This paper concerns implicit large eddy simulations of subsonic flows through a symmetric suddenly expanded channel. We aim at shedding light on the flow physics at a relatively high Reynolds number of 10 000, based on the inlet bulk velocity and the step height of the channel, and examine the compressibility effects for two Mach numbers, Ma = 0.1 and Ma = 0.5. Comparisons with experimental measurements are provided. In addition, we investigate the structure of the separated regions, turbulence structures - through the Reynolds stress anisotropy componentality - and turbulence kinetic energy budgets. The results reveal that compressibility influences particular flow physics.