TEST: SPL Phonitor

 When I first encountered the product description for the SPL Phonitor, I was immediately struck by a mixture of great hope and perhaps even greater skepticism. Why am I making such a fuss about this product? Well, if SPL manages to achieve their stated goal with the Phonitor, we'd be dealing with a revolutionary invention that a legion of producers, sound engineers, and audio technicians have been waiting for.

Enough with the cliffhanger - what exactly is SPL's goal? Anyone who has ever had the pleasure (and responsibility) of occupying a professional producer's chair knows the problem all too well. While you can confidently determine the frequency relationships and spatial imaging of a signal on your own studio monitors, you face significant challenges when working with unfamiliar monitoring setups in other studios.

The stereo image of an unfamiliar setup is positioned completely differently, frequencies resonate differently or are over/under-emphasized. The room acoustics of the control room do their part to turn the workspace into a natural adversary. Your personal sense of sound goes out the window, and creating the ultimate mix becomes an audio Russian roulette with a maximum 70% hit rate. This is why many producers, myself included, always bring their own reference monitors (not to be confused with "particularly good-sounding" monitors) when working on productions in other studios.

Like many colleagues, I would have loved to create a mix on a proper set of headphones, especially for late-night work at home. However, the sometimes unbalanced sound image and, above all, the complete helplessness regarding spatial localization due to the 180-degree stereo width ("through the head") of the signal has always been a major obstacle.

This is where SPL comes in, promising a device that - to quote - "generates music as it was produced, namely for playback over speakers." I must say, I'm quite intrigued!

Construction:

The Phonitor comes in a half-width 19" rack format (9.5 inches) with a height of 2U. The overall build quality is excellent, with SPL fortunately still adhering to the once highly esteemed "Made in Germany" trademark across the board.

A notable feature is that the Phonitor, like all products in SPL's Mastering Series, is based on 120V technology. A total of nine SUPRA-OPs do their duty in the Phonitor, offering a signal-to-noise ratio of 116 dB and an overload tolerance of 34 dB, resulting in a respectable dynamic range of 150 dB.

At first glance, it's clear that this device doesn't fall into the typical "headphone amplifier" category. Too many switches and controls allow for sound shaping possibilities, in stark contrast to the usually spartanly equipped "normal" headphone amplifiers.

On the front panel, we're greeted by an oversized volume control for the headphones. A Crossfeed control, adjustable in six steps, allows for level-dependent, frequency-dependent simulation of crosstalk between both channels. Changing this value is comparable to altering the room size while maintaining the same speaker setup.

The Speaker Angle control adjusts the frequency-dependent simulation of the stereo base width in terms of timing. Here, an angle between 25 and 75 degrees can be set. The Center Level control adjusts the intensity of the center signals in relation to the Crossfeed and Speaker Angle settings of the stereo signal.

In normal headphone listening experiences, the center signal (phantom center) is usually quieter than the side signals, which appear louder due to the super-stereo effect. The narrowing of the base width through Crossfeed and Speaker Angle can lead to an intensification of the phantom center, which can be very finely reduced using this control.

Two toggle switches allow you to deactivate the Crossfeed/Speaker Angle combination and Center Level, providing a good A/B comparison to a regular headphone amp.

Two large VU meters serve as the visual centerpiece of the Phonitor. The display range extends from -20 dB to +5 dB. If needed, the sensitivity can be reduced by 6 dB, extending the display range to +11 dB. In addition to their needles, the "portholes" also feature a signal LED that indicates the presence of a signal above -22 dB, and an overload LED that activates at +21 dB.

The VU meters can switch between two modes: VU and PPM. In VU mode, the needles show an average level and operate with a rise time of about 300 ms. In PPM (Peak Program Meter) mode, this value is reduced to about 2 ms.

The operation mode of the VU meters and meter calibration are also set using two small switches on the front panel. A DIM switch reduces the monitoring volume by 20 dB. This function is typically used in practice to switch between two defined volumes during mixing.

A Solo switch allows you to listen to the right or left channel individually in Solo-In-Place mode. If you want to listen to the respective channel in Solo-To-Center mode, you must also activate the corresponding Mono switches.

A phase switch allows you to activate the crucial phase inversion, which can flip the phase of either the left or right channel. When the Mono switch is activated simultaneously, a difference can be formed between the two audio channels. What remains is what's present only in the right or left of the stereo image.

On the rear panel, the Phonitor features XLR Left/Right inputs and outputs. The input signal passes unchanged to the output sockets, so no monitor output is lost. Additionally, there's a ground lift switch, a voltage selector switch, and an IEC power connector.

In Practice:

After powering on the Phonitor, the VU meters light up, indicating its operational state. Following the manual, I carefully work my way through the parameters, constantly comparing the headphone signal with the "real" monitors.

You wouldn't believe it, but with meticulous adjustment of the parameters, depending on your own monitoring setup, you can actually generate a true-to-life representation of your speakers. I'm completely thrilled! Admittedly, you should set aside several hours and initially focus on understanding the effects of the controls with full concentration. After all, the goal is to "replicate" your own monitoring environment, which can be a real challenge for the uninitiated.

Once you've grasped the workings of the parameters, you can literally build your own environment. All switches provide practical functionality and offer manifold possibilities for tonal control. Only the DIM switch, with its -20 dB reduction, feels a bit too strong for my personal taste, but this is subjective and doesn't detract from the overall impression.

Even with critical listening, I couldn't detect any tonal alterations or losses despite SPL's massive intervention in the phase landscape of the signal.

Expanding on the Phonitor's Capabilities:

While the Phonitor excels at recreating a speaker-like experience through headphones, it's worth delving deeper into its potential applications and how it fits into various workflow scenarios.

For mixing engineers, the Phonitor opens up new possibilities for creating balanced mixes even in less-than-ideal acoustic environments. By simulating a well-tuned control room, it allows for critical decisions on stereo placement, depth, and overall balance without being at the mercy of room acoustics. This can be particularly valuable for those working in home studios or when traveling.

Mastering engineers might find the Phonitor useful as a secondary reference point. While it's not meant to replace high-end speakers in a treated room, it can provide valuable insights into how a mix might translate to headphone listeners. The ability to switch between different speaker angle simulations could help in assessing how a master might sound on various playback systems.

For recording engineers working on location, the Phonitor could serve as a reliable reference when setting up temporary control rooms. Its ability to simulate different speaker setups could help in achieving consistent results across various recording environments.

It's important to note that while the Phonitor excels at creating a speaker-like experience, it doesn't address the frequency response characteristics of the headphones themselves. Users will still need to be intimately familiar with their headphones' sonic signature to make accurate judgments. Some engineers might choose to pair the Phonitor with headphone correction software for a more complete solution.

The Phonitor's VU meters deserve further exploration. In addition to their aesthetic appeal, they serve a practical purpose in gain staging and maintaining consistent levels. The ability to switch between VU and PPM modes allows engineers to monitor both average and peak levels, which can be crucial in maintaining appropriate headroom throughout a mix.

The phase inversion and mono summing capabilities of the Phonitor also warrant attention. These features, while simple in concept, can be powerful diagnostic tools. The ability to flip the phase of one channel and sum to mono can quickly reveal phase issues in a mix, helping to identify problematic frequency cancellations or enhancements.

For those working with binaural or immersive audio content, the Phonitor's crossfeed and speaker angle controls could prove invaluable. By adjusting these parameters, engineers can fine-tune the perceived spaciousness of binaural recordings or assess how well spatial audio content might translate to standard stereo playback.

It's worth considering how the Phonitor fits into the broader ecosystem of headphone-based mixing solutions. While some software plugins attempt to simulate speaker playback through headphones, the Phonitor's hardware approach offers several advantages. There's no latency to contend with, no CPU overhead, and the tactile control over parameters can lead to a more intuitive workflow.

However, the Phonitor is not without its limitations. Its fixed crossfeed curve might not be ideal for all types of program material or headphones. Some users might prefer systems that allow for more customization of the HRTF (Head-Related Transfer Function) used in the crossfeed simulation.

The lack of a built-in DAC might be seen as a drawback by some potential users, especially given the Phonitor's premium positioning. While this allows for greater flexibility in choosing a DAC, it also means an additional component in the signal chain.

For professionals considering the Phonitor, it's important to view it as part of a larger monitoring strategy rather than a complete solution in itself. It complements rather than replaces traditional speakers, and its true value becomes apparent when used in conjunction with well-understood headphones and in comparison with other monitoring options.

The Phonitor's potential impact on workflow shouldn't be underestimated. By providing a consistent, speaker-like reference point, it could allow for more efficient use of time when working away from a main studio. This could be particularly valuable for producers and engineers who split their time between multiple workspaces or who often need to make critical decisions outside of their primary environment.

In educational settings, the Phonitor could serve as a valuable tool for teaching critical listening skills. Its ability to switch between standard headphone playback and simulated speaker playback could help students understand the differences between these two monitoring paradigms and develop a more nuanced understanding of stereo imaging and mix translation.

Conclusion:

Well, I'll be damned! I wouldn't have thought it possible, but I'm actually hearing the stereo image of my monitors through my headphones! Finally, a way to precisely position instruments in the stereo field, even when only headphones are available. SPL has truly created an outstanding product here!

This opens up entirely new avenues for production. For example, you could set up sounds and frequencies in the studio during the day, take the production home on a hard drive, and finish the mix in terms of soundstage, etc., in your home office in the evening if necessary. Words like flexibility and independence come to mind. It's a real boon for anyone who still makes the effort to deliver high-quality productions in the age of "no-budget-over-virtual-knock-me-dead-simulator-cobbled-together-and-mixed-in-the-bedroom" subpar productions.

However, if you now believe you can set up EVERYTHING using the Phonitor, please keep in mind that to work exclusively with the Phonitor, you must know your headphones PERFECTLY in terms of frequency response, etc. The Phonitor only handles the stereo image; you're still listening through headphones, which have their own sound!

By the way, the extent to which music fans will be able to aurally grasp and appreciate this extra effort remains to be seen. I recently saw kids strolling through town with mono headphones that had the frequency response of a megaphone...

In the broader context of audio technology, the Phonitor represents an interesting bridge between traditional speaker-based monitoring and the increasing prevalence of headphone use in professional audio. As more content is consumed via headphones, tools like the Phonitor may become increasingly relevant in ensuring that mixes translate well across various playback systems.

It's also worth considering the Phonitor in light of emerging immersive audio formats. As technologies like Dolby Atmos and Sony 360 Reality Audio gain traction, tools that can accurately represent spatial audio information over headphones may become increasingly valuable. While the Phonitor is primarily designed for stereo content, its underlying technology could potentially be adapted or expanded to address these new formats in the future.

Ultimately, the SPL Phonitor is a specialized tool that addresses a specific need in the audio production world. Its value will depend largely on individual workflows and requirements. For those who frequently work on headphones or need a reliable reference when away from their main monitoring setup, the Phonitor could be a game-changing addition to their toolkit. For others, it may be an interesting but non-essential luxury.

As with any audio tool, the true test of the Phonitor will be in its long-term use across a variety of projects. Initial impressions are certainly positive, but its real worth will be determined by how it influences the quality and efficiency of users' work over time. For now, it stands as an intriguing and innovative approach to a long-standing challenge in audio production.