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Sonoma Model One Electrostatic Headphones System


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Ex VAT: 4162.5
Sonoma M1 Headphone System, made for today's high-res formats, uses a HPEL Transducer and delivers audio performance without compromise.

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Warranty length 2 Years
Fitting Over Ear
Brand Sonoma

Tech Specs


- Type: Open-back, circumaural
- HPEL Drive: single-end electrostatic
- Effective Diaphragm: 3570 mm2
- Frequency Response: 10 Hz – 60 kHz
- Compliant: EN 60065/A12:2011 (EN50332)
- Cushions: Cabretta top-grain sheepskin
- In: Polarized, 4-pin for L/R channels
- Drive Cable: 2m Ultra-low capacitance
- Cable: silver-plated OFHC copper
- Insulation: foam PE/Kevlar reinforce
- Weight: 303 grams (10.7oz)


- USB In: B (32/384kHz /DSD via DoP)
- Dig Coax In: S/PDIF (24/192kHz PCM)
- Analog In (High): Dual RCA; 2.1V rms
- Analog In (Low): 3.5mm; 850mV rms
- DAC: Dual mono, 32-bit/384kHz
- ADC: 32-bit/384kHz multi-channel
- DSP: 64-bit fixed-point processing
- Amp: Discrete FET, single-ended
- Amp Out: High-bias Class-A output
- Distortion + Noise: < 0.05%
- Bandwidth: > 65 kHz
- Enclosure: CNC-machined 6063 aluminum
- Ext Power: 24V DC, 60V A (fixed, class B)
- Int Power: Fully isolated, ULN linear
- AC: World (90-264V, 50-60Hz)
- Power Cable: 1.5m earth-ground
- Dimensions (HWD): 57 x 190 x 290mm
- Weight: 2.45kg (5.40 lbs)

Product Description

Sonoma M1 Headphone System is built for today’s high-res audio formats with each piece planned to carry unsurpassed heights of performance and acoustic quality. It is the world's first Headphone System to benefit from the ‘High-Precision Electrostatic Laminate’ (HPEL) Transducer developed by Warwick Audio Technologies Ltd.

New Transducer

Sonoma M1 is the first headphone in the world to use a patented HPEL audio transducer, a new architype of electrostatic drivers. Standard transducers use a membrane moving in response to the signal to create sound. The grids must be perforated in order to propagate sound through the grid/membrane ‘sandwich’.

HPEL uses a 15μm flexible laminated film, thinner than a human hair, for the ‘front’ grid. Attached to the cell module of an insulating spacer, The laminate and the film is very accurately cut in the x-y plane creating tiny ‘drum-skins'. A stainless-steel mesh forms the ‘back’ grid. When audio is overlaid on a bias voltage, the ‘drum-skins’ resonate producing sound while HPEL does not pass through a grid.

Finite Element Analysis

Patented Finite-Element Analysis refines the properties of the ‘drum-skins’ for various resonant frequencies. Each is acoustically autonomous but works in parallel. The individual resonances average out, evading significant interference peaks in the audio band. The thin, light seal material gives a long frequency response, with the panel staying linear to over 60 kHz.

HPEL has supreme transient performance and its surface area is optimised to carry a full frequency response. Due to the contemporary mechanical manufacturing techniques, the HPEL delivers unheard of consistency and matching between left and right channels. A super-rigid, high glass-fill polycarbonate ‘cassette’ lets the transducer perform optimally.

Injected Magnesium Ear-Cups

Merging great strength/weight ratio, rigidity and EMI/RFI shielding, Magnesium ensures optimum performance of the transducer. Low weight, Magnesium is roughly ⅓ lighter than aluminium, also contributes to outstanding headphone comfort and has incredible acoustic damping. The ear-cups are formed by accurate and high-pressure injection moulding creating a weight of 303 grams for ultra comfort. For strength and corrosion resistance, only high-grade stainless-steel screws and fasteners are used.

Nylon 12 Headband

Nylon 12 (Polyamide 12) is the chosen material as it not only naturally dampens noise, but is extremely hardwearing and flexible allowing perfect adjustment to almost any head size. The headbands internals are comprised of stainless steel with vapor-deposited titanium coating to ensure durability and smooth operation.

The handmade Cabretta leather used is sourced from Ethiopia, tanned by the experts at Pittards and then handsewn by specialists in Germany. The M1 ensures an ultimate listening experience by using top-grain sheepskin known for its softness, strength and flexibility.

Custom Low-Capacitance Cable

Partnering with the specialists at Straight Wire Inc, a revolutionary wire design was created for the M1. The cable features very fine strands of silver-plated OFHC ultra-pure copper. The foamed polyethylene insulation has a suitably high dielectric constant and is well damped. There is no shared ground between the left and right channel signal cables, and a fibre filler material in the jacket keeps the conductors as far apart as possible as well as helping to dampen any cable microphonics.

The cable capacitance is a low 50 pF/m. The jack is electrically isolated from the amplifier chassis, while the headphones high-precision self-latching connectors ensure a secure connection. An integrated sense loop runs to each ear cup, and if the cable is disconnected at either end, the unit automatically powers down.

Energiser & DAC

HPEL is driven by a high-performance, single-ended, discrete FET Class-A amplifier with very low distortion and optimally matched wide bandwidth. Built and optimised to drive the innate capacitive load of an electrostatic driver, the Class-A output stage works at a superior bias level giving an ultra-high slew-rate and better linearity.

The signal has a peak amplitude of 145Vrms, on top of the 1350V DC bias. The high voltages mean significant power, in spite of low current, at the amplifier output. Consequently, high quality devices used throughout are designed to cope with the power levels.

The amplifier provides inputs for USB, coaxial S/PDIF, dual high-level RCA jacks and low-level 3.5mm stereo jack. The USB accepts all Hi-Res formats up to 32-bit/384 kHz PCM and DSD via DoP, S/PDIF accepts all PCM formats up to 24-bit/192 kHz. RCA operates with a maximum signal of 2.1V (rms), while the 3.5mm jack accepts a maximum signal of 850mV (rms).


Sonoma M1 system was developed to deliver true high-resolution performance. For the critical D/A conversion stage, they turned to an established leader in the field; ESS Technology, globally known as the premier manufacturer of DAC chips. Sonoma opted for the Reference 32-bit DAC. Twin stereo DAC chips feature in a special mono mode to offer a signal/noise ratio of 129dB.

64-bit Fixed DSP

A flat frequency response is incredibly difficult to attain with a headphone. HRTF gives rise to a non-flat frequency response and changes depending on the sound direction. All filter responses within the DSP are minimum-phase, slow roll-off and are optimised for excellent time-domain response.

Further profiting from the extraordinary accuracy of the 64-bit DSP, Sonoma implements a wholly-digital interpolated volume control which drastically exceeds all the full analogue, step attenuators tested. The result is zero fidelity or dynamic range loss, seamless matching of left and right channels, eliminated noise issues and no non-linearities in the potentiometer.

AKM 32‑bit Premium ADC

For the DSP to attain the marked frequency response, inbound analogue frequencies need to be changed to digital signals. This happens in a multi-channel 32-bit AKM Analogue to Digital Convertor chip. Two unbiased, fully-optimised ADC signal paths are used each for the high or low-level inputs. In this way, the full dynamic range capability of the ADC is achieved regardless of the input selected. The measured SNR of the ADC stages exceeds 120dB.

Crystek Oscillator

The ultimate performance of any digital system is determined by the quality of its master-clock. Sonoma Model One is based around the ULN Crystek oscillator ensuring optimum performance whatever the input. On top of 100MHz operation, it has an ultra-low <90dB/Hz phase noise and industry-leading 82fms jitter level. Clocks used throughout are all taken from this greatly accurate lead oscillator through a complex distribution method using TI frequency dividers.

Optimum PCB Layout

In design, careful attention was granted to the arrangement of the circuit board to ensure minimal noise and distortion standards. Meticulous positioning of components enabled Sonoma to maintain an extremely low noise-floor of -129dB!

CNC-Machined Aluminum

Starting with a solid billet of high purity Aluminum 6063, the material is first extruded, and then CNC-machined to produce a shallow U-shape comprising the base and side walls of the amplifier. The metal walls which remain are 5/16th of an inch thick.

A top-plate of the same thickness, along with ½” thick end-plates form the complete enclosure. A special 3D-wave pattern is cut into the base and top-plate to facilitate heat dissipation. For desired metal finish, the parts are blasted under high pressure with fine glass beads then clear anodised. All logos and labels are laser-etched into the metal, so will not fade or rub off!

Superior USB Cable

As USB is the only connection which takes all the supported high-res digital audio formats, it was vital to ensure no compromise in performance when using this connection. The supplied USB cable was developed in collaboration with Straight Wire Inc. Featuring gold-plated connectors and a silver-plated data path, it is the ideal connection between your digital music source and the Sonoma M1 system.

Custom Universal PSU

M1 uses a two-part power solution in order to keep as much noise as possible out of the sensitive audio path. The first-stage involves a custom-designed, universal voltage, outboard switch-mode power supply unit. While it may look similar to the units provided with laptop computers, etc., internally it is very different. To avoid any headroom issues, our device is capable of delivering about 3.5 times the maximum power the amplifier is designed to draw under steady-state conditions.

Fixed Frequency Switcher

In addition, the unit uses a fixed frequency-switcher (over 85kHz) to avoid the possibility of the switching-frequency dropping into the audio band as the power draw changes. This unit is designed with improved internal filtering to yield extremely low noise and ripple (<50mV). It is connected to the amplifier via a custom, high-quality, shielded cable and, to ensure an ideal connection, it is fitted with a high-performance, Switchcraft locking DC power connector. A massive ferrite core filter has been added to the DC cable to reduce EMI.

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