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RTW TM3-Primus

Touch-screen Meter By Hugh Robjohns
Published September 2015

The German manufacturer RTW has a long history in the broadcast sector dating back to 1965, mostly in the areas of specialist metering systems and equipment interfaces. The latest member of its ‘Touch Monitor’ range is the diminutive TM3-Primus: a compact, fully integrated, multi-function desktop audio metering system. It measures 138 x 83 x 50 mm (WHD), weighs just 320 grams and houses a 4.3-inch capacitive colour touchscreen (272 x 480 pixels). It can be used in portrait or landscape mode, with a vertical swipe across the screen toggling the orientation. The rear panel carries four RCA phono sockets plus a Micro-B USB 2 connector, the latter used for power from a supplied wall-wart PSU or directly from a computer. Two of the RCA phono sockets accept a stereo unbalanced line-level audio feed (input impedance is 10kΩ) and adjacent multi-turn trimmers allow the input sensitivity to be adjusted over a range of -22 to +24 dBu.

RTW TM3-Primus

It’s unlikely that any physical adjustment will be required, though, as the software allows internal trimming with 0.1dB steps and automatically adjusts for the different meter scales. So a +4dBu input reads 0VU, 0dBu reads PPM4, and so on.

The other two RCA phono sockets accept a stereo S/PDIF input and provide a buffered S/PDIF output. The USB 2 interface can also carry either stereo or 5.1 surround audio from a computer if selected as an output device. The maximum sample rate is 96kHz, and the A-D converter defaults to 48kHz. Although an ASIO driver is required for Windows systems, it works natively with Mac OS X. Note that if connected via analogue or S/PDIF it’s helpful to use lightweight, flexible cables, as the cable otherwise tends to determine the display’s position!

When the unit is first powered up the user selects the default language and input mode (analogue, digital, USB stereo or USB surround), and pressing and holding the centre of the touchscreen for two seconds activates the settings menus. The initial power-up defaults and various other metering parameters can be viewed and adjusted, including the unit’s serial number, firmware version (1.01 in the review unit), firmware update, audio reference levels, loudness metering standards, meter scales and display configuration. There’s also a factory reset option.

There’s a comprehensive collection of display modes, although not all can be shown simultaneously due to the screen size. The unit intelligently manages what can be displayed together, though, as well as their relative sizing and placement. The first three options are stereo vectorscope, real-time analyser (RTA) and loudness chart. Then there are bar-graph or moving-coil-style level meters, a phase-correlator bar-graph, an integrated-loudness bar-graph (with absolute LKFS/LUFS or relative LU scales), loudness value numerical readouts and a ‘magic LRA’ bar-graph that indicates dynamic range. A set of optional touch buttons can also be displayed to start, stop and reset the loudness measurements. All of the current international loudness normalisation variants are supported, including the generic ITU BS.1770-3/1771-1 recommendations, EBU R128 (Europe), ATSC A/85 and CALM Act (USA), OP-59 (Australia), AGCOM (Italy) and ARIB (Japan).

The moving-coil meters are switchable between VU and BBC-style PPM, and usually appear side by side for the two channels. There’s also a twin-PPM mode which shows coaxial left (red) and right (green) on the same BBC scale, along with a third, blue needle for the integrated loudness (PPM 4 is the target level).

Configuring the TM3-Primus is simple and obvious, but some experimentation is necessary to arrive at a practical combination of displays. I had no trouble finding very workable solutions for a number of different situations, and each display section is very clear and easy to understand, and impressively configurable.

The Loudness Chart is particularly useful, with an integrated loudness bar-graph on the left, calibrated in relative Loudness Units, and the progress/history chart showing momentary loudness (with a user-selectable time base of one minute, five minutes or 1 hour). The chart can also show the history of the true peak level, short-term loudness or integrated loudness. The acceptable LU tolerances can also be superimposed, as can the relative gate level.

The RTA is exactly as you’d expect, displaying 31 one-third-octave bands with selectable peak hold, ballistics and reference levels, while the ‘magic LRA’ display emulates the old ‘magic-eye’ meters found on tape recorders in the 1960s! Its green bar lengthens and shortens to reflect the current loudness range, getting lighter towards the extremities as the range increases. A numerical readout is also included.

And talking of numeric readouts, the Loudness Values display mode can be configured to show any or all of the momentary, short-term and integrated loudness, LRA and true peak values. The number colouring reflects the status, too, green indicating an ongoing measurement, yellow when stopped, and red if tolerances are exceeded.

Selecting the level bar-graph meters allows a choice of meter scales (true peak, sample peak, DIN/Nordic, or BBC-PPM) and reference levels. A phase-correlation ‘LED’ between the meters glows green for positive values, red for negative, and white when there’s no correlation. The only negative is that it’s not possible to alter the bar-graph colours, for example to set safe, target and danger regions.

Most DAWs have comprehensive metering these days, but there are advantages to freeing up the computer screen with an external meter! The display is very clear with a surprisingly comprehensive and configurable range of metering tools. It’s easy to set up too, and although a downloadable handbook is available, the supplied quick-start guide is enough. Similar compact metering systems are available from DK Technologies, such as the DK1, 2 and 5 units, while RTW also offer several alternative compact meters, most of which separate the display from the interface hardware. However, the TM3-Primus enjoys the benefit of being a fully integrated solution, particularly if driven from a computer. I really enjoyed using it.

£712.06 including VAT and delivery.