  The generalized defect D(U) of a unitary NxN matrix U with no zero entries is
the dimension of the real space of directions, moving into which from U we do
not disturb the moduli |U_ij| as well as the Gram matrix U'*U in the first
order. Then the defect d(U) is equal to D(U) - (2N-1), that is the generalized
defect diminished by the dimension of the manifold {Dr*U*Dc : Dr,Dc unitary
diagonal}. Calculation of d(U) involves calculating the dimension of the space
in R^(N^2) spanned by a certain set of vectors associated with U. We split this
space into a direct sum, assuming that U is a Kronecker product of unitary
matrices, thus making it easier to perform calculations numerically. Basing on
this, we give a lower bound on D(U) (equivalently d(U)), supposing it is
achieved for most unitaries with a fixed Kronecker product structure. Also
supermultiplicativity of D(U) with respect to Kronecker subproducts of U is
shown.
