Short answer
Both are portable players, both at $3700.
The Astell&Kern SP3000 reaches 100 dB on 565 of the 567 models here, the Sony NW-WM1ZM2 on 552.
| Specification | Astell&Kern SP3000 | Sony NW-WM1ZM2 |
|---|---|---|
| Power into 32Ω | 340 mW | 30 mW |
| Power into 150Ω | 73 mW | 6.4 mW |
| Power into 300Ω | 36 mW | 3.2 mW |
| Power into 600Ω | 18 mW | 1.6 mW |
| Output impedance | 0.7 Ω | not published |
| Output noise | 3 µV unverified | not published |
| Price | $3700 | $3700 |
| Headphones it reaches 100 dB on out of 567 | 565 | 552 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Astell&Kern SP3000 | Sony NW-WM1ZM2 |
|---|---|---|
| Socket | 4.4mm and 2.5mm | 4.4mm |
| Power into 32Ω | 1.2 W derived | 125 mW derived |
| Power into 300Ω | 132 mW derived | 13 mW derived |
| Output impedance | 1.6 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 Astell&Kern SP3000 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 | Astell&Kern SP3000 | Sony NW-WM1ZM2 |
|---|---|---|
| 32 Ω | Upper bound | Derived |
| 150 Ω | Upper bound | Derived |
| 300 Ω | Upper bound | Derived |
| 600 Ω | Upper bound | Derived |
Neither column is a power rating, and the two are not even weak in the same way. The Astell&Kern SP3000 figures are ceilings worked out from a maximum output voltage, on the assumption that the amplifier holds it into the load. The Sony NW-WM1ZM2 figures are worked out from figures its maker did publish — power at other loads, or the voltage printed beside it. The second method understates; the first flatters. That is the wrong way round for reading the table straight across, so a gap in favour of the Astell&Kern SP3000 is the one to doubt.
13 headphones reach 100 dB on the Astell&Kern SP3000 but not on the Sony NW-WM1ZM2 — Beyerdynamic DT 880 Edition (600Ω), Beyerdynamic DT 990 Edition (600Ω), HiFiMAN HE-6se V2, 10 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: Astell&Kern SP3000 has +7 dB of headroom there against -3 dB. 11 dB is about 11 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Astell&Kern SP3000 and Sony NW-WM1ZM2 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Astell&Kern SP3000 headroom | Sony NW-WM1ZM2 headroom | Astell&Kern SP3000 hiss | Sony NW-WM1ZM2 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +34 dB | +29 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +14 dB | +9 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +23 dB | +12 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +18 dB | +8 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +15 dB | +7 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +12 dB | +1 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +7 dB | -3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +6 dB | -5 dB | not published | not published |
These two cost the same, $3700, so price settles nothing. Out of the 567 models here, the Astell&Kern SP3000 drives 13 models to 100 dB — and on the other side there is no such advantage at all.
Only published figures count here; blank axes are counted separately.
Each in full: Astell&Kern SP3000 and Sony NW-WM1ZM2.