  Bessel multipliers are operators defined from two Bessel sequences of
elements of a Hilbert space and a complex sequence, and have frame multipliers
as particular cases. In this paper an estimate of the spectral radius of a
Bessel multiplier is provided involving the cross Gram operator of the two
sequences. As an upshot, it is possible to individuate some regions of the
complex plane where the spectrum of a multiplier of dual frames is contained.
