Between the IE 900 and Monarch MKIII, the IE 900 comes out ahead in sensitivity and impedance, while the Monarch MKIII wins on driver count. Overall, the IE 900 scores 66.4 and the Monarch MKIII scores 72.9 on our Mars Score.
Which should you buy?
The Monarch MKIII edges ahead on the Mars Score (66.4 vs 72.9), but the 6.5-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the IE 900 if you care most about sensitivity and impedance. The biggest gaps in its favor are sensitivity, impedance.
Pick the Monarch MKIII 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 Monarch MKIII 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 — 9.82% more. 123 dB vs 112 dB.
- ▲Impedance — 6.00 Ω less. 16 vs 22.
Why ThieAudio - Monarch MKIII wins
- ▲Driver count — 9.00 more. 10 vs 1.
Spec comparison
Drivers
| Spec | Sennheiser - IE 900 | ThieAudio - Monarch MKIII |
|---|---|---|
| Driver count | 1 | 10lead |
| Driver types | Dynamic (X3R) | 1DD + 6BA + 2EST + 1 Bone Conduction Tribrid |
| Impedanceⓘ | 16 Ωlead | 22 Ω |
| Sensitivityⓘ | 123 dBlead | 112 dB |
Build
| Spec | Sennheiser - IE 900 | ThieAudio - Monarch MKIII |
|---|---|---|
| Detachable cable | true | true |
| Connector | MMCX | 2-pinlead |
Spec-level deep dives
More from the same brands
vsMars is reader-supported. When you buy through links on our site, we may earn an affiliate commission at no extra cost to you. Learn more.