Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Etymotic - ER4XR | Sennheiser - IE 900 |
|---|---|---|
| Impedance | 45 Ω | 16 Ω |
| Sensitivity | 98 dB | 123 dB |
Between the ER4XR and IE 900, the ER4XR comes out ahead in several specs, while the IE 900 wins on impedance / sensitivity. Overall, the ER4XR scores 39.7 and the IE 900 scores 66.4 on our Mars Score.
Which should you buy?
The IE 900 is the clear pick on raw spec strength, leading by 26.7 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.
The ER4XR does not pull ahead on any single popular-comparison spec — its strengths sit in the spec-table groups rather than the headline advantages.
Pick the IE 900 if you care most about impedance / sensitivity. Its strongest claims are impedance, sensitivity. The single most decisive one: Impedance — 29.00 Ω less. 16 vs 45.
Both ship with comparable driver count, detachable cable, so those specs do not 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.
Which should you buy: Etymotic - ER4XR or Sennheiser - IE 900?
Sennheiser - IE 900 leads the current Mars Score by 26.7 points.The more useful decision is the trade-off behind that result: compare impedance, sensitivity against the way you will actually use the product.
Choose Etymotic - ER4XR if…
Etymotic - ER4XR does not lead a decisive measured field here, so choose it for price, ecosystem, design, or availability when those matter more to you.
Choose Sennheiser - IE 900 if…
Sennheiser - IE 900 has the measurable edge on impedance ohm, sensitivity db.
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 Etymotic - ER4XR wins
- No decisive advantages.
Why Sennheiser - IE 900 wins
- ▲Impedance — 29.00 Ω less. 16 vs 45.
- ▲Sensitivity — 25.51% more. 123 dB vs 98 dB.
Spec comparison
Drivers
| Spec | Etymotic - ER4XR | Sennheiser - IE 900 |
|---|---|---|
| Driver count | 1 | 1 |
| Driver types | Balanced Armature | Dynamic (X3R) |
| Impedanceⓘ | 45 Ω | 16 Ωlead |
| Sensitivityⓘ | 98 dB | 123 dBlead |
Build
| Spec | Etymotic - ER4XR | Sennheiser - IE 900 |
|---|---|---|
| Detachable cable | true | true |
| Connector | MMCX | MMCX |