Electrostatic Headphone System with Amplifier 4 inch large circular electrostatic driver with a fully open back structure for exceptional depth and soundstage Ultra lightweight design at just 295 g, with optimized clamping force for extended listening comfort EHA-1 dedicated amplifier with a Bass Boost switch and a physical balance adjustment knob Standard 580 V polarization voltage for compatibility with most electrostatic headphones Includes EH-1 headphones, EHA-1 amplifier, 1.8 m detachable EC-1 cable, and a 12 V power supply A High End Audio Brand from Shanghai Founded in Shanghai in 2019, the Hongshu Audio brand is dedicated to the development and manufacturing of electrostatic headphones, amplifiers and loudspeaker systems. The team is made up of headphone enthusiasts and engineers with expertise in materials science, electronics, acoustic design and product development, and has many years of experience in the research, development and manufacturing of high end headphones. Over four years, Hongshu Audio built its own supply chain and production system for electrostatic drivers. Through careful engineering, precise manufacturing and continuous innovation, electrostatic audio products are created with high resolution, low distortion, excellent transient response and broad musical compatibility. A Complete Entry Into Electrostatic Listening Electrostatic headphones have always carried particular weight in the world of high fidelity. They stand for speed, transparency and a sense of openness that makes familiar recordings appear in a new light. They also stand for a long list of practical questions: bias voltage, amplifier matching, connectors, output level, customer support, and whether the headphone itself is only the beginning of a much larger system.It is in this context that the EH-1 V4 was developed. Hongshu Audio presents the EH-1 as a complete system together with the EHA-1 electrostatic amplifier, because for many listeners the system perspective counts just as much as any individual specification.Sound Character Electrostatic clarity for a wider musical spectrum High Resolution: Designed to reveal fine detail without losing musical coherence. Low Distortion: A clean electrostatic presentation built around controlled driver behavior. Fast Transient Response: Speed and precision support realistic attack, decay and texture. Broad Versatility: From classical and jazz to pop and rock, the goal is a wider electrostatic listening experience.An Expansive, Fatigue Free Soundstage At the core of the EH-1 V4 is a 4 inch circular electrostatic driver, combined with a fully open back design to create a soundstage of exceptional depth and breadth. The delicate resolution and smooth frequency response typical of electrostatic drivers let you hear the subtle nuances in music without harshness or listening fatigue.Remarkably Light for Long Listening SessionsThe EH-1 weighs just 295 grams, excluding cable. Combined with an optimized clamping force, it stays comfortable through extended listening sessions, so you almost forget you are wearing it.For hi fi listeners, comfort is not a lifestyle extra, it affects how carefully you listen. A heavy headphone can turn a full album into a test track session, while a lighter one gives you the time to hear stage depth, decay, and tonal balance without being reminded of the object on your head.Fine Tuning at Your FingertipsThe included EHA-1 dedicated amplifier offers extensive adjustment options. A Bass Boost switch transforms the sound into a powerful, punchy experience for large scale orchestral music or films, and a rear mounted knob allows physical fine tuning of the left and right balance.  With its standard 580 V polarization voltage, the EHA-1 is also compatible with most other electrostatic headphones. It delivers up to 300 Vrms of full range driving capability and operates conveniently from the included 12 V power supply or even a standard power bank, making it well suited to desks, offices, and dorm rooms. Built In House Four years building the electrostatic driver supply chainBecause there is no mature, ready made supply chain for electrostatic drivers, Hongshu Audio invested four years in building its own supply chain and production line for electrostatic drivers from the ground up. Through continuous work on materials, diaphragm treatment, driver structure, assembly, testing and quality control, a manufacturing system was developed that meets modern high end audio standards.Laser Quality Control LiDAR surface mapping for stator flatness Hongshu Audio uses LiDAR surface mapping with a scan precision of 0.1 μm to measure the stator plates of its electrostatic headphones. This non contact 3D process detects the smallest warping and local surface deviations and enables flatness to be controlled within a range of 10 μm. The improved geometric consistency of each stator results in a more uniform electric field and more controlled diaphragm movement. The result is lower distortion, better channel consistency and a clearer, more precise sound. The focus is not on accumulating individual specifications but on the complete relationship between structural precision and sonic performance. Every stator is checked by LiDAR measurement before being installed in the acoustic system, to ensure a stable, controllable physical foundation close to the intended ideal state.What Makes an Electrostatic Driver Different An electrostatic driver works by placing a very light, charged diaphragm between two stators. The audio signal changes the electric field, and the diaphragm moves in response. This is different from a dynamic headphone, where a voice coil, magnet, and diaphragm form a familiar moving system, or a planar magnetic headphone, where a conductive trace is driven across a magnetic field. Because the diaphragm is so light, the system needs both a bias voltage and a high voltage audio signal, which is why the EH-1 story keeps returning to its EHA-1 amplifier. The EHA-1 provides a 580 V polarization voltage from a compact, 12 V DC powered design, and the EH-1 operates within a 550 to 600 V bias range, placing it squarely within the established Pro Bias electrostatic standard.Driver Size and the Sense of Spaciousness Driver diameter alone never guarantees good sound. A large driver that is poorly controlled can sound vague, while a smaller, well designed driver can sound precise. Still, the 4 inch format gives the EH-1 a meaningful acoustic foundation, and combined with its fully open back structure, allows the headphone to aim for scale without relying only on treble emphasis or artificial staging cues.Engineering Consistency A driver diameter alone tells you where a design begins, not everything about how it performs. Diaphragm material, coating uniformity, stator geometry, channel matching, distortion behavior, and long term stability all depend on production and quality control.In house electrostatic driver work, diaphragm treatment, assembly, testing, and quality control are what turn a headline number into a real engineering claim, and what ultimately decide whether the driver, amplifier, and manufacturing process translate into the open, fast, low distortion character that listeners come to electrostatics to hear.SpecificationsHALO EH-1 Headphones Wearing Style: Over Ear Driver: 4 inch electrostatic driver Sensitivity: 102 dB at 100 Vrms Cable Length: 1.8 m standard (detachable) Capacitance: 100 pF (including 1.8 m cable) Frequency Response: 6 to 42,000 HzWeight: 295 g (excluding headphone cable) SpecificationsEHA-1 Electrostatic Headphone Amplifier Rated Supply Voltage: 12 V (DC) Rated Power: 5 W Nominal Input Level: 2 Vrms Maximum Output Level: 300 Vrms at 1% THD Harmonic Distortion: THD < 0.001% at 100 Vrms Input Impedance: 10 kOhm Frequency Response: 10 to 25,000 Hz (-1 dB) Bias Voltage: 580 V Weight: 375 gDimensions (excluding protrusions): 110 x 120 x 38 mm (L x W x H)Package Contents HALO EH-1 Electrostatic Headphones (with SP-1V ear pads) EHA-1 Electrostatic Headphone Amplifier 1.8 m EC-1 Headphone Cable (detachable) 2 mm Hex Wrench (stored in accessory box) 12 V Power Supply