@stevevn ,
This excerpt from JA of Stereophile. Keep in mind this speaker relative to the Tannoy is a more challenging load for an amplifier to manage. You may want to take this into consideration as you decide,
Bowers & Wilkins specifies the 804 D4’s anechoic sensitivity as 89dB/2.83V/m. My B-weighted estimate was the same. The 804 D4’s impedance is specified as 8 ohms, with a minimum value of 3 ohms. The solid trace in fig.1 indicates that the impedance magnitude, measured with Dayton Audio’s DATS v2 system, lies between 3 and 6 ohms in the upper bass and midrange, with a minimum value of 2.55 ohms between 121Hz and 131Hz. The electrical phase angle (dashed trace) is occasionally high; for example, there is a current-hungry combination of 3.7 ohms magnitude and –55° phase angle at 87Hz. The effective resistance, or EPDR (footnote 1), drops below 2 ohms between 22Hz and 33Hz, 62Hz and 116Hz, and 663Hz and 886Hz. The minimum EPDR is 1 ohm from 88Hz to 110Hz and 1.6 ohms at 886Hz. The 804 D4 must be used with amplifiers that don’t have problems driving 2 ohms.
Charles