Project Description

RTW 31900

Fully-featured 8-channel surround monitoring controller suitable for use in the most exacting professional environments. Includes surround sound analysis of 5.1, 6.1 and 7.1 (the RTW “House”), very flexible multichannel PPM/loudness metering integrated with  comprehensive 7.1 monitoring control and calibration. VGA compatible output, rack-mounting (1U).
Also available as half-rack-width (3U) unit with integral display (31960).


  • Comprehensive control of surround monitoring (up to 7.1) from desktop remote
  • Calibrated multi-channel level control with SPL display
  • Per-channel mute, solo, trim and phase reverse functions
  • Mono, dim and channel swap functions
  • Programmable per-channel delay for accurate time-alignment
  • Internal stereo downmix algorithm, available for metering and as an output (i.e. for secondary Left and Right speaker pair)


  • On-screen representation of surround sound field of 5.1, 6.1 and 7.1 (the RTW “House”)
  • On-screen bargraph metering of 8 audio channels
  • Scale options include PPM and loudness units (LU or LKFS) conforming to ITU BS 1771
  • Loudness history display with user-definable time-axis
  • Additional meter displays of short-, medium- and long-term loudness integrated over time (user-defined period)
  • Simultaneous phase correlation display of all channel pair combinations
  • 2- or 4-channel “Lissajous” vectorscope displays


  • Accepts both analogue and AES3 inputs; with AES3 loopthrough outputs
  • Optional Dolby E and Dolby AC-3 decoding
  • Optional HD/SD SDI de-embedding

Other features:

  • Dialnorm measurement
  • Built-in 1/3- and 1/6-octave spectrum analysis
  • Mic input for absolute SPL calibration
  • BLITS generator/analyser and reader
  • GPIO port
  • 1U 19” unit with separate desktop remote monitoring controller; VGA output for optional 8.4” TFT screen or user’s own display
    3U half-rack-width unit with integral display and monitoring controller (31960)

This unit is also available as the RTW Model 11900, which omits the surround monitoring controller functionality.


The RTW 31900 combines the power and flexibility of the Model 11900 8-channel audio metering system with a fully-functioned surround monitoring controller. It offers the user all the facilities necessary for accurate monitoring management when working in 5.1, 6.1 or 7.1 surround formats. Intended for use in professional environments such as broadcast, post-production or music recording, it provides the operator with total control of the multichannel speaker system as well as giving reliable visual monitoring of all aspects of the surround sound programme.

The desktop remote control unit has a multichannel level control and a numerical display of the absolute monitoring SPL (after calibration). Each channel of the surround set (5.1, 6.1 or 7.1) may be muted, soloed in the Left and Right front speaker pair and adjusted in level (to compensate for differing speaker sensitivities). A downmix function allows stereo compatibility to be instantly checked, on a secondary pair of Left and Right speakers if wished. Verification of the mix’s mono compatibility is also a single button press. A time delay may be added to all audio channels to compensate for any video processing delay in an LCD or plasma display; this may be finely adjusted per-channel if wished, to permit accurate time alignment of all the speakers in the system.

The 31900 is available in two mechanical configurations. One is in standard 1U 19” format, with a separate desktop remote control unit for the monitoring control functions. On this model, the data display output is in standard VGA format for use either with the optional Model 30010 8.4” LCD display, or any other suitable monitor. The alternative configuration, the 31960 is a 3U, half-rack-width unit with an integral 6.5” TFT display, which is ideal for mounting in OB vehicles and other situations where space is at a premium. This version has the monitoring controller built-in, with all controls on the front panel.

The 31900’s display layout and content may be configured in a variety of ways to suit the user’s operational preferences. As well as bargraph metering, a 2-dimensional analysis of the instantaneous surround sound field may be displayed (the renowned RTW “House” display).

Audio level monitoring is via large, clear on-screen bargraph meters. Meter types may be user-defined; these include standard PPMs and loudness meter scales conforming to the recommendations of ITU BS 1771 (both LU and LKFS units). In addition to metering of the individual surround channels, further meters may be placed on-screen, showing, for example, an internally-generated stereo downmix and overall programme loudness integrated over various timescales. The stereo downmix is also available as an output.

Phase correlation may be added to the analyser display, showing the phase relationship between every pair of adjacent channels. Dialnorm measurement is provided for subsequent inclusion with Dolby? metadata. Loudness history may also be displayed as a graph of loudness against time, the time axis calibration being user-definable. A further display option is an audio vectorscope, showing “Lissajous figure”-type phase relationships in 2- or 4-channel modes. Spectrum analysis is also included as standard, with 1/3-octave or 1/6-octave displays.

The 31900 has both balanced analogue and AES3 digital audio inputs. The two formats may be combined if wished, allowing (for example) simultaneous metering of a digital 5.1 console output alongside an analogue stereo mix. The unit’s input capabilities may be greatly extended by two optional modules; these permit decoding of Dolby E/Dolby AC-3 datastreams and de-embedding of 8-channel audio from an HD/SD SDI video signal respectively. The audio outputs from the monitoring controller are also available in both analogue and digital formats, the latter permitting direct connection to the new generation of “digital” monitors with AES3 inputs.

The 31900 incorporates a BLITS-compatible test tone generator for channel identification and studio monitor level matching. A microphone may be connected to perform this calibration, after which continuous accurate measurement and display of room SPL is enabled. The generated BLITS tones are available at the unit’s 8-channel AES3 outputs, which normally provide an active loopthrough of the AES3 inputs when the generator is not in use.

Control of the display and selection of the various options is by large on-screen buttons and a standard USB mouse; with OEM VGA monitors, a USB touchscreen overlay may be used if preferred. Contact closures on the GPIO port also mimic these buttons, allowing interface with external controls. The optional RTW 30010 TFT screen provides soft buttons below its display for this purpose. The 31900 includes a comprehensive menu system which allows the user to configure the primary setup parameters to his or her taste. Configurations may be saved as presets to facilitate rapid recall in a busy facility used by different operators. An import/export facility for presets is also provided. The unit’s GPIO port may be used to recall presets, if wished.

The 30010 VGA display pictured does not come as standard with the 11900.

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