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Earthworks Audio SR25

Cardioid Condenser Microphone

The SR25 is a cardioid FET condenser microphone with Earthworks’ characteristic 9mm cardioid capsule and extended high-frequency response.

The mic’s physical housing, particularly the internal components engineered to produce a consistent Cardioid polar response, are covered by David Blackmer’s July, 2000 patent #6,091,829. The patent describes a conical, tapered structure behind the capsule, which serves multiple benefits to the mic’s 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.

The SR25 was reportedly engineered specifically for use as a kick-drum mic within the DK25/R 3-mic set. It differs from its predecessor, the SR30, primarily in its frequency response, size, and cost:

	SR25	SR30
Sensitivity	10 mV/Pa	10 mV/Pa
Frequency Response	50 - 25,000 Hz ±2dB	30 - 30,000 Hz ±1.5dB
Self-Noise	22 dBA	22 dBA
Max SPL	145dB	145dB
Length	165mm	212mm
Weight	160g	225g
MSRP (2010)	$795	$1095

The SR25 is very similar in published specifications to the SR20:

	SR20	SR25
Sensitivity	10 mV/Pa	10 mV/Pa
Frequency Response	50 - 20,000 Hz ±2dB	50 - 25,000 Hz ±2dB
Self-Noise	22 dBA	22 dBA
Max SPL	145dB	145dB
Length	212mm	165mm
Weight	135g	160g
MSRP (2010)	$765	$795

According to Daniel Blackmer, all of the Cardioid microphones from Earthworks use a 9mm electret capsule. The extended frequency response of the higher-end models is created by proprietary combinations of mechanical (acoustic) and electronic equalization devices.

Note that although the SR25 is the designated kick-drum mic in Earthworks’ DK25/R, it was intended to be used in conjunction with the KickPad, a passive inline pad and filter device. The mic is billed as having numerous applications outside the kit — such as drum overheads within stage applications, or for close-miking any acoustic or electric instruments.

The mic’s high self-noise of 22dBA, typical of small electret condenser capsules, would tend to disqualify it from ambient miking of quiet acoustic instruments.

MIX, 2005

Detail and realism is where the Earthworks DrumKit [DK25/R] excels. The set will undoubtedly appeal to engineers more interested in capturing the sound of drums as opposed to artificially creating that sound. The microphones’ excellent transient response and ability to capture low-level detail make them a natural for acoustically oriented music.

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Specifications

Pickup Patterns	Pads & Filters
CHART Cardioid (10 mV/Pa; 50 - 25,000 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)
n/a	165mm (6.50'')	22mm (0.87'')	3-pin XLR male (1)

Power Specifications
Requires phantom power Phantom voltage: 48v

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