Wiring In Aftermarket Amp/subwoofer - Mk4 Ls400 (Some Pics/guide)

[Yoda400]

Hi chaps

Thought i'd do a little thread on wiring up a proper sub in my LS400. This is the first installment!

I was thinking to replace the stock sub with something beefier in the same location, but i've decided to go for a small ported sub in the boot instead (will hit much lower), which i'll then just disconnect and pull out if the whole of the boot space is ever needed. If i'm not happy then at least the hard bit of routing a power cable is done and I can try something else!

I'll just disconnect the factory driver and remove it so the sound can come through into the cabin.

I found one of these for £40 secondhand (JL Audio 12" Basswedge enclosure):

http://cdn.idealo.com/folder/Product/2803/3/2803372/s1_produktbild_mid/jl-audio-cp112-w0v2.jpg

Had some 4 guage power + earth cable, fuse etc from a previous install, and a Vibe Slick A7 amp (300w - so should be well matched to the JL 12").

I've started feeding the power cable from the engine bay to the rear, I think this one of the trickiest bits of the install - finding somewhere to route the cable through the bulkhead...

Looking in the engine bay I couldn't see any nice convenient grommets to feed a cable through and my research indicated it is very difficult to drill through the bulkhead. I spotted a pre-existing hole between the windscreen and arch/strut on the nearside (passenger side) which goes behind the wheel arch liner.

So, I took the wheel and the mudguard off, plus undid the wheel arch liner screws so I could peel it back hoping there might be some magic rubber grommets behind it that lead into the car. No such luck! There were a couple of grommets nearby, but it was box section behind them and I wasn't sure where it would come out in the car if I did drill through. There was also a hole there with no grommet (presume a drain hole), but nothing above it.

I then pulled down the carpet in the passenger footwell and lifted up the thick rubber matting/sound deadening. This revealed a hole that had metal behind it, but shining a torch through the drain hole under the car, I could see a bit of light come through into this hole! Bingo I thought! Alas I just could not feed any cable through, tried for ages but the angles were all wrong, the holes were too far apart! Decided in the end to drill through it as I knew it would end up behind the wheel arch liner and it really couldn't have been in a better place :)

I cleaned up the area around the hole, fed the cable through into the cabin and then sealed around the cable with some Stixall (very strong durable silicone/polyurethane sealant). Put back the arch liner, the wheel and then to concentrate inside the cabin! The cable is nice and protected as it is well behind the liner and it won't get wet either.

The cable has come through in a perfect place really, I routed it under the carpet and sills to the rear. The sills literally just pop off and back into place. Had to have a couple of attempts as my power cable is quite thick. I also popped off the B pillar trim slightly so I could wiggle the cable through to the rear sill, this was quite tricky as there isn't a lot of space behind there.

Have attached some pics which will hopefully help some of you out there who are planning to do the same, getting the power cable through is obviously one of the hardest bits, and this is a neat solution as it is quite a direct path.

This is as far as i've got so far, will update with a second installment soon hopefully when I find a home for the amp etc! Have to figure out where to pull a remote feed to turn on the amp as well. Anyone know where is best? ( I read somewhere it is a grey/white cable on the stock amp - wherever that is?!)

Hope this helps people route the power cable anyway as I struggled to find any proper guide for UK cars!

[ambermarine]

Hi MR

With regard to the amp it was on the earlier model Ls a seperate unit located on the petrol tank bulkhead located behind the boot liner.

I think on the Mark 4 it is an integral part of the Audio unit located in the dashboard and removal of the whole module is nessacary to get at the wiring plugs.

If I am correct in my theory the removal of the Nav/audio station is fairly straightforward and there is archive in the forum on how to remove this unit ,it is the same as removing the earlier audio Modules that didn'nt have a screen.

[Yoda400]

Thanks for the info ambermarine, thats a bit of a pain, ah well!

[Mybikes a cx500]

On my 1998 mk4 the power amp is under the drivers seat

[Yoda400]

On my 1998 mk4 the power amp is under the drivers seat

After some research I think all mk4's have the amp there, is it accessible without removing the seat? If you have to remove the seat, what is the process? One bolt on each corner of the seat rails?

[ambermarine]

Hi Mr

Good job we have this forum and its different views sorry for the misinfo must have got my wires crossed so to speak.

With regard to seat removal which I doubt there are as you say four bolts to the floor with carpeted plastic caps that need firm removal.

[Mybikes a cx500]

Yes, bolts at each corner, the back ones have plastic covers that take a bit of shifting. Running the seat back and forwards makes them easily accessible. My Parrot phone kit was tapped into the speakers at the wiring loom here. A request for the wiring diagram and pinouts will maybe get a result from some obliging knowledgeable soul on here.

[Yoda400]

Brill thanks for the info chaps :)