The "Business" head unit is most basic, least powerful etc. I want to add my sub but I can't just tap from the rear speakers for a signal feed as it's high pass filtered with no option anywhere for you to turn this off like you would an aftermarket head unit. Shame as this would be mega quick and easy with the battery in the boot!
You can get BMW to apparently code your stereo so the audio output is "flat" on all speakers allowing you to add an amp/EQ to control it all yourself with the OEM stereo but it sounds complex and expensive
So I need to tap into wires for the under seat subs for my signal feed for a little JL amp and sub. I will face facts the output from the OEM stuff is not very loud... but that's OK for now. Really I'd like to put a 4 channel in and amp some new door speakers and bridge the rears for the sub, but I don't know if a) I'll ever get around to it or b) if it's really worth the cost and aggro. Mine has the 4" full range door speakers but no tweeters, they're only about 15 quid so gonna add those in when I put my sub in to brighten the sound up a bit as the door speakers have pass through connectors to plug the tweeters straight in. I don't have it loud but the under seat subs just don't cut the mustard. Don't really want to waste money on this car like I usually do... but pretty confident if I turn the bass fairly low it'll stop the under seat subs distorting (obviously having tried this but leaves me with minimal bass) allowing me to get a bit more volume overall and then let my JL amp and sub do the work.
I was considering the Alpine upgrade (OEM; speakers, amp, wiring looms etc) and maybe swapping the under-seat subs to the 8" Earthquake ones people go on about but again I'm reluctant to spend loads due to an imminent house purchase. But I do miss a nice audio system!
Bring back my cheap and easy Ford's and Vauxhall's
Easy work!