  We reconsider the Kaluza Klein compactifications of D=11 supergravity on
AdS_4x(G/H)_7 manifolds that were classified in the eighties, in the modern
perspective of AdS_4/CFT_3 correspondence. We focus on one of the three N=2
cases: (G/H)_7=M^{111}=SU(3)xSU(2)xU(1)/SU(2)xU(1)'xU(1)''. Relying on the
systematic use of the harmonic analysis techniques developed in the eighties by
one of us (P. Fre') with R. D'Auria, we derive the complete spectrum of long,
short and massless Osp(2|4)xSU(3)xSU(2) unitary irreducible representations
obtained in this compactification. Our result also provides a general scheme
for the other N=2 compactifications. Furthermore, it is a necessary comparison
term in the AdS_4/CFT_3 correspondence: the complete AdS/CFT match of the
spectra that we obtain will provide a much more stringent proof of the AdS/CFT
correspondence than in the S^7 case, since the structure of the superconformal
field theory on the M2-brane world volume must be such as to reproduce, at the
level of composite operators, the flavor group representations, the conformal
dimensions and the hypercharges that we obtain in the present article. The
investigation of the match is left to future publications. Here we provide an
exhaustive construction of the Kaluza Klein side of our spectroscopy.
