Technology

With any fine loudspeaker system, there is always something special about the drivers and the enclosures that support them. But please read on about how we attain our uncomprom- ising sonic objectives.

Our founder not only has unique access to proprietary aspects of Arthur A. Janszen's original ESL technologies from the late 1940's on, but he is also an innovative engineer in his own right, with a lifelong exposure to acoustical engineering principles, and an extensive background in physics and engineering. Singularly true reproduction requires a singularly focused design, and the JansZen ESL achieves this.

The chief technical aspects of JansZen systems are:

Membranes: Common to all modern Electrostatic (ES) drivers is the use of thin, light membranes for producing the sound. Under the proper conditions, they can take nothing away from the sound nor add anything of their own. Also, with no need to accelerate a massive cone, coil and bobbin, or to flex a rubber suspension, or in the case of ED membrane speakers, to accelerate a heavy deposit of conductive metal in a magnetic field, a very large portion of the energy applied to these drivers actually moves air. Provision of the proper conditions is the key to getting the best sound from ESL's, and JansZen does this better than anyone.

Wide-dispersion tweeter geometry: Membrane loudspeakers and particularly membrane tweeters are known for their tendency to direct the higher frequency sound in a tighter beam. This creates a "sweet spot" in the listening area where the sound is best balanced. Away from this position, outside the high frequency sound beam, the high frequency content is reduced, and moving farther off-axis increases the effect.

In contrast, the JansZen Loudspeaker tweeter geometry eliminates this beaming effect, so that the full sound range can be heard from anywhere within a very wide listening area. This is done by using a narrow line array, and avoids the need for tipping multiple drivers away from each other or using curved radiating surfaces, which are techniques that disrupt accurate sound reproduction in numerous ways.

This geometry is found in ribbon tweeters, which must have got their name from the geometry. Electrostatic speakers have some advantages over ribbons, though, based on their low membrane mass and tensile modulus, which are reasonably well matched to the air load, and the lack of material fatique from sharp flexure of the metallic tracks or metallic membrane along its edges.

Unified midrange/upper bass drivers: With the primary sonic information co-radiated, rather than split out into separate areas, the sound delivery is exceptionally natural. Combined with their coherent radiation pattern, the placement of instrumentalists and vocalists on the sound stage is very realistic and precise.

Closed-back ESL enclosure: Most ESL systems, including the older JansZen full-range ESL designs, attempt to circumvent beaming (sharp directionality of high frequency sound from a large area radiator) by using a dipole arrangement, radiating sound equally from both front and rear. Reflections within the listening area are relied on for distributing the high frequency sound. This also slightly increases the sound pressure for a given amount of power by including the backwave in the sound field.

There are four drawbacks to this arrangement:

1) Low frequency output from the drivers is lost to interaction between the fronts and rears of the drivers,

2) The sound becomes very dependent on the surface and cavity related acoustics of the room (i.e., the ambience of the room is added to the ambience of the original recording),

3) The sound at different frequencies reaches the listener at different times, as well as inter- fering constructively and destructively along the way, and

4) The speakers must be placed a considerable distance from the rear walls (e.g., six feet) to prevent interference peaks and achieve suffi- cient distribution of the reflections, increasing their effective footprint.

As mentioned above, the new JansZen systems do not suffer from sound beaming. Because of this, a full, closed-back enclosure can be used, and the dipole arrangement avoided, so the drawbacks just mentioned do not occur.

The low frequency output is retained, the sound becomes largely independent of the wall acoustics, all the sound arrives at the listeners' ears after traveling the same distance, e.g., with its phase coherency and frequency balance intact, and floor space may be conserved by placing the units near a wall without harming the sound.

Line array ESL arrangement: Most loud- speakers are approximately point sources, meaning that the sound radiates in a spherical pattern, about equally forward, up, down, and to the sides. Because a significant part of the sound from such drivers reaches the listener after reflecting from the floor and ceiling, the acoustics of these surfaces and the recombination of reflected sound waves become important factors in the sound. The sound pressure also drops off rapidly with distance.

By using a line array arrangement, JansZen systems radiate sound in a cylindrical pattern, namely mostly to the front and sides, and very little up or down. As long as your ears are situated below six feet and above two feet from the floor, this has significant benefits:

There is minimal involvement of your room's acoustics, so JansZen systems sound very similar in different rooms and locations within a room, and are exceptionally easy to install to audiophile standards. Also, the sound level drops off at a much lower rate with distance, meaning that stereo imaging is preserved even when you are considerably farther from one speaker than the other.

Although room ambience is important for creating realistic sound, this is for the most part already present in any recording. Also, playback reflections from the floor and ceiling that are prevented from line arrays are largely absent in concert halls to begin with, so would thus detract from playback realism. Line arrays do involve the walls to a significant extent, and this is sufficient for adding that extra bit of ambience that finishes out the sense of realism.

Diffraction feathering. Although the enclo- sures are rectangular, the drivers are slightly tipped sideways. This creates an empty area along each edge of the driver that varies in width continuously from top to bottom. Not a new idea, but never before applied to ESL's, this variation distributes the frequencies and amplitudes of the interference between soundwaves that wrap around the edge and bounce back around to the front from the sides of the enclosure.

As a result, diffraction peaks are many but negligibly small in amplitude, while the critical cylindrical radiation pattern is given only an inconsequential twist. If the edges of the elements and the enclosure were parallel, this would cause at least one noticeable peak and dip in the frequency response.

Damping. To prevent natural membrane resonances from coloring the sound, it is impor- tant to provide acoustical membrane damping. Many ESL's use a see-though design that increases loudness at the expense of resonant coloration, as well as inviting intermodulation distortion during resonant excitations. In JansZen ESL's, membrane resonances are fully damped.

Impedance matching. The inherent modulus of our proprietary membrane material combined with our special tensioning methods improves the match between the acoustical impedance of the membrane and that of the air load. Improved air load matching reduces distortion in the sound, provides some inherent damping of reson- ances, and improves efficiency.

Constant Q: Because JansZen membranes are driven in a constant-Q polarization mode, the very slight asymmetries caused by inevitable variations in manufacturing do not introduce significant non-linearity in the force on the membranes. This keeps distortion inaudibly low in every unit made, regardless of how loud these units are played. Many ESL's use a variable-Q system to increase loudness at the expense of distortion, but JansZen achieves efficiency without this compromise.

Uniform force: Under the conditions present in a JansZen ES element, the membrane experiences a force that is applied evenly across its entire surface, so it moves as one. This differs from even the very stiffest electrodynamic driver cone. It is something not fully accom- plished even in electrodynamically driven mem- branes (ribbons and quasi-ribbons), because the distribution of their conductors can not be perfectly even, nor in curved ESL panels, due to their inherent font-to-rear gap width asymmetry.

Uniform force makes the phase coherence perfect, and also eliminates the possibility of multiple axial vibrational modes, preventing the peakiness and coloration that is practically impossible to eliminate in a wide-range cone driver.

Furthermore, the membranes of JansZen ES elements are tensioned especially evenly, and the extreme flatness and uniform manufacture of the stators (frames) maintains a very uniform gap between the stator electrodes and the membranes. This prevents transverse waves from being generated along membrane surfaces, which would be a hazard to smoothness of response as well as reliability. It also minimizes distortion that would be caused if different amounts of force were delivered in the forward and rearward directions.

Flat elements. JansZen elements are physically flat, and flatness is the key to providing force that is uniform across the membrane surface as well as equal front to rear.

Durability. JansZen ES drivers are unique in their use of a membrane material that does not degrade appreciably during decades of use in the presence of ionized oxygen, and which is fabricated so that arcing is inherently suppres- sed. This makes them so stable that they should last indefinitely.

Ultra-low distortion, long-throw woofer: In JansZen hybrid systems, an electrodynamic (ED) woofer is used for the lower part of the bass range, from about 225 Hz down, where the phase effects associated with this type of driver are inaudible. A low crossover from midrange to woofer is possible in a JansZen hybrid because our unified upper bass / midrange ES drivers exhibit an extended low frequency range for their size.

Covering only four octaves, and having substan- tial surface area, Doppler modulation in the critical midrange frequencies is completely avoided.

Relative to a full-range ESL system, this particular hybrid arrangement will not represent a sonic compromise for most listeners. At the same time, it offers a considerable size advantage, as well as sub- sonic impulse delivery that simply can not be provided by ESL's of any practical size.

State of the art magnetics and electronics: In ESL systems, where the loudspeakers themselves have extremely low distortion figures, the transformers and electronics tend to be the so-called weak links. In developing the step-up transformers that generate the high electrostatic voltages for moving the mem- branes, special materials and methods were used to prevent this component from introducing distortion into the system.

The ESL transformers are driven by PWM (Class D) amplifiers with features that provide linearity and noise figures that far exceed system requirements without squandering appreciable power as heat. Its base-band recovery filter network incorporates specially designed inductors for maximum linearity and minimum EMI. The woofer is also driven by Class D amplifier, in this case a 500 W RMS circuit with base technology from Bang & Olufsen.

You may have read of controversy regarding the use of Class D amplifier topologies. Suffice it to say that Class D supports quite a range of implementation that can be very application sensitive. In our case, it forms an integral part of a true hi-fi system. It may sound trite, but this is a case where we must repeat: "Believe what your ears say, not hearsay".

By using separate amplifiers for the ED woofer and each part of the ESL array, the primary crossover networks are run at line levels, eliminating the need for large pickup-prone capacitors and stray-field generating inductors. This also lets us tailor the transitions between drivers so that there is minimal phase interference, which avoids response nodes. All-class-D operation allows high power generation without the need for ventilation, so there is no fan noise or even much heat added to your listening environment from the electronics.