I consider a 21 x 21 foot room to be moderate size for a full-ranged speaker. The Altair is almost 3 feet deep. I would think both the speaker and the listener should be well into the room, with enough space for integration. I am thinking you would need 15-20 feet distance between you and the speaker. With the side-firing woofer, the room becomes an absolutely integral part of the speaker. IMO, more than a front-mounted woofer.