Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Sennheiser - IE 600 | Sony - IER-M9 |
|---|---|---|
| Sensitivity | 118 dB | 103 dB |
| Driver count | 1 | 5 |
Between the IE 600 and IER-M9, the IE 600 comes out ahead in sensitivity, while the IER-M9 wins on driver count. Overall, the IE 600 scores 61.5 and the IER-M9 scores 54.5 on our Mars Score.
Which should you buy?
The IE 600 edges ahead on the Mars Score (61.5 vs 54.5), but the 7.0-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the IE 600 if you care most about sensitivity. The biggest gaps in its favor are sensitivity. The single most decisive one: Sensitivity — 14.56% more. 118 dB vs 103 dB.
Pick the IER-M9 if you care most about driver count. Its strongest claims are driver count. The single most decisive one: Driver count — 4.00 more. 5 vs 1.
Both ship with comparable impedance, detachable cable, so those specs do not separate the two — focus on the differences below.
Bottom line: the IE 600 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Which should you buy: Sennheiser - IE 600 or Sony - IER-M9?
Sennheiser - IE 600 leads the current Mars Score by 7.0 points.The more useful decision is the trade-off behind that result: compare driver count, sensitivity against the way you will actually use the product.
Choose Sennheiser - IE 600 if…
Sennheiser - IE 600 has the measurable edge on sensitivity db.
Choose Sony - IER-M9 if…
Sony - IER-M9 has the measurable edge on driver count.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Sennheiser - IE 600 wins
- ▲Sensitivity — 14.56% more. 118 dB vs 103 dB.
Why Sony - IER-M9 wins
- ▲Driver count — 4.00 more. 5 vs 1.
Spec comparison
Drivers
| Spec | Sennheiser - IE 600 | Sony - IER-M9 |
|---|---|---|
| Driver count | 1 | 5lead |
| Driver types | Dynamic (TrueResponse) | 5 Balanced Armature |
| Impedanceⓘ | 18 Ω | 18 Ω |
| Sensitivityⓘ | 118 dBlead | 103 dB |
Build
| Spec | Sennheiser - IE 600 | Sony - IER-M9 |
|---|---|---|
| Detachable cable | true | true |
| Connector | MMCX | MMCX |