Modal analysis has been used in modeling of a large number of physical systems such as beams, plates, acoustic enclosures, strings, etc. These models are often simplified by truncating higher frequency terms that lie out of the bandwidth of interest. Truncation can introduce a large error. This paper suggests a method of minimizing the effect of truncated modes on spatial low-frequency dynamics of the system by adding a spatial zero frequency term to the truncated model. The feed-through term is found such that the spatial H-x norm of the error system is minimized.