From Stereophile measurements…
My estimate of the LS50 Meta's voltage sensitivity was 84.5dB(B)/2.83V/m…The Meta remains closer to 4 ohms for longer in the midrange but has a considerably higher magnitude in the crossover region. The new speaker's electrical phase angle (fig.1, dashed trace) is occasionally high, and I used the formula in a 1994 JAES paper to calculate the "equivalent peak dissipation resistance" (EPDR, footnote 1). The LS50 Meta has minimum EPDRs of 1.66 ohms between 135Hz and 140Hz and 1.7 ohms between 660Hz and 725Hz, both regions where music can have high energy. The partnering amplifier needs to be comfortable driving 4 ohms.
Bottom line, the LS50 Metas are not a tube-friendly speaker.