The Meze 109 Pro is 40Ω at 112.0 dB/mW; the ZMF Atrium is 300Ω at 96.0 dB/mW. This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The ZMF Atrium needs 16.0 dB more than the Meze 109 Pro to reach the same loudness — 2.5 mW against 0.06 mW.
| Specification | Meze 109 Pro | ZMF Atrium |
|---|---|---|
| Impedance | 40 Ω | 300 Ω |
| Sensitivity | 112.0 dB/mW | 96.0 dB/mW |
| Sensitivity (voltage) | 126.0 dB/V | 101.2 dB/V |
| Power for 100 dB | 0.06 mW | 2.5 mW |
| Voltage for 100 dB | 50 mV | 0.87 V |
| Current for 100 dB | 1.3 mA | 2.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 5.00 Ω | 37.50 Ω |
| Sources that reach 100 dB out of 280 | 280 | 277 |
3 of the 280 sources have the power for the Meze 109 Pro but not for the ZMF Atrium — Apple USB-C dongle (EU), Steinberg UR22C, Sony NW-A306.
19 sources are low enough in output impedance for the ZMF Atrium under the one-eighth rule but not for the Meze 109 Pro (Zoom AMS-22, Arturia MiniFuse 2, Arturia MiniFuse 1, 16 more).
15 sources stay below the audible-hiss threshold with the ZMF Atrium but cross it with the Meze 109 Pro (FiiO BTR11, FiiO K11 R2R, Lake People G103-S Mk II, 12 more).
277 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
The gap between these two in decibels does not change with volume — it is a property of the two headphones. What changes is the size of the numbers, and it changes fast: every 10 dB costs ten times the power. The row that matters is the one nearest the level you listen at, and for most people that is nearer the top of this table than the bottom.
The ZMF Atrium is more demanding than 96% of the 567 non-electrostatic models in this database; the Meze 109 Pro than 11%. Both figures use the same measure as the rest of the site: whichever runs out first against a 2 V, 100 mW dongle, voltage or power.
| dB SPL | Meze 109 Pro power | Meze 109 Pro voltage | ZMF Atrium power | ZMF Atrium voltage |
|---|---|---|---|---|
| 80 | 0.6 µW | 5 mV | 0.03 mW | 87 mV |
| 85 | 2.0 µW | 9 mV | 0.08 mW | 0.15 V |
| 90 | 6.3 µW | 16 mV | 0.25 mW | 0.27 V |
| 95 | 0.02 mW | 28 mV | 0.79 mW | 0.49 V |
| 100 | 0.06 mW | 50 mV | 2.5 mW | 0.87 V |
| 105 | 0.20 mW | 89 mV | 7.9 mW | 1.54 V |
105 dB is included because forum power figures are usually quoted there or higher. It is also a level that damages hearing in minutes — how many minutes is its own calculator.
| Source | Price | Headroom, Meze 109 Pro | Headroom, ZMF Atrium | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 25.8 dB | 1.1 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 34.0 dB | 9.4 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 31.0 dB | 6.0 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 277 reach 100 dB on both. That is the easy axis. 57 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 rest either fail one of those or never printed the number at all, and 205 of them are in the second group.
The cheapest of the 57 is the JadeAudio JA11, at $20. It leaves 25.8 dB of headroom on the Meze 109 Pro and 1.1 dB on the ZMF Atrium, its output impedance is 0.5 Ω against a one-eighth limit of 5.00 Ω and 37.50 Ω, and its noise figure puts the hiss floor 9 dB and 34 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
Cheapest that satisfies three published numbers is not the same as best, and none of it is about how either headphone sounds. To put either model against a source this page does not mention, or to change the target loudness, use the amplifier matcher.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Meze 109 Pro | 5 Hz - 30 kHz | not printed | not printed |
| ZMF Atrium | nothing printed | — | — |
Meze prints 5 Hz - 30 kHz for the 109 Pro. ZMF prints nothing at all for the Atrium.
So one side of this comparison has a frequency-response number and the other does not — which changes less than it looks. The range printed for the Meze 109 Pro comes with no tolerance beside it, and a range without a ±dB figure says nothing about how loud the headphone is at either end of it: thirty decibels down at the bottom and the sentence would still be true. On the only reading that would have made it a specification, the two sheets say the same amount: nothing.
None of this is a measurement. What each maker publishes, and what it is worth, is set out in the frequency response audit.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Meze 109 Pro and ZMF Atrium. Every figure on this page comes from what Meze and ZMF published, or is derived from it — what Meze publishes and what ZMF publishes, both counted.