Originally Posted by wondras
YES, WE CAN!
I just picked up a 2013 Crosstrek with the CM621UB HU. (Do I get partial credit for having most of an Impreza?) By piecing together info from various posts here, the service manual, and documents filed with the FCC, I figured out that it *is* possible to disable both the loudness and fixed EQ.
With these "features" disabled, it sounds significantly less awful, especially at lower volume levels. This should make it a much better candidate for use with upgraded speakers, or a line out converter and amps. From the schematics, I think it would be fairly easy to add proper RCA line outputs as well.
I don't know if these keys will work on earlier models, but hopefully they do.
Fantastic forum you've got here!
Worked for me, bass doesn't sound distorted and everything is clearer, thanks!