The Atmos 5.1 Controller

1.) The Triple-Gain-Stage Microphone Preamps

The Atmos 5.1 is equipped with five matched high precision microphone pre-amps featuring SPL's new Triple-Gain-Stage microphone pre-amps to capture the superb sound of Brauner's ASM 5 microphone in the most transparent, noiseless and uncoloured way.

An important feature of the Atmos 5.1 are its motorised Master Gain controls.

A Master Gain switch enables motorised control over all five microphones preamplifiers by just turning one control. This is important, when re-adjustment of the pre-amplification becomes necessary while recording. Re-adjusting the pre-amplification manually may result in losing the coherence of the room sound and will cause phasing effects between the channels when reproducing in 5.1.

While changing the pre-amplification the relative loudness relationships between all five microphones are maintained. The motorised Master Gain controls have proven to be most helpful in certain recording situations.

The microphone preamps also feature SPL's ServoDrive-Technology which detects voltage differences (DC-offset) between the positive and negative paths of the amplifying stages. Any offset increases noise and distortion and therefore compromises the signal quality. ServoDrive minimises DC-offsets to values between 0mV and 2mV. The recorded signal contains less noise and distortion and improved tonal transparency.

The mic preamps also employ Lundahl input transformers, pads, phase reverse, phantom power, low cut filters and a switchable insert, tape send/returns. All switches are luminated, high quality switches, and relays with gold plated contacts are used throughout.

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2.) 5.1 Surround Panning Matrix

While recording on location or mixing in the studio it may be necessary to vary the position of a microphone in the Front/Surround and L/C/R panorama to compensate for poor microphone positioning or for artistic reasons.

Mixing and 5.1 panning is possible from each channel via a Front/Surround and a L/C/R pan control with divergence for correcting the L/C/R image.

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3.) 0.1 Sub Channel & LFE (Low Frequency Effects)

In the 0.1 Sub Channel, the sub signal can be composited from the front, surround, and centre channels. A 24dB Butterworth low-pass filter at 130Hz can be activated to only let those frequencies pass up to where localisation begins. In the mixing/premastering stage the upper corner frequency can be reduced to the value required for i.e. AC3 or DTS encoding. If the low-pass filter is not activated a mono composite of the selected mic inputs can be send to a separate sub/LFE processor.

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4.) Stereo In/Out

Two additional balanced inputs are provided to mix a stereo source from additional room mics or from a multichannel sub mix to the front, centre and surround channels. The STEREO OUTs allow the stereo source to be forwarded to other units for further processing or recording.

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5.) ASM 5 Pattern Control/Stereo Expanders

Another difficulty in 5.1 recording represents the selection of the polar patterns of the microphones in order to achieve the optimum in capturing the room atmosphere and the sound source within. There is great demand for experimentation and the Atmos 5.1 system delivers maximum freedom in doing so. The Brauner ASM 5 allows continuous adjustment of the polar pattern characteristic of each microphone from omnidirectional up to figure-of-eight. These adjustments can be made directly from the Atmos 5.1 and can be monitored while recording.

Furthermore, the stereo soundstage of the front and surround channels can be widened using all-pass stereo spreading. This allows the electronic simulation of a continuously variable distance between the L/R and SL/SR microphones. The Stereo Expanders are equipped with a hard-bypass and a mono switch. Two phase meters display the L/R & SL/SR correlation both when the Stereo Expanders are active or in bypass.

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6.) Monitoring

Monitoring six channels represents another problem in 5.1. While recording and even more important while mixing and premastering the variation of the monitor level is delicate because level differences of just 0.5dB may cause phasing effects between the channels.

SPL has developed an electronic circuitry to realise monitoring level control of all six channels simultaneously with minimum tolerance. The monitoring speakers can directly be fed from the Monitoring Outputs of the Atmos 5.1 solving the monitoring problem in the studio.

When recording on location the Sennheiser Surrounder headset can directly be plugged into the Atmos 5.1. A conventional stereo headphone output is also provided allowing each bus to be monitored separately or in combination.

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The Brauner ASM 5 Adjustable Surround Microphone

The ASM 5 is based upon five matched microphone heads from the highly acclaimed Brauner VM 1 microphone. This microphone system represents a specific microphone set-up that has proven to be superior in blindfold tests over other surround recording techniques (ABC, IRT-Surround and other ambisonic techniques).

The Brauner ASM 5 offers a large flexibility and variability to capture any sound event and offering the recording engineer a platform for experimentation and artistic freedom.


Variability

The L/C/R microphone heads of the ASM 5 are positioned in a rectangle triangle with each microphone being positioned 17.5 cm away from the centre. The ASM 5 allows continuous adjustment of the polar pattern characteristic of each microphone from omnidirectional up to figure-of-eight controllable remotely from the Atmos 5.1. Furthermore the positions of the all microphone heads are variable +/-90 degrees.

The BRAUNER ASM 5 includes a top quality 25 m (or more if needed), 12-pair screened multicore cable to connect it to the SPL Atmos 5.1 Surround Recording Console.

Together, the SPL Atmos 5.1 and the Brauner ASM 5 provide the optimum 5.1 surround miking solution for studio and live recording, outdoor recordings, mixing and post production in music, TV and movie productions.