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603S Microphone Sets

OmnidirectionalCardioidHypercardioidMXL 603S

Detachable-Capsule Pencil Condenser Microphone

The MXL 603 is a small-diaphragm pencil condenser mic with detachable capsules.

The capsule diaphragm measures 17mm in diameter, and is mounted to a 20mm backplate whose outside housing diameter is 22mm. The Mylar membrane is 6 microns thick and plated with gold. The same capsule is used in numerous other MXL mics; see the 603S listing for more. See also the “capsule dissection” link in the sidebar to see an exploded view of the MXL SDC capsule.

Compare MXL 603/604 capsule backplate to Neumann KM-84The capsule used in the MXL 603 and 604 was designed as a copy of the Neumann KM-84 capsule, although in place of Neumann’s “crossed-slits” backplate design, the MXL version uses annular (circular) grooves to achieve similar effect.

Although this capsule has been described over the years as an excellent performer for the cost, the performance has been uneven over time. Many of the capsule we have tested over the past 5 years have expressed an uneven and sharp frequency response, with dips and boosts that cannot be easily corrected via EQ.

(KM-84 capsule photo credit: Klaus Heyne /

Although the 603S ships with only a cardioid capsule, it is compatible with the omni capsule sold with the MXL 604. The 603S capsule can be easily unscrewed from the “head amp.”

The transformerless preamp circuit uses a 2SK170BL FET and is based on the Schoeps CMC5 design. Internal wiring uses Mogami branded cable.

The mic body has a satin silver finish. It ships with a mic clip.


Initially, I was surprised and impressed at how much MX603 indeed does sound like an Oktava MC012. After a lot of use, I got over this first impression. In a nutshell, you’re not going to get a lot of bass out of these mics. It is slightly brighter than most small diaphragm condensers on the market including the MC012…

The MXL 603S is also known as: 603.

The mic was released in 2000.


Compatible Capsules
MXL 603/604 CardioidCardioid MXL 603/604 Cardioid
17mm Cardioid capsule
Sensitivity: 15 mV/Pa
Freq. Resp.: 30 - 20,000 Hz
MSRP: $79 | Still In Production
MXL 603/604 OmniOmnidirectional MXL 603/604 Omni
17mm Omnidirectional capsule
Sensitivity: 15 mV/Pa
Freq. Resp.: 30 - 20,000 Hz
MSRP: $79 | Still In Production
MXL 604-H HypercardioidHypercardioid MXL 604-H Hypercardioid
17mm Hypercardioid capsule
Sensitivity: mV/Pa
Freq. Resp.: n/a
MSRP: n/a | Still In Production
OktavaMod MJE-K47HCardioid OktavaMod MJE-K47H
large diaphragm Cardioid capsule
Sensitivity: n/a mV/Pa
Freq. Resp.: n/a
MSRP: $349 | Still In Production
Pads & Filters Impedance SPL/Noise
n/a 150 Ohms (Low) Max SPL: 137 dB
Self-noise: 18.0 dB(A)
Weight Length Max Diameter Interface(s)
136g (4.80oz) 133mm (5.24'') 22mm (0.87'')
  • 3-pin XLR male (1)
Power Specifications
  • Requires phantom power
  • Phantom voltage: 48v

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