Dynacord CXM15 Brochure
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The CXM 15 from Dynacord, a manufacturer
based in Straubing (Germany), is a 15"/1.4" box
with a wedge design. The cabinet has been
kept especially flat and compact so as to be as
unobtrusive and easy to position as possible
on stage. Despite the advent of in-ear monitoring, floor monitors are no relic of the past.
On grounds of cost alone and the relatively
time-consuming handling, in-ear monitoring
is often not possible, and a great many performers and technicians in any case prefer
classical monitoring on stage – and for a wide
variety of reasons. The demands placed on
the loudspeakers used on stage are very high:
"unobtrusiveness" is of particular importance
if the set is to remain uncluttered and the
lines of sight of audience members (and
cameras) unobstructed.
From an acoustic standpoint, a consistent
directionality and a frequency response
free from narrow-band ridges are what is
required, the aim in each case being to
reduce susceptibility to feedback, as – along
with the polar pattern of the microphones
– the performance of the monitors plays a
leading role here. Depending upon the
application, further factors, such as the ade-
Dynacord CXM15
Coaxial floor monitor with optional FIR processing
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PRODUCTION
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production partner 12/09_01/10 special reprint
Dynacord CXM15
TEST
quacy of sound pressure levels, are of greater or lesser importance. Since stage monitors are usually operated at close range –
between one and three metres from the
performer – the sound should as far as possible radiate from a single source.
CXM 15
For the aforementioned reasons, the CXM
15 is conceived as a coaxial two-way system. A further advantage of this construction is the reduced area of the front panel,
which makes the box more compact. The
two sides of the enclosure are angled at 33°
and 45°, the depth of the cabinet being 329
mm. These compact dimensions for a 15"
woofer indicate already that the box is not
necessarily optimized for deep bass reproduction, but this is in any case not what is
generally wanted in a stage monitor. The
size of the enclosure is clearly here the primary consideration. Genuine deep bass
reproduction on stage is only required, if at
all, for the drum monitor, which can always
be complemented, should the need arise, by
a subwoofer or shaker.
With a weight of only 19 kg, the CXM 15 is
one of the lightweights in its class and is
wonderfully easy to handle. Particularly
practical are the integrated gripping edges
running all the way round both sides of the
enclosure. The recessed side panels accommodate three Speakon sockets, the active/passive selector switch and an integrated stand adaptor. Two of the Speakon
sockets are on the side with the stand adaptor and the third on the opposite side. This
means that whichever way the loudspeaker
is mounted, a short Speakon cable is all that
is needed to run the signal from box to box.
The socket for the stand reveals that the
CXM 15 can naturally also be used as a 'normal' full-range box or as the top box in a
small PA or even as a fill system.
Overall, the birch plywood enclosure with
its textured finish has a very robust look to
it and the same goes for the equally solid
front grille with its foam backing. The way
the front grille is attached here, with very
solid threaded screws, represents a great
improvement over the screw or clamp
designs you usually find. You can remove
and replace the grille umpteen times here
with no problems whatsoever. Depending
upon the type of show, monitors on stage
can be exposed to a considerable amount of
dirt, so it is important to be able to clean
the front panel regularly and swiftly.
When you unscrew the grille, the 15" chassis with its coaxial high frequency horn
appears. The relatively large horn is positioned extremely close to the diaphragm of
the 15" woofer. For the woofer, the horn
functions as a type of small-volume bandpass chamber. Interference caused by the
sound radiating from the woofer diaphragm reflecting back off the horn is only
of relevance at very short wavelengths – in
other words, at high frequencies that are in
any case above the crossover frequency of
1,200 Hz. On the other hand, thanks to its
size, the directionality of the horn is already
so pronounced at the crossover frequency
that the woofer diaphragm lying behind it
is scarcely of any importance. The object of
this approach is to obtain greater control of
the sensitive midrange, which is otherwise
always a weakness with coaxial drivers.
And here, we can say at the outset, the
approach has proved successful.
If you unscrew the chassis, it is easy to
remove the driver with its two neodymium
magnets from the box. The saving of
weight that comes with the use of neodymium magnets is especially noticeable in
the case of coaxial systems with two drivers in one chassis. Comparable chassis
with ferrite magnets usually weigh more
than the entire box does here.
Active or passive?
Once we have removed the driver, we get a
clear view of the crossover: the circuit
board contains two passive second-order
filters – a high-pass and a low-pass – as
well as a protective circuit for the tweeter.
The compact circuitry on the board calculates in the manner of a simple analogue
computer the RMS power received by the
high-frequency driver and opens a relay
whenever necessary (i.e. whenever there is
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a danger of overload). The tweeter is not,
however, fully switched off when this
occurs but driven via two light bulbs connected in series, which offer secure protection against burnout. When the overload
condition no longer exists, the bulbs are
once again bypassed by the relay. A switch
on the panel allows you to choose between
Passive and Active modes.
In active mode, both the passive filter and
the high frequency protection remain in
the signal path, only the input to the passive crossover is now split so that the HF and
LF can be driven separately via pins 1 and 2
of the NL4 connector. This obviates the risk
of defects caused by faulty wiring. In active
mode, the only thing to bear in mind is that
the passive filter is already in the signal
path. The crossover frequency in the active
version can no longer therefore be raised
significantly beyond the 1.2 kHz of the passive filter, which is in any case something
best avoided. For active mode – naturally
for passive mode as well – Dynacord recommends a power amplifier from its own
Power H series equipped with the controller module IRIS-Net RCM-26. The H5000
power amplifier and the RCM-26 module
were already the subject of a detailed test
report in PRODUCTION PARTNER (Issue
10/2007) so we only need outline here those functions most relevant to the CXM 15.
IRIS-Net software and the RCM-26 module
The Intelligent Remote Integrated Supervision software platform (IRIS), which has
been available now for seven years, contains the manifold control and supervision
functions for Dynacord and EV power
amplifiers and loudspeaker controllers
equipped with their own DSP systems.
Independently of any signal processing
functions, the RCM-26 module adds a twochannel digital input and output in
AES/EBU format, a CAN bus interface and
two GPIO control and supervision connectors for external functions to the power
amplifier. The networking for the remote
supervision and remote control is handled
by the CAN bus.
To connect to the PC, a further USB/CAN
adapter is therefore needed. The UCC1
supplied for the test offers in addition to its
adapter function the possibility of listening
in to the signals of the connected amplifier
via an audio output, which is especially
practical when searching for errors.
For remote supervision, IRIS-Net offers a
series of useful functions both for the
power amplifiers and the connected loudspeakers. In addition to pilot-tone supervision, these allow the load impedance of the
network and the prevailing thermal conditions to be checked. Another very important function is measurement of the impe-
The RCM-26 IRIS-Net module
dance of the connected loudspeakers. Here,
instead of a single reading, an entire impedance curve for the frequency range 20 Hz –
20 kHz is measured. This can then be compared with a stored tolerance mask (see Fig.
14) so that a reliable judgement can be formed as to whether the connected loudspeaker is still perfectly OK or in fact defective.
With this type of measurement, you can
make a reliable and at times highly specific
diagnosis of most loudspeaker errors. Such
a function is extremely useful for the
supervision of fixed installations but even
more so in the touring and rental sectors, as
it makes it possible to conduct a swift and
reliable check at the end of each show to
make sure all the loudspeakers connected
are still functioning correctly.
The RCM-26 controller in the H5000 power
amplifier offers the choice of running the
CXM 15 in either active or passive modes –
in each case with either IIR or FIR filters.
With 2 x 2.5 kW of sustainable power into 4
ohms, the H5000 naturally offers more
than enough power for the operation of the
CXM 15, so one can easily imagine a configuration with four boxes per channel and a
total load of 2 ohms. In this case, the H5000
would deliver 3.3 kW per channel with 825
watts going to each box. The CXM 15's
power handling is given as 900 watts program and 450 watts RMS, so this configuration should suit it nicely. One H5000 can
power eight CXM 15s in passive mode and
four in active mode.
Measured values
The connectivity of the CXM 15 with its
individual LF and HF paths when set to biamp mode makes it easy to measure the
two paths separately. What this reveals
immediately is how well the two interact in
the 1.2 kHz crossover zone. Fig. 1 illustrates
this nicely. Despite the simple design of the
passive crossover, the response when the
two paths are summed is linear. Between
200 Hz and 3 kHz, the sensitivity is just
under 100 dB; above 3 kHz it is around 103
dB. The fine interference structure in the
high frequency range is not the fault of the
driver but largely an unavoidable sideeffect of the grille, as the black line showing the response when the grille is removed makes plain. Since the grille inevitably
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