Electrostatic headphones are the undisputed kings of headgear when it comes to sound quality – it is only their price and power consumption which stops everybody wanting them! Some of their mystique can be dispelled by knowing the internal workings, but they’re still going to impress!
They operate on the principal that ‘opposites attract’, although Paula Abdul is not involved here. The technique has a thin membrane of plastic held in place between two electrode plates called ‘stators’. The membrane is coated in a conductive substance which allows a static field to be built upon it, and this in turn reacts with any audio signal which is fed to the stators.
Being statically charged, the membrane is attracted by any positive force held within the stators, and opposed by any negative force within them. Since any similar forces in the stators either side of the membrane will be effectively cancelled out, one of the stators is wired out of phase so that one stator is pulling the membrane whilst the other is pushing it. The effect of this is to double any force acting upon the membrane, much like two sawyers operating each end of a large saw.
This is also happening on the opposite side of the headphones; so along with energy required to build up the static fields on the membranes, more energy is needed to move them.
The combination of ultra-light membrane and powerful moving forces makes for a very accurate sound with great separation; since the membrane is acted on as a whole, it does not bend and this also avoids distortion. Also due to the fact this technology can cover all frequencies well beyond 20kHz, there is no need for the crossovers and multiple drivers which would cause distortion in a dynamic or balanced armature equivalent.
STAX Earspeakers return with a new range of their world famous STAX Electrostatic headphones for 2011
Founded in 1938, originally manufacturing high frequency condenser microphones and later Record Player cartridges, in 1960 STAX launched the Electrostatic Earspeaker with the STAX SR-1 and has been building amazing headphones ever since.
Electrostatic Technology
Electrostatic drivers consist of a very thin electrically charged diaphragm, typically stretched and coated polyethylene terephthalate (a unique STAX polymer formula) is used for its high tensile strength to create the membrane. This is suspended between two perforated metal plates (the electrodes), when an electrical sound signal is applied to the electrodes, creating an electrical field, the diaphragm is drawn towards one of the plates depending on the polarity of the field. Air is then forced through the perforations, when combined with the continuously fluctuating electrical signal driving the membrane a sound wave is generated.
Due to the extremely thin diaphragm membrane, which is only a few micrometers thick, the frequency response of electrostatic headphones usually extends far beyond the normal human hearing range of up to 20kHz. The high frequency response means that the low mid band distortion level is maintained right to the top of our audible frequency band. The peaks regularly seen in higher frequency regions with moving coil drivers is almost completely absent with the result being much more stable and accurate sound reproduction.
Electrostatic headphones are powered by a special amplifier that is required to create the signal to deflect the membrane and needs electrical potential in the range of 100 to 1000 volts, these are often referred to as energisers. With this amount of power in proximity to a user’s head the usual method of making this safe is to limit the possible fault current to a low value with resistors.
What do they sound like?
Well, they sound great! Fast and fluid with superb separation – it is this separation of the instruments which really provides the difference between dynamic headphones and Electrostatics. You have the same sense of space normally associated with open backs but each instrument really feels contained in its own bubble, the incredible detail gives the sharpest image that seems vivid and realistic, strangely natural in its lack of grain. The precision of the sound, their natural airy feel and the sculptural solidity they give to instruments lends itself to Classical music, Vocal and Choral music, Folk and Acoustic and Jazz. Classic Rock and Pop mostly work well but the Contemporary love of heavy limiting and compression means many recent recordings have too little space and punch too hard to take advantage of the subtlety on offer.
STAX New range for 2011
This is the biggest shake up of the STAX range for a very long time. New features include –
-10 position ratchet adjustment on headband (SR-507 Only)
-New Diaphragm assembly (higher resolution)
-Casing is now a less resonant resin formula
-Sheepskin cushions (SR-507 Only)
Basic SystemSRS-2170–This is a combination of the SR-207 Earspeaker and SRM-252S compact size Driver unit. The SR-207 employs the same elements developed for the new Lambda Series. The LC-OFC cable of the SR207 gives clear high-frequency sound and lowered capacitance. The SRM-252S Driver unit incorporates an all-stage balanced circuit DC amplifier configuration despite its diminutive size.
Classic System SRS-3170–This is a standard combination of SR-307and SRM-323Swith all-stage direct-coupled balanced output. The SR-307 has a completely new diaphragm, now sharing more features with the Signature System there has been a fundamental change of specification, low capacity PC-OCC cable, gold plated terminals and open air enclosure all appear in the Classic System.
Signature System SRS-4170–This is the high-quality combination of the SR-407 Earspeaker and the SRM-006tS Driver unit with balanced input. The SR-407 features the same membrane technology as the SR-507, the top model of the lambda series.The SRM-006tS Driver unit with balanced input boasts a fully balanced circuit configuration from input to output through the custom made double-axis 4-gang volume controller.
