The Pinout
This is the pinout for the DB-15 connector at the rear of the subwoofer, or at least the only ones I used for this hack (sorry, if you needed the others I didn't spend any more time looking).
The Story
I recently bought a Logitech z623 subwoofer for a 10th of the price from a local used goods store, but I either missed the control speaker or it wasn't there. I was already prepared to hack/fix the subwoofer, so it wasn't really a worry for me. However, when I got home I obviously noticed the lack of control speaker.
Looking online, hoping to find out if I was doing something wrong, or if it someone had hacked it to work withouth the control speaker, I was never able to find any information when searching online for others having done this hack. I only found various bits of information as to why it didn't work, or pinouts for the wrong model to the pins didn't work for me.
I managed to find the right pins to use from piecing together various models schematics that I could find together, along with a multimeter.
I never had to tear into the subwoofer, as it didn't look too easy to access.
I will probably end up tearing into a VGA cable to make a plug and go mod, or else I'll just open the box a bit and put in a power switch and maybe repurpose the left speaker jack for input.
In the meantime, it is just jumper pins to power on, and jumper pins soldered to a RCA connector.
Using the sub
Also, if you want to use this with a stero speaker setup (2.0) to make it a stero plus subwoofer setup (2.1), at least on windows, you will need to enable "bass management" or something like that.
My audio card didn't support 2.1 for some reason, and 5.1 with optional speakers disabled didn't work and I'm too lazy right now to fix it. I'll either get a crossover to filter out the higher frequencies, or fix it in software.
Right now, I'm just using a splitter on the audio out for my PC.