Startup Acemile has crafted what it considers the world’s first commercially-available 360-degree surround sound wireless speaker with its Theatre Box, a unit small enough to carry around almost anywhere, yet with fidelity that can fill a room with ease. With speakers firing in four different directions, music and movie tracks are supposed to surround you. Can it replace a full-on home theater system? Of course not. But we’ve heard two-channel sound bars twice the size that didn’t sound as good, yet cost as much — that says a lot for this little speaker. But what about its merits as a portable speaker?