spj@hou3c.UUCP (Stephen P. Johnson) (10/03/84)
I had the opportunity last week to audition the new JSE 1 and 2's at an audio salon here in the Garden State. These speakers use two new devel- opments in loudspeaker technology to produce subjectively excellent sound. These are phase shift bass loading (pat.) and infinite slope crossovers(pat. pending). The idea behind the phase shift bass loading is to avoid problems often encountered when driving two woofers in the same acoustic suspension enclosure. According to the inventor, Richard Modafferi, this often results in excessive output in the mid-bass. To counteract this, he drives one of the woofers through an all pass filter which provides a phase shift as the frequency is increased. The result is that both woofers work in phase at the lowest frequencies, but are between 90 and 180 degrees out of phase at the crossover frequency, which supposedly eliminates the mid-bass hump. This similar, but different from the Nesterovic approach which Modaferri co-developed. The idea of using steep crossover slopes is not new, I am running 24db per octave active crossovers in my system. What is new, and I only have a partial understanding of this, is Modaferri's approach to the crossover filter synthesis; the patent application, the first few pages of which were given to the dealer by JSE, describes a novel approach to the design. The mathematics gets very complicated. After citing all of the "right" references and giving the advantages and disadvantages of each approach, Modaferri goes on to describe a new method, which appears to significantly extend the state of the art in crossover design. It is quite a bit beyond my ability to explain, but it involves placing the poles (zeros?) of the transfer function outside of the working range of each driver. It is claimed that this leads to excellent phase response, the steep filter skirts notwithstanding. The friend who went with me was impressed enough by the JSE-2's to plunk down $2200 to buy a pair. I was very impressed too. They really do sound great. Unfortunately, I can't afford them. The JSE - 1's had less low-end, but had tremendous imaging. They are about $1000 a pair. I can't afford those either. I now understand why Bill Mitchell was touting these things. If you have a chance to hear them do it! Steve Johnson