It’s not really secret but known as soundbar+ and also you need to be member.
No official web-site and phone/email. But I can say it’s really near from Eleven. hint is red door on the way to eleven from Roppongi street.
Small club but put in nice function one sound system in it. For the nice thing, the place is usually open till very late. So after most of club ended , party people enjoy after party at here.
At that night"VIX" the tokyo local graffiti writer had his live painting session at this small club.
He will do live painting at Eleven on tomorrow(22nd Apr). You can see cutting-edge of tokyo street style painting.