Rosson got in touch and expressed to me that they set out to provide a sound suitable for both professionals and audiophiles. They achieved this by blending a non-fatiguing tonality with a focus on a super-fast transient response. In turn, the RAD-0 isn’t designed to be perfectly flat but accurate enough to be a tool of reference. Soundstage space was sacrificed in favour of enhanced coherence and imaging acuity. I appreciate these comments that contextualize the intent of the headphone as many come to see colouration as a weakness of a design, Rosson has intentionally introduced some in order to optimize the headphone for their intended use cases.
Even then, the RAD-0 did surprise me. It didn’t help that many online reviews dubbed this a balanced, neutral headphone, and I didn’t find that to be the case. While this will depend on your point of reference, I found the RAD-0 to offer a lower contrast and slightly L-shaped sound to an extent. However, it isn’t at all compressed due to impressive spatial abilities alongside a highly controlled note presentation. True to the company’s goals, the first thing that stands out about this headphone is its tight, defined, and focused delivery.
Of course, this is a high-end headphone and the qualities you would expect are present if not entirely celebrated by its dense, structured voicing. Expect a sense of immediacy enabled by very high-level resolution rather than forwardness or boosted clarity. The downfall of this headphone is undoubtedly in this general aspect as, by swinging towards structure and power, the headphone strays from separation and clarity. At the same time, the room and general drive of this headphone mean it also isn’t the ideal easy listening instrument. To me, this is a headphone designed to be turned up, after which it provides a grand, almost enlightening sonic experience with some real meat on its bones.
The standout of this headphone, it measures very evenly but, to my ears, I am perceiving a slight mid to upper-bass bump that gives it a warmer voicing with full, enlarged notes. In addition, as the midrange and top-end of the headphone are laid-back by comparison, the bass is granted more perceived presence. Combined with sensational tightness and standout driver control, the RAD-0 achieves a sense of authority and authenticity that many planars do not possess. It is a highly textured bass and not an overly rapidly decaying one either, simply highly defined and very well damped. The result is a highly textured low-end with a lovely warmth but zero bloom that lacks the flubby impact and texture of many competing planars. In turn, despite not having the most sub-bass presence, the RAD-0 still strikes me as a dynamic, hard-hitting headphone.
This is atypical as usually, upper-bass biased headphones tend to be smoother, more relaxed affairs. While it isn’t especially pressurized or slam focused, it does provide a standout sense of punch and impact in the mid-bass. I would attribute this quality to its keen note attack, delivering a sensational sense of drive and dynamism. At the same time, it doesn’t sound muddy or poorly separated as sub-bass isn’t overly forward, giving the mid-bass room to breathe. That said, while it is nicely defined and well-textured, you can find a more balanced or articulate performer even below this asking price. The RAD-0 doesn’t strike as the most separated or hyper-responsive. However, in terms of slam, definition and power, it’s a uniquely strong proposition that few can match, making it an absolute pleasure for rock, pop and hip-hop.
The RAD-0 provides a powerful, well-structured, and somewhat roomy sound. The execution is impressively progressive with the aforementioned qualities stemming most from lower midrange enhancement rather than overt bass emphasis, in tandem with a slight 4kHz attenuation. The midrange sits slightly behind the bass but cannot be considered overtly laid-back as vocals are slightly pushed forwards with adequate head gain. Male vocals take slight precedence over female that achieve relative parity with midrange instruments. 3kHz presence is sufficient to uphold a natural voicing yet a robust character persists. As aforementioned, the lower-midrange focus equates to a roomy and full-bodied nature over a warm and bloomy one. This keeps excessive tonal colouaration and fuzz to a minimum, upholding a surprisingly clean tonality. While separation once again isn’t the highlight, this does permit a well-defined midrange presentation and one with excellent texture and layering.
The treble tuning aids this impression to some degree, being linear and of neutral presence above that of the dense upper midrange. This provides enhanced articulation that goes far to counterbalance the increased body and density within the midrange itself. The net result is a sound that carries convincing if not outstanding clarity but upholds an enlarged, coherent character devoid of any kind of rasp or intensity. Resolving power on a whole operates at a good level though this can be more difficult to appreciate relative to more revealing headphones. Small mouth sounds and fine midrange details are present but less forward in their display. While I wouldn’t say this tuning is conducive towards especially outstanding genre versatility, the style of colouration is easy to enjoy and provides excellent long-term listenability without excessive blunting. In the same sense, its powerful yet articulate tuning works tremendously well with male vocals and electric guitars.
As much as I love the bass, equal kudos must be given to the top-end tuning on the RAD-0 – it doesn’t stand out quite as much simply due to it being less forward. The top-end is superbly linear and offers a strong extension into the top-octave. There’s a hint of emphasis around 7kHz and a slight upper-treble boost that serves to enhance micro-detail presence and headroom. The RAD-0, though never bright nor overtly dark, offers a healthy medium with an authentic instrument timbre and a delightful sense of air above. Notes are rendered with accurate body and decay, enhancing texture and verisimilitude. I find the RAD-0 excels especially at capturing the metallic clang of old-school rock such as the opening of The Pixie’s “Where is My Mind?”. Where many headphones play it safer and smooth over this quality or succumb to glare or thinness to varying degrees, the RAD-0 is able to capture this track with aplomb owing to the headphone’s excellent, linear treble tuning.
The transient response is clean and sharp, notes have a defined leading edge too, though speed and definition remain a step below that of the new crop of summit-fi headphones – as you may expect given the large price difference. It feels appropriate to confront here that the RAD-0 does occupy an odd price point. Consider it appropriate given that its technical performance exceeds those below the $2000 mark but doesn’t challenge market leaders at the higher end. Nonetheless, in combination with its masterfully executed tuning, the RAD-0 separates and textures better than the vast majority. Fine detail retrieval in the foreground is especially standout and micro-details are nicely present but never pushed into the listener’s face. The upper-treble lift is in good moderation to avoid excessively skewing instrument timbre below, lacking that “tizzy” character of many. In turn, the RAD-0 feels especially focused and planted, excelling with layering and timbre.
Contrary to my experiences in the treble section, the RAD-0 provides one of the more intimate presentations amongst summit-fi headphones. I suppose this requires some context as we really are pushing into price ranges where headphones are absolute outliers in this regard. While the RAD-0 is intimate relative to these models, I do still think it is able to soundstage better than headphones south of the $2000 mark such as the Focal Clear and LCD-X 2021.
In addition, while it does have the ability to push width beyond the head, the level of room and slight vocal push in the midrange means it errs on the forward over spacious side. The presentation is well-rounded, that said, and the roominess also contributes to a delightful sense of layering. I found this style of presentation to offer an outstandingly sharp sense of direction. While distance portrayal performs below many competitors, the RAD-0 achieves a sense of holography with its sharp direction, intimate proportions, and articulate note presentation.
Layering as well is a standout, with excellent foreground/background contrast and an especially well-resolved background too. Separation is just ample but doesn’t stand as a highlight of this design due to the combination of full, large notes and smaller dimensions. There is just a hint of air surrounding elements in the midrange and a little more in the high-end. Still, as aforementioned, small details in the midrange aren’t highlighted to the listener even if they aren’t masked either. As always, this type of tuning is a tradeoff and in return, you do receive a winning sense of cohesion, layering and direction. It enables the headphone to uphold a multi-dimensional presentation without ever feeling vague.
The RAD-0 offers a higher 98 dB sensitivity combined with a low 29-ohm impedance. In listening, it appears more efficient than many competitors, even planars which should be considered a positive as it lowers the barrier for entry in terms of source matching. While it remains best practice to listen from a high-quality dedicated source, you can get away with something more economical than that required for many other high-end designs.
Output Impedance Sensitivity
Planar designs are usually relatively flat from an impedance curve standpoint and this was my general experience here. Comparing the THX789 (1-0hm) with and without a 50-ohm impedance adaptor revealed a drop in volume but minimal shift in tonality. That said, I did notice a drop to note definition and dynamics with a general drop in driver control; so a sub-4-ohm output impedance should be upheld for the best listening experience. I had a similar experience with the xDuoo TA-26 tube amp but found its OTL design to struggle with clipping, volume output and driver control on the low-impedance driver. In terms of colouration, I do feel the RAD-0 is best served by a transparent source and due to its impedance, a solid-state amp is best though SET or hybrid tube will work too.
The upside of the low impedance means this headphone is very easy to drive for solid-state amplifiers. Modern examples, even midrange sources like the Topping A30 Pro offer satisfying dynamics and control and larger, higher-end sources can further enhance this. You can drive the RAD-0 from a portable source in a pinch too. However, you will hear a loss to bass impact and overall note definition. The vast majority of truly portable sources also won’t give you the same soundstage experience.
Suggested Pair Ups
With its efficient design, the RAD-0 sings from a wide range of desktop sources and select portable sources though generally to a lesser degree. A good desktop stack is, of course, the best course of action as with any high-end full-size headphone. In addition, a lower output impedance would suit the headphone’s lower impedance for optimal damping factor. The RAD-0’s thicker voicing and linear treble make it suitable for more neutral leaning sources such as the Topping NFCA devices and THX amps. While you can pair the RAD-0 with a warmer source, I didn’t find this to be most conducive towards a fun listening experience due to the further loss of separation and dynamics. Hybrid tube amps may be a good avenue for those wanting a more laid-back presentation but this didn’t match my personal tastes.