On my 2014 MCS I spend a small fortune upgrading the HK audio system. Replaced everything. Bypassed the HK amp (left it connected for CanBus) Ran 2 Focal amps and upgraded the under seat woofers. It was pretty awesome.
My 2016 HK sounded way better right off the lot and have put up with it till now.

What I want from the upgrade is more clarity in the high end sounds and have better bass. Not 12" sub in the trunk bass but I want to go deeper and have slightly more. I've spent a ton of time checking out the BMW forums. Some BMW's (X1's etc) have the same bass box although most BMW's boxes are bigger so respond better.

My conclusions based on my car and my experience with my last F56.

1 - Replace all 3 front tweeters - I'm using 4 ohm JL AUDIO C2-075ct 0.75".
2 - Power the existing stock woofers. I'll do this by tapping into the back speaker wires before they go into the "Active Sound" (I have a bypass harness so will tap into the wires there. Then run the wires to a new Focal FD 2.350 amp.
3 - Will run a 4 gauge power wire to the right side of the car (opposite the ASD unit and out the very small amp under the trim so I can have access if I pull the rear seat.

The whole thing should be less than $400.

I'm not sure how the stock woofers will last with the extra power but I have a set of Jehnert XE200's just in case. I doubt I will hear much of a difference between stocks and the XE200's but they will handle more power. First off though I'm using the stock HK subs!

I'll let you know how it goes because I know that many people don't have big budgets and just want a decent "bump".

 

I went the BavSound route and got better clarity with more defined bass as well. Seems like you'll achieve the same at a much better price though. Curious to hear about your results.

 

Update:
Well as I stated before the 2016 HK system is not bad.
The tweeters really improve the top end. Clean and clear. Substantial improvement.
The HK under seat woofers are pretty much at peak performance with the HK amp. With the focal amp they give up a slightly better low end response and feel deeper. Not substantial though. by cranking up the gain I can get more bass but it is not proportional to the music. The system sounds better but the bass is a little disappointing. I am really surprised that the BravSound speakers are that much better without more power. I can see them improving the tweeters and mids but I would have to hear the low end to believe it. What I would imagine is that they are similar to what I have now.
I am going to try the XE200's next week. They have a good reputation in the BMW X1's so thinking with power I should get another bump. I just need to make another Plexi ring to lift them higher in the box.
I believe the Earthquake speakers are also good. Speaking to their rep. He tells me they make speakers for Bravsound but they have patented technology in the SWS 8Xi's that they claim to go deeper than any other under seat. Might try those too....

 

Update on this. I had misread the wiring diagram for my ASD bypass harness. Result was that the amps input was out of phase. Corrected that.
Wow substantial bass improvement over stock especially with hi qimput input (flac etc).
I still am going to try the Jehnerts but doubt they will go much lower just be tighter mid bass.
Basically though I would highly recommend this upgrade. Really transformative. ...and if you ruin a 4 gauge power wire you can always add more amps later. Easy!

 

you replaced the tweeters .......in the A pillars? ..... how difficult? can you give a 'how to' guide?

I have the HK in my F55 and the system sounds good enough .... am happy enough with the bass but would like more imaging in the high end ......in my '04 MC i had the base audio system and simply replaced the mid-range woofers that were in the lower area of the door with coaxial speakers that had their own tweeters but I kept the existing tweeters that were higher up in the doors connected and it did what i wanted, that the vocals and high end seemed more up front or in the air rather than having the sound be placed flatly at the speakers....ie, imaging

 

Umberto. Super easy. Hardest part is removing a A pillar covers. They pop out at the top and then slide up - there is a metal tab at the top that slides in a grove - it is easiest a best to slide it up then it pulls off.
With the tweeters I just pop out the originals then hot glue in the new ones. I've used this technique twice and they hold up fine. I've only ever use 3/4" tweeters but 1" would likely fit.

 

Just upgraded the underseat subs. SwS-8x Earthquake speakers (2 ohm).


This are the next level for bass. The amp made the biggest difference but these go quite a bit lower than the stock HK speakers and they move large amounts of air....so much so that you have to raise the covers off the carpet with spacers to stop them hitting.


I would highly recommend this upgrade if you don't want to add a trunk sub. This setup (amp and speakers) maxes out the bass with a stock looking setup.

 

Hi Gregory, how do you rate the SwS-8x with the Gladen 8s? I have the Gladen 8" drivers under the seats in my f56 at the moment.

 

The Gladen's do not go as low as the SwS 8s but work very well in the MINI's environment. They are really a better speaker IMHO. The SwS 8's lack the low-midrange so those tiny 4" door speakers have to cover. Depends on the type of music you listen to. Classical or acoustic guitar the Gladen's give a better more rounded out sound. The Gladen's with a truck sub is really the ultimate way to go...
I did not want a trunk speaker so the SwS-8's are a good compromise. I'm going to put in some better 4" speaker in the door to help the lower mids.

 

I replaced all the speakers in my F56, Gladens under the seats. Disconnected the 4" door drivers, and installed Hybrid Audio L3 and L1pro tweeters in the A pillars in custom housings (i still need to redo these and trim). Then a Diamond Audo TDX12 sub in a ported box in the boot (trunk), in a custom fibre glass box, sunk into the depth of the boot, still allows me decent room for bags etc in the boot. 2 Alpine amps, Audison Bit One.

Phew, thats a lot reading it back ha!

 

GregoryK, thanks for the regular updates as you work through the challenges. I've been immensely enjoying the updates as you post them!