I wanted to upgrade this stereo system in my 2017 Clubman JCW with the Harman Kardon system. When I was planning this, I was searching for threads that would help me disassemble the rear hatch - little tips, tricks, BMW/MINI specific things - and I was surprised nobody with an F54 had documented it. So I figured I'd step up to do it.

I'm a former professional mobile electronics installer and fabricator, and a lifelong audiophile - besides being an IT professional and car enthusiast.
Blend all that together, and you get a goal-oriented DIY-guy who has high standards based on hearing and seeing - and building - on a long history, since I'm a middle age guy now..

Did a little research on equipment - decided the MATCH UP 8BMW amp would be great for me, since I want to do my own tune. Lots of people will see that as a lesser option than the Bimmertech Alpha1 option - that one comes with a tune optimized for the car specifically and isn't significantly more expensive. In my case, I have experience, a laptop with REW, a nice, calibrated microphone setup, and my own personal preferences. Regardless, the amp replacement steps are the same, so I wanted to document the installation process here.

I was also researching the underseat woofers and settled on the MATCH UP underseat replacement woofers as well, particularly as I was planning to tackle the install in stages - do the midbass replacements, come back to it, do the amp replacement, come back to it, add on a proper subwoofer. I also upgraded from my non-touch NBT head unit to an EVO touchscreen head unit, so that was yet another phase - just completed that prior to this.

 

So lets start with the part that I was surprised not to find anywhere-
Taking the rear hatch apart to access the factory amp. We need to remove the driver's side (left side I should say - I'm in the USA) hatch panel. That's where the factory Harman Kardon amp is.

I started with popping this hatch LED out, thinking I might find a screw behind it. There isn't, but it's still good to pop out. If you have a slim tool like a putty knife, slide it on the car side (right side) of the light, and press against the retaining clip. You'll feel it, and then the light will pop out.



The plastic panel next to the window needs to come off. With the hatch doors open, pull the weather stripping and if you start to pull it with your fingers, you'll see two of the pressure clips that are holding the panel on. Use a panel tool to pop it off. No screws holding this panel on.


I got a little ahead of myself and forgot to take a picture - this is the other window panel, next to the rear seat. The SRS logo pops off, and there's a screw behind it that holds hte panel on. Remove that screw. The rest is held on with a pressure clip.


I also already removed this screw before I took the photo - this is under that panel - remove the screw:


Back at the hatch, there's one screw to remove, similar to that last one - which I already removed in this photo - below the hole that was from the pressure clip:


Up by the back seat again, there's a plastic clip - it's a round one that slides out, you should use a tool like this ideally to pull it out. Don't pull too hard because it is a two-piece clip - a receiver that has four prongs that splay outwards when the pin goes into it, and the pin that you are prying on here, with the cap on top. You don't want to lose either piece. Once the pin is out most of the way, the whole clip assembly comes out pretty easily:


The back seat is held on simply with pressure clips. I was feeling around with my fingers back here, and the seat back unclips by pulling up:



Under the rear seat side cushion, there are two plastic clips - same type as the others, pry carefully to release the pins and extract both of these two clips:


Here's a good picture of the clip, so you can see the two parts:


There is a Torx screw at the very bottom of the plastic panel that needs to be removed:


You have to pull back the carpet flap here to get to this torx screw - remove this one as well:


With that screw removed, you can start to lift the upper portion of the side hatch panel. You do NOT need to loosen or remove the larger torx bolts where the privacy cover clips in:


These spring holders for the floor (when you tilt it up) have a plastic bezel that are simply clipped on. You need to pry them off with a small tool like this. Be gentle as you pry, there are a couple areas that will "click" and it will pop off:


There is a plastic cover on this D-ring - it needs to be pried off from the top, so you can access the bolt holding it on:



Remove the bolt and remove the D-ring:


There are two more of the pin clip fasteners to pry loose down under where the false floor rests:


the trim panel covering the bottom of the hatch opening is held on with four more of those clips, need to be pried loose and removed:

 

You just need to peel off the weatherstripping then, that's all that's left holding the rear hatch sill in place. It'll just lift out after the weatherstripping is removed:


The side panel with the cubby will then just lift out (assuming you pushed the LED light through its hole - that's all I did, I didn't even unplug it):


And here's the factory amp!
Note the bolt just below it, and note the harness on the left side of the amp. Take a close look - there's a pivoting arm that's currently swung towards the wires and latches over a small detent just behind it:


Remove the bolt below the amplifier. That will allow the amplifier to slide in the direction away from the side window. You'll see there's some stamped metal that intersects that hold the amp in place, and release it when you slide it out:



For the wire harness, press the detent in, to allow the arm to swing down toward the amplifier. That will release the harness so it can be unplugged from the amplifier by pulling out from the amplifier:

 

Note these Harman Kardon amplifiers have need for extra power wiring.
The one I bought had two modes of operation:
1) Without a power augmentation, it will run in a low power mode.
2) ...or you can run separate power cable, to a separate plug - where you also install an additional fuse into the amplifier, allowing it to make more, cleaner power.
In order to run the amplifier this way, you need to run an extra power cable from the battery back to the amplifier.

Part of MY long term plan was also to add a separate subwoofer amp, and I happened to have 1/0 gauge wire from a now-defunct company called Ixos. They made a unique rectangular version of 1/0 gauge wire that was a little easier to lay under carpeting, but a little tougher to run through firewalls and gaps. If you aren't adding a subwoofer amp, you can probably get away with 4 gauge or even 8 gauge wire, which would be much easier to install than this fat 1/0 gauge wire.

I found this location that had a blank gasket:



I found by poking around that it does go all the way through. I used a pick tool to remove it, and then I found that I already had this rubber loom that's actually intended to run wiring into doors - it turned out that the grommet end was exactly the right size for the hole I found, and has length to it so I can cut it in half and that will also afford additional weather and waterproofing protection:

I apparently didn't take any good pictures of pulling the wire - I have a flexible rod that I pushed through the opening, and in my case here I pulled the wire through from my driver's footwell area by taping the wire to the rod. My wife had to help me here, because the square wire was getting hooked in the round hole.
Once it was through, I used silicone lubricant inside the rubber loom that I cut in half, and then it slid over the wire, despite it being a tight fit.
It was also a tight fit to get my hands in that little area, but I was able to clip that grommet end in securely for a weathertight seal, and the loom extends down the wire long enough to also be facing downwards.

I'll try to remember to take a pic and add it here.
(placedholder)

I then routed the wire back up above the battery, made a few small cuts in the panel above the battery so I could secure a 200A breaker to that panel, routing the wire to the output of the breaker, and then a short length of wire from the input of the breaker to the positive of the battery - conveniently, although this rectangular Ixos wire ring terminal was very thick, one of the two bolts on that positive bus at the battery terminal was plenty long enough to secure it:

**IMPORTANT NOTE** - the red box is a battery shutoff that I installed when I bought this car, mainly for the convenience of doing electrical work on my car - I can press "off" and the battery disconnects - just like removing the negative cable off the battery. it also has low voltage protection so it disconnects if my battery voltage drops too low - a nice side benefit.
You can see the display is off, not displaying voltage. That is because I HAD THE BATTERY DISCONNECTED WHILE DOING ALL THIS WORK.
Be sure to do the same with your car, when working on this installation.


I routed the power cable down the driver's side of the car the usual way (removing the door sills, partially popping the interior B-pillar, and stuffing it under the carpet).
Once it reached the rear hatch area I secured the wire in the following position using
This is ALSO a good time to run your subwoofer amplifier's remote gain control wire, if you are adding a subwoofer amplifier.
For ground, I used the factory ground locationn - the wire passes right by it - you can see the blue shrink on the ring terminal I used on my clear 4 gauge ground cable:


Since I'm going to be running both the Match amplifier's additional power and also a separate, large subwoofer amplifier, I chose to install a fused distribution block in the cubby below the rear sill of the hatch.
You can see in the picture that I made a large slit in the carpet panel that recesses in here, and I ran the main power cable in, as well as a piece of 4 gauge (overkill - but I already had it) wire going to the power plug on the MATCH amplifier. I then ran a ground wire through the opening here for the subwoofer amplifier, and I also ran a separate ground wire from that same factory ground post to the ground side of the MATCH amplifier's power plug:

Again, a pretty trick Ixos piece here - I love this design, whatever combination of fuses you bridge across each set of bars here is the total fusing for that output.
In my case, I have four 10 amp fuses (blue) in here for the 40 amps total of the MATCH UP8BMW amp, and I have four 15 amp fuses (white) in the other output for the class D subwoofer amp that I have for this project (power wire isn't plugged in there yet, in the above picture).

 

I'm also realizing I didn't take great pictures of the actual installation of the MATCH UP8BMW amplifier.
The power plug is clearly visible in the picture below. There are screws that secure your power wire to each terminal, then you just plug it into the amp.

Following the instructions in the manual, I had to remove the bottom panel of the amplifier, to make that fuse change I mentioned above (details are in the manual, but you actually remove the fuse that was inside from the low-power position, moving it over to the high-power section, and installing the second fuse as well), enabling the amp to operate fully.
Then you bolt on a panel that matches the mounting system of the F54, supplied with the amp. Also supplied with the amp is a wiring harness adapter, which plugs into the amplifier, and then plugs into that fancy swing-arm factory BMW plug on the other end. Very straightforward.
To install the amp, just slide that amp on its adapter panel in place, and secure with the same bolt you removed to release the factory amp.

One little quirk that threatened to foil my plan to add a subwoofer amplifier-
The MATCH UP8BMW amplifier comes with a separate RCA output to feed a subwoofer amplifier, and the DSP even has that extra channel for tuning. The amplifier, you see labeled clearly on the outside of the amp has a REMOTE IN wire (which is standard on the factory BMW harness, therefore is also populated on the wire harness adapter). It also has a REMOTE OUT, but that position in the 2 position plug is empty. No wire, no pin.

I had to buy this Molex female pin:
If that link doesn't work, it's a Molex 39-00-0038 female pin made for a Mini Fit Jr 5556 plug - which is what this plug is, so it fits and clips in place.

Once I had that, I crimped it onto a blue wire I had, and I populated the vacant spot in the plug, and plugged that into the MATCH amplifier:



Good news - the REMOTE OUT works.
It supplies voltage to turn on my subwoofer amp, no problem there.

 

I also didn't find too much info on replacing the under-seat woofers.
No matter the brand you pick, they all seem to come with an adapter plate or terminals that mate to the factory wiring for integration.
Interestingly, the ones that came with these Match Up woofers I personally selected required modification, but we'll get to that.

They aren't too hard to replace - I think it was a T45 torx required to pull the four bolts holding the seats down, one at each end of the two seat tracks.
Then, I just tilted the seatback all the way forward, and topped the seat back. The yellow plug, I unclipped from the underside of the seat by sliding it back, that allowed the seat to tip back and balance backwards while I worked so I didn't have to unplug the harness. That gave easy access to the speaker grilles:


All of these are the same size Torx - T20 I believe.
There are four screws for the grille, then you may have to bend the carpet back slightly to access the four on the speakers.


The factory speaker connector is a purple plug.
To release it, insert a screwdriver like I did here, to allow you to push the tab in and release the plug:



The Match Up speakers came with these adapters, allowing the factory plug to be used - no cutting of wiring.


However, the plug was keyed incorrectly.
If you look at the factory plug, there's a plastic ridge on one side of the plug that aligns with a groove on the socket in the factory housing.
However, on the blue adapters that came with the speakers - it almost seems like they were made as a mirror image of what they should be - you can see the purple plug wont' be able to slide into the blue socket.
Both sides were the same, it wasn't because I was using the left sde on the right or vice versa - i wish.



I ended up using a small fluxh trim pliers to cut the purple ridge off of the plugs, which allowed them to go into the blue plugs, and that worked fine:



These white spacers were supplied with the speakers, and the instructions were to install them, spacing the speaker grille up slightly to allow more clearance for the speaker.
I chose to use a dab of super glue on each - imagining the Murphy's Law scenario where you go to install the grille, one or more of them fall out, and lodge themselves somewhere impossible to find in one of the voids under that carpet, between the speaker... Don't take chances. Just glue them in, then they can't fall out.

Speaking of excursion clearance - I also was concerned about the carpet overhanging the speaker. With the speaker reaching any sort of excursion level, it could hit the carpet - best case limiting the excursion of the speaker, worst case making the speaker rock, rub the voice coil, and go bad.
Pretty easy to trim this much carpet, and still when I install the grille, you won't see what was trimmed.



Reinstall the grille - repeat on the other side.
​​​​​​​All done.

 

The subwoofer:
I want this post to help understand subwoofers for people who don't necessarily have expertise but want to add a subwoofer.

I've been a lifelong audiophile, fabricator, installer. Ever since I was into cars, it was a way for me to have my own listening space. It was a way to be social and bring me to my friends, and bring my friends along. It was a way to create something cool, make it both sound and look cool.
By contrast, my goal here is to be completely hidden. I'd love it to be small, cost me no storage, but sound big.

It just happened that three or so weeks ago, I was watching one of my chosen DIY audio guys on Youtube, and they mentioned this tiny company Prodigy. I have no affiliation,and neither did this guy. But he mentioned that the specs for this sub were exactly what I wanted to do, to create a hidden sub.

Quick lesson on subwoofer specs:
There's a thing called "Hoffman's Iron Law", because it defines the variables you get to play with in creating subwoofer enclosures. Or rather - the brick wall imitations you hit. It states the following:
These three things are mutually exclusive:

1. Small enclosure size
2. Low frequency extension
3. High efficiency (loudness per watt of power)

That means - the smaller you make your subwoofer enclosure, the less low it is capable of playing, and the more power it will take to reach the same decibel level of loudness. Even for vented types.
Then, subwoofers come with pretty cryptic spec sheets that not enough people understand. Worst, they buy subwoofers THEN figure out if they work in the enclosure that fits their car.
The specs that primarily help you determine how to work with Hoffman's Iron Law, how to shop for a sub that fits your installation goals and constraints, are these:

1. Vas is the air-spring factor of the subwoofer, intrinsically. The stiffer the sub though, the less efficient it is [all other things being equal].
2. Fs is the resonant frequency of the subwoofer. The lower the Fs, the lower the sub is capable of playing. Adding moving mass lowers Fs, so unfortunately that also can impact efficiency.
3. Qts is mostly Qes, which is a good parallel to BL, which is motor strength. It's also good to use to identify if the sub is "better for" a sealed (higher Qts = less motor strength), or vented (lower Qts).

Although lots of companies make "shallow" subwoofers, this Prodigy NB3 subwoofer stood out to me. Most companies who make shallow subwoofers don't particularly make it work in SMALL enclosures. This one, on the other hand, had a 36hz Fs. That's low for a shallow 10" subwoofer, helping keep it low in a tiny enclosure. It has a 0.4 Qts, making it good for a vented box, which gave me a great idea - even though "small" and "vented" go together like oil and water. And it has a relatively small Vas, so it should be comfortable in a small enclosure. It also handles 700 watts RMS, which means you can use a large subwoofer amp to overcome the poor efficiency you'll get from being in a small enclosure.

Now, typically when you build a vented box, you can't make them small even if you don't care about efficiency. That's because the smaller you make it, the longer the port needs to be for a given tuning frequency. The enclosure I designed for this car was only 0.5 cu.ft. inside, and that's tiny even if it was sealed. For a vented box, I'd need a port that would be something like 40" long for any decently low tuning frequency, and that couldn't be inside the box. It's already at that point where the port length (and volume IT eats up) works against your goals for a tiny enclosure.
But...
...a passive radiator is essentially the same thing as a port, but doesn't have length. I was already sitting on an Earthquake SLAPS-M12 passive radiator that I bought for another project, but didn't use.

So my thought was this:
Under the hatch floor in my F54, I have a compartment 6" deep. If I can fit a subwoofer down there, it can be completely hidden and cost me zero hatch space.
I designed an enclosure to be down firing. The subwoofer is only 3" deep but is vented, so it needs at least an inch behind it, That's still shallow enough to allow an inch of space below the subwoofer and still easily fit under that 6" well under the hatch floor. I made the enclosure wide enough for the 10" subwoofer and 12" passive radiator, and ended up with a total of 0.5 cu.ft. and a very low Fs, due to the large passive radiator.

I'll add some pictures here - I should have taken more construction shots.

Adding to the impossible aspect of this, was that I wanted to make it removable. I want my under-seat woofers to do all they can, and the subwoofer just to pick up where they leave off.
I needed a powerful amp (700w RMS) to power this, with all the inefficiency I intentionally built into this due to Hoffman's Iron Law, and my desire to play low and get loud in a small enclosure.
Making it removable meant that I needed that kind of power in a package that could bolt to the side of this incredibly slim enclosure, with enough room to not be right against the hatch floor, for heat dissipation.
Amazingly,the stars aligned, and this popped up in my feed, making me want to take the gamble on this particular subwoofer amp. Unbelievably compact, inexpensive, an unknown brand - a gamble in all respects - but sure enough, it's clean, and has plenty of power for this application. It really gets loud - way more than I need for a SQ system - it really lets dance and old-school rap tracks shake you up.

 

Again, the subwoofer here is mainly to show the use of the optional subwoofer output on the Match Up 8BMW amplifier. It's a nice option for a real audiophile.

Some pictures- You can see how tiny this amp is:

The red is a 4 gauge quick disconnect for the power, ground, and remote.



The black rectangles are the prickly side of Velcro, so it stays put in cornering. Two reasons for using a larger passive radiator (12") than my active subwoofer driver (10"):
1) Passive radiator excursion is similar to subwoofer cone excursion: the lower in frequency it plays, the more excursion the driver must reach to produce the same amount of output. Same with the passive radiator - and it has its own resonance, which is the equivalent of a port's tuning frequency.
2) The more moving mass, the lower the resonant frequency. I want a low tune for this box, so I want a passive radiator with a lower resonance. This also means at low frequencies, it can really reach high excursion levels. This particular passive radiator has incredibly high excursion capability, and is large enough to have the very low tuning frequency I want for a SQ system.


This shot shows how unique and high excursion the passive radiator is. With it mounted 3/4" further away from the floor, both still have plenty of clearance.


This is just my personal solution for bass in a tiny space. There's all-in-one subwoofers that could fit under this space (search "underseat subwoofers"), but most of them don't have the low end extension or output that I wanted, to pick up from where my new Match Up 8BMWs leave off. This one really can get down, and won't reach its limit until well after the other drivers in the car.

 

Let me just say... Nice job! I used to be into aftermarket speakers and subs, but I find the HK system in my F60 Countryman to be good enough not to mess with. The only part I "might" like to change is the factory subs to get a little bit more output. I might get some Earthquake subs and call it a day. But, I like where you're going, and it looks like its going to sounds great!

 

Thanks I appreciate it.
I'll have some tuning coming up, and then I'm already 3D printing some adapters to fit some Dynaudio 4" domes that I have, and some 4"x6" magnetic planar panels - two of my favorite midranges, and primary reasons for not going the Bavsound route on this amp DSP.

For yours, there are several underfloor woofer options, and obviously I'm no Earthquake hater (that 12" PR is Earthquake) but the downside of the SWS 8's is their low efficiency.
If you are planning on doing an upgrade, don't accidentally do a downgrade!

The Match and the Bavsound woofer options are the most "known quantity" with more efficiency than the factory HK woofers, if you are using the factory amp to power them.
If you want to run a more powerful external amp to power the underseat subs, then the SWS 8's would be a feasible option, but you do need to feed them, and that install would be more complicated.
I do see other options, even a DLS that I didn't spot (I'm a big DLS fan and might have even given those a try - but I'm saying that without knowing the specs).

Or, you would end up doing the same as me and upgrading the amplifier. Even with my using a "3 series estate" base tune. I did get significantly better sound quality - I was somewhat surprised by that. For the Match amp, there are no preconfigured MINI tunes. Bavsound does, I believe, but that route removes the custom tune paths, plus higher cost.
Time has been tight, but I'm planning the tuning over Thanksgiving break.

But I personally wouldn't go down the path of the Earthquake subs with the factory power, It'll be a downgrade.
Ironically, although the two options that I mention are considered "higher end" upgrade options, it is worth keeping an eye on the sensitivity numbers. That is traditionally a bad spec to use for a means of comparison, as it's inconsistent and really not comparable, and changes when you have a woofer in an enclosure (technically these underfloor woofers are "free air", so that's a little better), but cheaper subs are often lighter due to having lighter voice coils, fewer windings, smaller voice coils, and less stiff suspensions - there's often an inverse relationship between powerhandling and efficiency, so that's something to keep in mind when you are specifically shopping for a woofer that you wish to use with LESS power. You don't want to inadvertently buy woofers that perform less well with less power, by buying ones that are more capable with more power, if that makes sense.
That applies to more than jjust the SWS woofers.

 

Thanks for the insight. I understand speaker efficiency plays a roll. I’d like to just drop in new subs, and call it a day. I don’t want to replace or supplement the factory HK amp. The Earthquake subs have gotten decent reviews, from what I’ve read, I also don’t want to spend a ton either….