These are proper audiophile headphones — no noise cancellation, no Bluetooth, no app, no features beyond what matters: transducing electrical signal into beautiful sound. The HD 660S2 is Sennheiser's refined dynamic driver flagship at $600; the MM-100 is Audeze's approachable planar magnetic entry point at $400. Different technologies, different prices, both worth your serious attention.
Sennheiser HD 660S2
The MM-100 wins on imaging and low-end texture at a lower price; the HD 660S2 wins on midrange clarity and long-session comfort.
Specs Comparison
| Spec | Sennheiser HD 660S2 | Audeze MM-100 |
|---|---|---|
| Driver Type | Dynamic | Planar Magnetic |
| Impedance | 300 ohms | 18 ohms |
| Weight | 260g | 440g |
| Frequency Response | 10-41,000 Hz | 10-50,000 Hz |
| Open/Closed | Open-back | Open-back |
| Price | ~$600 | ~$400 |
Driver Technology
The HD 660S2 uses Sennheiser's refined dynamic driver — a transducer with a moving coil in a magnetic gap. Dynamic drivers are the traditional headphone driver type, and Sennheiser has been perfecting theirs for decades. The result is a natural, organic sound with excellent treble extension.
The Audeze MM-100 uses a planar magnetic driver — a thin membrane with conductors distributed across its surface, driven by magnets on both sides. Planar drivers are known for extremely low distortion, fast transient response, and exceptional bass texture.
Neither is objectively better. Planar fans cite the MM-100's physical authority in the low end and its distortion-free character. Dynamic fans cite the HD 660S2's more organic, lifelike presentation.
Sound Signature
The HD 660S2 has a warmer, more relaxed signature than the original HD 660S — slightly more bass, slightly rolled treble. It's an excellent headphone for long listening sessions with minimal fatigue.
The MM-100 is more neutral and more resolving in the low frequencies — bass lines are textured and detailed in a way that dynamic drivers struggle to match at this price. It's drier and more analytical.
For jazz, acoustic, and classical: the HD 660S2's organic presentation is gorgeous. For electronic music, hip-hop, and anything with complex bass: the MM-100's planar driver will show you things you haven't heard.
Practical Considerations
The HD 660S2 has an impedance of 300 ohms — you need a proper headphone amplifier to drive it to its potential. Out of a laptop headphone jack it will be quiet and not sound its best. The MM-100 at 18 ohms is easier to drive but still benefits from a DAC/amp.
Audeze's MM-100 weighs 440g — heavy for a headphone meant for desktop listening. The HD 660S2 is lighter at 260g and more comfortable for three to four hour sessions.
The MM-100 costs $400; the HD 660S2 costs $600. That $200 gap makes the MM-100's value proposition compelling.
Getting the Most Out of Either Headphone
Both headphones need a proper headphone amplifier. Budget $100-200 for a decent amp — the FiiO K7, SMSL SH-9, or Schiit Magni are all appropriate. Don't assume the headphone jack on your laptop is adequate.
The MM-100 benefits more from EQ than the HD 660S2. A shelf boost at 3-4kHz and slight bass shelf reduction can optimize its presentation significantly. The HD 660S2's default tuning is more suitable for extended listening without adjustment.
Both reward quality recordings. Streaming at 320kbps Spotify or Tidal HiFi is adequate; hi-res FLAC reveals more at this price tier.
Sennheiser HD 660S2 Strengths
- Natural, organic midrange with excellent treble extension
- Lighter at 260g — more comfortable for long listening sessions
- Open, wide soundstage characteristic of Sennheiser's house sound
- Well-supported with years of aftermarket cables and pads
Audeze MM-100 Strengths
- Planar magnetic driver with exceptional bass texture and low distortion
- $200 cheaper than HD 660S2
- Faster transient response — excellent for complex musical passages
- Audeze's Mobius-derived technology in an accessible package
Sennheiser HD 660S2 Weaknesses
- Requires a headphone amp at 300 ohms — adds cost
- Costs $200 more than the MM-100
- Rolled-off treble may frustrate detail-obsessed listeners
Audeze MM-100 Weaknesses
- 440g weight causes discomfort in sessions longer than 2 hours
- Planar sound can feel analytical/dry to dynamic driver fans
- Requires careful EQ to optimize the upper midrange
Best For
- a: Listeners who prefer a natural, organic presentation for acoustic and classical music
- b: Listeners who prioritize bass texture and low distortion — especially for electronic and hip-hop
FAQ
Do you need a DAC/amp for either of these?
For the HD 660S2 at 300 ohms, yes — a basic amp like the FiiO E10K or Schiit Magni is needed to drive it properly. The MM-100 is easier to drive but still benefits from a clean amplifier. Budget $100-200 for a basic stack when buying either headphone.
Which is better for critical music listening?
Depends on the genre. The HD 660S2 is exceptional for acoustic, jazz, and classical where midrange naturalness matters most. The MM-100 excels on electronic music, hip-hop, and any genre where bass texture and low-frequency detail are the priority.