CURVI HIFI UNIQUE SPEAKERS
The Curvi Model 1v2 launched in 2010 is iconic and has been quite influential in shaping other
designs. In the latest incarnation, a 128 mm balanced mode radiator (BMR) drive unit replaces the
Jordan JX92S contro-flex full-range aluminium drive unit. Whilst the original attracted critical
acclaim, the new model improves on the original in all key areas. The improvements in dynamics,
increased detail, off-axis performance, tonal accuracy and transient reproduction are due to the
benefits of BMR technology over the contro-flex approach. Improvements in bass reproduction, i.e.
greater speed/slam and extension are due to a modified interface between the drive unit and the
transmission line and a 197% increase in the radiating area, relative to the JX92S.
All the benefits of the laminated birch plywood cabinet are retained, though the some reworking of
the cabinet is needed to accommodate the larger chassis of the 128 mm BMR drive unit. A bezel
(attached viscoelastically and not user removable) hides the drive unit mounting hardware and
streamlines the interface between the roll surround of the drive unit and the cabinet. The bezel can
be machined from variety of materials and is available in a range of finishes. Birch plywood and
acrylic (any colour available) are the standard options. The standard cabinet finish is semi-matt
hand-rubbed acrylic lacquer.
The BMR drive unit selected is the largest available and has been customised for the Curvi – the logo roundel is airbrush stencilled in acrylic paint. The chassis is also reinforced with a laser cut 3 mm thick stainless-steel doubler which is epoxy bonded in place. A magnet brace in the cabinet checks any chassis and magnet vibration.
The baffle step equalisation filter is point to point wired and located in the CNC machined beech wood plinth. The components used are from Mundorf and include a bonded 1.4 mm wire air-core inductor and bespoke resistor made up of an array of thick film resistors. Alternative resistor values are available which enable users to alter the tonal balance to suit personal taste, room acoustics and audio system – all connections are solderless. The default equalisation is a step filter, consisting of an inductor in parallel with a resistor. If some treble lift is required, a parallel capacitor can be added (making a notch filter) – a capacitor is pre-installed but not connected and can be easily added using solderless connections. Alternative capacitor values are available which enable the frequency at which high frequency output increases to be varied. Internal wiring is supplied by Gekko cables and is insulated with cotton cellulose fibres that have point contact with the conductors – air is effectively the insulator.
Connection to the amplifier is via Tellurium-Copper alloy binding posts which accept 6.5 mm spade connectors and 4 mm plugs.
Figure 1. 1/6th octave pink noise frequency response obtained from a stereo pair at 2.4 m in a 55 m3 room. Note the peak at 45 Hz is room related
Impedance and Phase:
Figure 2. Phase (top) and impedance (bottom) versus frequency. Minimum impedance about 4.5 ohm. Average impedance (from 10 Hz to 22.2 kHz) is 7.05 ohms. Both 4 and 8 ohm taps on valve (tube) amplifiers should be tried. Phase angles are moderate (maximum +23° at 680 Hz and minimum -12° at 115 Hz) and the phase is essentially linear
Contact for more information:
Designer of the Curvi speakers