4070?
So, here's the story: I was exchanging headphones with a friend when he suddenly popped the question, ‘are you interested in the 4070?’ Without much thought, I replied, "For sure, why not? " I'd love to overclock my 4060 and turn it into a 4070 if possible, why refusing a REAL 4070 then?
I thought he was talking about the graphics card RTX 4070, even when I noticed a slight smirk on his face, still, I had absolutely no clue what awaited me. A few days later, I received a huge package, inside was indeed the 4070, but the trademark wasn't NVIDIA, it was Stax.
Actually, along with the 4070, there was also a Lambda Pro (Stax SR-Lambda Professional), and this is exactly what this review is about.
Design Background
From 1960 to 1982, a span of 20 years, marked the initial phase of electrostatic headphone development. During this period, the bias voltage of electrostatic headphones remained at 230 volts, and the gap between the stators was not particularly wide (0.3mm), while the thickness of the diaphragm (driver) was above 2 micrometres. These parameters largely hindered the improvement of electrostatic sound quality. Later on, around 80s, in response to the request from Mercedes-Benz, the initial professional-grade Lambda Pro headphone was developed for industrial purposes. The Lambda Professional was the first modern electrostatic headphone featuring high bias voltage (580V), wide stator spacing (0.5mm), and an ultra-thin diaphragm (1.5um). Subsequent electrostatic headphones did not undergo such significant improvements in technical parameters.
Design
Let's start with the design, the Lambda Pro in my hands exude a sense of ‘age’— or should I say ‘aged’... After all, it was released back in 1982. Assuming this pair is indeed produced in '82, wow, then this year, 2024, marks its 42nd birthday!
Over time, the headband plastic was severely aged and appears to turn white. (Presumably due to crystallization?) I'm a bit worried that one day, if I adjust the headband too forcefully, this old-folk might just snap and be gone for good…
The frame is mainly made of plastic and follows the classic Lambda frame design, which, has even been retained to this day. Although the Lambda series has been discontinued for many years, you can still see this design in today's L700/500/300 series.
Setup
Linn Selekt -> Berkeley Alpha DAC Series 2 -> Stax T8000 -> electrostat.
You might be wondering: "Wait, why are there two DAC?"
Well, here's the thing: I sold my Berkeley Alpha USB earlier, and since the Berkeley DAC doesn't support USB input, I found myself in a bit of a pickle. But then, I discovered that the Selekt actually supports SPDIF output, so, I ended up using the Selekt as a USB digital-to-digital converter (DDC).
Sound
Its debut note, which also leaves the deepest impression on me, this baby is all about vocal.Tuning
In my opinion, there's no obvious bias on Lambda Pro, with just a hint of warmth over vocals, but overall, it presents a neutral tone with a balanced tuning, it’s neither warm nor cold. Living up to its ‘Professional’ designation, it tends to lean towards a monitoring-like, straightforward sound signature.
Treble and ‘Tuning Magic’
The Lambda Pro exudes a distinct vintage vibe, with a strong sense of airiness. You'll notice a particularly strong contour and ethereal quality to the vocals, sometimes the imaging might sound slightly forward.
Because of its balanced tuning, the proportion of treble is just right—not overly emphasised, yet not easily overlooked. It exhibits good extension without being overly sharp, resulting in an overall gentle presentation. Additionally, there are no annoying sibilance or hissing issues in the mid-to-high frequencies.
Actually, this is a characteristic tuning from the last century. In principle, high frequencies are most easily absorbed by the air, so the farther away you are, the fewer high frequencies you hear, due to the limited recording capabilities of equipment in the last century, recordings of soprano voices and even some high-frequency instruments were often not ideal (of course, this doesn't mean there were no good recordings in the 80s, but for some smaller studios struggling to survive in the industry, they usually didn't have such good equipment for recording). To bring the vocals closer to the listener and make them feel like the singer is right in front of them (and also to mitigate the impact of high-frequency recording deficiencies), manufacturers used to deliberately boost the high frequencies. However, this habit of tuning has persisted to this day, so even though contemporary high-frequency recording is already quite good, sometimes manufacturers still deliberately boost the high frequencies, resulting in excessive sibilance and stimulation…
Vocal
The vocals of the Lambda Pro largely inherit the tuning magic that was mentioned above imo, the strong sense of airiness combined with the slightly emphasised high frequencies, giving it a rather unique sound signature that stands in stark contrast to most contemporary headphones. On the Lambda Pro, you can ‘feel’ the singer's mouth shape, and it’s like there's a soft aura enveloping the singer. The reproduction of the vocal makes me feel like being right there in front of singer in person, as if I actually saw the intricate mouth movements of her, rather than just listening to a plain recording!
Resolution
Despite the distinctive signature of the vocals, the shortcomings of it are also quite apparent. Although they are all ‘same old’ (released before 2000), Lambda Pro doesn’t have as good resolution as Sennheiser's 580 Jubilee or Sony R10. The resolution of the Lambda Pro tends to be more subtle, with a preference for softer imaging rather than highly intricate details and clear imaging. The issue in resolution becomes more pronounced when reproducing orchestral pieces, especially those involves multiple instrumental sections and a large number of instrumental performers, in rare cases, the positioning of instruments sound not sufficiently precise.
But hey, wait! Don't get me wrong, I mean, there's probably not much need to overly criticise the resolution of a headphone from 40 years ago with a modern perspective
Soundstage
Actually, its soundstage could be better, but it's constrained by the technology available at the time. The Lambda Pro's drawback lies in its relatively small driver (diaphragm) size (especially when compared to Omega series) and shallow earcup design. In most cases, the soundstage remains brilliant, with a decent horizontal soundstage that inherits the advantages of open-back headphones: natural; and there's no apparent sense of boundaries constraining you.
Bass
While the Lambda Professional doesn't suffer from the rumoured ‘bass deficiency’, the bass of the Lambda Pro is actually appreciable in quantity, but it could be improved in depth, layer and sub-bass reproduction.
The Lambda Pro does offer a commendable amount of bass, even to the point of being quite generous for a electrostatic headphone. However, it would be better if the bass could go deeper than the mid-bass. Part of issue in bass might stem from the design of the earcups imo. Firstly, they are too shallow to create a channel for bass to reflect inside. The shallow ear cups also lead to another problem: the drivers press directly against the ears, causing discomfort when worn for long periods of time, besides, it also results in poor sealing against the face, leading to bass leakage.
In summary, I find the sound of the Lambda Professional to be quite intriguing. As the first attempt from Stax to adopt the Pro bias (580v), it presents a strikingly different, straightforward sound signature compared to today's Lambda series. Even 40 years later, its sound remains remarkably engaging.
