I recently completed a pair of custom Planetarium Alphas in Walnut. The "custom" version of the Planetarium Alphas includes a built-in downfiring low-Q sealed box subwoofer, for situations where there simply isn't sufficient real estate available for a full-blown Swarm. If the space later becomes available, a pair of Swarm subwoofer modules can be added.
In this shot you can see that the enclosure is actually six-sided, with some of the angles 90 degrees and some of them 45 degrees. This makes it pretty easy to set the speakers up with 45 degrees of toe-in by eyeball.
The woofer is a new model that just came out about a year ago. It's about 1.3 dB more efficient than the original Alpha's woofer and has over twice the linear excursion of the original. The high frequency section has been adjusted accordingly.
Here's another shot:
The circular cut-out you see in the base is how the down-firing subwoofer is mounted and removed (if need be). The two subwoofers (one in each speaker) are driven by a single shelf-mounted amplifier that delivers about 500 watts total into the two of them, which are wired in series to present an 8-ohm load. If a second set of external subs are added, the wiring can be switched to series-parallel and the amp will then put out roughly a kilowatt into the resulting 4-ohm load.
Here's the thread on the original Custom Planetarium Alpha system, in black-stained oak, in case you're interested. There is a nominal upcharge for the walnut.
