  We compute the mass spectrum of glueball excitations of a special class of
strongly-coupled field theories via their type-IIB supergravity dual. We focus
on two subclasses of backgrounds, which have different UV-asymptotics, but both
of which exhibit walking behavior, in the weak sense that the gauge coupling of
the dual field theory exhibits a quasi-constant behavior at strong coupling
over a range of energies, before diverging in the deep IR. We improve on
earlier calculations, by making use of the fully rigorous treatment of the
5-dimensional consistent truncation, including the rigorous form of the
boundary conditions. In both cases there is a parametrically light scalar
glueball. In the first case, this is a physical state, while in the second case
this result is unphysical, since the presence of higher-order operators in the
dual field theory makes the whole (physical) spectrum depend explicitly on a
(unphysical) UV-cutoff scale.
