I just got my SMAS for my Pimax 8K+. When the speaker cable jacks are plugged in all the way, the sound is very very quiet, even when maxed out in Windows (the speaker settings in the Sound Control Panel were already maxed out o 100 before I started). If I pul the cable jacks out a little bit, the volume gets a lot better, but still needs the Windows volume at 100% to be almost normal volume. And the same sound is coming out of both ears, regardless of being plugged in all the way or not.
With normal headphones plugged into the left headphone jack, volume is perfect.