Tech Focus: XStat Transducer

The basic building block of every current MartinLogan electrostatic speaker is the XStat transducer that represents the summation of over 20 years of MartinLogan engineering expertise. What's visually startling about this distinctive ML feature is that you can see right through it. The actual sound-producing element is an ultra-low-mass PET (polyethylene terephthalate) diaphragm. The diaphragm is coated via a plasma-deposition process with a conductive coating that yields both abrasion resistance and an optimal electrical impedance.

The distinctive curved stator panels define a cylindrical section to significantly improve treble dispersion over what a large flat panel can deliver. Other manufacturers have attempted to approximate a curved panel using a large array of small cells. MartinLogan's solution is certainly more elegant. The carbon steel stators are optimally perforated to maximize the diaphragm's exposed surface area. This is accomplished by reducing the size of the individual holes and using many more of them than in a traditional electrostatic panel, almost doubling the effective diaphragm radiating area without compromising structural integrity. The increase in effective radiating area translates directly into higher efficiency.

Three key elements are critical to making the curved assembly work. First, a vacuum bonding process ensures uniform diaphragm tensioning. It's critical to keep the diaphragm precisely centered between the stators since the electric field strength in the gap increases dramatically as gap width decreases. Second, spacers are introduced into the gap to stiffen the diaphragm across its width making it possible to consistently tension it. The spacers are bonded to the diaphragm and stators with an aerospace adhesive whose hold-strength exceeds that of welding. Finally, a rigid, extruded-aluminum frame anchors the stators and diaphragm and ensures that the spacing of the elements remains fixed.

Adapted and excerpted fromĀ The Absolute Sound'sĀ Illustrated History of High-End Audio, Volume One: Loudspeakers. Copyright © 2015-2016 The Absolute Sound. All rights reserved.