How to Install BMW F15 Trunk Subwoofer – A Step-by-Step Guide

The Alpha One Lightwave Amplifier can drastically wake up the audio in your car. But if you really want to get things bumping, an external BMW subwoofer is the next step you should take and our amp makes that task seem like a breeze! 

Not only is it the perfect upgrade for your BMW with Harman Kardon, Hi-Fi Professional, or Individual Audio, but it also has three times more power than any of the factory BMW amps. And far more customization than they could offer. Additionally, Lightwave allows you to connect a trunk BMW X5 subwoofer, which we’ll be doing in this guide!

Coming up, you’ll learn:

• How to prepare for the installation of your trunk BMW F15 subwoofer?
  
• What does the installation process itself look like?
  
• What to pay special attention to when installing your own trunk sub?

For a better visual overview of all the steps described in this guide, check out the video below. 

  

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

If you already have our Alpha One Lightwave Amplifier installed in your car, connecting a BMW subwoofer to it should be a piece of cake for you. Completing the process is going to require taking off a few interior trim panels – so let’s 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

The whole process may take up to around 90 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. Remove the five 8 mm hex head screws. 
3. With the screws set aside for later, lift up the bin and gain access to the battery.
4. Unscrew the negative terminal with a 10 mm deep socket, crescent wrench, or box end wrench. Lay the terminal on the side so you can reconnect it later.

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

Trunk BMW F15 Subwoofer Installation – Explained Step-by-Step

There are two ways you can hook up an external sub to our Lightwave amp. 

The first is just like for our other amps, where you use the DSP-controlled RCA-out to send a low-pass filter signal to your secondary amp or your active sub. All you need to do is add a fused power cable, a ground cable, an RCA cable, adjust the DSP profile, and you're done. 

The second method is the one we're going to focus on in this guide. It's also something you rarely see in the car audio world. The Lightwave amplifier has one speaker-level output that delivers 400W RMS and 800W max power at a 2-Ohm load. 

That's enough for the external BMW subwoofer we're going to be adding, but you do have to make a sacrifice, as you are going to be losing your center channel. With the amount of bang you get for your buck with such a setup, we think it's well worth it.

You can perform this installation yourself with your DIY Essentials kit and BimmerTech Trim Tool Kit or find one of our certified installers near you. If you're in the Orlando (FL) area, you can stop by and we will do it for you. Without further ado, let's get to the installation.

Chapter I – Wiring Preparation for the BMW X5 Subwoofer Install

Step one is to prepare the harness. 

1. First, start by cutting the red and black wires to the same length as the pre-stripped ones. CAUTION: do not cut the red and black wires that are in the harness!
2. Strip the ends of the insulation off, remove the insulation from the pre-stripped ones, fan the wires out, and twist both black wires together.
3. Lift open one of the included WAGO connectors, slide the wires in, and snap it down. This will secure the ends of the wires from touching anything else. 
4. Repeat for the red wires – fan them out, twist them together, and snap them into one side of another WAGO connector. To tidy up the installation and avoid any shorting, separate and tape the other ends of the black and red wires to the harness.
5. For the sake of keeping everything clean and safe, pull the end of the pink insulation off as well and place this wire into the last WAGO connector. Even though we won't use it later, it will help us keep everything secure.

Chapter II – Connecting the Lightwave Amp to a BMW Subwoofer

Now we have to plug the harness in as well as the leads from the sub to the amp. If you’d like to learn how to install our Alpha One Lightwave Amplifier in the F15, we’ve got a video specifically for that BMW model (see below).

We're not going to show you how to run the leads from the sub. The reason is that it depends on which one of the many available BMW subwoofers you get – things like its size or shape could all affect where you put it.

Getting on with the installation.

1. In order to keep tension off the connection and to keep everything clean, we used a cable tie to secure the sub leads to the power leads.
2. Take the negative from your sub and snap it into the other side of the WAGO connector with the black leads. Then, take the positive and do the same with the WAGO connector with the red leads. 
3. Finish up by pushing the main connector in place to connect it and sliding the slide in, pulling the two halves together. 
4. Take the other end of the connector and place it into the amp with the purple arm down, then rotate it up to pull and lock it into place. Once that is complete, use some cable ties to clean up the installation.

At this point, it's time to set the DSP to output a low-pass filter signal to your trunk sub. If you need some assistance with that, don’t hesitate to contact Mac, our audio guy. Anyway, the final step that remains is to place the cover back and… you're done!

Alpha One Lightwave Amp – Making Your BMW X5 Subwoofer Upgrade Worth It

There you have it! 

An upgrade that is simple, but at the same time yields amazing results. If you want to squeeze out even more of your Alpha One Lightwave Amplifier, hooking up an external BMW subwoofer will really make that low end come alive. Want to learn more about the Lightwave? Make sure to visit our website linked above.