JBL Project EVEREST DD66000 User Manual page 14

Internal Crossover Network
The circuit topology, combined with the acoustic behavior of the 1501A L and
476Be provides a 24 dB-per-octave transition at 700 Hz. This is the primary
crossover point of the system. Additionally, the 045Be-1 is turned on above 20
kHz to provide extended response to beyond 50 kHz. A second 1501A L woofer
is used from below 30Hz to around 150 Hz at which point it is gently rolled off
at 6 dB-per-octave. The design intent is to use both woofers in the bass
frequencies and slowly transition to a single woofer in the midrange. This
technique allows a primary crossover point between just two drivers and
permits proper control of the directivity pattern of the system while providing
tremendous power and air movement capabilities at the lower frequencies. As
a result, the speed and power of the DD66000 system is unmatched from the
lowest to the highest frequencies.
All of the electrical components are of the highest quality and lowest internal
loss. The inductors used are air core so as to not introduce nonlinear hysteresis
effects. Capacitors are constructed using polypropylene foil, which is known
for having minimal distortion caused by dielectric absorption nonlinearities.
The mid, high and ultra-high frequency networks employ battery bias to
operate the capacitors effectively in a Class A mode. Every attempt is made to
present as smooth a system impedance as possible to the driving amplifier.
This design element is often overlooked in many loudspeaker systems.
Amplifiers work their best when they are given a smooth, level load impedance
in which to deliver current. (Fig.5)
Figure 5 – DD66000 system impedance
The aggregate of these attributes allows the DD66000 system to translate the
electrical signal from source material into an accurate and unencumbered
three-dimensional sound field. The system can do this at any desired listening
level from whisper quiet to big-band loud while at the same time, maintaining
unchanged acoustic characteristics.