Metal cone woofers have held potential for superior sonic resolution, but until now it was necessary to either live with the High-frequency ringing or attempt complicated solutions to suppress the ringing (mechanically or electrically). The patented Joseph Audio Infinite Slope(TM) Crossover, with its unique 120dB/octave roll off, is the natural, simple partner for the metal cone. Now we can hear the full potential of the metal cone, without the problems that have plagued them previously.

Metal Cones have incredible performance advantages over conventional woofers. Yet... In order to realize the huge potential of the metal cone woofer, one major obstacle must be overcome.

click on thumbnail to see larger image of Fig 1

As seen in Figure 1 , the woofer's response is dominated by sharp ridges of energy - ringing at 5000 and 7000 hertz. It literally wants to ring like a bell. Conventional crossover networks cannot correct this problem, and speaker designers either let the resonance remain, add complex RLC parallel or series networks in order to tome the resonance, or resort to using softer materials that distribute the resonances across a broader range. Less successful metal cone designs have been described as sounding "harsh" and "nasal".

click on thumbnail to see larger image of Fig 2

In Figure 2 , one can see how effective the Infinite Slope Crossover is at silencing the woofer before it has a chance to ring. No additional circuitry is needed. A silk dome tweeter (not shown in the graph) extends the treble response cleanly post 21,000hz without any ultrasonic ringing.

You'll only find this combination of technologies in Joseph Audio speakers.

The patented "Infinite Slope" Crossover is one of the key technologies responsible for the superior sound of our speakers.

Individual loudspeaker drivers (woofers, tweeters, midranges) cannot accurately reproduce the full range of sound detectable by the human ear. For this reason, crossover networks are employed, dividing the sound, and directing it to the appropriate driver, thereby allowing the drivers to be combined into a speaker system that can reproduce the audible range with improved accuracy.

The "slope" of a crossover refers to how its roll off appears on a graph of sound level versus frequency. Crossovers are charted in decibels (dB) per octave. The faster the roll off, the steeper the slope when it is graphed.

Before the invention of the Infinite Slope Crossover, typical crossovers featured gradual slopes from 6dB per octave to 24 dB per octave -- in a two way speaker system featuring a single woofer and a single tweeter, this meant that as one driver was gradually reduced in sound output, the other would gradually increase, allowing a broad part of the spectrum where both drivers were producing sound. Because the drivers were often of differing sizes, shape's, materials and play from different points in space, the drivers interact with one another. This well-documented interaction, known to loudspeaker scientists as "Wave Interference" is a serious obstacle to building accurate speaker systems. Even if a speaker exhibited perfect behavior on one axis when measured in a anechoic testing lab, a small shift from that point would destroy the accuracy of the system. Note the large area of wave interference in the graphs of the 6 dB per octave and 24 dB per octave graphs where the sound of the two drivers overlap.
 

Our "Infinite Slope" crossover at 120 dB per octave is steep enough to realize the benefits of an truly Infinite Slope if one could be built. (Such a feat is theoretically impossible!)

Slow-slope crossovers also present other problems. The drivers must be chosen not only on the basis of how they respond to their part of the range, but also with concern about how they react outside their optimum range. Tweeters must be selected that can handle the additional low frequency energy without self-destructing.

Exotic woofer/midrange cone materials such as Aluminum, Kevlar, and Hexacone™ exhibit lively activity at high frequencies that slow slope crossovers cannot attenuate satisfactorily. Loudspeaker designers excited by the midrange clarity and dynamic snap of these materials cannot use these drivers without adding additional circuitry to tame the high frequency resonances.

Our "Infinite Slope" crossover resides in the speaker cabinet, just like conventional networks. It is not an active filter. It is not a DSP chip. It is a passive circuit (some would say "passive-aggressive") that is carefully designed to maximize the performance of the speaker elements while providing a convenient standard connection to the system's amplifier or receiver. The speaker presents an easy load to the system's amplifier, getting the most out whatever amplifier you decide to use -- whether tube or transistor.

Reprinted from http://www.josephaudio.com with permission.