Hey guys I just recently installed a Kenwood double din my car and it seems like I have to turn it up louder than I did when I had the stock radio in ok there just to hear music.. It's an 05 base model mustang
Under the menu in the kenwood you should find a audio menu and in that you should have a "loudness" setting turning that from off to low or to high will increase or decrease the voltage outputting from your radio. Check what that is on. Also if you didn't use a wire harness make sure your speakers are not out of phase they should be + to + and - to - not + to -.