The Next Trend
Ratings
Pros
- Great starting price.
- Good Sabre DAC/AMP.
- Warm and smooth sound, big bass and sharp treble.
- Textile covered cable, metal finish and integrated microphone.
- DAC/AMP design allows you to see inside the circuitry.
- Integrated LED.
- Good sense of power.
- 32 bit/384 kHz PCM and native 64/128 DSD formats.
Cons
- Fade-in effect at the start of playback.
- Extensive bass can be imposed on detail and other frequencies.
- Compact and cohesive micro detail.
Purchase Link
Link to the WEB
https://www.hidizs.net/blogs/buying-guides/hidizs-st2-pro-nebula-next-gen-dsp-hifi-evolution
https://www.hidizs.net/blogs/buying-guides/st2-pro-nebula-vs-tws-earbuds-vs-wired-earphones
Introduction
Hidizs is on the bandwagon of combining IEMS with a DSP cable with an integrated DAC-AMP that replaces the audio connector. With today’s technology of reducing converter and amplifier devices, it is easy to combine these tasks. This is not the first model I have reviewed with this in mind. This time, it has an integrated microphone and is a more universal DAC/AMP, with 2Pin 0.78mm and MMCX terminations. As Hidizs comments, this cable was born as a response to the limitations of the Bluetooth system in terms of power, high resolution audio, better sound quality, compatibility with many more devices without the need of a Bluetooth emitter, etc. The Hidizs ST2 PRO Nebula cable has the ES9281AC PRO DAC chip, with a power of 70 mW at 32 Ω, a sensitivity of 108 dB and a very low distortion of only 0.0012 %. The advantages are obvious: higher power, zero latency, wider bandwidth (20 Hz-40 kHz), 32-bit resolution and support for PCM formats up to 384 kHz and native 64/128 DSD.
Along with this cable, capsules made of resin and aluminum alloy are supplied, incorporating a dual dynamic driver with a 10 mm PU+PEEK composite diaphragm. The IEMS have been tuned according to the H-2019 target curve for accurate audio response. They offer balanced tonality, powerful bass, rich mids and moderate high-frequency extension, meeting Hi-Res audio standards for a HiFi quality listening experience. HIDIZS liquid silicone earplugs are made of high permeability liquid silicone and feature an ergonomic design that fits perfectly in the ear canal. The custom pouch provided by HIDIZS ensures safe storage and extends the lifetime of the ST2 PRO Nebula without worry.
The Kickstarter launch date will be December 19, 2024, at 10:30 AM (EST):
- ST2 PRO Nebula (Super Early Bird): $39.00 (limited to 500 units).
- ST2 PRO Nebula (Early Bird): $49.00.
- ST2 PRO Nebula USB-C DSP 0.78mm 2-pin/MMCX Headphone Cable (Early Bird): $36.00
Specifications
- Driver Type: Dual dynamic with 10mm PU+PEEK composite diaphragm.
- Frequency Response: 20Hz-40kHz
- Sensitivity: 108dB
- Impedance: 32Ω
- IEM design: resin + aluminum alloy engraving.
- Connector cable: USB Type-C.
- IEMS capsule connection type: 2Pin 0.78mm.
- Cable connection type: Choice of 2Pin 0.78mm/MMCX.
- Weight: 7 grams approx. (excluding headphone cable).
- Cable weight: 16 grams approx.
- Cable color: Silver-Gray/Black-Blue.
- IEMS color: Transparent white/transparent black.
- Cable DAC: ES9281AC PRO
- Chip Architecture: HyperStream®II QUAD DACTM Architecture
- Resolution: 32-bit.
- Sampling Rate: PCM 32-bit/384 kHz. Native DSD 64/128.
- MQA support.
- Distortion: 0.0012%.
- SNR: 118 dB.
- DNR: 122 dB.
- Separation: 63 dB.
- Output power: Up to 70mW+70mW at 32Ω.
- Plug type: USB-C (Type-C/ USB Type-C) (Only compatible with iPhone 15 and later models) (Compatible with 99% of devices with USB-C output port).
- DAC case material: Aluminum alloy + transparent resin.
- Cable core material: High purity oxygen-free copper.
- Cable splitter piece: Aluminum alloy.
- Cable sheathing: Textile yarn.
- Cable core specifications: 4 Wires 260 Cores.
- Diameter: 4mm.
- Length: 1.2m.
Packaging
The Hidizs ST2 PROs come in a nearly square black box measuring 114x104x38mm. On the main side you can see the Hidizs logo in the upper left corner and the ESS, DSD, MQA and Hi-Res Audio logos in the upper right corner. All this is printed with holographic ink. In the center is a realistic photo of the capsule. Below is the model name in large letters and a description in smaller letters, also in holographic ink. On the back side are the specifications of the set in several languages. Around the edges is more information, as well as a label with the model option, in this case transparent black. After opening the lid, the capsules are in a foam mold lined with black cardboard. At the top is a cloth strip so that the first layer can be removed. Underneath is a black plastic bag. The accessories are inside. At the bottom are two cards. In summary, the complete contents are as follows:
- 1 ST2 PRO.
- 3 pairs of ergonomic white silicone ear cushions, sizes SxMxL.
- 1 USB-C to USB-A adapter.
- 1 HIDIZS bag.
- User manual.
- Warranty Card.
- Product Quality Certificate.
It still carries Hidizs’ synthetic leather pouch instead of a zippered case, as is already the case with other, even more expensive, models that only include a set of accessories. But the USB Type-C to Type-A converter is appreciated. Good.
Construction and Design
The capsules have a semi-custom shape and are made of resin, except for the outer part and the mouthpieces, which are made of aluminum alloy. The resin is transparent, so you can see the inside, the wires and the driver. The 2-pin, 0.78 mm thick, oval-shaped connection plate is located on the bottom edge. On the edge, in silver ink, you can read “Hidizs Nebula” and the marking indicating the channel. The mouthpieces are metallic, golden and have three diameters: base (6.6 mm), central part (4.8 mm) and crown (6 mm), and an approximate height of 5.5 mm. There is a hole in the center of the inner face.
The DSP cable is constructed with four wires and 260 cores. It is composed of two braided strands with black and purple textile coating. The metal parts are dark gray and made of aluminum alloy (DAC/AMP sleeve, splitter piece, cylindrical microphone container and button). The DAC/AMP case is oval, flat and has windows through which you can see inside the circuitry. The top face reads MQA on the end opposite the USB Type-C connector. On this side there are several LEDs inside that allow to generate various colors. On the opposite side you can see the ES9281AC PRO chip. Resin has also been used for the transparent parts of this connector. The cable has over-ear guides thanks to a transparent semi-rigid sheath. The connector sleeve is made of slightly angled transparent plastic. The letters indicating the channel are embossed and almost imperceptible. The cable has a branded Velcro strap.
The design of the capsules is quite conventional, with a transparent resin, and the difference is in the external aluminum alloy plate on which the brand and its logo are displayed. On the other hand, I like that the cable has a textile covering that gives it a little more resistance, comfort and softness. The metal parts enhance the look of the DAC/AMP cable, as do the transparent windows that allow you to see inside the circuitry. Other details are the colored LEDs, the USB adapter and the cylinder with microphone and button, which make the product an all-in-one device to replace any Bluetooth system. The next step should be a background noise suppression system for the microphone.
Adjustment and Ergonomics
The most significant thing about the capsules is their low weight of only 7 grams. The semi-custom shape makes for a great fit, but the slightly thicker mouthpieces and the angle to the ear canal can make it difficult to choose the right tips. I have tried my large foam-filled tips with no problems. However, I have found that the sound profile calls for tips with a wider channel to gain clarity and lighten the bass. For this I have used ultra large blue silicone tips, with low profile and large inner core. A good seal is achieved, although the isolation level is not so high. The set is very comfortable, but with these silicone tips the fit can be a bit more critical, as small variations in position can alter the bass response. It is not the fault of the model, but it is true that with my big tips filled with homemade foam, I get a very high bass boost that alters the natural response of the set in an undesirable way. I have looked for alternatives like the Tangzu Tang Sancai Narrow Bore or the black Penon Liqueur Silicone Eartips, but the ones that have worked best for me are these, much cheaper (blue color) and all in extra large size.
https://es.aliexpress.com/item/1005004615505310.html
Sound
Profile
The Hidizs ST2 Pro are a cable-integrated DAC/AMP assembly plus IEMS with a classic V-profile. According to the website, their profile is aligned with the H-2019 target audience. In my opinion, the ST2 Pro’s enhance more mid bass and less sub bass. It is also more noticeable in V, with a more sunken midrange and a somewhat steeper rise towards the treble. Then there is a slight area of control in the first treble and an extension that pales in the air area.
Overall, the set is somewhat more emphasized in the bass, with that wide curve in the low area. That’s why I’ve looked for some tips to lower the lower zone and favor the clarity of the whole.
Bass
Bass presence can be noticeable with some tips, but it is an easily correctable problem. I have used low-profile, wide-channel tips to promote separation, clarity and transparency. In this way, the bass does not appear saturated or overly boomy. They offer a clear sense of texture and low-medium speed. They have a moderately compact punch with good retrieval. The bass is rounded, with a sub-bass that is neither too pronounced nor too deep. The low-mid bass is the protagonist, feeling powerful and wide. It has plenty of volume and occupies considerable space, almost with a tendency to overpower.
In the very low frequency pure tone test, the limited emphasis on the sub-bass is noticeable. The audible lower note is barely perceptible, both aurally and sensorially. This detracts from its depth and accentuates its more physical character, centered at 60 Hz. As frequencies rise, the bass becomes more powerful, with a subtle color and wave-like appearance. In reality, this translates into a bass with a rough surface, expansive, powerful and extended, more noticeable than dark and physically powerful, with an obvious and forceful punch.
In the dirty, unfiltered bass test, it is noticeable that the lightness of the sub-bass brings a bit more color than sensory physicality to the sound. In any case, control is better than expected despite the somewhat more conventional sonority of its V-profile. The level of resolution is somewhat limited, although it does its job well in following the bass lines. Its sound is rounder and less defined, which gives a feeling of powerful bass, although relatively simple and not too tight.
Mids
The midrange starts warm and with some strength marked by the extension of the bass. This gives it some physicality in the lower mids and a more powerful base. The rapid descent into V makes the male voices thinner. The sharper they are, the more remote they feel. There is that sense of central hollowness that characterizes this profile. However, the instruments are well represented and are perceived whole and full.
The level of resolution is still on the soft side, appearing more rounded, with a blunt profile, bringing a rather relaxed sense of musicality and with a visible level of macro detail. The central micro detail is perceived as compacted, very attached to the surface, implying a medium level of layering and not too much depth. This micro detail is intuited, but it is not defined in a particular way, but is part of a somewhat thicker and more cohesive line.
The female voices are closer, although their base is not as marked; it is somewhat the reverse of the male voices. However, they are also perceived as warm and round, without too many nuances and with a soft aspect that limits sibilance.
In summary, the mids are musically pleasing, somewhat depressed in their center, cohesive, without too much depth, but remarkably resolved at the macro level.
Treble
The treble begins with a high point, after a slight zone of control, and a second sparkle appears that brings vivacity and a somewhat sharp extension. The level of refinement is medium, relatively pleasant, not too marked, but with a more incisive edge at times. There is a great deal of energy, though it feels somewhat limited in the air zone, already showing drier and more compact. But, although that energy is not predominant in the mix, it is so that the whole does not appear dull, dark or dull. The upper zone has its own entity and shows that it exists on its own and not as a mere accompaniment to the whole. In this way, both the high notes themselves and their harmonic contribution benefit the ensemble.
Soundstage, Separation
What strikes me most about the sound of the ST2 Pro is the volume of the bass. This feature enhances the sense of spaciousness and extension of the soundstage. On the other hand, the layering is simply good, with somewhat cohesive and compact mids. Details are perceived on the surface, while smaller details in the background come closer to it and connect, losing some ability to describe themselves with more rigor and definition.
The scene has good laterality, a level of closeness of the volume more noticeable than the depth itself, and an adequate height. The image is eminently frontal, connected, harmonious and conjunctive, without too much sensation of individuality. In this way, a warm, musical, melodious and soft sensation prevails, which moves away from any forced over-definition. The result is a fairly natural level of separation, with a sense of luminosity, transparency and clarity sufficient to prevent the whole from becoming thick, dark or overly nuanced. I don’t miss light, brightness or more transparency. It does lack a little more layering, layer generation and a more evident background.
Comparisons
KBEAR Robin
I like to compare IEMS with similar profiles. Although, in this case, it would have been more appropriate to make a comparison with the INTUAURA Reference 2019, the other IEMS that have a cable with a DAC/AMP. In fact, the Reference 2019 have a DSP that alters the original sound of the IEMS and fixes it to the Reference H2019. For their part, the ST2 Pro have a DSP DAC/AMP cable. The first difference is that both claim to be based on the H2019 curve. Who is closer to the H2019 curve? Judge for yourselves.
My real comparison will be against the KBEAR Robin, an IEMS that are somewhat cheaper than the final price of the Hidizs ST2 Pro set (estimated at $89). Both have a similar capsule, more classic and semi-custom in the Robin. As usual, KBEAR includes a zippered case and two sets of earplugs, though the cable is pretty basic. The Hidizs cable, excluding the DAC/AMP, has a better finish. However, Hidizs only includes a set of tips and a faux-leather pouch.
From an ergonomic standpoint, there should be many similarities, but I find the Robin’s fit better and tighter.
As a dongle to play the KBEAR Robin I used the Hidizs SD2.
The Robins have a V profile with a W tendency. They have more sub-bass enhancement and a double peak in the upper mids and first treble.
The similarity in bass is high, as can be seen in the frequency response of both IEMS. The difference lies in the greater presence of sub-bass in the Robins. The bass is large and voluminous in both models. They both have that slightly slower bass style with a longer recovery. It seems darker in the Hidizs, but has more impact and punch in the Robins.
The midrange is also very similar, with a similar transition from bass to midrange, as well as the same valley. Although the Hidizs are a bit darker, I find the male vocals crisper and better defined on the ST2 Pros. The upper mids have more overall energy in the Hidizs, despite that 2 kHz peak in the Robins. This is noticeable in that the ST2 Pro model is subtly more sibilant. However, female vocals seem to have a bit more prominence in the Robins, while there is a sense of overall darkness in the Hidizs, although you could also call it softness.
In the upper range, the highs of the Robins are somewhat softer and less bright. In contrast, I find the treble of the Hidizs to be more natural, distinct, bright, crisp, and realistic. They also have better extension, air and sparkle.
The Robins have a bit more definition, especially in the midrange, with a bit more clarity. The Hidizs are smoother, warmer and more mellow. The greater sense of depth and closer mids make the Robin’s soundstage seem a bit larger.
Conclusion
I think Hidizs has joined the new trend of USB DSP cables with integrated DAC/AMP. As smartphones move away from supplying 3.5mm audio output, this new set will become more relevant, especially if the integrated DAC/AMP is as adequate as the ES9281AC PRO. The cable includes microphone and a control button, so it is all-in-one and can be used with any mobile device. The cable can be purchased individually with 2-pin 0.78mm or MMCX interface and is compatible with any IEM on the market that incorporates these connection interfaces.
In this review, the cable is accompanied by IEMS with a V-profile. These are very lightweight capsules, with a dual dynamic driver with a 10mm PU+PEEK composite diaphragm. Their sound is characterized by punchy bass, warm and smooth mids, and bright and energetic highs. The starting price has been set at $39, and on the second pass it will be $49. For that price, the set is excellent.
Sources Used During the Analysis
- PC Windows 10.
- Hidizs AP80 PRO-X Red Copper LE
