Modern immersive sound audio systems manufacturers promote their products via showrooms, where customers can experience features of an audio system, its sound quality and technical possibilities. These showrooms require low reverberation time, similar to surround audio mixing rooms. The problem arises, when showrooms must be fitted in existing premises, especially if these are industrial gentrified premises, which is a common trend in Europe. Industrial premises, like production halls and storage rooms, are made using hard reflective materials – concrete, steel and brick. To fit room acoustics for showrooms function, in most cases extensive acoustical treatment is needed. This paper shows a practical case of acoustical treatment for L-acoustics L-ISA system showroom in Riga, Latvia. First, measurement results are presented for the untreated room, showing average T30 around 1.5 seconds. Next, acoustical design is shown, with emphasis on low frequency scattering and absorbing wall panels for bass control, based on Odeon modelling. Finally, post-treatment measurement results are presented, with T30 around 0.55 seconds, and conclusions are made about acoustical modelling techniques precision. Practical challenges and uncertainties due to various impact factors are addressed and discussed.