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CardioidEarthworks Audio SR40

Cardioid Condenser Microphone

The SR40 is a high-end Cardioid condenser microphone designed to deliver all the characteristic benefits of Earthworks microphones:

  • Extended high-frequency response
  • Minimal off-axis coloration
  • Excellent transient response due to fast diaphragm settling time
  • Consistent polar pattern control

As is typical of most Earthworks microphones, the SR40 exhibits ruler-flat frequency response. The published graph shows less than 0.5dB variation from 30Hz through 40kHz. Note, however, that the graph was measured at 30cm, where the mic’s proximity effect contributes some low-frequency lift. In a free field, the mic’s response is down 3dB at 100Hz; it begins rolling off at 300Hz.

(Note: through June, 2011, the SR40 manual incorrectly stated the measuring distance for the frequency graph as 15cm rather than 30cm.)

The mic’s Cardioid polar pattern is relatively stable across the frequency spectrum. At 90°, the polar graph shows only ~3dB variation in response, mostly at 8kHz. This is a marked contrast to most Cardioid microphones, which typically narrow in their sensitivity to high frequencies.

The null at 180° is not maintained at all frequencies; the mic develops rear sensitivity at 4kHz and above.

The marketing claims of a “near-perfect” Cardioid response refer to the mic’s unusual ability to provide a nearly flat, uncolored response across the front hemisphere (-90°–+90°), with very little attenuation even at the edges of the ±90° range.

SR20 HousingLike the other SR-series Cardioid mics, the physical design of the SR40 is covered by patent #6,091,829 (July, 2000). The patent describes a structural component — a tapered cone behind the capsule — that allows the mic to maintain an even Cardioid polar response.

Patent 6,091,829

The tapered structure has a generally conic shape to provide a gradually increasing acoustic impedance… [it] preferentially collects signal components from behind the microphone and ducts them into the rear ports of the [capsule]; and guides reflected, unwanted signals outwardly and away…

[It] improves the front frequency response of the microphone, and [provides] more-effective rear-port signal cancellation, thereby providing a better front-to-back signal ratio than provided in the prior art.

Permalink: Earthworks Audio SR40

The mic was released in 2010.


Frequency Response - CardioidClick Graph to Compare!
SR40 Cardioid Frequency Response Chart
Pickup Patterns Pads & Filters
Cardioid (10 mV/Pa; 30 - 40,000 Hz)
Capsule Dimensions Impedance SPL/Noise
Capsule diameter: 9mm
100 Ohms (Low) Max SPL: 145 dB
Self-noise: 22.0 dB(A)
Weight Length Max Diameter Interface(s)
225g (7.94oz) 250mm (9.84'') n/a
  • 3-pin XLR male (1)
Power Specifications
  • Requires phantom power

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