Digital Recording/Production Console
Reviewed by Mel Lambert
In more way than one, the new Studer D950 Digital Mixing System represents a unique, fourth-generation solution for facility owners that have considered an all-digital solution, but might have reservations about critical operational parameters. For example, what type or redundant power supplies should be offered in a design, to ensure trouble-free operation during, for example, live or on-air broadcast applications? And how can a budget-conscious operation justify the cost of specifying DSP capabilities that for the majority of the time will not being fully utilized, but which have to be available on-line?
It is obvious that Studer's Swiss-based engineering team paid close attention to these and other considerations. Available in two basic versions- the D950B with two-channel stereo panning, and the up-market D950S, which offers up to 7.1-channel virtual-surround panning and a separate multiformat monitor panel- this latest offering from a firm with a proven track record in digital topologies is literally bristling with carefully-considered and relevant features.
In essence, the D950's designers have acknowledged that, for many users, digital technology needs to be as reliable as analog; we simply cannot afford to run the risk of losing critical functions during a live date; to be forced to wait several minutes (maybe!) while the console reboots itself. In this respect alone, the D950 is remarkable. Redundant power supplies ensure that motive power is lost only under extremely adverse situations. In addition, audio paths will continue to function without the external PC being on-line; even the loss of the on-board system controller will not interrupt signal flow through the board- although such a loss will dramatically impact the types of functions we can control! (For enhanced data integrity, the PC that handles automation chores, as well as graphics displays, is supplied with a mirrored hard disk.) Boot time is between 10 and 20 seconds, dependent upon the console topology being rebuilt.
And if a hardware or software error is detected in a specific DSP board, the D950's master CPU immediately assigns its functions to any redundant DSP boards available within the system. A faulty board can even be hot-plugged and replaced without interrupting operation of the console. So now those seemingly unnecessary additional DSP cards can be used to provide redundant functions, just in case!
The D950's core was developed in conjunction with the Swiss Federal Institute of Technology, and features powerful parallel processing; the maximum DSP configuration of hot-swappable DSP cards provides almost 15 GFlops of processing power. Each DSP engine is capable of 40-bit floating point computation, and is fully scalable through load balancing- a topology that ensures 100% of the processing power is available for any console configuration. Each card will provide full DSP processing (EQ, dynamics, delay, etc.) for up to 12 signal paths. (If less processing is defined for specific module "types", then more channels can be accommodated per card.) Any DSP card that is left over, so to speak, is automatically assigned to serve as a back-up, and which can then be utilized instantly in the extremely rare event of a system component failure.
Each DSP board shares access to a central back plane buss that enables distributed processing and dynamic resource allocation. System boards can be supplied in a variety of formats, with or without eight on-board AES/EBU-format inputs (the first pair with integral sample-rate conversion) and eight AES/EBU-format output ports. The D950's DSP frame can accommodate up to 20 of these engines, in addition to boards that handle a pair of optical MADI-format inputs and two outputs for direct D-to-D connection, for example, to a Studer D827 24/48-track DASH-format recorder. In the event of a power failure, a UPS (uninterruptible power supply) will operate the entire control system for up to 20 minutes. The D950 rack draws just 800W of power form a single-phase supply; an electrical load that should make it ideal for mobile applications and remotes.
Analog inputs/outputs are accommodated via outboard converters, including Studer's new range of D19 Series interfaces, including the D19 MicAD (eight channels of 20-bit mic/line-level A-to-D converters, with or without front-panel level display), and the D19 MultiDAC, which provides eight channels of 23-bit D-to-A conversion. Outboard D19M MUX boards handle conversion in multiplex mode from analog line-level or digital AES/EBU-format signal to MADI format, or in individual mode with AES/EBU-frame outputs. (Companion D19M DEMUX boards are also available for providing analog line-level or AES/EBU-format outputs.) Finally, a separate Monitoring/signaling rack provides a variety of control-room and studio outputs, talkback and related functionality. A fully-loaded DSP frame will accommodate a large number of audio signal paths, (over 256 maximum, depending on the channel DSP load), with more than 128 Summing Busses and the ability to handle as many as 800 audio inputs and outputs via the system's built-in signal router.
Internal processing blocks can be configured during system setup to provide input selection, four-band parametric EQ, channel insert, variable delay, dynamics control (compression, limiting, gate and expander), output limiting, stereo or multi-channel pan, direct out and solos modes. The precise nature of the system topology is controlled via a Widows 95/NT-based Configuration utility that runs on the D950's external PC. The latter also accommodates Studer's optional AutoTouch Dynamic Automation, which adds a dedicated control panel to the console, plus a timecode reader/generator and P2-format nine-pin serial control. Overall digital processing delay is quoted at 480 microseconds, a figure that remains consistent no matter how much DSP is dialed into a signal path (such a multi-band parametric EQ and filters).
The external PC runs a Windows-based shell that controls such functions as system management, control, configuration and automation. In conjunction with a large onboard color VDU, the PC can also be used to generate signal-flow diagrams and display various channel features that have been included in a system configuration file. (The system can be hooked up to a modem for remote diagnostics and software updates, and also controlled via a facility-wide digital control network.)
The central control/monitoring section features a number of panels that can be arranged in virtually any configuration, including a pair of motorized joysticks (for the D950S Surround configuration), a MultiMachine Motion Controller (a joint development between Studer and CB Electronics, with three serial control ports), and PEC/DIRECT paddles for film-style control of recorder and replay/bus switching.
As will readily be appreciated, the D950's maximum configuration is dependent upon the DSP power available within its main rack. By way of an example, Studer's designers quote a "typical" system configuration based on a core array of 8-10 DSP-I/O cards that can provide:
Reconfiguration of the entire D950 to handle any of these assignments (and others) simply requires the recalling of a setup file via the onboard computer or external PC; the entire process needs no more time to execute than it will take to read the following paragraph.
In overall look and feel, the D950 resembles a conventional analog console. The on-surface controls retains the clean, accessible layout of an analog design; up to four surfaces can share a single DSP core, allowing maximum flexibility in multi-room installations. Each channel strip offers dedicated controls for input selection (one of three possible sources, including a test generator for system calibration and alignment); direct out; access to four of the multiple mono/stereo Aux Send busses; EQ in/out; Filter in/out; Compressor-Limiter in/out; Expander/Gate in/out; Insert on/off; Pan (stereo or surround) in/out; and Assign Select, which enables the quartet of rotary shaft encoders and soft switches to be used to modify parameter settings for the target channel.
A companion meter section above each channel strip provides two bargraphs displays for mono or stereo signals, plus overload LEDs, and indicators to show that the meters have been switched to monitor gain reduction rather than input or buss levels. A bank of LEDs display the current post-fader track (up to 48 available) or group assignment (up to 48 mono/stereo), as well as master bus assignments (up to eight mono/stereo) for the relevant channel.
The D950 features a very easy-to-follow and completely intuitive user interface. All channel strips are identical, with non-dedicated controls that can be allocated to any function from the central assignment section of the board, or locally on the channel strip itself. A display next to the control clearly indicates its current function until the control is touched, when it displays the current parameter value- a row of companion LEDs provide a visual indication of the setting. Parametric EQ, filters, compressor/limiters, expander/gates, inserts and pan facilities can be displayed either on a per-channel basis, or globally.
All channel controls are easy to locate and use; knobs and switches are digit-sized, but not so large that they get in the way. My only complaint is very minor: the low color contrast between the legends and controls means that you need to have a reasonable amount of light playing on the desk to see everything clearly. (I understand, however, that Studer is considering revising its current color scheme.)
The D950 offers both snapshot and dynamic automation. Each snapshot stores all console parameters, while dynamic automation offers all of the user creature comforts we have grown to expect from current-generation systems, with all of the familiar timecode-based update, take-over and glide modes.
The D950S' VSP function provides three-dimensional audio source positioning via a library of software panning functions that let you place sound sources in virtual 3D environments. Listener positions are calculated within the DSP engine utilizing a series of Studer-developed algorithms. In addition to the familiar intensity-panning functions- such as LCR, front/back, LsRs, divergence, etc.- the operator can dial in frequency-dependent panning filters and delay-based effects. In this way, it is possible to position a source in a surround mix as though it had been recorded within a three-dimensional environment, complete with sound reflections from distance walls and surfaces.
In operation, the D950 enables an adjustable number of discrete echoes to be produced and routed as non-correlated, diffuse signals to the surround channels. Echoes are modified using assignable Ambiance, Source Distance and Room Size controls, allowing the natural reproduction of audio sources from various distances and positions within a "virtual" room, without the need to revert to external processors. A number or special dynamic effects, such as the gradual disappearance of a close sound into the diffuse room, can also be achieved by accentuating its spatial components. A realistic simulation of Doppler Effect is also offered.
By way of an example, consider the panning of a distant source through the listener's position and exiting via a diffuse pan into the left and right surrounds. Utilizing the D950's position-specific ambiance algorithms, the signal source picks up different amounts of reverb and diffusion, depending upon its relative location to the sweet spot. While such effects could be generated using a combination of time-dependent reverb and ambiances from an effects processor, coordinating these with the pan location can be a pain in the butt. With the movement of a single control, it is possible to create the same kind of automatable effect on the D950. It's a remarkable achievement, and one that offers exciting potential for DVD remastering, Audio-DVD production, and related applications. All VSP parameters are dynamically automated within the console's AutoTouch automation.
In the near future, Studer says that it will be offering an interface for not only visualizing what's happening to sound sources via the computer screen, but which will enable the user to position a sound source dynamically within a virtual room using a mouse. Room parameters will be calculated automatically, freeing the user to concentrate on more creative aspects of a mix.
The central Multiformat Monitoring Unit (MMU) provides monitor - format selection with loudspeaker designation display; pre/post decoder monitoring; meter-to-monitor switching; additive mode selector; and, dependent upon the format selected, a readout of the names of loudspeaker channels. Each speaker output can be soloed or muted individually. For film mixes, loudspeaker outputs can be calibrated. A Dynamic Stem function allows stems to be reconfigured as different sound sources are processed. There are no restrictions on the number of stems, their width or name, aside from an upper bound limit of 96 simultaneously available group and track busses.
The D950S features a modular machine-control system that may be expanded to match different applications. Surround mixing normally requires access to and control of a number of playback and record machines, ranging from a simple, two//three-machine configuration, to several dozen machines for a complex dub. A simple, one-machine control interface is included in the D950's AutoTouch Dynamic automation system; an expandable multi-machine control system is also available.
The D950S can be supplied with an optional Record/Monitor Control Unit (RCU) which, in conjunction with the machine-control system, controls recorder track arming as well as the record status of each machine track. Up to 64 machine tracks can be accessed and controlled individually, or in groups. The RCU is equipped with control switches for multiformat monitoring paths, and also allows switching between Send (Bus) and Recorder returns (PB)- the familiar PEC/DIRECT switching. Four RCUs can be defined in a system to enable multiple-operator formats.
In extended listening tests, the system's D19 Series front- and back-end converters provided clear, transparent audio, while the dynamics and EQ sections are easy to implement and can be used to generate extremes without sonic anomalies. The system's total reset and AutoTouch dynamic automation provides the power and user functions that will dramatically simplify mixing chores. And for a number of failure-critical environments- including TV/radio broadcasting, live performance and theatrical installations- the D950's extended reliability, with DSP and power-supply redundancy, ensure that audio remains in place despite electrical and related funnies.
With access to more than 200 audio paths, plus flexible bus structure, configurable stems, full surround VSP-format panning, 10 layers, integrated machine control, multiple-operator layouts and PEC/DIR controls, the D950S will find ready application within film and high-end video facilities.
Essentially, the D950's design is based on scalability rather than modularity, an approach that reduces upgrading costs; DSP boards are less expensive and enable the basic functionality to be upgraded at minimum cost. As a bonus, the ability to run multiple surfaces from a single DSP rack can result in more economies of scale. Definitely a system worth checking out.