Auralex - 4 Inch Studiofoam Wedge- Purple
4" Studiofoam Wedges are recommended for rooms with pronounced low frequency problems or where sonic accuracy is mandatory and maximum acoustic absorption is required (e.g. voiceover or drum booths, forensic audio labs and mastering rooms). 4" Studiofoam Wedges provide 3x the low-end control of 2" and can effectively tame even the worst sonic anomalies. In some instances, using 4" acoustic Studiofoam can lessen the need for significant dedicated bass trapping.
