  The energy budget of cosmological first-order phase transition is essential
for the gravitational wave spectra. Most of the previous studies are based on
the bag model with same sound velocity in the symmetric and broken phase. We
study the energy budget and the corresponding gravitational wave spectra beyond
the bag model, where the sound velocities could be different in the symmetric
and broken phase. Taking the Higgs sextic effective model as a representative
model, we calculate the sound velocities in different phase, the gravitational
wave spectra and the signal-to-noise ratio for different combinations of phase
transition parameters beyond the bag model. We compare these new results with
the ones obtained from the bag model.The proper sound velocities and phase
transition parameters at the appropriate temperature are important to obtain
more precise predictions.
