Between the IE 900 and IER-M9, the IE 900 comes out ahead in sensitivity and impedance, while the IER-M9 wins on driver count. Overall, the IE 900 scores 66.4 and the IER-M9 scores 54.5 on our Mars Score.
Which should you buy?
The IE 900 is the clear pick on raw spec strength, leading by 11.9 points on the Mars Score. The margin is wide enough that the underdog only makes sense if its individual strengths line up with what you specifically need.
Pick the IE 900 if you care most about sensitivity and impedance. The biggest gaps in its favor are sensitivity, impedance.
Pick the IER-M9 if you care most about driver count. Its strongest claims are driver count.
Both ship with comparable detachable cable, so those specs don't separate the two — focus on the differences below.
Bottom line: the IE 900 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Why Sennheiser - IE 900 wins
- ▲Sensitivity — 19.42% more. 123 dB vs 103 dB.
- ▲Impedance — 2.00 Ω less. 16 vs 18.
Why Sony - IER-M9 wins
- ▲Driver count — 4.00 more. 5 vs 1.
Spec comparison
Drivers
| Spec | Sennheiser - IE 900 | Sony - IER-M9 |
|---|---|---|
| Driver count | 1 | 5lead |
| Driver types | Dynamic (X3R) | 5 Balanced Armature |
| Impedanceⓘ | 16 Ωlead | 18 Ω |
| Sensitivityⓘ | 123 dBlead | 103 dB |
Build
| Spec | Sennheiser - IE 900 | Sony - IER-M9 |
|---|---|---|
| Detachable cable | true | true |
| Connector | MMCX | MMCX |
Frequently asked
Spec-level deep dives
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