MBM-12 Mid-bass Module
The MBM-12 introduces our new patent pending concept of splitting up the bass frequencies. In most moderately sized rooms, mid-bass is best reproduced near the listener, while deep bass is best reproduced in a far corner. The mid bass module allows one to do optimally position the low frequencies nearby, for maximum impact.
The high direct to reflected sound ratio helps reduce room effects, gives excellent headroom (high SPL with low power since you are right next to the woofer), and low distortion. Low bass, on the other hand, is most efficiently reproduced when placed in a front corner (see figure below).
Just like the VTF concept, a woofer optimized for low bass reproduction is not the best for mid to upper bass reproduction. A heavy cone is best for low bass, but that reduces the mid to upper bass efficiency. The MBM-12 woofer is optimized for mid to upper bass reproduction - a very light cone, low inductance voice coil, and a strong magnet yields extremely quick response with high efficiency. It demonstrates excellent micro-dynamics and an extremely wide dynamic range that no single subwoofer can provide.
Industry Reviews"While this combination is relatively new to my reference system, it has been transformative. The combination of isolating and carefully presenting mid-bass frequencies (50-150Hz) through the mid-bass modules, and the superb performance of the VTF-3-Mark III true sub, has re-drawn my system in much larger and more substantial frame. The user ability to tailor these frequencies for room and source material adds a new dimension to the enjoyment of music, most especially that which may have come in a bit thin and threadbare. I don't care what the cognoscenti say about subs and audio, the slightly dry nature of the Hsu units, coupled with their flexibility and musicality add more to the experience of listening to music than you can possibly imagine without hearing them for yourself. At under $2000 for the complete system (two mid-bass modules and a true sub, with turbocharger) it is certainly one of the best values in audio. Add to this their entry-level STF-1 sub ($254 was sale price, currently $299.00), and you can turn a modest integrated amplifier and two-way speaker system into something remarkable. VTF-3-Mark III true-sub, with Turbocharger, $799, MBM-12, Mid-Bass Modules, $499 each "
— Dr. Sardonicus, The 4th Annual Positive Feedback Online's Writers' Choice Awards - for 2007, Audioholics.com
"One exhibitor, Hsu Research, had a setup that literally stunned me. In the back of the room where I was sitting, right behind my chair, was one of his new designs, called the MBM-12 Mid-Bass Module, that only reproduces the range from 50 to 150 Hz. He had it set for the range of 50 to 80 Hz. Since it is close to the sitting position, it does not have to be turned up very loud, although it has a 350 watt amplifier. The driver is lightweight, so it responds very quickly. The gunfight scene from Open Range was used for the demo, and the gunshots, because of that special woofer (of course, he had his regular subwoofers in there too, for the really low frequencies), sounded as close to real as I have ever heard in a home theater room. The effect stuck with me all afternoon. Anyway, if you ever have the chance to hear this demo at a local home theater show, be sure to sit in on it. Absolutely unbelievable! "
— Dr. John Johnson, Secrets of Home Theater and Hi Fidelity