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On
the work bench: the Serpula and Tylodina –
two tapered transmission-line
loudspeaker ranges
Boundary-mounted
Loudspeaker System
The
beautiful sessile marine tubeworm that lends this
loudspeaker range its name.
A
sketch of the enclosure of this new design.
The
name Serpula derives from a genus of calcareous marine
tubeworms. It was chosen to indicate the fact that this
entire range of loudspeakers has been optimised for
mounting against a boundary or wall. The first example
was an event loudspeaker, aimed at professional sound
reinforcement. It has been followed by a range of
similarly styled designs for high-end home audio use.
Construction materials for the top, face and back
comprise a laminate of solid 25mm Padauk with MDF, and
the sides are made of similarly reinforced OSB. The
downward-tapering geometry is purely functional and a
set of two carefully selected drivers, one a widerange
unit and one a supplementary low-frequency driver, will
complete the picture. Features include full-range
operation from 100Hz to 20kHz, with bass extending to
under 40Hz at ±
3dB, sensitivities ranging from 91dB/2.83V to 97dB/2.83V
at 1m, 40W to 350W noise power handling, an easily
driven load impedance, and a minimal first-order filter
network.
The
Tylodina, named after a sea mollusc, is identical to the
Serpula models except for the fact that they employ a
tuned port in lieu of the tapered, resistive terminus of
the Serpula range. All care is taken that the use of a
tuned port does not produce the excessive group delay
that this type of alignment has sadly become known for.
The Tylodina makes it possible to use drivers that would
be too problematic to optimise in the generally larger
Serpula enclosure.
RRP
= R33,886.00 (for the standard model – RRP is
calculated according to size, driver choices and build
details, and may vary)
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SINGLE-SOUNDFIELD
STEREO
PHI
has taken a step into the relative unknown by developing
and manufacturing a range of single-soundfield-stereo
loudspeakers. Already in the nineteen seventies, the
late Ted Jordan of Goodmans fame had suggested an
unorthodox placement of a loudspeaker pair. This
amounted to placing two loudspeaker boxes back-to-back
in front of the listener, with the main drivers of these
boxes firing sideways, away from the speaker pair and
perpendicular to the listening axis. The resulting
expanding wavefronts are intercepted by two reflectors
placed some distance from the back-to-back speaker pair,
reflecting them at the listener.
When
correctly approached, a considerable widening and
deepening of the stereo field is the result, and the
typical hole-in-the-middle effect of traditionally
placed stereo pairs is avoided.
Our
latest range takes this concept a little further by
combining the stereo pair in a single enclosure, while
adopting a number of strategies to ensure that whatever
channel “crosstalk” there is is limited to the
frequency ranges where this is inevitable, i.e. below
the Schroeder
frequency,
especially when employing a traditional stereo pair in a
typical listening environment.
We
by no means intend to replace traditional stereo
loudspeaker arrangements, but SSS has a number of very
attractive qualities that simply have to be experienced
to be appreciated. In fact, SSS often provides a more
convincing and accurate representation of the sound as
it would be experienced in the particular performance
venue where it was recorded. Add to this the fact that
the cost of a stereo set is reduced considerably, and
that it is often easier to optimally set up a single
speaker in a room than a pair, especially in smaller
spaces, and this type of setup soon becomes an
attractive proposition.
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THE
SERPULA SSS
Freshly
off the design bench:
The Serpula SSS (single-soundfield
stereo)
-
a wall-mounted transmission-line/aperiodic
enclosure
hybrid.
Wall-Mounted
Stereo
Audiophile Loudspeaker System.
The
prototype of the new Serpula Single-Soundfield-Stereo
loudspeaker, installed in a client’s lounge.
As
second offering from our new per[form]
stable,
the new Serpula design is a hybrid of a short-taper
tuned pipe and an aperiodic enclosure such as the Dynaco
A10
employed.
The
German-designed high-end widerange driver uses the tuned
pipe character of the enclosure to firm up its lower
frequency response and excursion characteristics, while
the American- or Italian-designed audiophile low
frequency driver, which only operates at full efficiency
between around 40Hz to 150Hz, uses the aperiodic reflex
characteristics of the enclosure to firm up its
low-frequency response. A high-quality, low-slope,
first-order serial crossover filter assures immaculate
integration of the two drivers.
Rather
unusually, the fullrange drivers fire sideways rather
than forward, depending on reflections from equidistant
walls or special reflectors to create a stereo field.
This arrangement, pioneered by no-one else than Ted
Jordan of Goodmans
fame,
produces a huge and surprisingly detailed and convincing
sound stage.
The
loudspeaker is designed
to
be mounted anywhere from ear height to
relatively
high up against a wall – this is as much a concession
to space considerations as to inevitable boundary
fall-off
in
modern, smaller home spaces. Simulations have indicated
that this configuration not only has a positive effect
on the sound character of the widerange driver, but is
substantially advantaged by the low frequency boost that
accompanies the placement of a loudspeaker against a
boundary. The upward-firing low-frequency driver (in the
case
of the two-loudspeaker stereo set) augments this boost
effect by acoustically coupling with the ceiling.
The
design employs solid hardwood for the face, back and top
of the loudspeaker, and an OSB/MDF sandwich for the
sides. 25mm of solid Padauk wood, reinforced with a 9mm
layer of MDF, was employed in the example above.
The
loudspeaker has been tested with a range of drivers in
various cost brackets and performs exceptionally with
all of the drivers we have selected. This not only
allows customisation, but makes possible an entry-level
model of this hugely enjoyable and musical loudspeaker.
RRP
= R19,210.00 (for the standard model – RRP is
calculated according to size, driver choices and build
details, and may vary)
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