I'm not sure about tech specs since I'm not a music fan, but he wrote it was SO powerful that he had to overload the floor with 750 kg of marble to avoid it from raising...
However, reading first lines, he writes:
The world's greatest double horn subwoofer; the highest efficiency ever obtained without using counterreaction and diffusers without crossover.
Audio room size is 6.95 x 8.70 meters.
Subwoofer horns are under the floor and a depth 1m each, so every horn is driven by 8 x 47cm woofers, for a total of 16 woofers.
Total amount is 110 dB/W/m and each woofer can handle 400W so you can deal with 6400 watt overall. All techniques used made possible getting a final out pure and corrected frequency of 10-11Hz.