Sonist's latest design, 97 dB efficient with fantastic full-range sound.
Design Goals: Sonist
are designed to work well with low-powered directly heated triode
single-ended amplifiers (SET's), using output tubes such as 2A3, 45,
300B, PX25, 6C33B, GM70, and 845, and EL84 and El34 in single-ended
mode. They also work well with push-pull tube amps and solid state amps.
Concenrto 4 features 97dB sensitivity and
tube-friendly benign impedance curves, nominal 8 ohms, not going below
6 ohms. It feature Auricap polypropylene capacitors,
Goertz Alpha-Core copper foil inductors, Cardas Tri Eutectic lead-free
solder, and Cardas 5-way binding posts. Both models are bi-wireable and
Bass Shelf (EBS) bass alignment extends the useable bass response by
10Hz, to improve the quality of the bass response when being
driven by SET's, which typically produce a warmer bass than solid state
amps, due to their lower damping factor. According to Dick
Olsher, noted audio reviewer, "Such an alignment [EBS] is best suited
for medium to small listening rooms where excessive midbass response
may be a problem. The EBS alignment achieves lower bass
at the cost of reduced response in the midbass. However,
room gain below 150 Hz usually fills in the missing bass at the
to compensate for the midrange emphasis of SET amplifiers, and to
provide a more linear system frequency response, a Zeta of 1.3 is used for the Concerto 4. The
tweeter leg of the crossover is first order for the Concerto 4. The woofer leg of the Concerto 4 is first order. The result is an
involving and lifelike presentation at both low
and high levels, improved low-level dynamics and resolution, and enhanced nuance and
Characteristics: In the Concerto 4, the tweeter waveguide provides
3-4 dB of gain between 2500Hz and 8000Hz, which provides lower
distortion at a given SPL level.
Also, dynamic transients in the tweeter frequency range are more
immediate and provide a greater sense of presence and immediacy. The
frequency range between 2500Hz and 8000Hz contains the harmonic
overtones, formants, spatialization cues, and timbral characteristics
of acoustic instruments and voice, so the subtleties and nuances of the
performance are reproduced in a compelling and immediate manner.
Since the tweeter output is acoustically amplified by the
waveguide, there is much lower distortion at both low and high levels.
This reduced distortion from 2500Hz on up provides a
smoother, silkier treble response unobtainable
without the use of the waveguide.
An additional benefit of the reduced distortion and increased
dynamic range is improved soundstage depth and transparency.
constant directivity waveguides for the tweeter and woofer are formed
in the 1 3/4" thick solid Poplar front baffle, which reduce
horizontal and vertical early
reflections and room effects, produce a
timbrally accurate and dynamic wavefront, and help reduce baffle
diffraction effects. In addition to providing
directional focus, the tweeter waveguide provides between 3 - 4dB of
2500Hz and 8000Hz, so the ribbon tweeter diaphragm
doesn't have to move as far for a given SPL level. This
improves soundstaging and transparency, and provides very low distortion
SPL levels. The woofer waveguide controls the wavefront of the 8"
woofer between 1000Hz and 1400Hz, which makes room placement easier
by reducing sidewall and floor bounce early reflections, thereby
reducing notch filter effects caused by the out-of-phase reflections
arriving at the ear later than the original wavefront. The woofer
waveguide also provides
1-2dB of gain between 1100Hz and 1400Hz, providing increased liveliness
dynamics. The ribbon tweeter is set back from the woofer to provide time
alignment, providing phase coherent response for fundamental tones and
their harmonic overtones.
Poplar Front Baffle:
baffles are made from 1 3/4" thick single billets of solid Poplar, highly
regarded for its low resonance. Acoustically, Poplar
highlights the treble and lightens the lower midrange and bass, with a slight
emphasis in the lower treble and the middle midrange. Poplar
the wood of choice for several well-known horn loudspeaker
manufacturers, in addition to Sonist. The 1 3/4" thickness of the
baffle provides mass loading to reduce baffle resonance. The
front baffle has a 3/4 roundover on all sides, contoured to eliminate baffle
diffraction effects. The constant directivity waveguides are
formed into the baffle itself, minimizing alignment anomalies and
mechanical resonance associated with
separately formed elements.
The bass tuning ports are also formed in the baffle, flared
to prevent "chuffing" with high energy bass content.
cabinets are made with ¾" Medite, a high-density
MDF, mitered panels, with a front baffle made from 1 3/4"" thick
solid Poplar, providing a mass-loaded platform for mounting the drivers.
The front baffle is glued to the cabinet face using a tongue
and groove design, and corner glue blocks are used throughout to stiffen
the cabinet. The tweeter waveguide is formed in the solid
Poplar front baffle, using three passes of a pin router with custom templates
to provide a smooth and uniform surface. The woofer waveguide
is formed with a single pass with a pin router, again using a custom
template. The inside circumference of the woofer opening
is chamfered to prevent cylindrical reflections. The
rear-mounted bi-wire terminal cup is inset into the cabinet to provide a flush-mount
with the rear cabinet wall.
Cabinet Finishing: The
front baffles, flared bass ports, and tweeter and woofer waveguides are
hand-sanded with coarse, medium, and fine grades of sandpaper, and the
front edges of the waveguides are also hand-sanded to round off the
transition between the waveguides and the front plane of the front
baffle. The cabinets are hand-sanded on the edges and
corners. The cabinets have one
undercoat, two coats of textured paint, and a clear semi-gloss lacquer topcoat. The front baffles have
one sealer coat, two coats of stain, and a clear semi-gloss lacquer
Bracing: In the Concerto 3, a 1/2" thick H-brace is dadoed into the rear inside
panel, front baffle, and both sides of the cabinet to stiffen the cabinet.
The H-brace is located 3/5 of the distance from
the bottom of the cabinet, 2/5 from the top of the cabinet, so that
there are no
coincident resonances, reducing common standing wave frequencies and
sympathetic panel resonances. In the Concerto 3, there are two 1/2"
thick H-braces, placed so that there are no coincident resonances.
Black Hole 5 Constrained Layer
Cabinet Damping: Black Hole 5 is applied extensively on the interior cabinet surfaces to reduce internal standing waves and absorb
acoustic energy that would otherwise radiate from the outside surfaces
of the cabinet. This reduces both bass
and male and female vocal "chestiness", so the
doesn't introduce colorations to the presentation.
rubber grommets are used for mounting the tweeter and
woofer, in order
to provide air-tight seals, using threaded inserts and Allen bolts.
A soft rubber grommet is used to seal the terminal cup
flange with the cabinet.
Isolation-Mounted Crossovers: The
crossovers are hand-made and hard-wired, no printed circuit boards,
using Cardas Tri Eutectic lead-free solder and Auric hookup wire. The
coil is mounted in a sandwich of Black Hole 5 which isolates the coil
from structural resonances from the cabinet, decoupling the coil from
the cabinet walls.
grill frames have outside and inside chamfers to conform to the woofer waveguide
angle, covered with black stretchy cloth, mounted with four small disk
magnets inset into the grill frame, so there are no mounting pegs or
holes. The disk magnets adhere to the metal frame of the