I caved in.

After recently purchasing the Q990F, I knew that the sub was amazing yet lacked the raw power of a larger ported sub. This was by design by Samsung, as they attempted and successfully created a small sealed subwoofer that delivers on strong, clean bass. However, I knew that I wanted more, even before I pulled the trigger on the Q990F. As per my last post, it hasn’t even been 2 weeks since I set it up in my room.

Now, I have a Klipsch R12SW running in parallel. After extensive research on YouTube videos and Reddit user stories of their similar mods, I’m glad to say I finally got it working. I have yet to see someone set it up with the new F series subwoofer, as it raises challenges with the mod in terms of wiring and keeping the enclosure sealed. I opened up the inside of the Q990F and essentially added a new RCA jack into back of the sub, creating a jack point that goes straight into the R12SW.

My goal in the end was to create a semi-flush RCA jack to the back of the Q990F, and have all the wiring be done inside in a clean, rattle-less way. Now, in the future, I can plug in any line-level sub anywhere in my room (next to the Samsung) as long as there is two outlets for power. Will report in the future if anything goes wrong. I asked Grok and it said that the additional power draw from the Russound converter I chose should be negligible to the Samsung's amp, so I hope I should be fine. Not planning on pushing the system too far anyway, as it's become somewhat of an absolute monster.

Here's how I actually did the mod:

I started by removing the bottom plate of the sub to get inside. I then fully disconnected the PCB in order to have room to work

Next, I drilled a hole in the back panel near the power cord entry, sized exactly for the panel-mount RCA coupler I bought (\~22.5 mm). The tricky part was avoiding any dust getting inside the box and landing on the driver cones (they're only a couple inches away). Luckily with some wet paper towels on the inside and some slow drilling, no dust made it in.

Once the hole was clean, I crimped 2 T-taps on one of the red/black speaker wire pairs coming off the amp board to one driver (the two drivers are wired separately but paralleled at the board, so tapping one pair gets the full signal).

I ran a short piece of 16-gauge speaker wire from the T-tap to the high-level screw terminals on the Russound ADP-1.2 converter (matched + to +, - to -). Screwed the converter down to the bottom inside the enclosure so it stays put.

Then I connected a 1-ft RCA cable from the converter's output (used one channel) straight into the panel-mount RCA coupler I pushed through the hole from the outside. I sealed the coupler in place with hot glue around both sides for an airtight fit.

Reconnected everything to the PCB, buttoned the sub back up, and fired it up. Took a couple hours total once I had the sub open—mostly planning, drilling carefully, and troubleshooting levels/phase at the end.

Overall, seems like it was worth the money and hassle! Bye-Bye Warranty!

Samsung HWQ990F + Klipsch R12SW