> would expect that algorithms implemented in the box are documented enough

You have no idea how much effort it was to get ANY documentation for the EQ. You're supposed to use Philip's Windows software to produce the data tables to program the EQ and then just generate some presets, like "Rock" or "Pop". We were frustrated with this because we knew the EQ was capable of fully parametric operation, and eventually we got some minimal documentation (after signing an NDA a mile thick) and worked the rest out ourselves (or rather, John did)!

I have to wonder whether any other car stereo manufacturer is using this chip for parametric EQ, or whether we're the only ones!

Rob