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Key Points

Key Takeaways

  • 1

    Open Your Ears

  • 2

    Soundstage: Noise canceling (Closed-back) creates silence but narrows Soundstage. Open-back releases sound to outside, creating spread as if in concert hall.

  • 3

    Sennheiser HD 660S2: Legitimate evolution of legendary masterpiece HD 600 series. Lushness of midrange (Vocal) is said to be world's best. Became S2, volume of low range reinforced, matching modern music.

  • 4

    Hifiman Sundara: Entry model of Planar Magnetic. Overwhelming resolution and speed feeling that Dynamic type cannot produce. Can hear even moment cymbal reverb disappears.

  • 5

    Listening fatigue: Open-back has less pressure on ears and does not tire (does not get stuffy) even if listened to for long time. Optimal solution for BGM for work at home.

Introduction: Remove Earphones

AirPods Pro is convenient. However, it is device to “ingest information”, not device to “experience music”.

Let’s release ears at least when at home. Open-back headphones are at midpoint between listening with speakers and listening with earphones. Sound does not stay inside head, but passes through naturally. Once you know it, you cannot go back to closed-back.

1. The Vocal King: Sennheiser HD 660S2

Treasure of Germany said to be “Should listen once”. Reproducibility of human voice (Vocal) is especially abnormal. Vividness as if singing in front of eyes.

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Sennheiser HD 660S2

Since impedance is high at 300Ω, true value cannot be demonstrated by plugging directly into smartphone. DAC/Amp described later becomes essential.

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The Veil is Lifted

Warm timbre that does not tire listening, called Sennheiser’s unique “Veil”. In S2, that veil was peeled off one layer, becoming clearer and deeper. This is sound that is not too “analytical” and can be listened to forever.

2. The Speed Demon: Hifiman Sundara

This is Planar Magnetic driver type. Since entire diaphragm moves uniformly, rise and fall of sound (Transient) is explosive speed. Attack feeling of drums and guitar cutting feel good.

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HIFIMAN Sundara

It is miracle itself that Planar Magnetic can be bought in this price range. Separation of sound is tremendous, hearing 'sounds that could not be heard before'.

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3. Comparison: Song or Instrument

項目 HD 660S2 (Dynamic) Sundara (Planar)
Specialty Genre Vocal / Jazz Classic / Rock
Sound Texture Warm Cool
Fit Strong Side Pressure Headband Comfortable
Drive Difficulty Difficult (300Ω) Normal (37Ω)

4. The Leakage

Disadvantage of open-back is “Sound Leakage”. It leaks grandly. Absolutely unusable in library or train.

However, that is not disadvantage but “Specification”. It is ritual tool to face music alone in room where no one disturbs.

Conclusion: Bathe in Music

during work, are you blocking ears with just noise canceling? That is wasteful. Please work while bathing in best soundtrack with best sound quality.

Sound that brain rejoices and dopamine comes out. That becomes fuel to maximize productivity.

# headphones # sennheiser # hifiman # audiophile # mix-mastering # 2026