Hello everyone, this is my first post. I recently got a Skoda Octavia 4 non facelift and besides some basic VCDS adaptations (still figuring out how to unlock SFD), my main focus is upgrading the audio system with a classic subwoofer in the trunk—I don’t have the Canton setup.

I’ve already found the speaker schematics and bought a high-low adapter with remote-on signal. What’s giving me trouble now are the power wires. Does anyone have a picture or some info on how to properly route a wire from the battery terminal to the trunk?

The part I’m most unsure about is getting through the engine firewall and knowing what needs to be removed or disassembled in that area.

Also, I found out that on the Octavia 3 there was a setting in unit 5F - Long Coding - Byte 12 - Activate Bit 2 (Sound System Internal Individual) to improve sound adjustment for non-Canton systems. Does anyone know if this option still exists on the Octavia 4 (non-facelift)?

P.S - I am using a high low as a full DSP can get so expensive while I want just a extra bass without changing the main speakers

I’ve started installing a classic subwoofer in my car and wanted to share how I routed the wiring:

Power cable (VCC): I ran it along the left-side plastic trim, under the rear bench. To get into the engine bay, you need to remove the plastic cover near the hood release handle. Behind it, there’s a rubber grommet in the firewall that becomes easy to spot once you peel back a bit of the foam. That’s the perfect spot to pass the cable through.

Ground (GND): In the trunk, on the left side, there’s a cover with an 8mm threaded bolt – a great grounding point.

I also had to remove the battery to pull the power cable upwards. The battery is held down by a bracket; once that’s off, you can slide the battery forward to release it from its lock.

To feed the wires more easily, I used a fish tape (the kind electricians use to pull wires through conduits). That saved me a lot of time and effort.

Helpful video : https://m.youtube.com/watch?si=anaXbne7mRiMxD2K&v=BD1Lb-lvHWo&feature=youtu.be

P.s

I have non-canton setup. can you share speaker schematics?

Forgot to post this earlier, but maybe it’ll help someone out.

for wiring the power cable:

I took a different approach and mounted the amplifier under the passenger seat, similar to the OEM setup. The signal sources are closer and easier to connect this way. I used a custom T-harness - check my comment here : https://www.briskoda.net/forums/topic/528741-quadlock-speakers-only-t-loom/#comment-5954679

Routed the amp remote into the side pocket.

The woofer is installed inside the spare wheel in a Basser 15L enclosure, paired with a 300W RMS woofer.

My approach was everything into the trunk cause I did not know how to bring the cables under the seat, and my subwoofer is also on the trunk since I don't have a woofer enclosure that fits in the spare wheel section

Splitted the wires and soldered them together under the dash

But overall very very happy with the outcome for me the total cost was

Wires : 15 Euros

Subwoofer and amplifier second hand : 50 Euros

It totally changed the sound of the system and I'm happy with it , could go for a custom fit subwoofer but that will raise the cost with about 500 euros