QSC Q-Sys custom IIR filter block problem

[EA Support]

EA Support

7 May 2025 at 9:19 pm #1032

Hello,

I’m trying to create an IIR custom filter for QSC Q-SYS. The coefficients generated for this seem to make sense to me (here is a simple example just for testing attached).
Unfortunately the import into Q-SYS doesn’t work: The frequency and phase response are not displayed in the IIR custom filter container.

The import of FIR filters in Q-SYS, on the other hand, works without any problems, and the frequency and phase response are also displayed there.
I’m using an emulated system with the Q-SYS Designer V9.4.

The examples for IIR coefficients given by QSC in their user manual also do not lead to any meaningful results when importing as IIR custom filters (frequency and phase response are not shown or only as vertical lines).
I am a little perplexed and suspect that the syntactic definition of the coefficients could be the cause.

Thanks for your feedback.

Since the QSC example coefficients are not plotted correctly, I suggest contacting QSC directly. (Our export matches the expected format, according to their documentation.)

You could try designing a system just a single custom IIR filter block, load the block with coefficients for a simple filter (like a 1 kHz 2nd order LPF), download the design to a Q-Sys core, and actually measure the core’s processing using a tool like SMAART. This will confirm whether or not the custom IIR block is behaving correctly, despite the display problem.

Regards,
EA Support