The Audio-Technica ATH-M40X is 35Ω at 98.0 dB/mW; the Audio-Technica ATH-R70xa is 470Ω at 97.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The ATH-R70xa needs 1.0 dB more than the ATH-M40X to reach the same loudness — 2.0 mW against 1.6 mW.
| Specification | ATH-M40X | ATH-R70xa |
|---|---|---|
| Impedance | 35 Ω | 470 Ω |
| Sensitivity | 98.0 dB/mW | 97.0 dB/mW |
| Sensitivity (voltage) | 112.6 dB/V | 100.3 dB/V |
| Power for 100 dB | 1.6 mW | 2.0 mW |
| Voltage for 100 dB | 0.24 V | 0.97 V |
| Current for 100 dB | 6.7 mA | 2.1 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.38 Ω | 58.75 Ω |
| Sources that reach 100 dB out of 280 | 280 | 275 |
5 of the 280 sources have the power for the ATH-M40X but not for the ATH-R70xa — Apple USB-C dongle (EU), FiiO BTR11, Steinberg UR22C, 2 more.
33 sources are low enough in output impedance for the ATH-R70xa under the one-eighth rule but not for the ATH-M40X (Zoom AMS-22, Audient EVO 4, ART HeadAmp 4 Pro, 30 more).
1 source stays below the audible-hiss threshold with the ATH-R70xa but crosses it with the ATH-M40X (Schiit Mjolnir 3).
275 of the 280 sources here reach 100 dB on both.
The ATH-R70xa is more demanding than 98% of the 567 non-electrostatic models in this database; the ATH-M40X than 64%.
| dB SPL | ATH-M40X power | ATH-M40X voltage | ATH-R70xa power | ATH-R70xa voltage |
|---|---|---|---|---|
| 80 | 0.02 mW | 24 mV | 0.02 mW | 97 mV |
| 85 | 0.05 mW | 42 mV | 0.06 mW | 0.17 V |
| 90 | 0.16 mW | 74 mV | 0.20 mW | 0.31 V |
| 95 | 0.50 mW | 0.13 V | 0.63 mW | 0.54 V |
| 100 | 1.6 mW | 0.24 V | 2.0 mW | 0.97 V |
| 105 | 5.0 mW | 0.42 V | 6.3 mW | 1.72 V |
| Source | Price | Headroom, ATH-M40X | Headroom, ATH-R70xa | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 12.4 dB | 0.1 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 20.6 dB | 8.5 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 17.6 dB | 5.1 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 275 reach 100 dB on both. 68 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 68 is the JadeAudio JA11, at $20. It leaves 12.4 dB of headroom on the ATH-M40X and 0.1 dB on the ATH-R70xa, its output impedance is 0.5 Ω against a one-eighth limit of 4.38 Ω and 58.75 Ω, and its noise figure puts the hiss floor 23 dB and 35 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| ATH-M40X | 15 - 24,000 Hz | not printed | not printed |
| ATH-R70xa | 5 to 40,000 Hz | not printed | not printed |
Audio-Technica prints 15 - 24,000 Hz for the ATH-M40X and 5 to 40,000 Hz for the ATH-R70xa.
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: Audio-Technica ATH-M40X and Audio-Technica ATH-R70xa. Every figure on this page comes from what Audio-Technica published, or is derived from it — what that maker publishes, counted.