Yamaha STJ Personal Studio

The original shape was oval and the mic was very audible, but the last two I have bought I thought would be greatly improved, but the sound quality is a little on the weak side, also what ever happened to the multi user mixer so four or more could practice together? would it be possible to connect using blue tooth instead of cables that get in the way?

The device really does the trick and allows me to play unbeknownst to my neighbours (I live in a community building, similar to university dorm, with very thin walls between rooms) and I can listen to myself playing in a convincing manner. It helped me a lot to train when I couldn't before.