HypSpace Wood Sound Diffuser-24×24×2.8 Inches Triangle Design Acoustic Wall and Ceiling Panel for Music Studio Theater (Triangle) : Amazon.ca: Musical Instruments, Stage & Studio
How to Make a DIY Sound Diffuser (step by step) - Soundproof Expert
Making A Quadratic Diffuser From Plywood - Acoustics - YouTube
Sound Diffusers 101: Free Designs for DIY Diffuser Panels