B&O system door, tweeters, and rear are 4-ohm. Dash is rated 8-ohm on its tag, but meters a bit lower at 6.5. Most of them actually meter about 12-15% lower than marked. Only one I haven't bothered to test is the subwoofer, but I assume it's 4-ohm as well since it's off the B&O amp like the door and tweeters.