DSP Low Frequency Artefacts

After my success at setting up room correction using a DIGI2 Pro + DSP board, I have encountered an issue.

When setting it all up, I was of course using bass-heavy content to audition the effects, and I was pleased at how well the room humps were tamed.

But when I started listening in earnest, I noticed some curious low frequency background rumblings in quiet sections of music. The nearest analogy I can give is that it sounded a bit like turntable rumble, where the level of the noise keeps changing.

Wondering if I was imagining things, I played something while toggling the filters on & off, and the curious rumbling was definitely only present when the filters were active.

It's quite subtle and at very low frequencies - I couldn't hear it on a set of fairly inexpensive headphones, only my Meridian active speakers. Some of the filters have fairly large adjustments and high Q. Here they are:

Filter 1: ON PK Fc 54.3 Hz Gain -19.2 dB Q 2.831
Filter 2: ON PK Fc 71.1 Hz Gain 9.0 dB Q 3.982
Filter 3: ON PK Fc 75.2 Hz Gain -5.4 dB Q 7.677
Filter 4: ON PK Fc 89.3 Hz Gain -5.5 dB Q 11.271
Filter 5: ON PK Fc 148 Hz Gain -13.3 dB Q 13.429
Filter 6: ON PK Fc 202 Hz Gain -6.2 dB Q 5.000
Filter 7: ON PK Fc 225 Hz Gain 6.3 dB Q 5.000

Are low frequency artefacts to be expected with such extreme filter settings?


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