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Musicalhead reviews the APERIO

English Translation – Original Review in German found here


Review of the WARWICK ACOUSTICS APERIO on Musicalhead

Fidelio - Muscialhead

Here I am again. And finally the time has come – today I’m reviewing the electrostatic headphone reference system APERIO by the British manufacturer WARWICK ACOUSTICS for all knights of the Grail of fine tones.

The proprietary APERIO (lat. for revealing, uncovering) was, according to the high-end manufacturer, developed specifically to set new standards in the headphone segment with regard to perfect audiophile reproduction and also to redefine the sonic level. Or to put it simply – to build the best headphone system in the world.

This ambitious development goal also describes the philosophy of WARWICK ACOUSTICS, which is firmly anchored in every product from the initial concept to series production – in order to reproduce the musical source material unaltered and truthfully, the system, and therefore every element in the signal path, must be 100% transparent and free of distortion. The reproduction system must at no time negatively influence the sound or impose its own character on the sensitive audio content. All available data, whether in analog or digital form, should be able to be reproduced at any time without discoloration.


Innovative Complete System Design

At its Automotive Technology Center (MIRA Technology Park) in England, WARWICK ACOUSTICS is therefore pursuing a rigorous approach to complete system design for its product series. This includes the engineering of each individual component in the system’s signal path – from the first tap of analog or digital audio data to the final musical reproduction.

In the opinion of the British manufacturer, a complete system optimized with this approach is fundamentally superior in sound quality to separately developed HIFI components – even if they operate at the highest technical level.

Already the SONOMA M1 convinced in the test on Musicalhead by first-class workmanship, high-quality materials, as well as a tonally balanced and authentic sound image. The distinct edge sharpness and a sensitive accentuation of voices and instruments were just as inspiring as the superb fine dynamics with excellent spatial reproduction.

The new WARWICK ACOUSTICS APERIO is the culmination of this stringent product philosophy, especially since compromises for every element of this cost-no-object headphone system were categorically excluded in the development phase.


APERIO review Musicalhead


Balanced Drive HPEL-Transducer

Compared to the SONOMA M1, the significantly larger and heavier Energizer unit with a weight of 7.4 kg has a significantly higher power output (2 x 15 watts) than the first movement in the current development stage. The new Balanced-Drive HPEL diaphragms in turn have a future-oriented electrostatic drive. Although the effective diaphragm area of 3570 mm2 is basically identical to that of the SONOMA M1, the British manufacturer has completely redesigned the transducers from the diaphragm construction to the stator design to the operating voltage of now 1,800 volts, via which the required electrical field strength is generated.

As a result, the comparatively higher voltage enables greater deflection of the diaphragms than with conventional electrostatic designs. Thus, the APERIO not only has a greatly extended dynamic range, but also a more excessive bass response, which should also play completely distortion-free.

The Balanced-Drive HPEL diaphragms are centered between two thin, high-precision electrical stators using laser-cut polypropylene spacers. This is an innovative composite construction consisting of two layers of biaxially oriented polypropylene films (BOPP).

BOPP films have almost optimal properties for the diaphragms – a stable dielectric constant, a very low dissipation factor, high dielectric strength, and very low hygroscopy. In addition, a vapor-deposited conductive layer of 24 Kt. gold is applied between the films – acrylic-based adhesion promoters within the lamination also help to avoid undesired resonances.

The diaphragm construction is of a very filigree nature – less than 25% of a human hair measures the thickness of the diaphragms and as a result they are extremely low in mass. The diaphragms are custom-made in Germany and Austria according to specific requirements of WARWICK ACOUSTICS and then laser-cut in our in-house R&D facility in England.

The membrane design is also impervious to moisture and resists arcs even at voltages significantly higher than the actual operating voltage. The stators are also formed by photochemical etching of OFHC copper, which is gold-plated directly afterwards.

The British manufacturer naturally uses only the finest copper quality available on the world market for this purpose – the oxygen content and other impurities can thus be reduced to less than 0.001%.


Freedom From Resonance As A Development Goal

The described assemblies are combined in a high-precision chassis consisting of 40% glass-filled polyphenylene sulfide (PPS) and an ultra-rigid engineering polymer. This highly stable frame ensures that the electrostatic transducers are also permanently resistant to deformation or bending stresses.

Since freedom from resonance was one of the main design goals, other structural components, such as the ear cups, were also made of injection-molded magnesium. Additional elements made of stainless steel serve the electrostatic ear loudspeaker both as damping and to eliminate unwanted partial vibrations.

The black anodized magnesium headphones are also quite light at 399 grams. It has a new headband construction, covered with very soft Cambretta lamb leather, which is one of the finest sheepskins in the world. In addition, the mechanical adjustment has been optimized and the contact pressure has been reduced to allow completely stress-free and extended listening evenings.

The general quality of workmanship of the proprietary reference system of the British is beyond any doubt and, as with the SONOMA M1, the energizer unit of the APERIO is of course also made from a solid 6063 aluminum block.

The material is extruded and CNC-machined to create the typical flat U-shape, which includes both the base and the side walls of the amplifier. In addition, a special 3D wave pattern is cut into the base and upper aluminum plate to facilitate heat dissipation.


Quality With Attention To Detail

The WARWICK ACOUSTICS APERIO has not only balanced and unbalanced analog inputs, but also AES3 (AES/EBU), S/PDIF coaxial, USB and Ethernet (LAN) digital connections. The analog inputs have individual amplification via a buffer circuit, which also maximizes performance, regardless of whether the source is a semi-professional or professional audio source.

Using a separate Linux-based subsystem, the APERIO also exceeds typical DLNA limitations and enables digital audio playback of native DSD and PCM formats at sample rates up to 384 kHz. Audio signals are always retained in their original format. PCM is therefore not converted, the signal path remains unaltered at all times.

In addition, the digital data, as well as the USB inputs, are asynchronously clocked to minimize any jitter. The APERIO has a separate line output in class-A configuration to control further electronic components, such as downstream pre- or power amplifiers or headphone amplifiers.

This special line-out function, in combination with the implemented DAC chipsets of reference type ESS9038 PRO in balanced 32-bit dual-mono configuration with 8 channels each, an intelligent preamplifier functionality and superior sound quality, enables the WARWICK ACOUSTICS APERIO to act as a central control unit in studio monitoring or in first-class audio systems.

The APERIO displays the output level in precise 0.1 dB steps on a full-color, high-resolution display on the front panel. The firmware can be easily updated via the USB input with an application for any Windows/MAC/Linux-based host. Continuous updates allow the proud owner to keep the headphone system up to date throughout its lifetime.

WARWICK ACOUSTICS also shows great attention to detail when it comes to the cables used. The headphone cable consists of 66 strands of microfine OFHC copper per conductor, which are coated with pure silver and wrapped with silicone insulation. Kevlar-reinforced fibers guarantee extreme tensile strength, high internal attenuation and reduce microphone effects to an absolute minimum.


Headphone System At Reference Level

The WARWICK ACOUSTICS APERIO is manufactured in England in very small quantities and exclusively by hand. With the aforementioned tendency to perfection, only the highest quality and best possible materials are used, which are processed in the highest quality.

The British manufacturer thus uses its decades of experience in the field of professional studio technology to offer even the most demanding knight of the Grail of fine tones a reference system that could possibly revolutionize the market due to its technical requirements. Which, of course, would still have to be verified in the subsequent listening test.

And since the APERIO is also delivered in an extremely robust and unbreakable polypropylene hard shell case, it would certainly not have been a problem to parachute the package, which actually weighs more than 30 kg, down over Aachen – the UPS delivery person would undoubtedly have been grateful for the high transport weight.

Apart from the ear loudspeaker and the corresponding headphone cable, as well as the corresponding energizer unit with deliberately removed power supply, there are other high-quality cable sets (USB, Ethernet) after opening the matt black “suitcase”, which are in no way inferior to the quality of the aforementioned one. All cable connections are manufactured by the German manufacture STRAIGHT WIRE according to specific requirements.



In order to test the limits of the WARWICK ACOUSTICS APERIO as fully as possible, I chose the AURALIC ARIES G2 as my primary source, which passes on the musically complex fare to the digital section of the APERIO via a TELLURIUM SILVER DIAMOND USB-cable, accurate to the beat and without any loss of quality.

As sound source material I use selected audio samples from the usual genres of classical music, jazz, blues, pop and rock, stored either on the 2.5 inch SSD hard disk of the ARIES G2, or via WLAN using the streaming service QOBUZ – of course in high-resolution.

I would like to thank Martin Roberts of WARWICK ACOUSTICS in particular, who kindly and unbureaucratically provided me with the latest version of the headphone system ex works for my review on Musicalhead. Further information about the WARWICK ACOUSTICS APERIO can be found on the pages of the German distributor: https://www.audiodomain.de/marken/warwick-acoustics/


Sound Test

To come straight to the point – after just a few minutes of listening, I am convinced that the current version of the WARWICK ACOUSTIC APERIO is one of the best acoustic reproduction systems on the planet, regardless of price. And for many knights of sound, the search for the sonic grail could most likely be over at this point.

Because the level of perfection in terms of a highly authentic reproduction of music is nothing less than phenomenal. Even loudspeaker-based solutions in the 6-digit price segment have to surrender to the incredibly fast transients and the exorbitant resolution of the APERIO.

The electrostatic system of WARWICK ACOUSTICS is not only capable of scoring with first-class bass dynamics, fantastic impulse fidelity, natural timbres and a grandiose attention to detail, but also knows how to inspire on an emotional level.

The immediacy of the dynamic attack and the complete lack of any attempt to reproduce even complex sound structures, which seem to be staged from nowhere in front of a pitch-black background in a grandiose manner, are among the most impressive experiences I have had so far via headphones.

The ear loudspeaker itself completely recedes into the background, allowing the musical events to be viewed apparently without the acoustic limitations of the reproduction system. For tonal coloration is as foreign to the APERIO as spatial dissonance. This electrostatic tool acts tonally neutral at the border of the ideal.

The bass range is significantly improved compared to last year’s version and convinces with a merciless depth, especially for the electrostatic working principle. The bass of the APERIO also has an excellent texture and impresses with absolutely outstanding impulse response.

The British headphone system descends linearly and without pressure loss effortlessly down to the lowest frequencies and stands out in direct comparison to other electrostatic competitors, such as the STAX SR009 or a DAN CLARK VOCE, which sometimes emphasize the mid-bass a little more to hide the slight deficits in the low bass range.

Especially since the big brother of the SONOMA M1 is completely unfamiliar with its slight weaknesses at higher monitoring volumes. The APERIO is free of any distortion up to deafening levels and amazes with an amazing dynamic quality.

An ABYSS AB1266 PHI TC can easily outperform the APERIO in terms of bass quantity, but the American monster has a disadvantage in terms of the more precise modification of individual bass notes by the electrostatic fraction. The APERIO also has minimal advantages in terms of transient speed.

Based on a slag-free, yet substantial fundamental tone, the WARWICK ACOUSTICS APERIO finally delivers a musical gala performance in the sound-relevant mids that is unparalleled. With eyes closed, the impression is at times gained that one is actually at the scene of the action.

The British system creates in a fascinating way an exceptionally airy and realistic sound stage with razor sharply focused individual events in the room, which in my opinion can hardly be surpassed in credibility. Even the most subtle shades in finely dynamic musical passages are meticulously peeled out of any sound network and reproduced at lightning speed. In particular, the reproduction of voices and acoustic instruments already appears eerily real. Goosebumps factor guaranteed.

Even the HIFIMAN SUSVARA cannot surpass this formidable masterpiece of the APERIO. It undoubtedly provides especially voices of actors with more tonal enamel and consequently caresses the musical soul of every Grail Knight with its sound – in the best sense more honest, because it is even more lifelike, however, the electrostatic combination acts. As so often, a matter of taste.

And almost as expected, the WARWICK ACOUSTICS system crowns this ingenious performance in the high frequency range. In my opinion, the resolution of the APERIO is unparalleled in headphones. Ear loudspeakers and playing partners weave in congenial union a spacious and delicate sound network of absolute world class format.

Sometimes even inconspicuous recording errors in pieces of music become obvious, which even the respective sound engineer should not have noticed. Or simply ignored, in the hope that no audio system would even be able to record and play them back.

And the STAX SR009 must inevitably give way to the British system at high frequencies. Even though the Japanese ear loudspeaker still sets a benchmark in terms of high frequency resolution after 10 years of construction, the WARWICK ACOUSTICS APERIO impressively demonstrates what is possible today with uncompromising technical effort.

Are there any points of criticism? Well, of course the APERIO also has to struggle with the system-immanent problems of headphone reproduction. Even the top system from WARWICK ACOUSTICS is not really able to create a loudspeaker width and depth in the room, although the out-of-head localization is very successful.

However, the APERIO has this in common with all other test devices of this fraction. Only free field ear loudspeakers such as the RAAL REQUISITE SR1a have a better command of the spatial stage image and are therefore closer to very good near field monitors.

In addition, a practical remote control of the energizer unit would in my opinion have been (technically) possible.


My Conclusion

The WARWICK ACOUSTICS APERIO is without a doubt the best proprietary headphone system I have reviewed on Musicalhead to date. The electrostatic system solution is tonally so perfectly balanced that individual tonal aspects almost fade into the background.

The authenticity of the reproduction is absolutely astounding and opens up new sonic dimensions with regard to the perception of beloved music collections. Especially selected audiophile treasures appear in a completely new acoustic light via the APERIO. The system-immanent advantages of the electrostatic principle with regard to a transparent, subtle and sharp-edged accentuation of the musical source material are taken to the absolute top by the new reference system from WARWICK ACOUSTICS. The reproduction of transients is exemplary, the impulse fidelity is it too.

In my opinion, the supposed weaknesses of the electrostatic principle are also almost eliminated – the APERIO has excellent bass quality and convinces with precise fine and explosive coarse dynamics. With the APERIO, WARWICK ACOUSTICS has perhaps even succeeded in creating the ultimate musical headphone reproduction system. Only the price of the APERIO makes even the most ambitious knight of the Grail of fine tones flinch painfully and leave the room slightly stunned – because an enormous 25,000 Euros purchase sum is due when the end point of the personal search for the Grail is to be marked.

However, it should also be taken into consideration that the interested party acquires a perfectly coordinated complete system with the APERIO, which could not be put together in a more favorable way with an individual selection of adequate single components.

The WARWICK ACOUSTICS APERIO receives my unconditional recommendation, if monetary means do not play a central role in the decision and all possibilities regarding an optimal musical reproduction by means of a reference system via headphones should be exhausted completely.


Yours Fidelio 

To read the full review in German on the Musicalhead website, click here.