The Sony Model ECM-22P
electret condenser microphone (1972)
The Sony microphone Model ECM-22P is a cardioid condenser type with uniform response from 40 to 15,000 Hz. The capsule is 17 mm in diameter and made of a high-polymer film utilizing the electret principle of polarization and two output impedances: 250 or 600 ohms can be selected by changing the impedance switch. The ECM-22P can be operated on an external DC power supply without any additional conductors or cables, besides battery operation.
The condenser microphone has long been known for its several desirable characteristics: flat frequency response, high sensitivity, wide dynamic range, and good transient response along with physical durability and ruggedness. The need for an external power supply has been one drawback to the condenser microphone. The Sony Electret Condenser microphone retains the desirable qualities of regular condenser types while eliminating the external power requirement, representing a significant advancement in the production of a simple, low-cost, high-performance microphone. The Sony electret-treated high-polymer film diaphragm reduces physical size requirements, needs no additional power supply and provides outstanding performance.
Another milestone is the built-in impedance translator amplifier which uses a Field Effect Transistor (FET). The combination of the electret condenser with the FET amplifier results in a microphone product representing the most advanced state-of-the-art development. Following is a summary of engineering features made possible by these advances in microphone manufacture:
- High sensitivity for small size (minimum diameter available is as small as 7 mm).
- The light weight of the diaphragm assures higher fidelity.
- Noise from any possible vibration is minimized.
- The dynamic range is wide (92 dB or more).
- Type: Electret condenser microphone
- Battery: Eveready No. 206 dry cell (9 V), No. E-126 mercury cell (8.4 V), or equivalent
- Power Supply: Nominal operating voltage: 8.4 V
Minimum operating voltage: 3.7 V
(Acceptable external power supply of DC 4.5 to 54 V)
Current drain: approximately 600 µA
Battery life: more than 1,000 hours with E-126
more than 500 hours with E-206
- Frequency Response: 40 to 15,000 Hz
- Directivity: uni-directional (cardioid)
- Output Impedance: 250 ohms or 600 ohms at 1 kHz balanced
- Noise Level: S/N ratio: 64 dB (1 kHz, 10 µbar)
Inherent noise: less than 30 dB-SPL
- Maximum Sound Pressure Input Level: 124 dB-SPL
All text is from the Sony Service Manual 2D0682-2, Revised, ECM-22P, ©1972, available
below for downloading. Schematics, disassembly, and exploded views are included.