The ESL X concept emerged in 2019 as part of a comprehensive overhaul of QUAD Electrostatic's manufacturing facilities, a suite dedicated exclusively to the production of QUAD ESL loudspeakers.
With a unique four-panel design, but sharing the same treble and midrange panels as the flagship ESL 2912X model, the more compact 2812X model delivers QUAD's signature sound: ultra-transparent, highly detailed and natural, with a midrange so realistic that vocals and acoustic instruments seem to be in the room. However, all this is offered in a smaller, lighter and less imposing format: just 1070 mm high.
The ESL-X concept emerged in 2019 as part of a comprehensive overhaul of QUAD Electrostatic's manufacturing facilities, a suite dedicated exclusively to the production of QUAD ESL loudspeakers. Under the expert guidance of Paul McConville (recognised as the world's foremost authority on QUAD ESL engineering, with 40 years of experience), every aspect of the original design was subjected to exhaustive evaluation and meticulous refinement. This approach included a thorough analysis of every process, step, technique, material, tool and jig used in the construction of a QUAD ESL, with the aim of improving the quality and accuracy of the electrostatic loudspeaker assembly.
Using techniques such as advanced precision laser metrology, QUAD performed a comprehensive review of the ESL design basis. Systematic improvements to the sputtering, etching, tensioning and assembly processes were implemented to ensure maximum performance. Rigorous upgrades were applied to implement passive and active components, improving the overall system integrity of the then current ESL 2912 and 2812 models.
The QUAD engineering team considered the results of this extensive and laborious self-imposed audit so significant that they deemed it worthy of a new model in the ESL programme line.
It is widely accepted that improving an ESL is fundamentally an exercise in building on existing structures through incremental improvements, rather than seeking radical innovations. Therefore, QUAD did not require a complete overhaul of established methods. However, these incremental advances have culminated in a significant transformation of the 2912 and 2812 models into what is now known as ESL X.
In 1957, QUAD founder Peter Walker broke with convention with the introduction of the first full-range electrostatic loudspeaker, achieving a transient response and clarity then considered impossible.
Subsequent models (ESL-63, ESL988/989, ESL 2805/2905, ESL 2812/2912) introduced incremental improvements. Critics have long praised these models for their light and fluid media, and their natural transparency without the need for a box.
Understandably, you may be familiar with the ESL but unaware of its differences from typical loudspeakers. It's true that a QUAD ESL is not just any loudspeaker to begin with. Unlike conventional loudspeakers that use moving coil transducers, the ESL employs a completely different principle: an electrostatic panel.
At the heart of a QUAD ESL are panels containing a diaphragm of thin Mylar film, ten times thinner than a human hair. The Mylar film is coated with a high-strength conductive material and suspended between two perforated metal plates called stators. This unique diaphragm is incredibly light and therefore very dynamic. It is much lighter than any moving coil transducer cone and can therefore respond to signal transients with incredible speed and accuracy.
The Mylar diaphragm is loaded at a constant high voltage in excess of 5.2 kV DC. An audio signal is applied to the two stators to create an alternating electric field that causes the electrostatically charged Mylar diaphragm to alternately push and pull towards them. As a result, the diaphragm vibrates precisely in response to the musical signal, producing the ultra-pure sound reproduction for which QUAD ESL loudspeakers are known.
QUAD ESL mid-high frequency panels are configured with a "concentric ring" electrode design, originally conceived for the innovative ESL-63. Rather than allowing all sections of the diaphragm to move uniformly, the loudspeaker is meticulously designed to ensure that the audio signal appears to emanate from a single point in space. This sophisticated arrangement produces an exceptionally accurate stereo image, where instruments and vocal performances appear to float in the listening environment, as if enveloped by the musicians themselves. This point source characteristic is expertly facilitated by an innovative delay line system, which supplies the outer rings of the stators with gradually delayed iterations of the audio signal.
A critical factor influencing the ESL's performance is its remarkably high operating voltage, approximately 5250 volts. This high voltage substantially improves the control and linearity of the diaphragm, allowing it to move precisely in response to musical signals, while significantly reducing distortion.
A QUAD ESL tightly regulates this high voltage via a multiplier circuit that amplifies the standard AC power supply, complemented by a protection circuit designed to prevent saturation (excessive input power), thus protecting the loudspeaker from damage and distortion.
The intricate details of the manufacturing process contribute significantly to the ESL X's more than audible improvements. For example, the manufacturing time of a single QUAD ESL panel is extended, which means greater care is taken in the assembly of a complete ESL loudspeaker system. The process requires extreme care and attention to detail.
The first technical improvement is to split the operational PCB of a monolithic design into three fully independent modules. The system consists of a high voltage multiplier module, a control and protection module, and a low voltage signal module. Together, these components form an integrated unit designed for optimum performance and reliability. By physically isolating the 5.25 kV multiplier stage from sensitive low-voltage circuits, QUAD significantly reduces high-voltage stray electric fields. This isolation strategy not only minimises interference and crosstalk, but also significantly improves stability and acoustic performance. The result is crystal-clear audio signals that faithfully reveal every nuance, even during the most powerful musical peaks.
Secondly, it is important to note that, specifically for the ESL X, QUAD has once again used UK-made audio transformers. These transformers have been custom designed, refined and supervised by QUAD's renowned service team, led by Rob Flain, with meticulous quality control. The transformers are specifically designed to improve signal dynamics, especially in the mid and high frequency ranges. This results in a considerably more detailed sound and exceptionally high linearity. The wide bandwidth ensures a flat response that extends beyond 18 kHz, creating a fluid sense of spaciousness and spaciousness. Thanks to robust regulation, these transformers effectively eliminate flux modulation artefacts when operating at high sound pressure levels.
Ultimately, these transformers significantly improve mid-treble dynamics, sharpen transient attacks and extend the perceived depth of the soundstage with superior micro-dynamic resolution.
Features:
- Floorstanding loudspeakers in dipole format with 3º inclination
- Built with multiple electrostatically driven membranes at 220V AC current
- Progressive concentric rings with point-source time delay
- Chassis construction: Aluminium and high-strength composite steel
- Panel Elements: 6 units per loudspeaker
- Maximum output: 2 N/m² at 2 m on axis
- Sensitivity: 1.5 mbar per volt referenced at 1 m (86 dB/2.83 V rms equivalent)
- Nominal Impedance: 8 ohms
- Impedance variation: 4-20 ohms
- DC input voltage (rms): 10 V.
- Program Peak for distortion-free output: 40 V
- Allowable peak input: 55 V
- Frequency response: 32 Hz - 21 kHz (-6 dB) or 28 Hz - 23 kHz (usable)
- Distortion (100 dB at 1 m): Greater than 1000 Hz
- AC Input: 220-240 V or 100-120 V (selectable)
- Power Fuse: 100 mA (surge protection, 200-240 V) and 200 mA (surge protection, 100-120 V)
- Power consumption: 8 W
- Dimensions (H x W x D): 1470 x 690 x 380 mm
- Weight: 44 kg each.
Price per pair.
