The Sennheiser IE 400 PRO is 16Ω at 105.0 dB/mW; the Sennheiser IE 600 is 18Ω at 100.6 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The IE 600 needs 4.4 dB more than the IE 400 PRO to reach the same loudness — 0.87 mW against 0.32 mW.
| Specification | IE 400 PRO | IE 600 |
|---|---|---|
| Impedance | 16 Ω | 18 Ω |
| Sensitivity | 105.0 dB/mW | 100.6 dB/mW |
| Sensitivity (voltage) | 123.0 dB/V | 118.0 dB/V |
| Power for 100 dB | 0.32 mW | 0.87 mW |
| Voltage for 100 dB | 71 mV | 0.13 V |
| Current for 100 dB | 4.4 mA | 7.0 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 2.00 Ω | 2.25 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
3 sources stay below the audible-hiss threshold with the IE 600 but cross it with the IE 400 PRO (FiiO BTR11, FiiO K11 R2R, Rupert Neve RNHP).
280 of the 280 sources here reach 100 dB on both.
The IE 600 is more demanding than 39% of the 567 non-electrostatic models in this database; the IE 400 PRO than 22%.
| dB SPL | IE 400 PRO power | IE 400 PRO voltage | IE 600 power | IE 600 voltage |
|---|---|---|---|---|
| 80 | 3.2 µW | 7 mV | 8.7 µW | 13 mV |
| 85 | 0.01 mW | 13 mV | 0.03 mW | 22 mV |
| 90 | 0.03 mW | 22 mV | 0.09 mW | 40 mV |
| 95 | 0.10 mW | 40 mV | 0.28 mW | 70 mV |
| 100 | 0.32 mW | 71 mV | 0.87 mW | 0.13 V |
| 105 | 1.0 mW | 0.13 V | 2.8 mW | 0.22 V |
| Source | Price | Headroom, IE 400 PRO | Headroom, IE 600 | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 16.8 dB | 12.9 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 28.9 dB | 24.3 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 25.8 dB | 21.2 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 66 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 66 is the JadeAudio JA11, at $20. It leaves 16.8 dB of headroom on the IE 400 PRO and 12.9 dB on the IE 600, its output impedance is 0.5 Ω against a one-eighth limit of 2.00 Ω and 2.25 Ω, and its noise figure puts the hiss floor 12 dB and 17 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| IE 400 PRO | 6 - 19,000 Hz | not printed | not printed |
| IE 600 | 4 – 46,500 Hz | not printed | not printed |
Sennheiser prints 6 - 19,000 Hz for the IE 400 PRO and 4 – 46,500 Hz for the IE 600.
Neither range has a tolerance printed beside it, so a wider range on one sheet is not deeper bass or more treble.
Not a measurement; maker by maker.
Both have a page of their own. In full: Sennheiser IE 400 PRO and Sennheiser IE 600. Every figure on this page comes from what Sennheiser published, or is derived from it — what that maker publishes, counted.