I posted most of this over in the 2 series forum, but I thought I should share my experience in upgrading the M2 audio system here as well.
I took delivery of my 2018 M2 last October and decided a couple months ago I was tired of dealing with the stock Harmon/Kardon audio system.
Here's a pic of the subject:
Here's the list of audio upgrades I've added to the M2:
Audiotec-Fischer Match UP 7BMW 7 channel amp/DSP
JL Audio XD300/1v2 1 channel sub amp
Earthquake Sound SWS 8Xi 8” woofers
JL Audio 10W3v3 10” subwoofer
Musicar NW F22 sub enclosure
Morel Hybrid 402 component speakers
I'll be keeping the OEM HK center and rear speakers installed for now..
I was going to go with the MusicarNW Level 2 4-way package at first. But they couldn't provide me with the DSP I wanted. Then I happen to find out about the Match UP 7BMW amp made by Audiotec-Fischer; the same company that makes the Helix DSP.
The Match amp is a plug-and-play amp for BMW hifi systems in 3 series and higher cars. In 2 series and lower cars it will work with both the hifi and HK systems. This is because 2 series and lower cars don't use the MOST net for audio. Instead they use differential balanced analog connections to the rear mounted amp.
Also, the Match amp uses the same DSP that is in the Helix DSP. It's also rated at 5x65watts at 4 ohm and 2x160 watt at 2 ohm and has one line level pre-out for an external amp. Plus a optical digital input.
The amp came with a mounting bracket for the BMW and a custom wiring harness; no need to cut any wires.
It fits perfectly in the oem amp location. That other "amp" is the Active Sound Design amp; or the fake engine noise thingy. I don't know why BMW keeps putting this in new cars. If you can't tell by the pic, I have this thingy bypassed.
BTW, I'm surprised my 14 year old POS Windows XP laptop worked at uploading the sound file. I hope it handles the tuning session with my MiniDSP UMIK-1 hooked up as well.
One thing I noticed on the Match amp; while it's powered through the OEM wiring harness, you can also hook up 8 gauge wire directly to the amp. The manual says that if you have any system noise you should try that. I don't have any noise as of yet, but I'll keep that in mind.
I stuffed the JL XD300/1 on the right side of the trunk under the storage tray. It fit in there with about 1 inch of clearance. With it being right next to a cabin vent, I'm thinking it should get adequate ventilation.
I ran 4 gauge wire to the battery lug. JL says you can use 8 gauge-- F that...
The MusicarNW sub enclosure is built pretty robust. I didn't measure it, but it seemed to me that the fiberglass is about 3/4" thick. I'm not sure what the internal volume is though.
It's secured to the body by one plastic rivet up in the corner of the trunk. That and the fact that it fits VERY snug keep it from moving anywhere. It also comes with a quick connect for the speaker wire that runs through the hole where the 12V trunk outlet used to be.
While I was at it I installed the pair of SWS 8Xi's. I know the Jehnert XE200's probably sound better, but I got these cheaper and I was worried about the impedance difference between the two drivers. The SWS 8Xi is 2 ohm and the Jehnert's are 6 ohm.
The Morel Hybrid 402 speakers were not a direct drop-in replacement for the BMW HK speakers. I had to modify the OEM sail panels for the Morel tweeters. But since I got the Morel's from MusicarNW, the modifications to the crossovers were already done and the mids came with the correct speaker adapters.
MusicarNW set up the Morel crossover with OEM connectors so no wires had to be cut in the doors. The crossovers mount low in the front corner of the door panel.
The Morel's are a big improvement over the stock HK speakers. I'm still working out the tune. It's a PITA to tune in an oven of a garage. I'll probably get a better tune once the outside temps go down and I learn how to use Room Eq Wizard. For now, it sounds good to me. Way better than the stock system. I've got the center channel turned off and the stock rear HK speakers turned down to where I can just barely hear them. The soundstage is right up on the dash and centered on the drivers position. I rarely have passengers so the sound is all about me.
Here's the setup on the front Morel Hybrid 402's.
Here's the setup for the rear stock HK's.
Here's the setup on the SWS 8Xi's.
Here's the setup on the JL 10W3v3.
I'm sure I'm not done tuning; I'll always be tweaking it. I'm think of getting a Helix Director just so I can have more than 2 sound profile presets, we'll see...