The phrase "wider soundstage" refers to the perception of audio coming from different directions. It means that the sound feels like it is coming from a broader and more spacious area, rather than a confined space. Full definition
Not only did they provide pristine, detailed high frequencies, they also helped to generate a seamless and exceptionally wide soundstage with outstanding imaging properties. (digitaltrends.com)
I was surprised to find that I could discern no difference between the sound produced by the v3 Prism and that from the well - respected wide soundstage of the AKG 240. (tomsguide.com)
Taken from the film's original monaural stems, the mix attempted a pretty wide soundstage. (dvdmg.com)