This chapter deals with some absorbers and diffusers that do not easily fit into categories but are nevertheless important to airborne acoustics. The first subject is seating and audience absorption. In many auditoria, the audience form the main absorption in the room, and consequently, being able to correctly measure and predict the absorption coefficient of the audience area is very important. The second subject is how to make efficient absorbers from Schroeder diffusers (phase grating devices). Researchers started by looking into why the absorption from badly constructed Schroeder diffusers could be large, and ended up inventing a new style of absorber.