Welcome to my review! I write reviews to document the interesting headphones I've tried;
As time may pass, headphones may break, but knowledge can be passed down forever!
——Brandfuchs
A while ago, I managed to collect the three TOTL:
the dynamic: LB-Acoustics Mysphere 3.2,
the planar: Hifiman Susvara,
and the electrostatic: STAX X9000
Although I had already written reviews on local forum, I thought it would be a good idea to write an English version and share it on Head-Fi. Thus, this article was born.
Unboxing
The X-9000 follows STAX's classic two-layer packaging: a cardboard outer cover and a storage boxSpecifically, a Paulownia wood box, known as Kiri in Japanese. This hardwood grows quickly and, thanks to its lightweight, warp-resistant, moisture-proof, and insect-resistant properties, has been used for centuries in Japan to make storage chests.
To be honest, I was hoping for a carrying case like the one that came with the 009. Personally, I think the carrying case of the 007a is much more impressive and useful.
Design
The moment I took out the x9000, I was already impressed by how well it was made, deeply. If I were to say that there is any headphone that is more of a work of art and symbolises contemporary craftsmanship, I’d definitely nominate the x9000. This is what truly deserves the title of a totl product.
The craftsmanship behind it is so exquisite that most other headphones I have seen pale in comparison.
The housing of the X9K’s driver is made of aluminum, with the golden driver securely fixed within and clearly visible through the open protective mesh. Unlike the Lambda series, there is no cheap plastic hinge used anywhere in the frame.
Metal, metal, all metal! Yes!!! the head spring, case holder, speaker body, and guard mesh are ALL made of metal. This is exactly what I wanted and what justifies the money I spent.
The part of the earpads that touches the cheeks is made of genuine leather, with the rest made of protein leather. (I hope that one day Fostex will adopt a similar approach for their earpads to make the TH900’s pads more durable)
Technology & Improvement
It seems that most reviews of the X9000 have already covered the MLER-3 driver characteristics. Therefore, there’s no need to repeat that here.However, I'd still like to discuss an interesting improvement on the X9K: the dust cover. If you look closely, you'll notice that the dust mesh is no longer attached directly to the frame as in previous generations. It has become two layers, with the outer layer placed outside and above the driver frame, supported by six pillars and angled slightly. STAX explained this design choice: "A protective net installed parallel to the sound unit produces direct reflections, which adversely affect sound."
If you're curious about the reason: from an acoustic standpoint, the dust cover functions as a reflective surface for sound waves passing through it. The density and size of the holes in the cover determine how much sound is reflected. In the case of the X9000, compared to the 007A, the holes in the dust cover are significantly larger.
When sound waves encounter the protective mesh, a portion of these waves is reflected back, creating a reflection wave. This reflected wave typically has a phase that differs from the original sound wave produced by the driver. This phase difference can lead to Constructive and Destructive Interference at specific image positions and frequencies.
Constructive interference occurs when the peaks of the reflected wave align with the peaks of the direct wave, amplifying the sound. Destructive interference happens when the peaks of the reflected wave align with the troughs of the direct wave, reducing or canceling the sound, in short, causing distortion. This interplay of reflections and original sound waves creates the interference effect, which can affect the overall sound quality. By increasing the size of the holes in the dust cover, it seems that the x9000 aims to reduce the impact of these reflections, thus minimizing unwanted interference.
Well for me, the biggest benefit of enlarging the holes in the dust cover is that: I can clearly see the shiny golden drivers inside, visual-fi!
What you're most interested in, sounds and comparisons
Signature in a word
The X9000 generally has a neutral tuning. From the moment you hear it, you can sense that it delivers a healthy, neutral and balanced sound with no obvious biases, only a slight warmth in the mids/vocal.Brief comparisons
The X-9000 is the long-awaited successor to the SR009 and SR009S. Naturally, people will compare its sound to that of its predecessors. However, I must say: it's not the same. The X9000 has an entirely new and independent tuning, it emerges as a flagship in its own right, with a brand-new sound signature.In my opinion, one interesting feature of STAX headphones is that each generation has its unique tuning and charm. Just as people still yearn for a pair of Omega, you can always find your favorite among different product lines at various price points. This is why even with the X9000, I've kept my 009BK, L300LTD, and 007A.
Comparing to the 007A
As mentioned earlier, there is no obvious bias for the X9000, unlike the 007a, where you can clearly perceive its warm tonal character. The 007 has a notable roll-off in the sub-bass, which was compensated by boosting the mid-bass and low midrange, giving the bass a more significant presence, nevertheless, this also results in a larger low-frequency imaging and a higher proportion of bass in the sound profile. The X9000, however, has sufficient energy in the bass overall, although there is still a sub-bass roll-off, it sounds more natural than the 007, with deeper extension, making it fuller and more complete. The mid-bass is appropriately controlled, ensuring the bass punchy without sounding unnatural or overly dominant among other frequencies.Comparing to the 009
In my opinion, the 009 has an emphasised mids, specifically between 350Hz to 3kHz, making vocals more prominent and closer, creating an intimate feeling as if the singer is right in front of you. This is pleasant, and I absolutely enjoy this characteristic. However, the X9000's midrange and vocal imaging are more precise and realistic. It places the imaging exactly where it should be, with the appropriate size that feels just right. Both headphones avoid sibilance, and the vocal extension is incredibly smooth. This is a particularly striking characteristic of Stax's Omega series.Comparing to the L300ltd
Unlike the L300LTD, which has a significant amount of mid-bass but lacks layering and has minimal sub-bass presence due to roll-off, the X9000's bass is more refined. It doesn't have the same large quantity as the L300LTD; instead, it is few but refined (I'll go into more detail on this later). The L300LTD's tuning is more engaging and passionate, whereas the X9000 feels much more serious. Both, however, inherit Stax's excellent vocals performance.Sound Reviewing Part
Treble
The X9000 excellently showcases the strengths of electrostatic headphones, with a luxurious, smooth, and highly extended treble. It achieves a perfect balance of brightness and extension, making it sound "smart." The highs are controlled to an intriguing extent—if you're looking for the utmost highs extension, you might be disappointed, as the X9000 doesn't emphasise the upper mids like the 009. Instead, it's highly natural and balanced.I spent a few weeks listening to my familiar tracks, and discovered an interesting characteristic: the mid-high frequencies are filled with detail yet remain very delicate and gentle, never fatiguing. It strikes a perfect balance between being "dark" and "overly bright." It avoids the pitfalls of sounding either "unable to reach high notes" or "going too high and becoming harsh or overly stimulating."
In short, I'm very satisfied with its treble, even though it's not the type that immediately wows you.
Mids
X9000's rendition of vocals is nothing short of remarkable, displaying an unparalleled mastery over every nuanced detail. With immaculate control over sibilance, it delivers vocals that are velvety smooth, devoid of any harsh edges or unwanted sharpness. Each note flows effortlessly, like a gentle stream winding its way through the landscape of sound.Bass
Regarding the bass, the X9000’s bass is well-balanced and just right as well. Unlike the L300LTD, which has a large amount of mid-bass but a rather flat impact, largely affected by roll-off imo. The X9K’s bass is more refined, it doesn't have the overwhelming quantity like the 007A; instead, it presents a much more restrained amount. Due to its neutral tuning, it doesn’t allow the bass to overpower other frequencies. The X9000 provides precisely what a good bass needs: sufficient energy, adequate depth and layer for an electrostatic headphone, and a slight sense of rebounded bass. The X9K meets all these criteria. Its bass is problem-free, in various pop music, it offers drum hits with enough tension and strength to complement the main tune of the song.Soundstage
Regarding soundstage, the X9000 performs remarkably well. Compared to the L300ltd series, it’s like moving from the studio to the theatre to listen to a song, the X9000 has a broader soundstage both vertically and horizontally.However, if I were to speak about the most impressive soundstage, I would still lean towards the Mysphere 3.2. I had the chance of hearing the Mysphere driven by the Zahl HM1 during a demonstration by my friend Sayed. It left a lasting impression on me: it was as if the sound wasn’t coming from headphone drivers, but rather from everything around me. I can’t use the word ‘soundstage’ to describe it anymore, because it was a boundless sound, as if the natural world itself was producing the sounds that coalesced into the music.
The X9000’s expansive soundstage meticulously and precisely places each instrument as if arranged in a ‘theatre,’ reproducing each instrument with exquisite detail. When listening to Beethoven’s Symphony No. 7, you can distinctly and clearly differentiate between the positions of each section. There is a distance between each instrument, they are not overlapping or merging together. The separation between the strings and brass section is particularly well-defined in terms of depth, because in the live section layout, the violin section is positioned in front of the flutes and oboes section. When using headphones with insufficient resolution, the imaging of these sections tends to overlap, making it difficult to distinguish their positions.
But on x9000, you can clearly perceive the closer positioning of the violin sections and the farther placement of the timpani and horn. Each is presented with remarkable clarity. The X9000 excels in presenting the dynamic shifts and nuanced performances of each section in the finale of Symphony 7, the cello melodies, periodically interrupted by the loud, rhythmic blare of trumpets and timpani, are perfectly reproduced overwhelming vitality and dynamics. The bassline’s semi-tonal hum and the extreme dynamic shifts of the violins and violas are vividly portrayed.
Even after the music has stopped, I find myself reluctant to leave my seat or take off the Stax x9000, sitting there and savouring the heavenly music that lingers in my mind.