The front doors can be tapped from the rear inside the pop out section with the mesh net on it. The connections will be wrapped in foam and will have capacitors connected. The capacitors are in series with the front doors speakers. Ie cut bass to them. This series combination is in parallel with the subs. Messy eh! The result is that at low frequency only the subs are in circuit and then present 4 ohms to the head but at high frequency the capacitors are low impedance and thus the front doors are directly in parallel with the subs and thus present 2 ohm to the head unit. I think a cheap way to cut power output from the head nti at low frequency. Not sure what happens to the rear door speakers btw. The gory details can be seen here:
Select your car and happy viewing.
The subs I had to run cables to and from. Not too hard. Pull out the rear seat and you can thread cables from the sub location under the door sills and to the empty section in the rear. wiring to the front speakers is easy then as just have to disconnect the capacitors in the rear and connect to the speakers making sure you drive the speakers and not the head unit lol. A 9volt battery can be used to test by listening or a ohm meter. Btw those connectors that connect the capacitors are a pain. Use a sharp pointed implement to insert in the connector and then gently prise apart.
VW Touareg V6 TDI 4Motion with a smooth as AISIN 8 speed auto gearbox that WORKS!
X3 3.0d 2006 (MY07) sold