Between the Aria 2 and IER-M9, the Aria 2 comes out ahead in sensitivity, while the IER-M9 wins on impedance and driver count. Overall, the Aria 2 scores 65.4 and the IER-M9 scores 54.5 on our Mars Score.
Which should you buy?
The Aria 2 is the clear pick on raw spec strength, leading by 10.9 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 Aria 2 if you care most about sensitivity. The biggest gaps in its favor are sensitivity.
Pick the IER-M9 if you care most about impedance and driver count. Its strongest claims are impedance, driver count.
Both ship with comparable detachable cable, so those specs don't separate the two — focus on the differences below.
Bottom line: the Aria 2 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Why Moondrop - Aria 2 wins
- ▲Sensitivity — 18.45% more. 122 dB vs 103 dB.
Why Sony - IER-M9 wins
- ▲Impedance — 14.00 Ω less. 18 vs 32.
- ▲Driver count — 4.00 more. 5 vs 1.
Spec comparison
Drivers
| Spec | Moondrop - Aria 2 | Sony - IER-M9 |
|---|---|---|
| Driver count | 1 | 5lead |
| Driver types | Dynamic | 5 Balanced Armature |
| Impedanceⓘ | 32 Ω | 18 Ωlead |
| Sensitivityⓘ | 122 dBlead | 103 dB |
Build
| Spec | Moondrop - Aria 2 | Sony - IER-M9 |
|---|---|---|
| Detachable cable | true | true |
| Connector | 0.78mm 2-pinlead | MMCX |
Frequently asked
Spec-level deep dives
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