This. Speakers work by making air vibrate so the air gets moved. If there's nothing behind the speaker to contain it, the sound will scatter al over the place. This is especially bad for low frequency sounds, so bass essentially. If you check the spec sheet of the speaker, it'll tell you what the volume of the box should be, usually in liters.

Create a small box for this speaker, and also pad it with some of that speaker cloth or mousse. It'll be a world of difference and make even the crappiest speakers sound acceptable.