Recording - March 2014 - 18

B Y M I K E M E T L AY

Grace Design builds preamps, signal
processors, and monitor control solutions
world-renowned for their elegance and
clean, clear sound. With the m905, the
brothers Grace and their team have pulled
out all the stops to offer a no-holds-barred
solution for monitor switching, confidence
monitoring, and more. It combines the very
best D/A conversion Grace can offer with
a slate of input and output options that
make it suitable for the very largest studios.

Grace Design m905 Reference Monitor Controller
The ultimate monitor control system?
Here and there
The m905 comes in two parts. The guts of
the machine are in a 2U rackmountable
mainframe, the Audio Control Unit (ACU),
and the controls and readouts are on the
Remote Control Unit (RCU), which connects
to the ACU via a flexible Mogami cable, 25'
long, with DB-15 connectors on either end.
To learn what the m905 can do (at least in
part), look at the ACU's rear panel. You'll find
the following analog I/O: Balanced In,
Unbalanced In, Cue In, and Talkback Mic In;
Speakers 1, 2, and 3 Out, Sub/DAC Out,
Cue Out, and Talkback Mic Out. Aside from
the Talkback Mic I/O, everything is in stereo,
and aside from the Unbalanced Inputs (on
RCA), everything is on XLR. In the digital
realm, there are two AES3 Inputs and an
AES3 Output on XLR, coaxial S/PDIF In and
Out on RCA, optical Toslink and ADAT
Lightpipe Inputs, and Word Clock I/O on
BNC connectors with switchable termination.
The rear panel is rounded out with USB
for interfacing, a second USB connector for
upgrading the ACU's firmware, a conventional IEC power cable, and a 1/4" Talkback
Switch input. The front panel is virtually
unadorned, with only a green Power button
and a 1/4" headphone jack.
The RCU comes in a sturdy and beautiful
metal chassis with an adjustable tilting
base. It's dominated by a large color LCD
with eight input source selection buttons.
There are three Speaker select buttons, with
Speaker 1 being largest and easiest to
reach; opposite the Speaker 1 button on
the other side of the large Volume knob
(push to control the headphones) is a bright
red backlit Talkback button.
There are five dual-function buttons (press
and hold for the second function, which
18

RECORDING March 2014

makes the button flash): Mute/Solo, Dim/XFeed, Sub Mute/Sub Solo, Mono/L-R, and
Mon > Cue/SPL Clear. A final button
accesses the Setup menu. On the back of
the RCU is a small USB port for firmware
upgrades and a second 1/4" headphone
jack. There's also a built-in mic on the RCU
for talkback and/or SPL measurements.
Functions and operation
Reading the above succinctly sums up
what the m905 can route and where.
Balanced or unbalanced analog audio, two
AES3 sources, S/PDIF, or ADAT (two channels at a time, either standard resolution or
SMUX for high sample rates) can be routed
to any of three sets of monitors plus a pair of
subs (or other source for a direct DAC output)
and headphones. The Cue Input and Output
are used to feed a headphone cue system
(with the Mon > Cue button switching over to
the monitor signal when desired), and the
Talkback signal is fed into the Cue signal path
as well as being available on its own output.
But there's a lot more than that. The RCU
has a built-in SPL meter that constantly reads
SPL in the room via the internal mic and displays current and peak readings. Volume settings are displayed in dB for the currently
active speaker (on the left) and headphones
(on the right), with the level currently controlled by the Volume knob in green. The

USB port makes the m905 a class-compliant
audio I/O device that can handle data up to
24-bit/192 kHz or DSD up to 2.8224 MHz.
And the Talkback Mic Input, by the way, is
actually a full-on Grace preamp with up to
70 dB gain, in case you need one-you can
set a pair of jumpers so it's always "on"
rather than slaved to the Talkback button.
The system is designed all around for you
to be able to set up your monitors with
matched and reproducible levels and to
recall these settings at the touch of a button.
You can set the level displays to an absolute
dB amount from 0.0 to 100.0 in half-dB
increments, or calibrate them to a chosen reference SPL in dB; you can also fine-tune the
level, panning, and subwoofer output type
(mono, stereo, dual mono) for each speaker
choice. Once your settings are stored, simply
selecting a speaker button tweaks your levels
and offsets so that A/B comparisons are
level-matched and best suited for the placement of each speaker set relative to the subs.
In practice, it takes a good several hours to
get all these levels set up just right. But once
it's set, it stays set, and worries about level
mismatches are a thing of the past. You can
even name each input source and speaker
output so you know at a glance if you're listening to your Genelecs or your KRKs.
Setup mode offers lots more in the way of
convenience features. You can determine

Recording - March 2014

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