Not a nice sound with Hertz in Punto

Tag! The system is completely built-in and consists of Pioneer MP3 Radio, Hertz HSK165 and Hertz ES250 and unfortunately still a Magnat amplifier. Somehow I’m not satisfied with the sound at all!! The bass is good, only the front system sounds just funny … Voices of e.g. Bon Jovi are really annoying in the ears, although it is not hissing or shrill. Now I have tried with the Equilicer on the radio and when I choose the setting Vocal it sounds a lot fuller, and w I’m back on flat and I’m just missing everything at the front. What can that be? Doors are insulated with Brax, doorboard is still set…. Classical music like the musical Elisabeth sounds good again, at least I didn’t notice that the basic tone is missing. What can I do? lg Mo