If you want ultra-wide frequency accuracy and a lightweight electrostatic design for critical listening, choose Koss ESP/95X; if need a spacious soundstage with premium wood craftsmanship and planar magnetic detail for long study sessions, choose SENDYAUDIO Apollo Pro.
• Koss ESP/95X: Delivers the widest frequency range (8–35,000 Hz) with an ultra-lightweight 353g build, but requires a dedicated energizer and is strictly wired. Best for audiophiles seeking absolute frequency fidelity and extreme lightness.
• SENDYAUDIO Apollo Pro: Features massive 78mm drivers and a rich wooden enclosure for a natural open-back experience, yet runs slightly heavier at 354g and targets a lower frequency floor. Best for listeners who prioritize soundstage width and tactile comfort during extended focus time.
The Koss ESP/95X stands apart because of its electrostatic architecture, a technology that prioritizes speed and precision over sheer power. When you look at the specifications, the frequency response range of 8 to 35,000 Hz tells a clear story about what this device is built to do. It is engineered to reproduce the full spectrum of audio with a flat response that minimizes coloration. This makes it an ideal tool for anyone who needs to hear exactly what was recorded, down to the faintest details in the upper registers. The inclusion of advanced damping materials and a proprietary diaphragm coating suggests a system designed to eliminate distortion, ensuring that the sound remains pure even at high volumes.
For students or professionals using headphones for study, the weight of this unit is a significant advantage. At just 353 grams, it balances substance and comfort without weighing down your head. This is not a heavy pair of cans that will cause fatigue after an hour of use. The pivoting ear cups and adjustable headband further enhance the fit, allowing you to customize the seal and pressure to your specific head shape. You get leatherette cushions that feel durable, wrapped around steel acoustical grills that protect the internal components while maintaining an open-air design. If you are looking for open ear earbuds for study in terms of the acoustic openness these provide, this model offers a similar airy quality but with the isolation of an over-ear form factor.
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-27 · 6 min read · Independent comparison
However, this product is not for everyone. The requirement for the E90 Energizer means you cannot simply plug this into any standard phone or laptop jack; it demands a specific power source to drive the electrostatic drivers. The connectivity is limited to a 3.5 mm jack, which is standard but wired-only. Furthermore, the packaging includes a premium leather case, indicating that this is a delicate piece of equipment meant to be protected rather than tossed in a backpack daily. If you need a set of best kids headphones for study or something rugged for commuting, the fragility of the electrostatic design and the need for extra hardware make it less suitable. It is a high-end studio tool, best suited for a dedicated listening environment where you can sit back and appreciate the precision tuning done by Koss in the USA.
The SENDYAUDIO Apollo Pro takes a different approach to high-fidelity audio, focusing on the physical scale of the driver and the acoustic properties of the enclosure. The centerpiece here is the 78mm planar magnetic driver, which is significantly larger than the typical dynamic drivers found in many consumer headphones. This massive size, combined with the nano-scale composite diaphragm, allows for fast response times and excellent resolution. The EB evaporation diaphragm technology adds another layer of sophistication, creating a dense aluminum circuit layer that improves vibration control. This results in a sound profile that feels stable and layered, perfect for getting lost in complex tracks or focusing on intricate musical arrangements.
When considering who this is for, the design choices point strongly toward someone who values the tactile experience of their gear as much as the sound. The earcups are crafted from zebrawood, a material known for its visual appeal and acoustic resonance, which contributes to a natural, open-back listening experience. The headband features soft lamb leather, and the ear pads are made of breathable velvet. These materials work together to reduce heat buildup and minimize pressure, making the Apollo Pro an excellent choice for those who wear headphones for study for several hours at a stretch. The open-back structure ensures that the air flows naturally, preventing the "clamped" feeling that some over-ear headphones impose.
The connectivity setup is equally thoughtful for the serious listener. It comes with a detachable triple-composite cable featuring Furukawa OFC, silver-plated copper, and enameled gold-plated copper strands. This level of attention to signal transmission suggests a desire for clarity and detail. However, the impedance of 27 ohms and the sensitivity of 93 dB indicate that while it is relatively easy to drive, the 4.4mm balanced connection is the primary interface. This is a feature often sought by enthusiasts who have balanced outputs available. Unlike the Koss, which emphasizes the absolute limits of frequency, the Apollo Pro emphasizes the richness and spatial depth of the mid-range and highs. It is a strong contender for anyone wanting best bone conduction headphones for study in terms of environmental awareness, though it achieves this through open-back acoustics rather than bone conduction technology.
• Best for frequency range → Koss ESP/95X (8–35,000 Hz captures sub-bass and ultra-highs better).
• Best for soundstage width → SENDYAUDIO Apollo Pro (78mm drivers create a wider, more immersive image).
• Best for lightweight comfort → Koss ESP/95X (Slightly lighter at 353g vs 354g, with a focus on fatigue-free listening).
• Best for premium materials → SENDYAUDIO Apollo Pro (Zebrawood earcups and lamb leather offer a luxurious aesthetic).
• Best for detailed cables → SENDYAUDIO Apollo Pro (Includes a specialized 4.4mm balanced cable with multi-strand construction).
• Best for durability of finish → Koss ESP/95X (Steel acoustical grills and robust leatherette against potential impact).
• Best for open-air ventilation → Both are open-back, but Apollo Pro uses velvet pads for breathability while Koss uses leatherette.
• Best for portable setup → Neither is truly portable due to wired nature, but Koss includes a protective leather case for travel.
I would choose the SENDYAUDIO Apollo Pro if my primary goal is to use headphones for study. While the Koss ESP/95X offers incredible frequency range, the combination of the large 78mm planar magnetic drivers and the zebrawood enclosure creates a warmer, more engaging soundscape that keeps me focused without becoming fatiguing. The velvet ear pads and lamb leather headband provide a level of long-term comfort that feels superior for marathon study sessions. The Apollo Pro strikes the perfect balance between technical performance and physical luxury, making it the smarter investment for daily, extended use.
Both models feature an open-back design, which means they do not block external noise effectively. They are best used in quiet rooms where you need to hear every detail of the music without distractions, rather than in loud public spaces.
Yes, both require a dedicated power source. The Koss ESP/95X needs the specific E90 Energizer to drive its electrostatic drivers, while the SENDYAUDIO Apollo Pro, though having lower impedance, benefits from a high-quality amplifier to fully utilize its planar magnetic capabilities.
The Koss ESP/95X is built with steel acoustical grills and a lifetime warranty, suggesting extreme durability. The SENDYAUDIO Apollo Pro uses wood and delicate metals, offering a premium feel but requiring more careful handling to avoid damaging the zebrawood finish.
Neither connects wirelessly. The Koss uses a standard 3.5 mm jack, while the Apollo Pro uses a 4.4 mm balanced jack. You will likely need an adapter or a dongle to connect them to most modern smartphones.
As an Amazon Associate I earn from qualifying purchases.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
When you buy through links on this page, we may earn a commission from qualifying purchases at no extra cost to you.
Amazon and the Amazon logo are trademarks of Amazon or its affiliates. This site is an independent third-party review and is not affiliated with, endorsed by, or sponsored by Amazon or the product brands mentioned.