logo

                            CM-1C Instrument Condenser microphone                            BACKDARK 


micpic

The CM-1C is a  19mm Pencil small diameter open cardioid condenser microphone designed                                                                Ideal for:
for instrument applications-particularly acoustic guitar.
It features a vintage style transformer coupled class A head amplifier design.                                                            guitars

Design features:

Design Philosophy:

The goal was to create the warmth of earlier transformer coupled discrete solid state microphones without
the exagerated high frequency peak so common with modern units. An open cardioid pattern was selected
to give a more complete pickup of extended sound sources like acoustic guitar without emphasizing a particular spot.
An added benefit of the open cardioid pattern is reduced proximity effect.

The capsule:

The capsule is a true condenser, not an electret.

The diaphragm uses special 12mm 6 micron nickel/gold sputtered PET construction. This is typically smaller than a usual
small diaphragm condenser, and was selected to offer better polar patterns and less diffraction effects than larger units.

The backplate behind the diaphragm is precision lapped for the ultimate in accuracy. It is drilled with a specific number of
0.66 mm holes to provide proper squeeze film damping and communication to the rear port of the microphone.

Behind the backplate is the phase shift chamber that provides a delay for rear port entry sound. That delay is adjustable                                        
with a shutter mechanism that  variably exposes the silk and stainless mesh acoustic resistance element.

Each capsule is individually voiced at assembly on a special test rig.

The electronics
Most condenser mic electronics these days are transformerless and based on the concertina FET phase splitter.
We chose a more vintage aproach...a single ended common source FET with bipolar output driver and transformer
Balancing. We didn't choose this just to be more vintage...it gives us more options to control the harmonic structure,
dynamic range, and frequency compensation. The custom output  transformer also provides the extremely high
common mode impedance that results in superior  balance and noise rejection.

We use selected ultra low noise Linear Systems N channel JFETS.

A special feature is the attenuator switch for very high sound pressures. The usual method is to simply put a capacitor                            miccutaway
across the capsule, forming a divider. This works, but it causes the capsule to behave non linearly. Switching in the
capacitor often results in a pop or click.

Since our capsule is a true condenser (not electret) we chose to alter polarization voltage in a gradual manner when the
 attenuator switch is actuated. This eliminates the distortion mechanism and pop sounds while increasing dynamic range
due to reduced diaphragm suckin.

We set the output lower than some condenser microphones, but more than enough for any good preamp.
 Phantom power is weak, and we don't want to compromise performance just to put out huge output levels.

The voicing
I envisioned this microphone as something designed for recording stringed instruments, particularly acoustic guitar, mandolin,                    violin, and similar. I wanted a clear detailed sound, but without the high frequency hype that so many mics have.
So I went for a fairly flat response without the usual 10kHz peaks. The low frequency response is tailored for micing at about
300mm distance. A low cut filter is supplied for closer distances without undue proximity effect.
The rather small diaphragm gives good off axis HF response....a guitar miced at 300 mm is a broad rather than point source.

The Specifications
Typical frequency response on axis (each unit is supplied with the individual measured response)

testgraph






Polar pattern:








Output level: 4mV RMS balanced at 1 Pascal Free field (94dB SPL)
Maximum SPL: 140dB with attenuator
Self Noise: 25dB SPL A weighted
Weight: 0.6kG
size: 19mm diameter x  182 mm length (without shock mount)


Single microphone    $599
:
Stereo matched pair:  $1400
Available  with tighter restrictions on capsule and  electronic components.
Although all units are already individually tightly controlled for performance this is suggested for XY and other dual
mic applications.

TO ORDER CALL US AT (706) 212-0242 0R EMAIL AT   leswatts@windstream.net