  The large N limit of mean spectral density for the ensemble of NxN
sub-unitary matrices derived by Wei and Fyodorov (J. Phys. A: Math. Theor. 41
(2008) 50201) is calculated by a modification of the saddle point method. It is
shown that the result coincides with the one obtained within the free
probability theory by Haagerup and Larsen (J. Funct. Anal. 176 (2000) 331).
