One of the main downsides of the BMW E46 is its poor standard audio system that doesn’t really offer a proper audio experience. If you’re looking for a better and more powerful sound, here’s how you can install an aftermarket amp and subwoofer on a BMW E46 318i or 316i. You will benefit from a deeper bass frequency that enhances the overall audio experience offered by the vehicle.
How do I install a subwoofer and amp on a BMW E46?
We’ve chosen 318i and 318ci models since they have the battery placed inside the engine bay, somewhere in the front of the car. Since the vehicle is well soundproofed, you’ll need a subwoofer outputting at least 150W – 250-300 W RMS is recommended.
The amplifier must provide the same power in bridge mode and feature a high-level input for processing signal directly from your car’s speakers.
What you’ll need
- Dual channel car amplifier (featuring bridge mode, 2×75 W minimum output and 175-200W minimum bridge mode output) which has high-level inputs (so you won’t need an extra high-low adapter
- Car subwoofer outputting 150-200W RMS
- Power cables for the amplifier (10-12 mm in diameter) and speaker cables (1.5mm in diameter)
- Cable connectors
- Philips screwdriver, cutter, duct tape or thermo-contracting tubes, pliers.
The first step is to provide a power source for the amplifier that will be set in the trunk. You will need to route current through a cable from the plus pole of your battery to the rear of the car.
Remove the two cables connected to the battery and remove it from its compartment. Beneath the battery there’s a plate fixed by 3 screws that you will have to remove. Beneath the plate, a rubber cap covers a hole – that’s where your cable will go through. Make a hole in the middle of the rubber cap, large enough to let your power cable pass.
The next step is to remove the glove compartment. It’s connected to the car by 6 screws and can be easily removed by watching this tutorial. After the glove box is out of the way, partially remove the floor cover beneath the dashboard and you’ll see the rubber cap mentioned above.
Push the cable from the outside towards the inside then keep moving it towards the rear of your BMW. Fit the cable on the right side of the car, hiding it beneath the plastic covering of the floor. The cover gets out fairly easy – you just need to remove a few clips.
To reach the trunk with your power cable, you will have to remove the rear seats of your car. Lift the corner of the bigger seat and it will come out of its place. Do the same with the other seat so you have more space to work on. Follow the path of the OEM cables and you will reach another rubber cap.
Fit your cable through the cap along with the ones already there – it might take a little practice as the space is quite small. Once the cable reached the trunk, the power source is established. You’ll have to remove the trunk cover on the right side to be able to see the cable – position it in such way that it will reach your amplifier.
You’ll now need another cable to carry the negative charge towards the amplifier. The closest is this screw beneath the trunk carpet, but you may use any screw or metal component around the trunk.
The amp is now connected to a power source, so next it needs an audio signal to process. As mentioned above, a high-level input amp is recommended, allowing you to provide audio signal directly from the rear speakers of the car – the radio-cd unit doesn’t have a separate output for amps. If you amplifier doesn’t come with a high-level input, you’ll have to buy a separate adaptor.
The high-level amplifier automatically gets starting signal through speakers, removing the need of an extra cable for remote control.
The next step requires you to remove the rear speakers from the E46 trunk support. Remove the safety caps from the speakers, unscrew the 3 screws holding the speakers then take them out. Beneath the speakers, two cardboard enclosures will be found and must be removed. First of all, remove the left speaker – if you can see the cables for both speakers, you won’t need to remove the second one.
Now you can modify speaker cables to connect them to the amplifier. Connect the cables from the speakers’ holes towards the inside of the trunk.
Negative charge carrying cables are brown, and positive charge carrying cables are blue for one speaker and yellow for the other. You have to bind these cables with other wires that will carry audio signal to the amp. Using a cutter or pliers, remove the insulating material on a 1 cm area of each cable. Make sure you don’t sever the cables, just the cover. Using the speaker cable you have acquired beforehand, do the following:
- Connect the + and – poles on the left speaker while the other end of the cable goes into the rear-left+ and rear-left- of the amplifier high-level input.
- Using another piece of cable, connect the + and – poles of the right speaker to the rear-right+ and rear-right- poles on the amp’s high-level input.
Once you’re done, properly isolate the areas where the cables were uncovered, then start reattaching the speakers. The newly attached cables will go through the speaker holes and into the trunk, where the amplifier rests. Add the enclosures then the speakers, then the safety caps. For better aesthetics, try to hide the cables beneath the trunk cover.
We’re almost there.
So far, we’ve connected the E46 speakers to the high-level inputs of the amplifier and we’ve added a power source.
Now you need to connect the subwoofer to the amplifier – the + and – cable of the subwoofer will be connected to the bridge output of the amp. You might find them as dedicated subwoofer outputs marked on the amplifier.
The only thing left to do is to place the subwoofer wherever you feel best in the trunk, doing the same with the amp. You can attach the amp to the side of the subwoofer by using 4 screws.
You’re done; you are now benefiting from a deeper and more powerful sound on your BMW E46. Don’t forget to fine-tune your amplifier according to your preferences.