Did you turn off the ANC or ASE system? I have just added a JL Audio Sub with a JL Audio mono amp but it doesn't work too well. The treble seems like it blasting. Oddly enough when I roll the windows down it sounds great!
Not sure what sub you are running but sounds like you are pressurizing the interior of the car with that sub to its make ability. When you open the windows it allows the sub to move air more freely. Less back pressure.
If you want more volume while windows closed you would need more power to help overcome that back pressure.
And if you add more power may need a different sub.
Even with the stock sub you can hear and feel the difference when windows are down.
There is a balance to how much cone area and power you need to get the sound you want in the environment you are in.
I received the wiring harness from OWC yesterday, it's a thing of beauty. I was so excited to get things underway that I forgot to take a picture before wiring things up but I've got a few.
This harness makes the entire process feel like I'm cheating. After pulling the bose amp each connecter plugs right in. I've got RCAs for both the Kicker Key amp and the HS10 powered sub. The only line I had to run is main power, the kicker key amp and HS10 sub both pull signal and turn on automatically however the OWC adapter has provisioning for a remote out should you need it.
I plugged everything in and ran some but splicing on the speaker wires to ensure everything works properly. I'll redo this and pull excess wiring once I finalize on a layout.
In short, the OWC adapter allowed me to swap in a kicker amp, upgraded door & dash speakers and a powered sub all without running any speaker wire nor splicing a single factory connection.
Here is the majority of the wiring. The RCAs are for the Kicker Key 200.4 amp (front and rears for bi-amp mode dash and doors) along with the HS10 powered sub. The black & gray wires, once plugged in, are lines to all front speakers.
This is the heart of the install from a connectivity standpoint. Kicker AMP's speaker outs to factory speaker outs, RCAs coming in from head unit all via the OWC adapter. Only thing not seen here would be ground and power.
Ok got everything staged and tuned. I initially had the amp in bi-amp mode but tuned it in standard mode since I have inline crossovers on the dash speakers and the results are fantastic.
Tuning mic that comes with the kicker Key amp. It has a 10' wire that runs from the amp to wherever your head is going to be. Essentially it has a button that you press during a test tone phase that allows the amp to auto-tune all connected speakers. It takes about 3 minutes for the tuning phase to complete. It sets the stage and everything, pretty slick and accurate. This is done with the factory EQ zero'd out.
Not the cleanest install just yet but I wanted easy access to both the amp and sub while I get everything tuned. Before firing up the subs, the 6x9s alone shake all the mirrors and I've only got the kicker key amp up about halfway.