I have a 2021 Audi A3 35TFSI and paid the additional cost for the Audi Sound System which is supposed to be an upgrade of the basic system but not to the B&O standard. How can I tell if Audi have installed it? I only seem to have Bass, Treble, Balance and front rear Fader settings. I thought that there is a sub woofer in the side wall of the boot and that I would have a setting in the MMI to control the level. Your comments would be appreciated. Thanks. Colin