How were installs like this calibrated? How are home installs calibrated, for that matter? Open source solutions/recommendations especially appreciated.
Check out Duff Room Correction for an old school open source option. There's also Room EQ Wizard, but that is not open source.
In high end home theaters there were proprietary installer tools like JBL's ARCOS (which I worked on). And there are pro calibration tools like Smaart.
In any case it's some combination of measurement, gain calibration, delay compensation, and generation of FIR or IIR filters to control frequency and phase response. Followed by subjective tweaking by the installer. Plus maybe some secret sauce for various things in the proprietary algorithms.
