Overview

The Sendy Audio Apollo is an open-back headphone featuring 68mm planar magnetic drivers, priced at 499 USD. Released around 2022 by Chinese company Sendy Audio (a subsidiary brand of Sivga Electronic Technology Co., Ltd.), it incorporates the company’s proprietary Quad-Former technology. Standard equipment includes CNC-machined rosewood housing and high-quality cables, with a 16-ohm low impedance design enabling compatibility with a wide range of devices. It is positioned as a relatively easy-to-drive product within the planar magnetic category.

Scientific Validity

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Multiple issues are confirmed in measurement data. The frequency response shows a strong V-shaped signature, significantly deviating from the transparent standard of 20Hz-20kHz±0.5dB. The midrange dip at 1-2kHz and high-frequency emphasis particularly compromise fidelity to master recordings. More seriously, distortion suddenly appears in the bass region at moderate to high volumes. Dynamic classical music and other content with forte passages produce unpleasant distortion, failing to meet THD standards. While the 95dB sensitivity and 16-ohm low impedance are excellent for drivability, there are significant problems with scientific transparency in the crucial aspect of sound quality.

Technology Level

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The Quad-Former technology represents a highly unique approach in the industry. While conventional planar designs place one coil on each side of the diaphragm, the Apollo places two coils on each surface for a total of four coils. Combined with the large 68mm driver size, this theoretically contributes to force distribution and efficiency improvements. The CNC-machined rosewood housing considers resonance control, and the standard 4-core 6N OCC cable demonstrates high technical standards. However, judging from measurement results, this technical investment doesn’t necessarily translate directly to sound quality improvements, which is unfortunate.

Cost-Performance

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For the 499 USD price point, multiple more affordable alternatives with equivalent or superior performance exist. Most notably, the HiFiMan HE400se (110 USD) offers equivalent planar magnetic functionality while exhibiting fewer distortion issues and more neutral sound characteristics. The calculation yields: 110 USD ÷ 499 USD ≈ 0.22, resulting in a cost-performance score of 0.2. Even compared to the similarly-priced HiFiMan Edition XS (499 USD), the Apollo shows insufficient technical advantages or sound quality differentiation. While the high-quality construction is commendable, the pure performance-to-price ratio requires a harsh evaluation.

Reliability & Support

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Sendy Audio is a relatively new company established in 2015, but including parent company Sivga, there are few reports of quality issues and product reliability is good. Warranty periods and repair systems also receive evaluations of providing above industry-standard support. Considerations for user convenience include standard 4.4mm balanced terminals. However, being an emerging manufacturer creates some uncertainty regarding long-term business continuity compared to established manufacturers, leaving slight concerns. The product construction itself is robust and built for long-term use.

Rationality of Design Philosophy

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The adoption of planar magnetic technology and Quad-Former design has technical rationality. However, the decision to adopt a strong V-shaped characteristic in final sound tuning is questionable from a scientific high-fidelity reproduction perspective. The intentional midrange dip particularly affects the fundamental frequency ranges of vocals and many instruments. Additionally, distortion at high volumes suggests fundamental design issues that cannot be resolved through simple volume adjustment. Conversely, the 16-ohm low impedance design enabling use with a wide range of devices was a rational decision prioritizing practicality. Overall, while technical potential is high, there is room for improvement in the final product direction.

Advice

The Sendy Audio Apollo offers excellent build quality and comfortable fit, but at the 499 USD price point, other scientifically superior alternatives exist. Particularly, the HiFiMan HE400se (110 USD) uses the same planar magnetic technology while exhibiting less distortion and more neutral sound characteristics, achieving overwhelming cost-performance. If you have a 499 USD budget, the HiFiMan Edition XS would provide greater technical advantages and sound quality satisfaction. Apollo consideration should be limited to those who prefer V-shaped sound characteristics or particularly value the aesthetic appeal of rosewood housing. However, for those anticipating high-volume use, we recommend making decisions with full awareness of the distortion issues. For those seeking scientifically excellent sound quality, we strongly recommend other alternatives.

(2025.7.28)