Isodynamic (aka orthodynamic)

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Orthodynamic driver principle, fragment from Peerless brochure
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Orthodynamic driver principle, fragment from Peerless brochure

Isodynamic (aka orthodynamic) driver principle

Yamaha Orthodynamic driver diagram, fragment from Yamaha brochure
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Yamaha Orthodynamic driver diagram, fragment from Yamaha brochure

Isodynamic drive headphones have drivers with flexible plastic film diaphragms into which a flat voice coil (spiral or serpentine in shape-- see photos below) is embedded or glued on for even distribution of the drive force. That is, the diaphragm is driven more or less equally over its entire surface at once, obviating the need to make the diaphragm rigid so that it can therefore be as lightweight and agile and nonresonant as possible. Isodynamic diaphragms are either lightly tensioned or corrugated to supply restoring force.


Magnetic assemblies (bar magnets or perforated disc magnets) on both sides of the diaphragm supply the magnetic field against which the voice coil's varying magnetic field reacts, which makes the diaphragm vibrate.

Isodynamic diaphragms are more massive than electrostatic diaphragms, but the equal-force drive principle allows them to move very quickly and in a coherent, uniform way, so provided there is sufficient mechanical damping, an isodynamic headphone gives excellent transient response and a sound quality not unlike that of an electrostatic.


Below you can find several brochures and pictures of various isodynamic drivers:


Brochures



Pictures of drivers

Links to Articles of Interest


Yamaha Ortho Line Overview

Fostex Ortho Line Overview

PMB / MB Quart Overview

Other orthodynamic headphones

Orthodynamic Headphones Rating Chart

USSR Headphone Clone Chart

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