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.

E60 Audio: RCA Feed from Rear Speakers - quick n dirty guide.

**Caution: This guide is for fitting extra component/coaxial speakers and is NOT suitable for fitting subs as the rear-speakers receive no low-end frequencies. If you are fitting subs then see THIS GUIDE on getting bass-RCA from the stock-subs.

This guide covers a very quick and easy way to get an RCA-feed into the boot on your BMW E60 and other iDrive models. This method is only suitable if you are fitting extra component or coaxial speakers [inc. 6x9s etc.] where the range of frequencies handled by the rear speaker-EQ are required.

PROCESS:

** If you are fitting extra component/coaxial speakers then adding a crossover-box to the RCA-feed before the amp should not be necessary. If you intend to use a crossover, substitute the 4 wires of the Red/White RCA-cable in this guide for 4 lengths of normal wire and see THIS GUIDE on how to install it.

1. Take a normal Red/White stereo RCA-cable, cut both plugs off from one end and separate the two wires down most of its length. An RCA-cable of about 4 feet should be plenty to reach up to both rear-speakers.

2. Carefully unwind the earth-wire from around each coated-wire and twist them off, so each of the coaxial RCA-wires is now split into two, as shown.

3. Bend each of the four wires over about 5mm from the end and completely sheathe the two bare earth-wires up to here, so they are well separated from the red/white live wires, as shown.

4. Gently prise off each rear-speaker grille using a flathead screwdriver, starting at the front edge.

5. Remove the 3 screws holding each rear-speaker using a T20 Torx-head wrench/driver, then lift out and unplug both speakers.

6. From inside the boot, light can be seen coming in through the empty speaker-recesses. Route one cut end of the RCA-cable up into each speaker-recess. They should easily be reached now from the parcel-shelf.

7. Splice the coated live-wire of the RCA-cable to the + speaker-wire on each side and the bare earth-wire to the - speaker-wires. The colours are as follows:

O/S - Yellow/Black +, Yellow/Brown -.
N/S - Black/Red +, Black/Purple -.

8. Push the wires down into the parcel-shelf and replace the speakers/grilles.

Done in 5 minutes!

Another subs/amp issue - not enough low-end getting through.

The plot thickens with my aftermarket subs and amp install. Following the addition of a crossover between the rear-speakers and amp RCA-input I'm definitely getting cleaner bass, but the really low-end frequencies don't seem to be present at all. I doubt the crossover can't handle the frequencies and I know the amp can, so this leads to me think the frequencies are being cut out before getting to the rear-speakers.

One US forum says low-end frequencies are cut from all but the stock amp in the boot and subs under the front-seats. Today I got 2 screws out of the plastic-grille under the passenger seat and bent it back to see a flat type subwoofer under it with the magnet facing upwards. Still, there is no stock amp present at either side of my boot. To get a definitive answer I started a thread on BMW-Land - http://www.bmwland.co.uk/forums/viewtopic.php?f=5&t=159000.

Turns out all E60s do have the stock subs under the front-seats, but if you don't have the amp they are controlled from the head-unit as well. Patching into the wiring to these could be the solution to getting the proper bass I'm after, but it will involve undoing the rear speaker splice and running the wires through to under the front-seat, so will have to wait for the time being.

http://musicarnw.com/bmw-factory-audio-explained/ - yep, seems to be the case, rear-speakers are EQ'd to high and mid frequencies only.

http://forums.5series.net/diy-do-yourself-14/add-subwoofer-e60-models-without-amp-trunk-121323/ - here is a good guide on how to tap into the sub-woofer wires, but it involved removing the front seats.