Larry Murphy, staff engineer at Tierra Studios, begins his Mic’s With Murphy series with an overview of microphones. Watch the video and read more about mics below.
(This image is from the Wikipedia Blumlein entry)
The Blumlein pair recording technique is a type of stereo recording technique invented by Alan Blumlein designed to create recordings that replicate the spatial characteristics of the recorded signal.
A Blumlein pair consists of two matched microphones set to the bi-directional, or figure 8, pickup pattern and positioned 90° from each other. This configuration should allow the transducers of the microphones to occupy the same physical space, or at least as close to the same space as possible. The mics are then positioned so that the audio signal is in a line bisecting the angle between the two microphones. The pickup patterns of the pair, combined with their positioning, delivers a high degree of stereo separation in the source signal as well as the room ambiance.
Properly used, the Blumlein pair can produce a “true” stereo image.
The traditional microphone for Blumlein Pair recording is the ribbon microphone, although some microphones are purpose-built for the type of coincident arrangements that are required for the Blumlein pair.
Unlike most ribbon mics designed today with an offset ribbon, the Cascade FAT HEAD houses a hand-tuned ribbon element that incorporates the legendary symmetrical ribbon design. This design offers a true figure 8 pattern. The corrugated aluminum membrane itself is positioned in the center from front to back, thus producing a balanced audio input signal to both sides of the ribbon assembly. This design is very useful when executing a mid-side or Blumlein recording set-up and also great for live stage use. The FAT HEAD warm full-bodied signature and increased sensitivity is what you would expect and demand from a professional ribbon microphone and the FAT HEAD delivers. The FAT HEAD is suited for guitar cabinets, drum over-heads, vocal, piano, horns, strings and much more.
The Neumann M 149 is THE universal high-end tube microphone with a unique sound and a comprehensive selection of settings, including 9 directional characteristics and a 7-level low-cut filter! The capsule is derived from that of the legendary U 47 and M 49.
There are nine polar patterns to choose from, making this microphone an ideal choice for a wide range of recording situations.
As its ancestors, the M 149 Tube is a superb vocalist microphone, not only because of the capsule, but also due to its modern circuitry, characterized by extremely low noise level.
The M 149 Tube is addressed from the front, marked with the Neumann logo. Also on the front is the switch for the selection of the polar patterns.
The capsule is mounted elastically inside the headgrille to eliminate structure borne noise. The surface below the capsule is shaped like a cone to disperse any reflected sound from the acoustic upper half space. This avoids any interference with the primary sound arriving at the capsule directly.
A large headgrille surrounds the capsule. It is acoustically very open and therefore increases the sonic realism.
The polar pattern switch selects one of nine directional patterns: omnidirectional, wide-angle-cardioid, cardioid, hypercardioid, figure-8, and one additional intermediate pattern between each major position.
The circuit of the M 149 Tube microphone has been developed to exceed traditional designs. We have selected a modern tube (triode) and combined its exceptional transmission characteristics with the advantages of our proven transformerless output circuit.
The aim was to provide a more controlled environment for the audio signal on its path from the capsule to the output section.
The final stage is an integrated amplifier, especially designed for such applications. It features very low distortion (THD < 0.002 % at ± 10 V), very low self-noise, and high output current capability.
As a result, the tube circuit is completely decoupled from the microphone output and its characteristic response curve will be unaffected by very high signal levels or varying load conditions.
The lower output impedance and higher output current capability allow cable lengths up to 300 m (1000 feet) without any degradation of the audio signal.
The tube amplifier changes the high impedance of the capsule and adds 10 dB of gain to the audio signal, providing optimum operating specifications. The wide dynamic range is impressive, as peak output can be ±10 V, at 20 mA.
The ideal operating point of the tube is maintained throughout its entire life expectancy. Plate current and filament voltage are constantly regulated. A sensor circuit monitors and compensates for any voltage drop across the microphone cable. The tube is heated up slowly through inverse current limiting to guarantee long life. Optimum operating conditions are reached within a very short time.
A seven-position slide switch is located on the back of the microphone. It selects a high-pass filter, advancing in half-octave steps between 20 Hz and 160 Hz (-3dB). This filter is useful to suppress rumble from air-conditioning and in windy situations.
In addition, the filter provides an effective tool to control the audio signal when the microphone is used at close distance and therefore proximity effect alters the program material.
The C 414 B-ULS is THE reference microphone for almost all comparative microphone tests and one of the most used condenser microphones in the world. It is the microphone of choice for miking up vocals, grand pianos, percussions, and any other sound sources with complex waveforms.
A gold-sputtered 1-inch dual-diaphragm and Ultra Linear Series electronics combine to provide an extremely smooth frequency response.
Four selectable polar patterns allow the microphone to be used for every recording technique and two bass cut filters suppress low-frequency noise. Extremely low self noise and high headroom result in a dynamic range of 126 dB, which is wider than that of digital recording equipment.
Switchable 10-dB and 20-dB preattenuation pads let you record instruments with sound pressure levels beyond 150 dB SPL at less than 0.5% THD. We have 2 sets of matched pairs of these microphones on site.
The U95 is a multiple pattern tube condenser microphone, designed by David Bock and then sold by Soundelux. It was Soundelux’ flagship tube condenser in 1998.
The mic has 9 polar patterns, switchable via the external tube power supply (which is a dual-voltage design).
The capsule in the U95 was originally made by 797 Audio in China; it was a dual-membrane, large-diaphragm design made with a gold-coated Mylar membrane measuring 6 microns in thickness. Later, a single-diaphragm version of this capsule was developed and untilized in the Soundelux U915 (which is a cardioid-only microphone). The U95 amplifier circuit uses an 6072A dual-triode tube. The 6072 tubes must pass four tests before they end up in a U95; a distortion test at normal levels, a maximum SPL rating with less than .5% distortion, a microphonics check and a frequency correlative noise check.
Though the U95 has all the warmth and midrange detail usually associated with tube mics, it’s one of the few with extended response to 20kHz. This extended response gives it a sense of “air” and top end magic that is undeniable. Though its creation was inspired by the great mics of the past, its unique two stage tube electronics were an industry first. Top quality components are used exclusively in both the mic and power supply, which are designed for decades of trouble-free service.
