BMW G01 External Subwoofer Step-by-Step Installation Guide

The Alpha One audio system is great, but pairing an external BMW X3 subwoofer with the Alpha One Amplifier will elevate it even further. In our BMW X3 (G01), we've already installed our Alpha One Speakers and Amp. This time, we’re going to be focusing on how to connect an external BMW G01 subwoofer to our amplifier.

Coming up, you’ll learn:

• Why is it so easy to install BMW X3 subwoofers with our Alpha One Amplifier?
  
• How to prepare for the installation of your own external BMW subwoofer?
  
• What does the installation process look like for the trunk sub?

Want to get a better look at all the steps described below? Then watch this video. 

Let’s Prepare! The Tools You Will Need & Safety Tips

With our Alpha One Amplifier already in your car, installing a BMW subwoofer is super easy! To transform the sound of your car, all you have to do is take off a few interior trim panels. Enough talk – it’s time to get started. 

Here are the tools you will need for the job:

• BimmerTech Trim Tool Kit
• Torx screwdrivers (T20, T15, T50)
• Phillips head screwdriver
• Zip ties
• Electrical tape
• Double-sided mounting tape
• Heat gun

The whole process may take up to around 120 minutes, but it's not difficult with the right tools. Just to be safe, we also strongly recommend disconnecting the car battery. How to do that? Simply follow the instructions below:

1. Lift up the floor panel in your trunk.
2. Rotate the two locking tabs 90 degrees to access the battery compartment. 
3. With a 10 mm socket, remove the negative battery terminal and set it aside. 
4. While you're here, pop open the side terminal cover for later.

PRO TIP: wrap a towel around the latch to prevent it from locking you out if it closes.

Onto the installation part…

Step-by-Step External BMW G01 Subwoofer Installation Tutorial

So, how do you connect a trunk BMW subwoofer to the Alpha One Amp? Your trunk sub will be either passive or active. This means that it can either have a built-in amplifier or require a separate one. In both cases, the wiring needed is similar. You’ll need to source:

• Ground wire.
• Fused power wire to supply the trunk BMW subwoofer’s amp with power.
• A set of RCA cables to connect the low-frequency output from the Alpha One Amplifier to the secondary amp.

Note: there are many online calculators that can help you determine the gauge of wire needed based on the length and power consumption of your trunk sub amp. 

Additionally, you might also need a remote-out wire to ensure your trunk sub amp only powers on when the vehicle is in use to avoid draining the battery. It’s worth noting though that many amplifiers for trunk subs have input signal sensing, so this wire won’t always be required. 

Not certain if yours has the signal sensing? Consult the user guide of your external BMW subwoofer to make sure. If you have a passive trunk sub with a separate amplifier, you’ll need speaker wires to connect them.

Finally, remember that to start the installation, you'll need to have our Alpha One Amp installed in your car. For detailed instructions on BMW G01 amplifier installation, check out our video guide linked below.

That’s all the prep work. Now, how to go about actually mounting the trunk sub? 

Chapter I – Trim Removal for BMW G01 Subwoofer Installation

Let's begin by making ourselves some room to work. 

1. Start by opening the hatch and lowering the rear seats to access the screws holding the core panel in place. Lift the hinged covers and remove the two T40 screws, one on each side. Once they are removed, lift the floor panel up and take it out of the trunk. 
2. To gain access to the battery, use the BimmerTech trim tool to rotate the two locking tabs 90 degrees, then pop up and remove the two fasteners in the middle. This will allow you to lift the tray up and out, just like the floor panel.
3. Next, remove all the side paneling to give yourself space for running the custom harness. Start with the amp access panel – use a trim tool to remove the plastic cover on the upper portion of the panel, then remove the fastener underneath. 
4. For the final bit of access, first remove the seat bolster by pulling it and then take out the side panel. 

PRO TIP: if the tab pops off and remains in the vehicle, pinch it to remove it. After that, snap it back into the bolster for reassembly later. 

Chapter II – Wiring and Trim Reassembly for the BMW G01 Trunk Subwoofer

With all of that weight reduction work behind us (just kidding!), let’s get on with the most important part of the BMW subwoofer installation, the wiring. Note: when running the harness, keep in mind that if you're not installing the same sub we did, your steps can vary. 

1. First, plug the RCA cable into the line-out on the amp. Next, connect the Alpha One rem and out connector to the rem and out slot. CAUTION: if you have any extra slack, you can tidy it up, although you may need to wait until after the sub is in its final place to know just how much of the cable you should secure.
2. When feeding the harness to where the sub will go, you can make use of the existing path. Simply pop open the retaining covers and snap them back down once you’ve fed the cable through. 
3. To feed the harness under the seat hinges, tape it to a large cable tie and just feed it through below the backrest. Make sure that you still have access to your ground cable, since now is a good moment to ground it. We’ve decided to place it behind a 10 mm nut near the left seat belt retractor. 
4. To pull power, loosen a 10 mm nut, place the fork of the positive lead under it, and tighten it down. Tidy up the wiring by securing the positive cable to the vehicle and reconnect the negative battery terminal. 
5. Lastly, reinstall all trim pieces you removed earlier. Put the side cover in its place and reinstall the two fasteners as well as the plastic cover, then replace the amp access panel and reinstall the seat bolster. Insert the storage tray back in and reinstall the fasteners, rotating the locking tabs 90 degrees. Finally, reinstall the two T40 screws.

Chapter III – BMW Subwoofer Placement in the Trunk

Now for the fun part. 

1. Place the sub in the area where you want it, ensuring you can secure it and that it will clear the seats. 
2. There are many ways to secure the trunk BMW subwoofers to your vehicle, but since this is one of our research and development vehicles and we plan to remove it frequently, we used velcro strips on the bottom. 
3. Insert your ground and remote turn-on. Next, connect the line in RCA cables, put the seat back, and… you're done!

Is the BMW X3 Subwoofer Upgrade Worth It with Alpha One Amp?

While we can make your underseat woofers sound much better than the factory setup with our amp, they won’t generate the window-shattering bass like a trunk BMW subwoofer. That being said, if you aren’t sure if you can commit to such an expensive upgrade, getting just the Alpha One Amplifier will definitely quench your Hi-Fi thirst.

And if you already decided on getting the BMW subwoofer, our amps come with a dedicated RCA-out and a remote-out. This makes it easy to connect the trunk sub and DSP tune it so that it syncs perfectly with the cabin speakers. You’ll no longer have to worry about it sounding half a beat late! 

With DSP, we can set up the low pass filter, time alignment, and even EQ the trunk sub individually. If you have our amplifier and need some help, feel free to email us, as your pre-loaded tune might not have the line out active.