  We present a spectroscopic and photometric study of the Double Period
Variable HD170582. Based on the study of the ASAS V-band light curve we
determine an improved orbital period of 16.87177 $\pm$ 0.02084 days and a long
period of 587 days. We disentangled the light curve into an orbital part,
determining ephemerides and revealing orbital ellipsoidal variability with
unequal maxima, and a long cycle, showing quasi-sinusoidal changes with
amplitude $\Delta V$= 0.1 mag. Assuming synchronous rotation for the cool
stellar component and semi-detached configuration we find a cool evolved star
of $M_{2}$ = 1.9 $\pm$ 0.1 $M_{\odot}$, $T_{2}$ = 8000 $\pm$ 100 $K$ and
$R_{2}$ = 15.6 $\pm$ 0.2 $R_{\odot}$, and an early B-type dwarf of $M_{1}$ =
9.0 $\pm$ 0.2 $M_{\odot}$. The B-type star is surrounded by a geometrically and
optically thick accretion disc of radial extension 20.8 $\pm$ 0.3 $R_{\odot}$
contributing about 35% to the system luminosity at the $V$ band. Two extended
regions located at opposite sides of the disc rim, and hotter than the disc by
67% and 46%, fit the light curve asymmetries. The system is seen under
inclination 67.4 $\pm$ 0.4 degree and it is found at a distance of 238 $\pm$ 10
pc. Specially interesting is the double line nature of HeI 5875; two absorption
components move in anti-phase during the orbital cycle; they can be associated
with the shock regions revealed by the photometry. The radial velocity of one
of the HeI 5875 components closely follows the donor radial velocity,
suggesting that the line is formed in a wind emerging near the stream-disc
interacting region.
