You are correct, the BD-32 is passive. You can see the dual Speakon connectors in the first picture Chris posted. Likewise, EQ was used to extend the response to what was observed. Indeed there is no free lunch here, but we do need to put this boost in proper perspective. First, above 30Hz, the nominal sensitivity is roughly equivalent to 106dB @ 1W/1m. This means that even where the sub is 14dB down, we are still at the same sensitivity as a ContraBass. The PE-17 only has 12-15dB of boost, yet we were still able to achieve the response shown in my measurement. The tightly sealed, double drywall construction of Jeff's room provides for significant low frequency gain as compared to anechoic conditions or outdoors. This is why we still see significant level at 10Hz. While I am not certain yet at what frequency we finally see all horn loading lost, below this frequency you still have the volume diplacement of 4 12" drivers which can survive 2" p-p travel (about 1" p-p linear). What makes this more significant is that where the horn loading is effective to ~30Hz, excursion is VERY low at any resonable playback level. Where most subwoofers have to work fairly hard so far as excursion to produce the 30-50Hz range, the horn makes this a very easy task for the driver. The strong acoustic loading and greatly reduced excursion makes for a system with less than 1% distortion to VERY high levels. We still have to take distortion measurements of the final product, but an earlier design which did not load as well was surprisingly low in distortion, and this one appears to be even better. Another unusual factor here is with respect to power handling and efficiency. Most subwoofers are around 1% efficient or less. The BD-32 is 25-50% efficient, which means that 1/4 to 1/2 of the power delivered by your amplifier turns into sound, not heat! As such, a driver in an efficient horn has 50-100% more power handling than what the individual drivers would be generally rated at.
What this all means is that for signals above 25-35Hz, the horn is loafing along, typically near 1W average drive levels to the pair of boxes. This makes dynamic peaks very effortless. 100W per sub (50W per driver) should yeild roughly 120dB peaks at the seats
in Jeff's fairly large room above 30Hz. This leaves the bulk of the power and excursion of the drivers available for the lower frequencies. Similarly, while the horn is rolling off, there is still loading present, still allowing much greater headroom than would be seen from a pair of sealed 12" drivers per box. We did bring with us an "arc-welding" pro amplifier we often use to insure we had enough power. This was a BGW GTA amplifier
, which we bridged into the pair of BD-32s. This translates to 3-4kW of burst power on tap, but in reality less as two 15-20A breakers are required for such power. We started using this amplifier on the subs, and after determining that things were working well, we swapped things over to Jeff's 4 channel Citation amplifiers. At the time we only had one connector for the subwoofer, so we had one sub to a bridged output on each amplifier. This should be >500W to each subwoofer. This is a bit of a difficult load for these amps when bridged, and the plan is to drive each subwoofer with one amplifier, where each driver will then have a ~400W bridged amp. I would expect this 1600W plus should be plenty for all but the craziest of ultra deep bass scenes.
So far as the MSRP, this is a rather interesting development as we didn't know the BD-32 would work SOOO well in a home theater setting. Basically, for large rooms, it would be hard to provide this much power and clean headroom without many multiples the number of boxes. Now that the product is finalized operationally, we are working out options for the Theater Calibrated version. The retail price is slated for $3450, with the Line-X coating as seen in the photos above, with options possibly varying the cost some. It should also be made clear that proper setup requires a flexible EQ and measurement capability. A 1/12th octave RTA or system of similar resolution is strongly recommended. This sub also requires enough delay/offset capability within your processor to account for the additional 7-12' of "virtual distance" wrapped up inside the box. IOW, in a typical pre-pro, you would measure the distance to the subwoofer, and then enter this number plus 7-12' depending on how you have it set up and where you are measuring from. Fortunately more and more custom installers are realizing the benefits and value of such capabilities.