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Phonic MRS1-20

Analogue Surround Mixer
By Paul White

Phonic's MRS1-20 console brings analogue surround mixing to the project studio market for the first time.

PHONIC MRS1-20Photo: Mike CameronAlthough some companies want to be seen to be 'surround aware', until now nobody has actually produced a project studio mixer that could monitor in surround. For example, my otherwise excellent Yamaha 03D has a surround mixing mode, and it can be configured to provide surround outputs to feed a multitrack recorder, but the control room monitoring is only designed to handle stereo.

Phonic's MRS1-20 is in most respects a very straightforward analogue mixer with no 'tape monitor' section, no automation and a basic three-band EQ. It has 20 input channels, and had it been a simple stereo mixer it might have been quite unremarkable. However, the provision of full 5.1 mixing and monitoring at this end of the market makes it the first of its kind. Which brings me to a question of terminology: if a stereo mixer with 20 channels is a 20:2, does that make this 20-channel surround mixer a 20:5.1:2?

Routing & Control Layout

Conceptually, the MRS1-20 is set out much like a regular stereo console, with most of the channel facilities being perfectly conventional -- see the 'Main Channel Features' box for details on these. The main difference is that, in addition to the usual left/right pan control (which in this case pans via the centre speaker), there's also a left/right surround pan control (for the rear speakers) and a front/back balance control. By juggling these, the mono channel input can be positioned anywhere in 5.1 space.

A number of options are available for feeding the Low Frequency Effects (LFE) channel, where pressing the channel LFE button sends the low-frequency component of that channel's signal to the LFE mix buss. A rotary switch in the master section then selects one of the six aux send busses, the channel signal or the sum of the five full-range busses as the LFE source.

The mixer includes a 120Hz low-pass filter at the LFE output (the standard for cinema), though an internal jumper enables this to be reset to 80Hz, as is preferred by some surround music mix engineers. Similar surround panning controls are used for the effects returns, though the adopted three-knob system provides no way to adjust how much of the channel's front signal is sent to the centre speaker. Centre-panned front signals always feed into the Centre channel. Similarly, handling stereo signals, while perfectly possible, requires two channels and six surround positioning knobs, so setting even a static position is a little fiddly, and dynamic 5.1 panning is out of the question.

Main Channel Features

PHONIC MRS1-20 main channel.Each of the input channels is identical and features a mic/line switch with Gain control but no pad or phase reverse switches. The mic inputs are on balanced XLRs, while the line inputs are on balanced jacks, with the microphone phantom power switchable in blocks of five channels. The three-band EQ comprises shelving high and low controls operating at 12kHz and 80Hz respectively, with a sweep mid-band covering 100Hz to 8kHz. All sections provide ±15dB of gain while a switchable low-cut filter (18dB/octave) comes in at 75Hz. There is no EQ bypass.

Four aux send controls feed six busses, with the first two sends fixed pre-fade for foldback applications. The other two controls are post-fade effects sends to aux busses three and four, but they may be switched to feed aux busses five and six instead. That leaves the three surround positioning controls, as described in the main text, plus a short throw 60mm level fader (described in the manual as long throw!). The Solo button and On switches both have status LEDs.

Each channel has its own bar-graph meter on the in-built meterbridge, and in addition to the main inputs, there's a direct output and a TRS jack insert point. The insert point is configured pre-EQ and can be reset to post-EQ via internal jumpers. Similarly, the direct output, which defaults to post fader, can be set to pre-fader via jumpers if the need arises.

The Master Section

As with the channels, the master section would be pretty straightforward were it not for all the surround options and control. There are eight 12-segment meters to monitor the six elements of the surround mix plus a stereo mix, while below the meters are the six Aux Send Master controls with Solo buttons. Solo can be pre-fade or post-fade (PFL or solo) as set by a Pre/Post button in the master section. Given the complexity of the 5.1 positioning controls, the provision of five channels of effects returns seems very generous, and all have the same 5.1 panning controls as the main channels, as well as level control, Solo button and sends feeding the first two aux send busses. However, these are again all mono, so stereo effects take up two returns, and it's as fiddly positioning them in 5.1 as it is with the main channels.

Stereo mixers invariably feature a two-track tape return, and the MRS 1-20 is no exception, but as surround mixing means using a multitrack recorder with six available tracks, there's also a six-track return for surround playback. Because of the amount of panel space individual sockets would require, both the six-track and two-track sends and returns are wired via a pair of Tascam-style D-Sub connectors.

The master section.The master section.Photo: Mike Cameron

Level controls are available for all six surround return channels, though I'd be happier if these were trims that couldn't get reset by accident. When the 5.1 button is pressed, the six-track input signal is sent directly to the 5.1 surround output, whereas if the Ctrl Rm button is pressed the signal is sent to the control room monitors, provided that you remember to set the 5.1/ST button in the control room section correctly. The two-track return section features a simple level control, plus buttons for selecting St Mix or Ctrl Rm as the source. Next to this section is the LFE source selector switch.

Each channel of the 5.1 output has its own fader which controls the levels feeding the XLR surround outputs, the tape outs and the control room monitor gain trims. A further fader controls the level of the stereo downmix fed to the two-track output and the monitor section. Associated post-fader Gain and Pan controls are available for positioning the surround elements when submixing to stereo.

Each surround channel has a Solo button, essential for quality-control purposes, and the control-room monitor section includes gain trim knobs for all six channels as well as a master level control. Again, I'd like to see these gain trims more secure against accidental adjustment, though a workable strategy would be to set them at maximum and then finely adjust the speaker gains either at the speaker (in the case of actives) or at the amplifier.

Things get more traditional with the headphone section, which feeds two sets of stereo phones at once, and directly above is the solo Pre/Post button along with a separate Solo Level meter, but no master solo status LED. Solo To Cntrl Rm sets whether the solo signal feeds the left and right channels or the centre channel of the control room monitor output. This is fine so far, but to adjust the solo level, you have to use the C or L/R monitor output trims, which is, to put it mildly, crazy given my conviction that these controls should be carefully calibrated once and then welded in place!

A built-in omni electret mic provides talkback and comes with a level control and three non-latching routing switches for Aux, Stereo or 5.1. By default, Aux sends the talkback to the first two aux sends, but internal jumpers can be set to allow it to feed additional aux sends at the same time.

MRS1-20 Connections

All the MRS1-20's connections, other than the headphones, are on the rear panel of the mixer, including a socket for the included external power supply. Aside from the insert points and the control room monitor outputs, which are unbalanced on jack connectors, the remaining connections are mainly balanced, including the D-Sub connectors for the tape sends and returns, which are wired to the Tascam DTRS standard. Rather awkwardly, the control room outs have a single TRS jack for centre/LFE and another for surround left/right.

The surround and stereo outputs are available directly on balanced XLRs wired after the surround faders (which is convenient for live surround mixing) while the line inputs and channel direct outputs are on balanced jacks, as are the aux sends and returns. A 12V BNC connector is available for connecting a gooseneck lamp.

Session Notes

Most aspects of this mixer are straightforward, but trying to build surround compatibility at a price invariably means compromises. My main reservations, other than the ease with which gain trims can be accidentally moved, is that stereo signals are not adequately catered for, and that there is no provision for separately adjusting what each channel sends to the centre-channel buss. For example, in some applications you may want centre-panned sounds to go only to the centre speaker, but in others you may prefer to use conventional left/right panning with no centre information. You may also want to combine these two ways of working in different proportions, but with this system centre-panned signals always go only to the centre speaker.

I'm also a little unsure as to why separate front and rear panning controls take priority over something as fundamental as independent centre-channel level control, as I can envisage few situations where it would be important to me to have the front signal panned right and the rear signal panned left (other than if I wanted to use the front/back control to pan from rear left to front right). Using the same number of knobs, the designers could have provided us with left/right and front/back knobs, as well as a control for determining whether mono signals went to the centre channel or to the left and right channels, which would have been much more useful. I'd also have liked to have had some dedicated stereo channels, as I think a lot of potential users would want to use the mixer to integrate hardware synths into an existing computer surround mix.

As a studio mixer, the inability to switch the pre-fade sends to post-fade is unnecessarily limiting, and many people would prefer an EQ with more flexibility than provided by just a swept mid-band, but the fact remains that if you want an analogue surround mixer at anything like a sensible price, the MRS1-20 is pretty much the only game in town, and it does provide usable surround monitoring.

The six-track return can be routed to the main surround mix busses, which would allow you to mix surround outputs from your soundcard with MIDI instrument outputs feeding the 20 channel inputs.The six-track return can be routed to the main surround mix busses, which would allow you to mix surround outputs from your soundcard with MIDI instrument outputs feeding the 20 channel inputs.Photo: Mike CameronCuriously, the handbook is written with an apparent bias towards live sound, but there are plenty of studio applications for a mixer like this, even though it doesn't have a multitrack monitor section, which precludes it from being used as the main mixer in a hardware-based multitrack studio. Nevertheless, in a situation where a hard disk recorder is being used to record relatively few tracks at a time, via separate mic preamps or voice channels, the MRS1-20 is perfectly adequate for monitoring the multitrack outs and for mixing, both in stereo and surround. It is also fairly well suited to mixing MIDI sound sources into stereo or surround, with the caveat that mixing stereo sources is a bit clumsy.

You might take it from my comments that I've got a bit of a downer on the MRS1-20, but you have to remember that it is the first affordable surround mixer, so it is bound to have limitations. Using mainly mono sources, you can mix in surround very easily, and the sound quality is perfectly good. Tests with the mic amps revealed them to be comparable with those of other well-designed budget desks, with no loss of clarity or excessive noise, while I thought the EQ sounded rather better than on many competing designs.

Where MIDI gear is being used in conjunction with a computer-based multitrack, the ability of the MRS1-20 to route its 5.1 six-track return to the 5.1 mix buss is immensely useful, as it provides a way for the 5.1 outputs from a multi-channel soundcard to be fed into the mixer without taking up any additional input channels. The computer surround mix would then be combined with any MIDI instruments fed into the mixer to derive the final 'computer plus hardware' surround mix, which could even be recorded back to six spare channels of the computer rather than to a multitrack hardware recorder.

Verdict

The MRS1-20 is a brave first step into affordable surround mixing and it provides a reasonable degree of flexibility, even though some aspects of the surround positioning are limited, specifically the centre speaker level and the handling of stereo signals. I also felt that providing five mono returns, rather than stereo returns kitted out with simple left/right and front/back steering, was perhaps not the right move. But, those comments aside, the mixer performs well, is easy to use, and does enable you to both mix and monitor in surround.

Because the MRS1-20 isn't a full recording console (it isn't designed to record and monitor at the same time), it is perhaps best suited to computer audio systems or for use alongside hardware recorders where recording is done via separate preamps. This probably describes a lot of home studios, and within the limitation of mono-only channels, it does provide a practical means of integrating hardware MIDI instruments with a computer-generated surround mix. For anyone looking to take their first steps into surround mixing, the MRS1-20 offers a lot of scope and decent audio quality for relatively little money in the UK. It's not the perfect solution, but these are early days for surround and I suspect we'll see a lot of evolutionary steps in mixer design before anything like a standard is adopted.

Pros

  • The first affordable analogue surround mixer.
  • Good sound quality with quiet mic preamps and musical EQ.

Cons

  • No means to decide how the centre speaker should be used.
  • Solo level must be set using the control-room monitor trimmers.
  • Gain trim pots on the six-track returns and surround monitor feeds are easy to alter accidentally.
  • All channels and returns are mono.
  • No EQ bypass.

Summary

The MRS1-20 is really a very simple mixer that has been expanded to give it surround capability. It has its limitations, but is currently the only mixer of its type at this price point.

information

£1380 including VAT.

www.phonic.com

Published July 2002