SPL Phonitor xe

The 5.1 kg cabinet alone is enough to make the heart of every hi-fi lover beat faster. SPL, who are based in Niederkrüchten on the Lower Rhine, pull out all the stops here: The Phonitor xe, available with fronts coloured silver, black and red, is manufactured to be as decorative as it is high-quality and robust – and the power supply unit is integrated. In terms of technical design and features, the manufacturer draws on its long experience in the field of audio engineering and mastering, which is why the series also bears the name Professional-Fidelity.

Features

The analogue version we tested offers unbalanced RCA and balanced XLR inputs, while the version with an integrated converter offers four additional inputs. The front panel features a large, smooth gliding Alps RK27 level control, a switch for source selection, a built-in Phonitor Matrix with two adjustable parameters, and a mono/stereo switch with an additional option for adjusting the stereo balance (laterality).

Headphones can be used via a 6.3 mm jack or a balanced XLR-4 connector. Both types of jack are available and can be switched over on the front and rear. In addition, there are two classic, three-way switchable illuminated VU meters that visualise the input level. Finally, the Phonitor xe offers two DIP switches on the bottom of the unit, which can be used to adjust the reference level for the RCA input (-10dBV/0 dBu) and to provide the headphone output with a level boost of 22 dB.

On the analogue side, SPL relies on its built-in Voltair technology. Specially developed operational amplifiers with an operating range of +/- 60 volts are used, which exceed the voltage range of conventional components by a factor of 4 and are supposed to result in improved signal-to-noise ratio and increased dynamics. Indeed, the performance data of these components are impressive, with a dynamic range of 140 dB and a signal-to-noise ratio of 114 dB (based on the manufacturer’s data). The overload reserve increases, and the amplifier almost never needs to operate in its limit range, relative to the reference level.

The section dedicated to stereo balance is unusual. Here, the sound reproduction can be switched between mono and stereo, and the Laterality Control can be activated to compensate for differences in the channel volumes – useful for hearing impairments, but also for unbalanced stereo signals.

If you order the unit with a converter, you also have access to the AES/EBU, S/PDIF coaxial and optical connections, as well as USB 2.0. The converter used is the DAC768 with analogue filtering (DLP120). The D/A converter used comes from AKM (AK4490) and allows interface-dependent sampling frequencies of up to 768 kHz and 32 bits as well as DSD up to 11.2 MHz (DSD256). The analogue filtering in the DLP120 is designed separately for the PCM and the DSD part and, in contrast to the Phonitor se, also relies on Voltair technology.

I was initially puzzled by the transducer option. However, as SPL is targeting customers who have the highest music reproduction demands, who often own expensive transducers that they want to continue to use, there is not necessarily a need for the extra cost of an integrated transducer.

In practice

Functionally, the Phonitor xe gave me nothing to complain about apart from the missing Pentaconn interface. The operation is straightforward, and the associated controls are comprehensive and high quality. The output power is impedance-dependent between 0.7 and 8 watts per channel (XLR-4, 32/600 ohms). In practice, with the addition of the DIP switch, even explicitly quiet compositions can be pushed to powerful levels.

Thanks to multiple outputs, there is a suitable connection for every situation. The outputs are deliberately not connected in parallel due to changed impedances. So only one person can use the Phonitor xe at a time.

An impressive detail is the ability to control the volume by remote. The programming process is delightfully simple and works with any infrared remote control. As a result, the level control is moved as if by magic.

The analogue implemented Phonitor Matrix aims to approximate the sound image of a loudspeaker via headphones. The background to this: Almost every sound recording is mixed and tuned via loudspeakers. However, the reproduction via headphones differs from this tuning for various reasons. For example, there is a perfect channel separation that is not found in loudspeakers or naturally (or at a concert). In fact, signals from the left channel reach the right ear and vice versa. In addition, due to human physiognomy, this crosstalk is even accompanied by a filtering of the high frequencies. Furthermore, with headphones, sound events are localised “in the head”, while a loudspeaker plays “in front” of the listener. Accordingly, there are further differences in the auditory impression, which, depending on the source, affect level components of individual frequencies, the width of the stereo stage and the depth gradation. SPL provides an explanatory video on this topic.

However, anyone who says that the sound is spectacular with headphones is at a disadvantage when it comes to a realistic assessment of a mix. And this is exactly where the configurable Phonitor Matrix comes in. It sets the filtered crosstalk between the channels with a six-step switch (Crossfeed, up to 30 per cent) as well as the placement angle of the speakers with a four-step switch (20 to 55 degrees). The latter parameter controls the so-called interaural time difference, which is between 150 and 490 microseconds, depending on the angle. An additional level compensation of the centre signal (centre level) for a correct embedding of the stereo centre after applying the Crossfeed parameter is preset to -1 dB, as in the Phonitor se and Phonitor One models. Again, SPL offers support in the form of audio samples, which you should listen to with headphones if you are interested: https://youtu.be/UoOv7NImi84.

You will be familiar with using the stereo balance control of your stereo system to compensate for the asymmetry of the speakers. And one should not snobbishly dismiss a corresponding function as a disturbing link in the playback chain, because there are people who live with a health-related or age-related hearing impairment that can naturally manifest itself differently in both ears. Depending on the intensity, such differences are compensated for by the brain, but they also require more “processing” by the brain – especially when using headphones with a perfect left/right split. But that’s not all: human hearing is individually distinctive. The perception of space, depth and level intensity differs from person to person – physiognomic characteristics that are evaluated by the brain and adapted for everyday life. Perhaps you are not even aware of such a “deviation” from perfect linearity. And that is exactly why the Phonitor xe offers a switchable laterality control with which the stereo balance can be changed. The control works in a rather discreet but finely resolved range of a maximum 2.25 dB and offers an automatic compensation of the opposite side in the opposite direction.

Since the test unit came without a digital converter, this could not be tested. However, I anticipate an identical and thus problem-free connection using Windows, macOS and iOS as with the Phonitor se.

Sound

As a headphone amplifier, the Phonitor xe leaves virtually nothing to be desired. In our test, it worked well with the HD 800 S and HD 660 S from Sennheiser. The richness of detail and the dynamic and spatial reproduction was simply breath-taking, particularly in combination with the first of these headphones. The technical data on the signal-to-noise ratio and frequency response were equally at the highest level.

Compared to more simplistically designed dedicated headphone amplifiers, there is a noticeable increase in sound quality, especially when compared to integrated solutions for audio interfaces or hi-fi components. However, I wouldn’t go so far as to call the Phonitor xe “twice as good” as the Phonitor se model. In terms of design, this unit is in the upper range, which makes it comparatively more expensive in every respect. The high expectations in view of the price, however, are in my opinion fulfilled throughout and become all the more obvious the better the overall quality of the signal chain from the transducer to the amplifier to the headphones becomes.

One of the strengths of such a combination is the outstandingly fast response, the precise localisation in the stereo panorama and the highlighting of even the finest nuances in the temporal range, texture of voices and ambient noise. With the Phonitor xe, these sounds can be enjoyed to the highest degree. But it also offers the possibility of using an acoustic magnifying glass to delve deep into the frequency and temporal spectrum of the source material, which professional users will appreciate.

The impact of the Phonitor Matrix is coherent and depends on the source material. Sometimes a change is more noticeable, sometimes more subtle. In general, the mix becomes somewhat narrower and moves towards the front. Sound elements placed far to the left and right may subsequently drop in level. The sound experience with the Phonitor Matrix is not a showy effect, but natural in the best sense of the word. If one assumes that a mix was created on loudspeakers, then the desire to be able to hear it in headphones mode, as it was created by the sound engineer, is justified.

The Phonitor Matrix fulfils this goal to a great extent by approximating the sound of a loudspeaker reproduction. The phantom centre is strengthened, reverberation spaces recede further into the background.

You should, however, allow your ears to get used to the adjusted sound over a few tracks before switching back to the standard configuration on a trial basis. In quick A/B comparisons, the headphones score points with their superb sound. If, on the other hand, you switch back from the Phonitor Matrix, the same Superpanorama may be perceived as unnatural.

The system definitely offers sound engineers and critical music listeners increased compatibility with loudspeaker reproduction and thus with the “truth of a mix”. This was exemplified by Tori Amos’ “1000 Oceans”, where the sound mix sounded clearly different with and without the Phonitor Matrix. The sound in the headphones was broader, but also more disjointed. At the same time, there were differences in the richness and tonal character of the Bösendorfer grand piano. I would not say that either of these variants was worse, but I heard two different mixes. Something similar was noticed with Slayer’s “Repentless”, which was clearly less mid-emphasised and leaner via the Phonitor Matrix.

Last but not least, I would like to praise the presence of the Phonitor Matrix and the mono switch for another reason: Oversized sound images are partly based on phase manipulations, which affect the mono compatibility of a signal and can be identified more quickly here. The mono compatibility of stereo mixes is part of the sound engineering standard that takes into account the requirements for vinyl, on broadcast tracks, television, in soundbars and other Bluetooth/WLAN speakers, and can also have an effect in operation with audio codecs.