DSP engine - what happens below 20Hz?

Hello Roon team,

Can anyone tell me what the DSP engine does below 20Hz?

We all now that the engine doesn’t allow to set filters below 20Hz, unfortunately.

But once for example a low shelf filter is used, what does it do below 20Hz? Nothing? Or continuing the shelf, if yes down to which frequency?


Hello @NOA and thanks for the questions! I’m going to clarify this 20Hz limitation with the technical team during our meeting this week and will get back to you with their feedback.

Thanks @nuwriy!

Yes it “continnues the shelf” down to 0Hz.
For example if you set a high-pass filter @20Hz and 24dB/Oct slope (subsonic filter), it will lower level of -24dB@10Hz and -48dB@5Hz.
Same with low shelf.
The limitation of Roon DSP is to set the center frequency of a filter withing the 20Hz-22000Hz rangle but all frequencies are processed even below 20Hz and above 22000Hz, no worries.

1 Like

Thanks @alec_eiffel.

Allow me the question, how do you know that for sure?
I assume that it’s the way, also,from listening expertise, but only Roon software engineers can tell 100%.

But anyway thanks, and it would still be good to visually see what the filters do down there, the window is limited to 20 Hz, as is the value input.


I have actually measured it by intercepting Roon output in numerous occasions.
IIR filters implementation in Roon DSP is accurate and reliable.
Roon engineers should confirm of course.

Good to hear, thanks!

Hello @NOA, and thanks for your patience here! I confirmed with the team that @alec_eiffel has the correct answer here. Roon’s filters effect all frequencies. It does not allow you to set center frequencies lower than that. Please let me know if you have any further questions, we’re happy to help!

Note you can set filters at lower frequencies with other programs (such as Rephase), save the impulse response as .wav and use Roon convolver.

Hello @nuwriy,


Good to hear that filters work in that range.
Bad to hear that it’s not possible to set filter frequency below 20 Hz.

It would be helpful if the graphics would at least display that range to double check what applied filters are doing down there!


We appreciate the feedback, @NOA. I’ll make sure it gets passed along. Please feel free to reach out if you ever have any other questions or concerns. Happy listening :headphones:

This topic was automatically closed 36 hours after the last reply. New replies are no longer allowed.