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.

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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.

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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.

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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).

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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.

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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.

Intro.​

Similar yet different
As a portable player featuring vacuum tubes, the N8ii, as the successor to the N8, shares some similarities while also introducing some differences.

Similarities include the use of KORG vacuum tubes, but this time, there are two, as it implements balanced tube amplification. However, unlike the rich and warm tube sound of the N8, the N8ii's tube mode tuning approach is surprisingly closer to the C9 rather than the N8, offering a more neutral and accurate sound. The N8 first generation is noticeably warmer in tonality, partly due to the AKM4497 chip, while the N8ii this time employs Rohm's BD34301EKV. The new circuit architecture brings about a different tuning, making the N8ii sound cleaner, clearer, and more direct.


In addition, the iconic golden triangle smiley face was abandoned to accommodate the touchscreen. This makes it less 'characteristic' compared to the previous generation. However, if I were to choose, honestly, I think I would still prefer the touchscreen because of its practicality.

Switching to a healthier diet?
The N8ii aims for transparency and neutrality, with a slight warmth in tuning. Some believe this symbolises the 'loss of spirit of vacuum tubes,' which is also one of the controversial points about the N8ii.

In my opinion, the 'flavour' in the N8ii's tube mode is indeed reduced compared to the N8, but the rest were significantly improved. The N8ii's tube mode becomes more delicate, more detailed, striking a good balance between sound flavour, resolution, and dynamics.

Its flavour is akin to adopting a healthier diet, becoming much milder. This is a point that can be seen as either good or bad, depending on personal preference.

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Settings
The settings I used for review: Solid-state, Class AB , P power mode.
And I used the 64 Audio Noir and tia forte, as well as a LCD-4z for review.

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Sound​

Class A/AB
When it comes to the Class A/AB mode, it's the first noteworthy feature of the N8ii, the newly designed switchable Class A/AB amplification circuit. The entire amplification circuit delivers astonishing dynamics and detail in AB amplification mode; however, in Class A amplification mode, there's a slight loss in dynamic, especially noticeable in concerto, symphony, and rock tracks that require large dynamic swings. Nonetheless, the difference is less distinct in pop and vocal performances.

Bass
Firstly, the bass is finely tuned, exceptionally clean and cohesive, with moderate weight and energy concentrated at mid bass. There's noticeable elasticity without a sluggish rebound thanks to its fast speed. In the tube mode, the bass is slightly softer, slower, with less emphasis on texture and impact, and a slightly reduce in quantity compared to the solid-state mode.

Overall, it's a bass that's impactful, with excellent depth and emphasis on texture and rebound speed. I really appreciate this balance because it's just right, if it were to emphasise bass impact a bit more, it might appear too dry and hard.

Vocal
The vocals are also finely tuned for transparency, without any obvious bias. They exhibit high density with moderate thickness, emphasizing clarity in articulation and precise positioning of vocal sources. Additionally, unlike the previous generation N8, which tended to soften vocals, the N8ii doesn't apply too much smoothing to vocals. Sibilance doesn't disappear completely, aiming to preserve the natural texture of female vocals, again, this is a point that can be seen as either good or bad, depending on personal preference.

As a result, vocals sound clear and bright without being overly stimulating, demonstrating a well-balanced tuning.

Treble
Then onto the treble. Clean, natural, and transparent, with smooth and excellent extension. Though clean, it doesn't appear palm; though extends quite high, you don't feel harshness or fatigue; the treble is well refined.

In the tube mode, the imaging of vocals is brighter and clearer. And speak of brightness, in my opinion, it is moderate on N8ii, it doesn't artificially enhance the highs to make it sounds 'brighter', instead, the N8ii maintained smoothness while emphasised the good extension. The appropriate brightness also ensures listenability, I mean, you won't feel fatigued even when paired with iem with a rather offensive treble like the tia forte, of which has a quite offensive treble peak and could appear a bit too bright sometimes. However, on N8ii, the highs of the tia forte is well controlled in various scenarios.

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Personally, I prefer using the tube with the P+ power mode for solo or sonata pieces. Although it may not deliver the same level of resolution as the solid-state mode, the overall performance of instruments, including the layered bass of drums and the airiness of string instruments, are just excellent. Another suitable direction for the N8ii is metal rock, in the tube mode, the bass remain tight and clean. Additionally, the brightness, clarity, and energy of the treble are better than solid-state mode imo.

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Could be better?
Actually, there are two points I feel could be improved.

Firstly, the thickness. The N82's thickness reaches 2.5cm, and I don't know whether or not your pants have pockets that big, but at least mine don't. I remember years ago when Sony dominated the portable DAP market, I bought a ZX2, slipping it into my pocket and putting on a pair of headphones to wander around was a distant yet beautiful memory.
But today, it's hard to say that portable players can still be described as "portable".

Secondly, speaking of pocketing it, there's another issue: heat. If you're running the tube mode, Class A amplification, at P+ mode, and then use it in a non-ventilated environment like inside your pocket, what you'll probably get is a device that's really hot. Sometimes, when I use it as a desktop DAC/amp in my office, opting for USB input while powering it, it also generates a considerable amount of heat. Under certain circumstances, it may overheat, triggering protection mode and stopping the charging process.

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Epilogue​

The N8ii tube mode indeed sounds more like what you'd expect from a solid-state mode. Well it's like in the era of film cameras, we would commend a photographer's skill by saying, "It's so clear as if you shot it with a digital camera."

In conclusion, the N8ii does indeed has a much lighter flavour compared to the N8. But if we set aside the inherent impression of the warm tuning of the N8, we would find the sound becomes more mellow, delicate, and airy. This fresh tuning really strikes a fine balance between the accuracy and pleasing of the tube sound.

Prelude​

When it comes to the TH909, most discussions revolve around two main points:
1: whether the 909 is an upgraded or even "ultimate" version of the 900;
2: whether the sound of the TH909 is much more neutral than the TH900; or even to the extent that it loses some of the distinct characteristics of the TH900.

Regarding the first topic, personally, I don't consider the 909 to be a true "upgrade" or "ultimate" version, because the drivers in the 909 are very similar to those in the th900s. I believe Fostex has mainly made some tuning adjustments, similar to what they did with the Blue 900, White 900, and Purple 900 versions (the Green 900 essentially being a repainted TH900 mk2 Red); or perhaps they've made very minor tweaks.

Driver of TH909

Although marketed as open-back, the TH909 doesn't quite resemble typical open-back headphones, as you can't see the drivers from the outside.
Upon disassembling the TH909, I discovered a dual-layer acoustic material behind the waffle-like outer structure, isolating the drivers from the outside. The first layer consists of black high-density foam (underneath the white bio cellulose film), topped with a layer of white Bio cellulose film (similar to the paper-like film on the driver).
From this perspective, I don't really consider the TH909 to be an fully opened-back headphone.

Sound​

Tuning

The TH909 has indeed, 'compromised' a lot compared to the TH900, TH909 didn't inherit the iconic V-shaped tuning of TH900 series. It leans more towards a neutral and balanced tuning style, although objectively speaking, it's not entirely neutral.

I once owned a TH900 MK1 Red, and I believe it has an issue with the midrange: mids is quite thin, with imaging positioned towards the rear; on this basis, the V-shaped tuning is like pushing the mids way behind the bass and treble, which further encroaches on the mids' existence.

The tuning of the TH909 is like dulling both ends — the highs are no longer piercingly bright, and the lows are no longer overwhelmingly powerful. Though the sound signature remains similar to the TH900, the tuning sets them apart as two distinct headphones. It's like a bottle of aged whisky—no longer harsh and spicy, but rather composed.

The TH909's standout characteristic lies in its departure from the legacy V-shape tuning of the TH900 family.

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Soundstage

I think the TH909 and TH900 don't show very significant changes in terms of soundstage; they both have brilliant soundstage with ample spaciousness. Both of them have brilliant horizontal soundstage that is wide enough to precisely demonstrate the separation of instruments, you can distinctly and clearly sense the instrumental placements, with sufficient spacing between each instrument.

I believe the difference between the soundstages of the TH909 and TH900 lies in the vertical dimension. The TH909 exhibits better vertical soundstage, allowing you to perceive more differences in the layout of instruments in depth.

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Bass

The bass of the TH909 is no longer aggressive and fierce but appear more 'civilised'.

Bass texture of the 909 is similar to TH900's, with good extension, different layers and decent impact. However, the depth of the bass isn't as deep as TH900 imo, the sub-bass doesn't goes as deep as the TH900. With the TH900, the overwhelming bass always drew all of my attention when listening to EDM tracks, I mean, that cool, that's the point I like TH900 so much, the depth of TH900's bass is like a ’Journey to the Center of the Earth', both energetic and stunning.

One of my favourite EM: Enough Is Enough (feat. Richard Caddock) - Puppet & Cormak

In contrast, the TH909 tends to remind you that 'this part is the bass, and that's it', without drawing your entire attention away . It lacks the TH900's striking bass impact, not that punchy.

Overall, the bass on TH909 has a more cohesive characteristic, especially when listening to rock tracks, the performance of the TH909 is more like the drummer's beats complementing the band's performance, while the TH900 is like the drummer has ‘knocked out all the other members' and then taking the opportunity to pound vigorously on stage.

Speaking of rock, I highly recommend this one: Come Close - Saosin

In summary, while traces of the TH900's bass characteristics can still be found, there's a noticeable difference in impact and depth.

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Mids/Vocal


The vocals have now reached a completely acceptable level. Although there hasn't been a significant increase in mids thickness, the vocal imaging distance has been pushed forward a lot, and, most importantly, thanks to the balanced tuning without peaks at both high and low ends, vocals can now be heard more clearly.

So, with all these improvements combined, vocals have become much more natural. Furthermore, they've become very smooth, without any piercing or harshness at the peak of vocals, although under some circumstances there might be sibilance, it's not overly jarring. Listening to anime tracks won't feel like the highs are piercing your eardrums, and vocals won't sound like they're coming from a distance. It truly provides an enjoyable vocals.

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Highs/Treble

When listening to the TH900 previously, I sometimes felt that the treble was way too bright and sharp, to the point where my ears would even ring after taking off the headphone. But now on the TH909, the energy in the treble has returned to a more normal level. It's no longer like a wild horse running unrestrained, reaching to endless high. The tuning of the TH909 is like taming that wild horse, it largely resolves the issue of piercing and uncontrollable treble.

Since the problem of sharpness is no longer present, the remaining issue is sibilance. Sibilance only occurs in a few instances, perhaps only about 1/6 as much as with the TH900, which is within an acceptable degree.

However, in terms of brightness, if you're accustomed to the bright sound of the TH900, you may feel that the TH909 has lost some of its brightness and appears somewhat dimmer. This feeling is akin to painting a light gray coat over a bright white light bulb, resulting in an overall decrease in brightness and a sense of dimness.

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Epilogue​

Overall, the TH909 makes me feel like it's a product of compromise, a concessions to the market in order to appeal to a wider audience, it's leaning more towards balance though in fact it's not entirely balanced as neutral.
For me, its benefit lies in saving me the trouble and expense of buying mod kits one by one to try out the effect. It achieves a non-fatiguing sound with smooth and forward vocal imaging. However, my biggest regret is that the bass and sub-bass are no longer as impactful and deep as the TH900. If it could retain the bass punchy while achieving this sound signature, I believe I would be absolutely satisfied.

Disclaimer: This review has no commercial intent; but simply to document the sound of the TH909, a distinctive member of the Fostex family that I greatly adore.

Disclaimer: This one is not a tour unit, I purchased it. I didn't participated the tour because HFM didn't organise it here in China..

The purchase of the Jade II came about when I decided to take a break from the dynamics headphones, I tried a lot of them back then, various colours of TH900, HD800/s, Denon's D7000 series, etc.,
I was thinking, ‘why not try something else? like electrostatic headphones?’
Coincidentally, I stumbled upon an alluring priced STAX T8000, so I grabbed the bargain and started my electrostatic journey.
However, I still needed a pair of electrostatic headphones to complete the system. Initially eyeing the L300LTD, yet I couldn't find one at the reasonable price. So, I turned to a local dealer and bought a Jade 2 instead.
So basically, I didn't buy the officially matched Jade II Amplifier because, well obviously, I had better ones; besides, my friend told me that the official ones can't really drive it very well...

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Setup
Linn Selekt Organik→STAX T8000

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Back to the topic
I'd like to start with an introduction to the Appearance first
I don't know if you'd call it that in your neck of the woods, but in China, whenever the Jade 2 is mentioned, people tend to use another word to describe it: fly's eye (because of the mesh grille and the gradient purple-green color)

In fact, fly-eye green is a rather deprecating description, there are way-better words to describe this kind of green. I personally have a strong fondness for the green tone of the Jade II's driver. It embodies the verdant hues that could be found in the lush foliage of the forest——
It's like a glimmer of morning light weaves through the towering trees and dense canopies, creating dappled, deep, and saturated green. This is what Jade 2 looks like to me.

Although the current stealth version of he1000 v2 and arya have been coated with a film of the same green colour, the jade2 looks much more impressive with such a complete and LARGE verdant driver.

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Design
Though the black matte finish of the Jade2 frame looks very metallic at first glance, it's actually made of plastic. The frame is made of plastic as is the driver hanger making it kinda feel like a cheap plastic toy when you hold it in your hand...

By the way, the angle of the driver is fixed and not adjustable... which, I do really think should be improved

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Sound impression:
Overall tuning
The tuning of the Jade 2 is quite balanced, without any apparent bias.
The overall style is slightly bright, but as I mentioned above, its three-frequency distribution is very balanced, so it won't make the vocals sound particularly bright or any part of instrument feels very bright.

Vocal
The vocal of the Jade2 is as neutral as its overall tuning, very neutral without any obvious seasoning, maybe slightly leaning towards cool but not to the point of being cold or unpleasantly harshness. The transition between the mid and high frequencies is very smooth. Perhaps different from most users here, the tracks I listen to most often are anime tracks. During the audition, I chose the song "Aiobahn - resonance (ft. KOCHO)." In this song, the transition of the Aiobahn's voice from low to high tones is very smooth, and such natural transition and crystalline clear vocals are the two main reasons why I like electrostatic headphones.

Resolution
As for the resolution/instrument separation, although the Jade 2 has a rather 'decent' resolution, it doesn't seem to emphasise it much; instead, it presents the vocal and instrument more softly. Jade 2 doesn't much emphasise the separation between instruments to make the spacing between each instrument distinctly noticeable, the boundaries between instruments are not very sharp; instead, sometimes, the boundary sense of instruments on the Jade 2 is slightly blurred, or should I say 'soft'?
Interestingly, my TH900 was quite the opposite in this aspect; the TH900 violently separated details, making it possible to clearly distinguish the contours and boundaries of each instrument.

Points I think could be improved
Bass
As a basshead, I feel there is room for improvement in the bass of the Jade 2. Of course, the bass of the Jade 2 are by no means deficient or incomplete; the lower midrange is sufficiently full, ensuring adequate vocal density without sounding hollow. Overall, the issue with the bass lies in its lack of 'existency'. Sometimes, there is insufficient impact, making it feels weak and somewhat insubstantial. Besides, there could be more low rumbles to create a sense of atmosphere, but that's also what Jade 2 in lack of I think.

Highs
If the high frequencies were raised slightly further, the Jade 2 would likely achieve the airy quality characteristic of STAX headphones: that sense of sound freely flowing on stage, as if you were immersed in a vast theatre.

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In summary, I think the Jade 2 is pretty good.
Of course, if the headband frame could be replaced with metal, the hanger designed to be adjustable in angle, and the cables made replaceable, that would be perfect.