Short answer
Both are portable players, $2959 against $3700.
The Shanling M9 Plus reaches 100 dB on 566 of the 567 models here, the Sony NW-WM1ZM2 on 552.
| Specification | Shanling M9 Plus | Sony NW-WM1ZM2 |
|---|---|---|
| Power into 32Ω | 520 mW | 30 mW |
| Power into 150Ω | 111 mW | 6.4 mW |
| Power into 300Ω | 55 mW | 3.2 mW |
| Power into 600Ω | 28 mW | 1.6 mW |
| Output impedance | 1 Ω | not published |
| Output noise | not published | not published |
| Price | $2959 | $3700 |
| Headphones it reaches 100 dB on out of 567 | 566 | 552 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Shanling M9 Plus | Sony NW-WM1ZM2 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 1.1 W | 125 mW derived |
| Power into 300Ω | 120 mW derived | 13 mW derived |
| Output impedance | 1 Ω | not published |
| Output noise | not published | not published |
| Headphones it reaches 100 dB on out of 567 | 567 | 561 |
Through the balanced sockets the Shanling M9 Plus reaches 100 dB on 567 of the 567 models here and the Sony NW-WM1ZM2 on 561. Derived figures are worked out from the loads the maker did publish.
| Load | Shanling M9 Plus | Sony NW-WM1ZM2 |
|---|---|---|
| 32 Ω | Published | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Shanling M9 Plus publishes one at 32 Ω; Sony NW-WM1ZM2 publishes none at any of these four loads, so its column is worked out from power it published at other loads. Both are arithmetic on a maker’s own figures rather than guesses, and the method used for the Sony NW-WM1ZM2 understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
14 headphones reach 100 dB on the Shanling M9 Plus but not on the Sony NW-WM1ZM2 — Beyerdynamic DT 880 Edition (600Ω), Beyerdynamic DT 990 Edition (600Ω), HiFiMAN HE-6se V2, 11 more.
552 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Sennheiser HD 600: Shanling M9 Plus has +9 dB of headroom there against -3 dB. 12 dB is about 17 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Shanling M9 Plus and Sony NW-WM1ZM2 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Shanling M9 Plus headroom | Sony NW-WM1ZM2 headroom | Shanling M9 Plus hiss | Sony NW-WM1ZM2 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +36 dB | +29 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +16 dB | +9 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +25 dB | +12 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB | +8 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +17 dB | +7 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +13 dB | +1 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB | -3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +7 dB | -5 dB | not published | not published |
The Sony NW-WM1ZM2 costs $741 more than the Shanling M9 Plus, and on these three axes the money buys nothing: among the 567 models here there is not one that the Sony NW-WM1ZM2 handles and the Shanling M9 Plus does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Shanling M9 Plus drives 14 models to 100 dB that the Sony NW-WM1ZM2 does not.
Only published figures count here; blank axes are counted separately.
Each in full: Shanling M9 Plus and Sony NW-WM1ZM2.