Bedienungsanleitung JBL Project Everest DD67000 (Seite 11 von 26) (Englisch)

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JBL’s proprietary diamond-pattern surround is utilized to maintain

proper control and tuning of the diaphragm’s second resonance

(the surround resonance mode). The proper control and

placement of this surround resonance is critical for good high-

frequency shape, extension and level.

These features, when taken as a whole, create a new large-format

compression driver with the greatest high-frequency extension,

lowest distortion, smoothest response and greatest sonic detail.

045Be-1 AND 045Mg ULTRAHIGH-FREQUENCY

COMPRESSION DRIVER AND BI-RADIAL® HORN

Like the original 045Be used in the Everest DD66000, the 045Be-

1 used in the Everest DD67000 incorporates a 1-inch (25mm)

beryllium diaphragm and 2-inch (50mm) neodymium magnetic

structure. The pure-beryllium diaphragm is less than 0.04mm

thick and has a mass of only 0.1 gram. The single-layer aluminum-

ribbon voice coil is wound without a former and is attached

directly to the diaphragm. This driver employs the smallest

annular-slit phasing plug that JBL has ever designed. The 045Be-

1 has been re-designed to improve manufacturing efciency and

consistency. Small changes have been made to the top plate and

some signicant improvements were made to the surround shape

and clamping methodology. As a result, the driver’s output above

30kHz has been increased by nearly 5dB.

Newly created for Everest DD65000, the 045Mg incorporates

a very high purity magnesium diaphragm – the same material

used on the 476Mg. This material was selected to maintain

acoustic consistency between the high-frequency and ultra-high-

frequency drivers. Also new to the 045 family is a new precision

cast magnesium phasing plug. Compared with the plastic phasing

plug used in the previous design, this new magnesium phasing

plug offers improved stiffness and better ability to wick heat away

from the voice-coil/diaphragm assembly. The extremely low

mass of the moving system combined with the high magnetic ux

density and high rigidity of diaphragms produces response that is

very smooth from below 8kHz to beyond 50kHz in the DD65000,

and beyond 60kHz in the DD67000.

The response curve has a slight downhill tilt, due to the constant-

directivity nature of the horn used in this system. The Bi-Radial®

horn used with the 045-series driver is properly scaled to maintain

a coverage angle of 60 degrees in the horizontal plane and 30

degrees in the vertical plane over the frequency interval from

10kHz to 50kHz.

INTERNAL CROSSOVER NETWORK

The circuit topology, combined with the acoustic behavior of the

1501-series and 476-series transducers, provides a 24dB-per-

octave transition at 750Hz in the DD65000 and at 850Hz in the

DD67000. This is the primary crossover point of the system.

Additionally, the 045-series transducer is active above 20kHz to

provide extended response to beyond 50kHz in the DD65000,

and beyond 60kHz in the DD67000. A second 1501AL woofer

is active from below 30Hz to around 150Hz, at which point it is

gently rolled off at 6dB 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

system’s directivity pattern, while providing tremendous power

and air movement capabilities at the lower frequencies. As a

result, the speed and power of the Project Everest systems are

unmatched from the lowest to the highest frequencies.

All of the electrical components are of the highest quality and exhibit

the lowest internal loss. Air core inductors are incorporated to avoid

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

ultrahigh-frequency networks employ DC voltage 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 amplier. This design element is often overlooked in many

loudspeaker systems, yet ampliers work their best when they are

given a smooth, level load impedance in which to deliver current.

The aggregate of these attributes allows the DD65000 and

DD67000 systems to translate the electrical signal from source

material into an accurate and unencumbered three-dimensional

sound eld. These systems can do this at any desired listening

level, from whisper-quiet to big-band loud, while at the same time

maintaining unchanged acoustic characteristics.

045-Series Compression Driver Section View

Surround

Back Plate/

Driver Exit

Gold-Plated

Input Terminals

Die-Cast

Aluminum-Alloy

Back Cover

1" Edge-Wound

Aluminum Voice-Coil

1" Diaphragm

Magnesium

Phase Plug

Stainless-Steel

Mounting Bracket

Top Plate

Neodymium Magnet

20Hz 50 100200 5001k2k5k10k 20k

Ohm

Impedance vs Freq

DD65000 System Impedance

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