KEF LS50 Meta on a Yamaha RX-V4A: safe at the impedance dip?
The LS50 Meta is 8 Ω nominal, inside the 6 Ω rating of the RX-V4A, but it dips to 3.5 Ω. Fine at normal volume. Go easy on long, loud bass. Published specs.
Everyday listening is fine. The nominal impedance of the KEF LS50 Meta is inside what the Yamaha RX-V4A is built for. The dip below that rating is a caution, not a thermal overload.
At 2.5 m in a typical room, the stereo pair reaches about 102.1 dB. The second speaker and the room each contribute roughly 3 dB, which is the usual allowance for home listening. That sits 2.9 dB under a 105 dB theatrical peak, so loud film moments are where an amplifier with more voltage starts to matter.
Behind that level: the RX-V4A is rated 80 W into 8 Ω, and the LS50 Meta works out to about 85.0 dB for 1 W at 1 m from the sensitivity the maker actually published. Nominal impedance is 8 Ω.
The published minimum impedance is 3.5 Ω.
Do not declare the amplifier unsafe because of the dip, and do not ignore it during long, loud sessions: sustained bass asks for more current than the nominal rating describes. A more powerful amplifier does not erase a dip. It only helps if the current one is running out of voltage and clipping.