The picture shows a stereo setup, but illustrates the principles for mono. The signal flow is from left to right.
Recommended cable
Use a 1/4 inch (6.3 mm) Tip-Ring-Sleeve cable for best results.
You can use and 1/4 inch (6.3 mm) Tip-Ring-Sleeve to XLR cable, but you will have to turn down the volume on the S1 Pro System to avoid clipping the input.
If you use the S1 Pro system as the sound source (e.g., microphone and guitar and backing tracks via Bluetooth)
The S1 Pro system will sound the same as without the subwoofer (62 Hz - 17 kHz)
The Sub1 or Sub2 will cover from 40 Hz (Sub1) 37 Hz (Sub2) to 150 Hz