After weeks of experimenting, measuring, and tuning with the HouseCurve measurement tool, I finally found a process that reveals the full potential of the Q990C.
Many people think firmware 1010.5 reduced bass, but it actually improved accuracy. The bass is now tighter and cleaner once calibrated properly. Here is how to do it:
Step 1 – Subwoofer Placement
Before any calibration, correct sub placement is critical. Even a small 20–30 cm movement can completely change your bass response.
Play a 20 Hz to 200 Hz sweep.
Sit in your main listening position.
Move the subwoofer slowly around the front of the room until the bass sounds smooth (no boom or hollow areas).
Keep it about 20–30 cm from the wall, with the port facing outward.
Step 2 – Level Matching
Use pink noise to match channel levels evenly. My final balanced levels in the SmartThings app:
Turn ON Bass Enhancement (keep it ON during the entire process).
Set sound mode to Surround.
Turn ON SpaceFit Pro.
Play pink noise through LFE and let it run for 30 seconds each at these volumes: 23, 18, 15, 11, 8, 5, 3
After finishing, turn SpaceFit Pro OFF but leave Bass Enhancement ON.
This multi-level process lets the DSP learn your room’s real bass behavior at different loudness levels. It naturally flattens the response without overcompensation.
Step 4 – Final Sound Settings
Bass: 5 Treble: 1 Subwoofer: 1 SpaceFit Pro: Off Bass Enhancement: On Firmware: 1010.5
Step 5 – Results (Measured in HouseCurve)
Extension down to around 30 Hz
Smooth transition from 40 to 150 Hz
Clean midrange and natural vocals
Tight LFE without boominess
Movies, music, and games now sound clear, balanced, and immersive — very close to a calibrated AVR setup.
Final Tip
After running the calibration, keep SpaceFit Pro OFF for regular listening. Leaving it ON permanently can cause the DSP to keep adjusting and slightly shift the tonal balance.
