Preamp = -12dB!) A lot of volume is lost, but fortunately this tends to happen mostly in presets for small listening rooms, when volume is not an issue.

I've heard that high-Q filters have floating-point issues, but have no idea about how far Q could be increased without resulting in unstable filters. Perhaps 10 or 12 is already a sensible value for max_Q... If this is the case, please ignore the Q part of my request. Having an upper limit on Q is much better than ending up with bad filters!
 

Edited July 3, 2022 by reverbel

[reverbel]

@maxmp: Thanks also for the observation regarding the cascade mode for the overlapping bands and the max band gain reduction. I see the "Smooth Equalizer/Tone Gains" option in the settings of the Poweramp EQ, but could not find a "Bands Overlap" option there. Found it the settings of the standalone EQ app, but not in the Poweramp EQ.