I just wanted to give a heads-up to any AC members interested in OB designs, attending RMAF to visit the BPT room (9016). One of the speakers we will be using is an OB 20Hz-20KHz 2-way. This project is not a commercial one but built just for fun out of curiosity. I call it the NB² (no box & no baffle). This custom dipole designed by me was an experiment to test the sonic virtues of what is basically a full range 2-way, open box design with no baffle used for the ribbon panel (6’ ribbon driver is mounted directly to the solid aluminum support structure) and the smallest baffle possible for the dynamic woofer drivers that still allows the structural integrity needed for the huge amount of energy generated by two long throw dynamic 15” woofers (per side) operating in free air. Wiring is our custom BPT copper Litz wire for superb transient response and high current capability. Crossovers, frequency response correction and time alignment of the displaced woofer section is done digitally by a TacT Audio processor. There are numerous possible advantages to this design: no panel reflections, the superb speed and transparency of a ribbon driver from 150Hz to 20KHz, the dynamic capability and 20Hz bass performance of cone drivers, separate “enclosures” so the vibrational energy created by the woofers does not directly effect the ribbon, the ability to place the woofers close to the wall for bass reinforcement while the ribbons remain farther away from the wall to minimize reflections, along with the polar radiation advantages of a dipole. This may be quite an ear opener for many boxed audiophiles. A fun project that produces great sound.
Chris Hoff
BPT
