I started out with response plotting at the drivers seat, ended up with center console measurements to cover the stereo image. These are individual ride plots that can be compared/ distortion via response amplitude peaks and troughs. Do you have a ride in mind? - or I can send a sample.
Sorry, I couldn't fig how to do it (age factor). Lot easier with attach feature, but I can see why the forum doesn't want to use it. If anyone wants a plot; you'll have to send me your email addr.