The Architectural Speaker Tuning System is a sand-filled plastic reinforcing sub-baffle for an architectural custom installed loudspeaker mounted in drywall paneling. The mechanical acoustical resonance of the drywall distorts the sound of the custom loudspeaker. The speaker tuning system shifts drywall resonance to a more suitable frequency. The sand-tuned result revives the fidelity of the loudspeaker. The sub-baffle shipped empty, filled with sand provided by the installer, installs through the loudspeaker drywall panel cut-put, and adheres to the rear of the drywall. The custom loudspeaker is then inserted and clamped to the sub-baffle system.