A diffuser assembly comprising: a flexible diffuser membrane defining a perimeter edge bead along four edges, the flexible diffuser membrane being rectangular in plan view; a diffuser body defining: an underlying body portion underlying the flexible diffuser membrane; a perimeter edge frame covering a covered portion of the perimeter edge bead such that the flexible diffuser membrane is retained to the diffuser body and an airtight seal is created therebetween; an opening underlying a region of the flexible diffuser membrane; wherein the perimeter edge frame defines an inside surface that conforms to an outside shape of the covered portion of the perimeter edge bead; wherein the perimeter edge frame is integral to the underlying body portion; characterized in that the diffuser body further defines: a receiving portion at a proximate end of the diffuser body and defining: a hollow-cylindrical straight-walled sub-portion; and a hollow-cylindrical internally-threaded sub-portion at a terminus of the hollow-cylindrical straight-walled sub-portion; an internal vertical tube in gaseous communication with the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion and running transverse to these sub-portions, the internal vertical tube terminating in the opening so that the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion are in gaseous communication with the opening; and a plug at a bottom of the internal vertical tube opposite the opening; wherein the perimeter edge frame defines a plurality of slots therein, each of the plurality of slots exposing a respective outside surface portion of the perimeter edge bead; and wherein the underlying body portion defines an arc having curvature transverse to a longitudinal axis of the underlying body portion. a flexible diffuser membrane defining a perimeter edge bead along four edges, the flexible diffuser membrane being rectangular in plan view; a diffuser body defining: an underlying body portion underlying the flexible diffuser membrane; a perimeter edge frame covering a covered portion of the perimeter edge bead such that the flexible diffuser membrane is retained to the diffuser body and an airtight seal is created therebetween; an opening underlying a region of the flexible diffuser membrane; an underlying body portion underlying the flexible diffuser membrane; a perimeter edge frame covering a covered portion of the perimeter edge bead such that the flexible diffuser membrane is retained to the diffuser body and an airtight seal is created therebetween; an opening underlying a region of the flexible diffuser membrane; wherein the perimeter edge frame defines an inside surface that conforms to an outside shape of the covered portion of the perimeter edge bead; wherein the perimeter edge frame is integral to the underlying body portion; characterized in that the diffuser body further defines: a receiving portion at a proximate end of the diffuser body and defining: a hollow-cylindrical straight-walled sub-portion; and a hollow-cylindrical internally-threaded sub-portion at a terminus of the hollow-cylindrical straight-walled sub-portion; an internal vertical tube in gaseous communication with the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion and running transverse to these sub-portions, the internal vertical tube terminating in the opening so that the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion are in gaseous communication with the opening; and a plug at a bottom of the internal vertical tube opposite the opening; a hollow-cylindrical straight-walled sub-portion; and a hollow-cylindrical internally-threaded sub-portion at a terminus of the hollow-cylindrical straight-walled sub-portion; an internal vertical tube in gaseous communication with the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion and running transverse to these sub-portions, the internal vertical tube terminating in the opening so that the hollow-cylindrical straight-walled sub-portion and the hollow-cylindrical internally-threaded sub-portion are in gaseous communication with the opening; and a plug at a bottom of the internal vertical tube opposite the opening; wherein the perimeter edge frame defines a plurality of slots therein, each of the plurality of slots exposing a respective outside surface portion of the perimeter edge bead; and wherein the underlying body portion defines an arc having curvature transverse to a longitudinal axis of the underlying body portion.