WiiM Amp with KEF LS50 Meta: does 2.67 ohms cover the 3.5 ohm dip?
The most-searched amplifier pairing for these speakers, and the first amplifier in this catalogue whose published minimum clears the LS50 Meta's dip. It passes — but the whole verdict rests on which half of one WiiM spec row you believe, because the row names two different lowest loads.
It passes — and the whole verdict rests on which half of one spec row you believe.
Level. The LS50 Meta is 85 dB per watt at one metre, the lowest sensitivity in this catalogue. The WiiM Amp publishes 60 W at 8 Ω:
| Distance | Continuous SPL | Against the 105 dB reference |
|---|---|---|
| 1 m | 102.8 dB | −2.2 dB |
| 2 m | 96.8 dB | −8.2 dB |
| 3 m | 99.2 dB | −11.8 dB |
| 4 m | 90.7 dB | −14.3 dB |
For comparison, the Cambridge Audio CXA81's 80 W on the same speakers at the same three metres gives 94.5 dB. Twenty extra watts are worth 1.25 dB.
Impedance. This is why the pairing gets asked about. KEF's nominal is 8 Ω and the catalogue records a 3.5 Ω dip. The WiiM Amp publishes a 2.67 Ω minimum, so the dip clears it by 31 % and this page reads safe. Amplifiers rated to 4 Ω — the CXA81 among them — do not clear it.
Cable. Fifteen feet of 16 AWG into 8 Ω costs 1.5 % of the voltage and leaves a damping factor of 47. Moving to 12 AWG raises that to 82 and changes the level not at all.
The pearl: the 2.67 ohms and the wiring case printed beside it contradict each other. WiiM's row reads «Speaker Output: 8 ohms, 6 ohms, 4 ohms / 2 pairs 8 ohms in parallel / Minimum Impedance 2.67 ohms». Two pairs of 8 Ω speakers in parallel present 4 Ω, not 2.67 — 2.67 Ω is what three 8 Ω loads in parallel would give. Believe the 2.67 and this page says safe. Believe the wiring case and the amplifier is a 4 Ω design, the 3.5 Ω dip falls 12 % below it, and the same page becomes a marginal-impedance warning. One row, two lowest loads, two verdicts. Worth noting alongside it: the 60 W and 120 W come with no distortion limit, no frequency band and no statement of channels driven, and the only distortion figure on the sheet is taken at 5 W.