Specifications

Not surprisingly, each of the approaches described above has its own

unique set of pros and cons. The electrostatic, because its diaphragm is

so thin and light, offers exceptionally good transient response and

reproduction of subtle, low-level musical detail. And, because it is a true

push-pull device (i.e., its diaphragm is, by design, driven from both the

front and the rear), the ESL operates in a linear fashion. Typically, gross

distortion results only when the driving amplifier clips into the speaker,

or when, in an attempt to play the speaker louder than its design allows,

its step-up transformer reaches a point of saturation.

On the negative side of the ledger, the ESL does require passing the

amplified musical signal through a transformer, which can introduce its

own colorations and non-linearities. Also, some ESLs are prone to a

condition known as arcing: Under the conditions of stress induced by

playing an ESL loudly, it is not uncommon for an electrical spark to jump

between one stator and the diaphragm (a phenomenon exactly analogous

to lightning), burning a minute hole in the diaphragm and, over time,

ruining it.

As for the planar magnetic, its strengths are similar to those of the ESL--

although the addition of several feet of wire and an adhesive coat make

for a somewhat more massive diaphragm, limiting this design’s transient

capabilities by comparison. But the planar magnetic requires no step-up

transformer or bias voltage supply, and it has the added benefit of being

an extremely manageable load for most amplifiers. However, the most

specific drawback of the traditional planar magnetic is that it is a single-

ended (as opposed to push-pull) device: As the diaphragm’s physical

excursion increases, the voice grid moves further away from its optimal

location within the permanent magnetic field (at least in one direction).

Thus, at the very instant when this speaker is called upon to reproduce

large-amplitude waveforms, it is least able to do so without distortion.

In many ways, a ribbon driver can be an excellent performer: the moving

element (the “ribbon” itself) is extremely light, allowing good “speed”

and transient performance as well as freedom from coloration. And there

is no significant physical structure on either side of the ribbon’s radiating

pattern. The ribbon’s main problem is not one of performance but of

application: it cannot be used to reproduce low frequencies. To create a

moving element large enough to generate frequencies lower than a few

hundred Hz would mean moving opposing magnetic poles so far apart

that they would no longer exert a sufficient magnetic field over the entire

area of the ribbon.

Evaluating

Earlier

Approaches

Electrostatics

Planar

Magnetics

Ribbons