  The open critical XXZ spin chain with a general right boundary and a trivial
diagonal left boundary is considered. Within this framework we propose a simple
computation of the exact generic boundary S-matrix (with diagonal and
non-diagonal entries), starting from the `bare' Bethe ansatz equations. Our
results coincide with the ones obtained by Ghoshal and Zamolodchikov, after
assuming suitable identifications of the bulk and boundary parameters.
