E60 Audio: Getting a Bass RCA (Audio) feed from the Stock-Subs.

If you want an aftermarket amp + subs in the boot then you need an RCA-feed and tapping into the rear speaker-wires does not work on the E60 and other iDrive BMWs as it does on the E39, E46 etc. All US E60s and others with factory-upgraded sound-systems have two subs under the front seats run by a stock-amp in the boot, on the left-hand suspension turret behind the panel. If you have this see this guide on //// to tap into the wires on the stock-amp.

Most non-US cars don't have a built-in amplifier in the boot, but they still have subwoofers under the front seats. These are driven by the head-unit and the EQ sends a different set of frequencies to each set of speakers. [See: http://musicarnw.com/bmw-factory-audio-explained/]. The rear speakers are only 4" so they don't get much low-end at all. To get proper bass it's worth going the extra mile and running cables all the way to the stock-subs, which get the real low-range frequencies.

** NB: This is to fit subwoofers on a bass-only channel. If you are fitting component speakers or 6x9s then you will need a broader range of frequencies and are better to tap the rear speaker-wires, covered in THIS POST, which is a lot easier. **

PROCESS:

Getting to the sub-wires is quite involved, but not difficult if you have the right tools. There is a + and - wire to each sub, so two new speaker-wires will need running either side. I used one length of twin-core 1.5mm wire on each sub, about 6 feet of wire is plenty.

1. Slide the seat all the way back and remove the plastic caps from the front of the runners.

2. Remove the two bolts from the front of the runners using a T50 Torx-head wrench.

3. Slide the seat all the way forward and remove the two bolts holding the rear of the runners using a T50 Torx-head wrench.

4. Lift the seat up. tilt it back out of the way and prop it up.

5. Remove the four crosshead screws from the plastic-grille above the sub and lift it off.

6. Move the carpet on the door-sill out of the way and cut the fabric-tape binding the wires going to the sub together so they can be pulled apart.

7. Splice your new speaker-wires into the wires going to the sub as pictured below. O/S - Red/Blue for [+] and White/Brown for [-]. N/S - Red/White [+] and Brown/Yellow [-]. [Soldering would be the best way, but I just went for the quick and easy Scotch-lock way again].

8. Run the new speaker-wires out from under the carpet and
along underneath the door-sill trim, up the side of the back seat and along the top of the back seat to the middle.

9. Lower the centre arm-rest and remove the plastic-trim panel from behind it by pulling out the two push-clips from the lower edge and working it off.

10. Thread the new speaker-wires down behind the back-seat at the centre. Be sure to thread the wires just behind the seat-back, but not down against the parcel-shelf, which ends at an annoying ledge. If you see the wire passing down behind the small round hole near the top of the seat-back behind the arm-rest then your on the right route.

11. Inside the boot the new speaker-wires should be seen poking down into the boot, or if it isn't you should be able to reach under the lip at the back of the boot and pull it down.

12. Install the four wires to your amplifier either directly by adding red/white RCA-type connectors to them, or via a crossover-box, which is the better method. Fitting a crossover is covered in THIS POST.

E21: Seat Fitment Guide:

Swapping seats round in a BMW E21 3-series is a nightmare, thanks to the floor-mounts being two different heights. To fit level-based seats from another car requires chopping out the welded floor-mounts and once this is done there is no going back.

1. Check if your floor-mounts have been chopped:

Check the outer floor-mounts on either side, spot-welded in place just inside the door-sill. They should look the one in the left photo below.

If they don't, and they look more like the right photo [with or without the wood], then you have chopped mounts and seats not originally from an E21. You also won't be going back to E21 seats very easily, so to preserve the style and make the ride a lot better, throw in seats from a newer BMW.

2.1 Fitting stock BMW seats from E30, E36 etc. :

This makes sense. E21 seats are sprung and uncomfortable and were dropped in almost every succeeding model. Other BMW seats are easier to come by and cheaper. E30 seats preserve the look almost identically and are far superior in construct. They also fit the inner seat mounts on the E21, the ones against the trans.-tunnel, so only the only outer ones need adapting. I am sure this is the case with seats from other 80s BMWs, possibly the E36 and E46 as I've seen it done, but need confirmation.
Modifying the outer floor-mounts, the ones against the door sills, is impossible as they just sit that much higher than the inner ones, the E21 of course having a crazy odd-height sub-frame design, so they need cutting out. Putting in new ones is pretty straight forward though, you can fabricate them with steel or alloy C-channel, wooden blocks, improvised stilts - these are all popular methods. Tilt-forward seats don't tend to be very strong anyway, so the new mounts don't have to be rock solid as long as they're bolted or welded securely to the floor-pan. Mine used the stock inner floor-mounts and a wooden block on the outer side to get the height - this presented no problem to the UK MOT (roadworthiness-test).

Check out my guide here: http://e21dub.blogspot.co.uk/2013/09/e30-sports-seats-fitted.html

Or check out HSVTurbo's guide HERE [where I got my idea] in THIS THREAD on bimmerforums.

2.2 Fitting rigid Racing bucket-seats:

If you're building a track car then it's obviously best to keep things as stiff and secure as possible. The neatest and most weight-saving method is to cut some steel cross-beams to fit and weld them across the floor-pan, from the trans.-tunnel to the door-sill. This could be done with or without removing the outer floor-mount, but you will probably have to do this to get the seat low enough. Two cross-beams under each seat would probably be best, but it is most often done with just reasonably thick one.

More info. HERE on bimmerforums.

2.3 Fitting non-BMW stock seats (VW, Ford Recaro etc.) :

To get the right height and a central-position with stock seats from non-BMWs there is a lot of modification to the mounts - these seats will always have the bolt-holes in the wrong place. The tidiest way would probably be to weld in rigid cross-beams like in the above guide [2.2], otherwise you will need to fabricate custom mounts. [I used a combination of wood-block and steel cross-beam to fit Ford RS Recaros to mine in THIS POST].

Check out my guide here: http://e21dub.blogspot.co.uk/2013/08/recaro-seat-base-adapter-finally-solved.html

3. Re-fitting stock E21 seats:

I have never seen anyone online do this. If you have level floor-mounts then I see no reason to switch back to E21 seats. All but the Recaros are uncomfortable, sprung nightmares. They give a truly bouncy and uncertain ride - only the most restoration mad would want it. The Recaros are super-rare and overpriced to fit the E21s mounts. E30 Recaros are a fraction of the price, have level mounts and are better anyway. If you are so desperate to restore your E21 dutifully, then I would consider it having cut floor-mounts a deal-breaker and to find one with stock seats, because the car will never be the same again.

There are 3 ways I see to achieve refitting stock seats:

1. Build custom outer mounts using a combination of the methods above, building them back up to the original and rather tall height for the stock seat-frames. [].

2. Locate a pair of original outer floor-mounts that have been cut out of another E21 and refit them to yours. These would first need to have been cut out carefully from the donor car and preserved by someone. Whether they would advertise them for sale is another matter, but asking on the forums can't hurt. Otherwise, you'll need to find someone with a scrap / breaking E21 and ask to neatly cut out its floor-mounts for a few quid. Either way, obtaining a useable pair is going to be tough.
Once you do though, they would just need to be measured up to where yours were cut off and welded into place. How neat a job you do will determine whether they fit or if it's unnoticeable.

3. Fabricate new outer mounts from the ground up out of steel and weld those in. I will endeavour to make a note of the dimensions of my cut one before passing it on and do a quick CAD design to fab-up a simple one.

**Also, I still have the passenger-side (N/S, Euro/US Driver-side) floor-mount [above], so if anyone wants it to try and weld back in message me! [Sadly, I cut the driver-side one out more severely and this is probably going to be the case if yours are chopped as it gives the wood or whatever more to grab on to.]

E39 Audio: On/Off Switch for the Amp/Subs

The system remote shuts off with the ignition [see: Getting a Remote Signal for the Amp], so I've no worry about getting a flat battery, but it would be nice to have a manual On/Off switch inside the cabin so I can mute the subs while driving if I need to, without having to cut out the rest of the speakers.

While I had the back seats out I ran a wire through the bulkhead into the o/s rear footwell [see: Adding an On/Off Switch], so I got hold of a beacon-switch from a tipper at work to fit inside the cabin. The plan was to run the wires out from the middle of the seat and under the carpet on the transmission-tunnel, then fit the switch inside the armrest-compartment. Neither of these panned out. Running the wires under the carpet is doable, but to lift the carpet [and the sponge backing] up enough involves completely removing the armrest console, as well as all the side trim and clips, so I've taken a shortcut for now and run the wires under the trim below the o/s door, then under the driver's seat and through a gap in the side of the console. The wires are exposed, but they're well hidden and I've made sure to keep them well away from the seat-runners.

As for the placement of the switch, which is over an inch deep with the wire terminals on, it turns out there's just no room for it inside the centre-console. The base of the armrest-console is a solid steel tray with an electronics-module right under it and the storage-tray below the armrest angles up to fit flush with it too. I don't want to go further forward on the dash and mess up the wood so I've fitted it in the storage-slot under the rear air-vents. The plastic slot was missing anyway and the vents were hanging loose, so at least it looks complete now even if it's a pain to reach. Not a problem for people in the back though and that might not be such a bad thing if one is screaming we've missed our turn-off and we can't hear over the drum and bass. I just used a piece of thin plywood for the panel, covered in the leftover vinyl wrap from my ScoobyLab stickers. It's a bit shiny, but the vinyl gives it more of a trim look than black paint.

E39: Amp Swap

With the RCA-feed splitting off the rear-speakers there's no separate controls for the amp on the head-unit. I can turn the Bass up and down in the Tone settings, but its making the rest of the speakers tinny and not lowering the subs enough, so they're just overpowering the sound. They're getting the entire frequency band too, most head-unit sub controls have a lo-pass filter as standard, so I'm getting a lot of unfamiliar hums and wobbles.

My awesome Alpine V12, which matches my Alpine R subs, is a straight mono-block amp and has no controls for volume and filtering either, so I've been forced to make the decision to devolve back to my old, less good Toxic Audio amp. It's not a pretty amp, but it still kicks out 1000w like the Alpine and it has a host more features - 2, 3 or 4 channels with separate volume knobs for each and tunable lo-pass + hi-pass filters. The answer to all my prayers, or so I thought. You can tell the drive of the sound is of a lower quality straight away and it doesn't feel as thumping as the Alpine even turned up loud. The lo-pass filter is also crap and cuts off everything above the low-end rumble, so I've switched it off anyway.

At least the volume of the subs is better matched to the rest of the system now so the speakers are sounding natural again. We'll give it a week while I mess with the settings, but I can't help thinking the Alpine just sounds better. A solution is at hand though - I've found separate sub-crossover units on eBay for less than £10 that have vol. for each channel and great looking filters. It's something else to draw power, but it seems this is the only way left to get this system sounding as good as it could.

E39: Fitted Subs/Amp and kept BMW Head-Unit...

* The Full How-To Guide is on this page: Audio: Wiring Amp/Subs into Standard Head-Unit

The standard BMW Business stereo is a masterpiece and takes up half the dash, but sadly it lacks the RCA-output and remote-signal that are essential when fitting an amp. A fascia-converter is about £10 and a wiring-adaptor about £7, so it's not expensive to throw in any after-market head-unit, but if I do that then I lose my CD-changer, tape-deck and the excellent steering-wheel remote. The cheapest remote-adaptor for Pioneer I can find is £85! and there's no way of knowing if it'll fit my dinosaur model. Worst of all the new fascia would ruin the teutonic look of the dash.

I started checking the forums and found a few people who managed to splice an RCA-cable from the rear-speaker wires, so I thought I'd give it a go. It turned out to be one hell of an involved process. The back seats / parcel shelf have to come out, the speaker-wiring is perplexing and I eventually found a way to get a remote 'on' signal for the amp from a parking-sensor relay. The remote-input on the amp will take any signal up to 12v, so you could just wire it from the battery and have a manual off switch, but at least the fiddlier way means it goes off with the ignition - no flat batteries in the morning. The battery is in the boot too, so there's no need to touch anything up front or run cables under carpets.

The system works brilliantly, there's a LOT of bass there, which I'm quite surprised about with the RCA audio-signal coming off from the rear-speakers, but they are still working fine too. As you can see above, I've also set the subs facing inwards this time so I can make use of the magnificent boot - I'm sure the bass is being stifled a bit this way, the back seats are vibrating like crazy, but it's plenty loud enough either way. The only downside is no separate controls for the subs, so they pump out at the master volume, can't be turned off and receive a completely un-filtered audio-signal - there's some nasty higher frequencies creeping in. My 1000w Alpine V12 amp is a solid mono-block and has no controls either, which is a disaster really because it's the matching unit to my 12" Alpine R subs, but it'll have to make way for a lesser 1k watt Toxic Audio one soon that came with my old Subaru. It's not a pretty amp, but it's got a volume-knob, lo-pass filter to single out the bass and 2 channels, so I can give each sub its own terminal instead of twisting the two wires together. Everything I need basically, but I'll miss that blue-glow screen...

This is where I'd normally put the 'How-To Guide', but the process is too intricate to throw on the wall, so I've given it a page of its own, split into five sections, linked below:

Audio: Wiring Amp/Subs into Standard Head-Unit

Wiring Power / Ground to the Amp
Removing the Rear Seat / Parcel Shelf
Wiring RCA from Rear-Speakers
Getting a Remote Signal for the Amp
Adding an On/Off Switch