Ollo Audio HPS S4X

The Ollo Audio HPS S4X are studio reference headphones from the relatively young Slovenian headphone manufacturer, who have made it their business to produce studio headphones with very special sound characteristics and to limit themselves to a few models. And so, after the production of their S4 mixing headphones was discontinued, Ollo Audio’s range of recording headphones now only includes the S4R and the HPS S4X which we are testing here, these are supposed to sound “neutral and brutally honest”. So, in practice, do the S4X actually sound like Ollo Audio claims?

Package

As well as the headphones, Ollo Audio S4X’s completely environmentally friendly outer packaging conceals a small cardboard box containing a detachable cable with screw adapter and a transport bag with drawstring. A leaflet with instructions on how to use the headphone’s wooden ear cups and ear pads is also included. But that is not all. In a black envelope you will also find an English manual, a hand-signed certificate of authenticity and – please note (!) – a printout of the individual frequency response of the enclosed headphones, including the date of measurement, the signature of the measurement engineer and the corresponding serial number. This sheet also contains information about ambient air pressure and temperature, the humidity at the measuring place and the setup used, including microphones, audio interface and software. This whole package is therefore a real winner in terms of quality and transparency. And last but not least, the manufacturer also provides a 5-year warranty on the device.

Design, material and processing

At first sight, the Ollo Audio S4X are special. The ear cups, made from sanded but unvarnished American walnut wood, are immediately striking. In addition, matt black elements characterise the rest of the headphones. Their design is simple and rustic, giving an impression of being down to earth and natural. Ollo Audio describes the design as timeless. The backs of the half-open ear cups are protected by an eight hole screwed perforated sheeting. The inside of the ear cups are fixed with two Allen screws. Even the fastening of the stainless steel headband is rustically designed with a knurled screw. It also holds the headband, which is made of nautical imitation leather, as used in shipbuilding. I was surprised that the exchangeable cable is only partly covered with fabric. And I was also surprised by the colour combination of black and bright red, because for me it doesn’t really match the natural design of the headphones. However I did like that all the plugs are gold-plated for rust protection. This also applies to the plug adapter from small to large jack.

Technology

The Ollo Audio HPS S4X use powerful neodymium magnets and double-layer voice coil wire to dynamically drive their PET membrane. Furthermore, a special net material made of monofilament fibre protects the inside of the headphone cups from dust, dirt and droplets. A glance at the technical values specified by the manufacturer shows that the S4X, with impedance of 32 ohms, should be well suited for weaker amps such as those usually installed in Smartphones, tablets and laptops. Their frequency range of 20 Hz to 22 kHz extends beyond the typical human hearing range in the high frequencies and on paper promises an open sound experience. I was therefore curious to see how it would sound in practice.

… can be right or left

The self adjusting headband uses a stretchy strap. Unfortunately, this only ensures that the headphones don’t slip forward or backward from your head. However, the Audio HPS S4X’s ear cups are still strongly pulled down and are not really held by the headband and strap, but stay on due to their contact pressure. This means that the headphones do not fit very securely. A strip of soft velour/hybrid velvet is sewn around the inside of the exchangeable ear pads. This means the 90 mm diameter ear cups can be worn comfortably on the ears. The manufacturer describes the leatherette covered ear cushions as using memory foam but unfortunately, in practice this is not noticeable.

Surprisingly, the ear cups can be rotated through 360 degrees. This is also possible because no cable routing had to be considered in the headphone construction. The enclosed cable has a Y-splice and is plugged in on both sides. However, this is usually not very practical with studio headphones. What is unusual is that it does not matter which ear cup the left and right channel of the cable is plugged into. The shape of the S4X is absolutely symmetrical, so it doesn’t matter which way you put the headphones on.

The Ollo Audio S4X’s package is not entirely well thought out, considering the use that the manufacturer imagines for these headphones. As studio headphones the S4X could have done with a longer cable. The existing one is “only” 2 meters long and quickly reaches its limits in the daily routine of recording and mixing. And to be able to use the S4X on smart devices while on the move, the included cable is simply too long. In this case, cable lengths of around 1.20 m are clearly an advantage, because they can be stowed away better under clothing with little excess cable length. But here you have to give Ollo Audio’s manufacturer credit for the fact that they were probably primarily thinking of using them with laptops.

Rustic, warm sound

The Ollo Audio S4X delivers enough low frequency audio material from subtle low bass over an equally subtle bass range to make it possible to judge the lower end of the mix spectrum. In the mids, the sound of these headphones seems as smooth as its frequency image looks unspectacular on paper. Between 3.5 and 6.5 kHz, this frequency response boost produces good speech intelligibility. A treble boost between 9.5 and 15 kHz ensures brilliance. In between, damping the frequency response at 7.5 kHz prevents the headphones from sounding too sharp.

The reproduction of the trebles with the S4X seemed to me to be somewhat muted, as the energy in the super-high frequency range dropped sharply. Although the trebles were noticeably present, they were just unspectacular. This also prevented a really good subjective signal resolution. Even dynamically, these headphones remained comparatively dull to me. Although the depth staggering was okay, the reproduction of transients was not very concise. Trying to describe sound characteristics with visual language often brings its own difficulties, but on the whole the sound of these headphones seemed to me, to be very like their appearance: woody warm, for the lack of a better description.

A few words about volume. The S4X cannot manage to play back dynamic classical recordings without distortion at high volume. Orchestral tuttis quickly demonstrate their limitations. I also noticed a small construction flaw, touching the ear cups or even lightly touching the headband causes the headphones to vibrate and thus creates a metallic structure-borne sound. The manufacturer should definitely provide a mechanical decoupling to remedy this.