The act of reproducing sound ultimately amounts to faithful recreation of physical phenomena. Yet what we seek from music is not merely vibrations in air—it is the tide of emotions, the echoes of memory, and sometimes metaphysical experiences that shake our very souls. Perhaps only those who sincerely contemplate this chasm between physics and sensibility possess the qualification to create true hi-fi equipment.
Berlin-based HEDD Audio embodies precisely this philosophy. Founded by physicist Klaus Heinz and his son, musicologist and mastering engineer Dr. Frederik Knop, this workshop has consistently pursued “complete accuracy and exceptional signal fidelity” 1. For them, audio equipment is not a tool to decorate music with pleasant tones, but something closer to a measuring instrument designed to expose recorded signal truth with surgical precision.
The crystallization of this philosophy lies in the HEDDphone series, featuring the world’s only full-range Air Motion Transformer (AMT) driver. While the original model earned acclaim for its groundbreaking technology and unparalleled resolution, its mass exceeding 700g was overwhelmingly heavy as a physical presence 3.
Now, after three years of user feedback and relentless research and development, its successor “HEDDphone TWO” appears before us 4. Is this merely an improved version? Or does it represent a new acoustic philosophy where the physicist’s soul and musician’s ear have fused at a higher dimension? This review aims to reach that core.
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HEDDphone TWO — Overview
- Manufacturer: HEDD Audio (Heinz ElectroDynamic Designs)
- Model: HEDDphone TWO
- Release Date: Around 2023
- Price: $1,999 USD 6 / ¥295,000 (tax included) 7
Key Specifications 4
- Type: Air Motion Transformer (AMT) with VVT technology
- Form: Open-back, over-ear (circumaural)
- Frequency Response: 10 Hz - 40 kHz
- Impedance: 41 Ω (flat)
- Sensitivity: 89 dB SPL at 1 mW
- Recommended Power: 1000 mW or more
- Weight: 550 g
1. Third-Party Assessment Trends
HEDDphone TWO has sparked active discussion throughout the global audio community due to its unique origins and technical background. Here we survey the evaluation trends and organize consensus points and contentious areas.
| Media | Quote (Translation + Original) | Rating |
|---|---|---|
| Headfonics | ”A flatter more muscular sound signature with a heavier emphasis on midrange excellence.” | 8.7/10 |
| The Ear | ”The overall timbre is just spot-on gorgeous, the treble a sheer delight and the neutrality to die for.” | ★★★★★ |
| Ear-Fidelity | ”It’s a very neutral, technical-sounding headphone with one of the best technicalities in the market.” | Recommended |
| Tape Op | ”The sonic presentation of the original HEDDphone was already impressive and unique, but the enhancements to transient response and accuracy of the HEDDphone TWO model make it even better suited for implementing mix decisions.” | N/A |
| Headphones.com | ”The HEDDPhone TWO exudes a sense of speed that I’ve almost forgotten headphones can have.” | N/A |
| Reddit User “Dr. HiFi" | "The sound reminds me of the Susvara, though at a slightly lower technical level…” | N/A |
Assessment Summary and Analysis
Surveying major review sources reveals clear consensus in evaluation criteria.
Positive trends: All reviews unanimously praise the overwhelming speed and detail reproduction capability delivered by the AMT driver 8. Particularly, microdynamics capturing minute changes in sound attack and decay, and “timbral resolution” reproducing instrument-specific resonances are evaluated as unmatched levels 9. The dramatic improvement in weight and fit comfort—the original’s biggest challenges—also receives unanimous high praise 3.
Negative/divisive trends: However, several contentious points emerge. First is insufficient bass quantity. Sub-bass roll-off is particularly noted, potentially leaving listeners seeking punch and quantity unsatisfied 3. Second,
soundstage width receives mixed evaluations. While some praise its “speaker-like” expansiveness, others find it “somewhat narrow for open-back” 10. Third is its
high driving requirements. There’s consensus that portable device driving is difficult and powerful desktop amplification is essential for realizing its true potential 13.
Bias considerations: Many of these reviews are based on manufacturer-provided samples, creating structural bias toward focusing on improvements over the previous model. User opinions from forums where actual purchasers gather provide more realistic perspectives on amplifier compatibility and long-term usage challenges, making them valuable information sources. This review attempts multifaceted analysis considering evaluations from these different standpoints.
2. Embodiment of Acoustic Philosophy: Technical Insights
To understand HEDDphone TWO, we must first touch upon the source of its design philosophy—the founders’ philosophy. This headphone is not merely an industrial product but the embodiment of an acoustic philosophy.
HEDD Lineage: Physicist’s Precision and Musician’s Sensibility
HEDD Audio’s story is the history of physicist Klaus Heinz’s acoustic exploration itself 1. Known as ADAM Audio’s founder, he has devoted his career to improving Air Motion Transformer (AMT) technology invented by physicist Oskar Heil 2. His goal has always been flawless signal reproduction following physical laws.
This scientific pursuit gained new dimensions through participation by his son, musicologist and mastering engineer Dr. Frederik Knop 2. Father pursuing physical correctness and son evaluating how that sound resonates as music—this fusion of two perspectives defines HEDD’s house sound. Their products stem from professional monitor philosophy prioritizing not pleasant coloration but faithful presentation of recorded source truth 1. HEDDphone TWO’s analytical, neutral acoustic characteristics are inevitable consequences of this lineage.
Mechanical Heart: Full-Range AMT Driver
HEDDphone TWO’s core lies in its unique full-range AMT driver. While conventional dynamic or planar magnetic drivers “push/pull” diaphragms piston-like, AMT “squeezes out” air through accordion-folded diaphragms that “contract/extend” 3. This operating principle enables moving air up to 5 times faster than diaphragm movement speed, becoming the source of remarkable transient response performance (speed) and low distortion 3.
However, AMT was originally tweeter technology specializing in high-frequency reproduction. Making this unprecedented challenge of full-range reproduction in headphones possible is HEDD’s proprietary VVT (Variable Velocity Transformation) technology 4. This geometric innovation varies diaphragm “fold” width and depth by location, achieving linear reproduction across the vast 10 Hz to 40 kHz range. This represents groundbreaking innovation in AMT history.
Physical Construction: Battle Against Physical Laws
The original HEDDphone bore the enormous burden of 718g mass in exchange for its revolutionary sound 3. This stemmed from the massive, powerful magnetic circuit required by AMT drivers covering wide bandwidth—a physical destiny of sorts.
HEDDphone TWO’s development is also a record of this battle against physical laws. Engineers strategically employed lightweight materials like carbon fiber headbands and magnesium earcups, successfully reducing weight to 550g—approximately 25% reduction 6.
Furthermore, addressing how to efficiently distribute remaining mass, they presented the original solution named HEDDband 4. This patent-pending dual-strap system allows independent adjustment of headphone height and lateral pressure (clamping force) 16. This complex mechanism isn’t mere decoration—it represents functional beauty born from necessity, devised to overcome physical constraints imposed by AMT driver technology while achieving ergonomic comfort.
Competitive Technical Specification Comparison
To understand HEDDphone TWO’s technical uniqueness, let’s compare specifications with major competing products in the same price range.
| Model | Principle | Impedance | Sensitivity | Weight | Reference Price (USD) |
|---|---|---|---|---|---|
| HEDDphone TWO | AMT | 41 Ω | 89 dB/mW | 550 g | $1,999 |
| Audeze LCD-5 | Planar Magnetic | 14 Ω | 90 dB/1mW | 420 g | $4,500 |
| Focal Utopia (2022) | Dynamic | 80 Ω | 104 dB/1mW | 490 g | $4,999 |
| Sennheiser HD 800 S | Dynamic | 300 Ω | 102 dB (1 V) | 330 g | ~$1,799 |
Source: 4
This table clearly shows HEDDphone TWO’s 89 dB/mW sensitivity is significantly lower compared to Focal Utopia’s 104 dB/1mW. This suggests this headphone requires extremely powerful headphone amplifiers to fully realize its performance.
3. Acoustic Characteristics from Measurement Data
Sensory impressions captured by our ears gain clearer definition when reflected in the objective mirror of measurement data. Here we analyze HEDDphone TWO’s acoustic characteristics from a physical perspective based on published measurement data.
Frequency Response
Synthesizing multiple measurement sources reveals HEDDphone TWO’s frequency response eloquently tells its design philosophy story 9.
- Bass: The most prominent feature is gradual sub-bass roll-off beginning around 60Hz 9. This represents tuning intended for acoustic compatibility with HEDD studio monitors, reflecting emphasis on texture and precision over quantity 26.
- Midrange: The 200Hz to 1kHz band is generally flat, forming the foundation for this model’s transparent, analytical midrange. However, some measurements observe small peaks around 700Hz and dips around 2kHz, potentially contributing to some reviewers’ noted “slight cabinet resonance” or “retreat of sonic directness” 16.
- Treble: Proper pinna gain peaks appear around 3kHz, but after dipping from 6-8kHz, prominent peaks return in the 10-14kHz ultra-high range 9. This “unusual combination of warmth and brightness” 9 forms HEDDphone TWO’s distinctive acoustic signature. The 6-8kHz dip softens upper-midrange aggressiveness while 10-14kHz peaks contribute to AMT driver’s characteristic “speed” and “airiness” perception. However, this peak can simultaneously emphasize sibilance for some listeners 9.
Distortion Characteristics
The original HEDDphone showed unusual characteristics in measurements—extremely low bass distortion while distortion increased in the 2-5kHz upper-midrange where hearing is most sensitive 28. This highlighted technical challenges in full-range AMT driver implementation.
HEDDphone TWO shows clear improvement in this area. The manufacturer claims new drivers reduce audible distortion, particularly in high frequencies 20, with multiple reviews confirming reduced harmonic distortion and ringing below 100Hz and significantly improved transient response 10. With bass distortion suppressed to “basically non-existent” levels 20, users can apply EQ correction for sub-bass roll-off with minimal distortion increase concerns. This represents important technical progress ensuring user sonic adjustment freedom.
4. Sound Anatomy: Listening Impressions
Let’s translate technical insights into sensory experiences. Here we dissect HEDDphone TWO’s sonic world based on listening impressions quoted from various reviews.
| Reviewer / Media | Quote (Translation + Original) |
|---|---|
| Resolve (Headphones.com) | “Notes bloom with microdetails that give me a more complete picture of an instrument’s character.” |
| The Ear | ”Listeners wanting thump-thump bass should look elsewhere; these are refined headphones…” |
| Audio46 | ”The HEDDphone TWO GT offers a soundstage that feels narrower than one might expect from an open-back design.” |
| Tape Op | ”Because the AMT drivers are quite large and are positioned as much around your ears as they are outside of them, the soundstage feels expansive – not limited to the space between your ears” |
Sound Signature Analysis
Overall character: HEDDphone TWO’s sound is not warm, enveloping embrace but cold surgical dissection. Its character is determined by “speed” and “clarity” stemming from AMT driver physical properties 8. This shows pronounced character as an analytical tool rather than musical enjoyment device.
Bass: HEDDphone TWO’s bass should be discussed in terms of texture and speed rather than quantity or slam. Sonic contours are extremely clear with virtually no distortion 20. However, as many reviews note, sub-bass gradually attenuates, lacking the body-shaking depth and weight of planar magnetic or dynamic flagship models 3. This represents tuning for discerning subtle nuances of upright bass strings against fingerboards in jazz trios rather than seeking physical impact of EDM 808 kick drums.
Midrange: This frequency range is where HEDDphone TWO reigns supreme. Vocals, strings, and piano—elements forming music’s skeleton—are rendered with breathtaking transparency and vividness 12. What reviewers tried expressing as “timbral resolution” is precisely this ability 9—the capability to precisely decompose instruments’ complex harmonic structures and reproduce their unique “voices” without deviation. Here, physical accuracy ascends to musical artistry.
Treble: The treble is very extended, rich in fine detail, greatly contributing to overall soundfield airiness and resolution. However, it’s also double-edged. While some reviewers praise its transparency 10, others note it can be somewhat hard, potentially emphasizing sibilance in certain recordings 9. This demonstrates HEDDphone TWO as an extremely honest monitor that mercilessly exposes recording quality.
Soundstage and Imaging: Here we find the most interesting conflict among reviews. Some describe its soundfield as “somewhat narrow” 9, while others call it “expansive and speaker-like” 10. What does this contradiction mean?
Perhaps both are discussing different aspects. HEDDphone TWO’s soundfield width may not match the panoramic vastness of Sennheiser HD 800 S. However, imaging precision and depth within that soundfield are remarkably accurate and three-dimensional. The “speaker-like” description many reviews mention likely refers not to mere width but to the sensation of sound liberating from within the head to form clear images forward. In other words, HEDDphone TWO competes on image precision rather than scale.
5. Value Balance: Multifaceted Evaluation
Based on our analysis, let’s objectively score HEDDphone TWO’s value across multiple evaluation axes.
| Evaluation Axis | Score | Commentary |
|---|---|---|
| Technical Performance | 4.5 / 5 | The transient response speed and resolution delivered by AMT drivers are undoubtedly summit-level in this price range. Microdynamics and timbral reproduction are particularly noteworthy. However, insufficient macrodynamic impact and extremely high amplifier requirements prevent a perfect score 9. |
| Musical Charm | 3.5 / 5 | Provides unparalleled joy for analytical listening but may lack immersive engagement or warmth for surrendering to music. Its tendency to expose recording flaws means it selects listeners and sources. This reflects design philosophy and can’t be universally considered a flaw 8. |
| Build Quality | 4.0 / 5 | Robust construction using carbon fiber and magnesium evokes German product quality and functionality. It has the bearing of a “professional tool” prioritizing function over luxury. The HEDDband adjustment mechanism is original but requires some familiarity for intuitive operation 6. |
| Price-to-Value | 4.0 / 5 | The $2,000 price point is highly competitive in the flagship market considering its unique technology and exceptional performance. However, realizing maximum value requires implied additional investment in powerful upstream systems 8. |
| Future-Proofing / Serviceability | 4.5 / 5 | Standard 3.5mm connector adoption enables easy cable replacement for sonic exploration and maintenance. Five-year extended warranty through user registration reflects manufacturer confidence and provides long-term peace of mind 9. |
6. Exploring Existential Significance: Market Positioning
The high-end headphone market is a warring states period with distinctive powerhouses vying for dominance. Within this competitive landscape, where does HEDDphone TWO find its existential significance?
Specialist vs. All-Rounder
In conclusion, HEDDphone TWO doesn’t aim to be an all-rounder. It cedes certain territories to rivals: Focal Utopia’s overwhelming dynamic slam 21, Sennheiser HD 800 S’s expansive panoramic soundstage 22, and Audeze LCD-5’s profound bass authority 23. HEDDphone TWO doesn’t compete head-to-head in these arenas.
Its existential significance lies in proposing an entirely different game. The rules of this game are rooted in AMT driver physical advantages: “transient response fidelity” and “timbral resolution.” This headphone places value emphasis on how accurately it captures sound’s momentary behavior from birth to death, rather than sonic quantity or spatial breadth. This represents an extremely specialized approach distinct from other headphones’ directions.
As Tool, Not Toy
This specialization deeply relates to HEDD Audio’s origins as a professional audio manufacturer. HEDDphone TWO has stronger character as a “tool” for dissecting musical structure than a “toy” for pleasant musical enjoyment. Its mission is presenting recorded truth faithfully, for better or worse 8.
This positioning makes HEDDphone TWO invaluable for two user types. One is sound creation professionals—it serves as a reliable reference monitor. The other is audiophiles finding supreme joy in analytical listening—for them, it becomes a challenging yet immeasurably discovery-rich exploration tool.
7. Conclusion: For Whom Does This Sound Exist?
HEDDphone TWO is not a headphone for everyone. It is an extremely specialized acoustic instrument created with clear intent and philosophy. Therefore, the final question should not be “Is this headphone good or bad?” but “For whom is this headphone intended?”
Recommended for:
- Audio Professionals: Engineers and producers needing accurate understanding of source details during mixing and mastering 8.
- Analytical Audiophiles: Listeners pursuing technical aspects—microdynamics and detail reproduction—more than emotional musical enjoyment.
- Acoustic Music and Vocal Enthusiasts: People prioritizing midrange’s exceptional transparency and vivid instrument/voice timbres above all 12.
Should Reconsider Purchase:
- Bass Enthusiasts: Listeners seeking deep, quantity-rich bass resonating in their core 11.
- Relaxed Listening Seekers: Users preferring “musical” sound that warmly, tolerantly reproduces any source 8.
- Expansive Soundstage Devotees: Those considering soundfield breadth the essence of headphone listening 22.
Future Possibilities: If HEDDphone TWO’s analytical character feels too strict, HEDD Audio later released HEDDphone TWO GT as an option. This model maintains TWO’s analytical clarity while being tuned for warmer, more musical response, potentially bridging professionals and audiophiles 12.
Overall Rating: ★★★★☆ (4.0 / 5)
HEDDphone TWO is a rare headphone where physicist’s rigorous laws and deep musical insight beautifully crystallize. It challenges existing value systems, presenting new evaluation axes of sonic “speed” and “accuracy.” Its uncompromising stance becomes the ultimate tool for some while proving unwieldy for others. However, its solitary presence and overwhelming performance in its carved niche deserve praise. This is nothing less than an acoustic measuring instrument for sincere explorers wishing to peer into audio hobby’s depths.
References
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