Hey all, I have 2017 Equinox 2.4 LT with base 6 speaker system and have been wanting to add bass for a while. Reading here and elsewhere, learned that the factory sub is there just to provide low frequency ANC, and that swapping for the upgrade Pioneer amp doesn't work and is impossible to wire in (as I gather). So here's my successful hack to add bass to the factory sub, and keep ANC working.
The pic shows the harnesses and connectors that go to the factory amp pulled and being probed and attached to. What I learned looking at the sub, is that it has a dual voice coil. I stole one of the coils for bass, and left the other connected to the factory amp for ANC signal. From the green connector which has 4 wires going to the sub, I cut green and blue off the end, that is one voice coil. I confirmed this by feeding an audio signal into the wires and hearing it out of the sub.
Second, I got power, ground, and turn on signals from the *********** connector, red, black, and white. Last, I got one end of a front speaker with a signal containing full range audio and fed it to one input of an old Bazooka 6 inch unit. This is brown and on the other end of the green connector. Their wiring instructions say just connect one end to the high level input wire and don't worry about the other one. It must be referenced to ground somewhere. I assume the bazooka input is high impedance and a few volts amplitude. I set the bazooka to auto turn on sensing a signal originally, but that feature didn't function in my old unit so activate it via the white wire instead. I think auto turn on would be preferable.
So connecting power and the high level signal, the bazooka came to life and gave great bass, at low volumes which is my goal. I set the crossover and level controls, then removed the amp assembly from the bazooka, discarding the speaker and tube. The amp output is a pair of spade lugs on the board, those wires now go to the blue and green car factory sub voice coil I liberated. Voila, success. I hear good bass coming from the sub in the hatch area. I swapped the speaker spade lugs back and forth, listening for good bass, one way is out of phase with other car speakers and will sound weaker.
Last, tidying up the wiring, I slid the bazooka amp assembly into a cardboard box and just sat it in the space above the knee guard under the steering. I don't plan to crank the volume up a lot, although honestly it sounds pretty good turned up, it's not pro audio but it does add the missing bottom end I needed for regular listening. And I'm no longer grumbling to myself each time I open the hatch and see a sub that didn't actually make any bass! Driving before/after with the radio off, I can't tell any difference in engine noise.