My radio doesn't have CD playerBass mechanic CDs
Gonna be from a USB driveIf you're going to be playing your music from an Apple touch device or an Android device you can download signal generator apps from the App store and Play Store respectively and use those. It'll let you test numerous frequencies quickly. I usually test between 30-50Hz for the subs as I've noticed sometimes a 40Hz signal can be clean, but they'll be some clipping in the mid thirties
I just downloaded a bunch but they are all 0db-3 db is what I'd do