I’ve had a good day. Got loads of chores done this morning (like arranging for an estate agent to come and look at the house), and then set about trying to improve the audio in the M5. It has a fairly standard audio setup, with components in the front doors and some additional speakers on the rear shelf, but ultimately while the system is clear, it is gutless. I’ve got some audio equipment lying around that I’ve used in a variety of cars in the past, so I thought I’d attempt to improve the sound quality at zero cost.

First step was to find some audio signal wires. I removed the CD changer and had a good rummage. Speaker wire pairs were easy enough to discover, so I spliced into those and extended my way into the boot. While I was there I also found a wire that hit 12v with the ignition in auxiliary or higher, and 0V when the ignition was off, so that would provide the amplifier’s remote power signal.

The next challenge was to get this signal into my old Goodmans amplifier. It is designed to take both speaker level and line level inputs, but sadly a custom connector is required for the speaker level input. A custom connector I don’t have.

I had a good rummage in my parts bin and found three BMW connector cables that were spares from my DVD player installation in the 330d. Remarkably these fitted the amplifier’s terminals perfectly, but of course I needed four, and could only find three. So I used a crimp connector on the fourth. No cost!

This done I could begin to put everything back together.

I then ran power from the battery, but forgot to photograph matters there. My bad! Finally, I screwed the sub enclosure to the floor and did a bit of cable tidying. It does of course require quite a bit more cable tidying, but those who know me know that’s not especially likely any time soon.

That photo makes it look as though the sub takes up loads of space in the boot – that really isn’t the case at all. It’s not meant to be pretty by the way. The sound though, is extremely good news.

Sure, the E39’s boot does contain the sound well so plenty of beans is required to get much penetration in the cabin, but this does have the benefit that the sound isn’t shared too much with pedestrians, and I’m pleased that the car doesn’t rattle with the kick drum.

By turning down the bass on the head unit and adding some boost on the amplifier in the boot I’ve been able to shape the sound nicely. Without any low frequencies heading their way the components in the front cope nicely at high volume, and the sub neatly rounds off the experience. Nothing stupid, just a well balanced sound.

I’m really, really pleased to be able to sample my favourite tracks while in the M5. I’ve just spent the last 90 minutes pottering around scanning through the CD changer testing the overall balance, and it’s great! I only stopped because I’ve got a meal to go to – Good Friday indeed!

This is the 6th BMW this sub and amp have been in – here are the predecessors:

That’s a pretty fast sub and amp!