Vintage Orthodynamic Monitoring Headphones Echo N16-40S (TDS-16) Planar Magnetic.
Made in Ukraine.

Manufacturer: NII "Kvant", Kiev, 90s years

ECHO N-16-40S (also known as TDS-16) have even more flat frequency response that is great for professional work with sound due to their extraordinarily accurate and natural sound reproduction: irregularity in 20 to 20000 hz range is +2,-6 db only.

Technical Specifications

Impedance: 40 ohms;

Sensitivity - 91 db;

Flat frequency response - 20-20000Hz;

Sound pressure level at 500 Hz, in summing up the rated power, dB, not less - 91;
The unevenness of the frequency characteristics of the sound pressure in the range of 20 to 20000 Hz, dB, not more than - 16;
Non-uniformity between the frequency characteristics of the sound pressure of the left and right stereo headphones averaged in octave bands in the frequency range from 250 to 8000Hz, dB, not more - 3;

Harmonic distortion < 0.3%;

Weight of the cable, kg - 0,18;

Size, mm - 220 х 170 х 68 

Connector - 6,3 mm (you can attach 3,5-6,3 adapter or solder new 3,5 mm, compatible with notebook, computer, smartphone and other non-proffecional equipment)

Headphones is always ready for upgrade by your needs, they can be demountabled.

About Orthodynamic / Isodynamic Headphones

Orthodynamic headphones were very popular worldwide in the 1970s. They are considered by some to be old technology but have a revival now.

Manufacturers include Audeze, Fostex, Hifiman, Kenwood and Dual.

Orthodynamic headphones have flat and bigger voice coils, which cover the diaphragm. This means that the current is better distributed to the diaphragm, which in turn produces sound waves. Bigger voice coils mean bigger diaphragms (even bigger than electrostatic headphones) and that means that more electricity is needed to drive them.

Pros of Orthodynamic headphones are that they give excellent response and sound quality similar to that of an electrostatic.

Cons of Orthodynamic headphones are that they are generally bigger and require a headphone amp to drive them thus they are not portable. They are also generally more expensive than dynamic headphones.