Abstract: The duct connector of the present invention preferably has a rectangular inlet and a round outlet. An intermediate passage is located between the rectangular inlet and the round outlet. Preferably, the intermediate passage provides a smooth transition that is substantially free from steps, sharp corners, breaks or facets, and acts to smoothly funnel airflow from the rectangular inlet to the round outlet. The intermediate passage preferably includes transitional surfaces that connect adjacent walls of the duct. Each transitional surface preferably provides a single smooth continuously curved surface connecting a side wall and an adjacent end wall along the intermediate passage. The smooth transition of the intermediate passage and the use of transitional surfaces as just described reduces turbulence and noise within the duct connector and results in greater fan or blower efficiency.

Abstract: The duct connector of the present invention preferably has a rectangular inlet and a round outlet. An intermediate passage is located between the rectangular inlet and the round outlet. Preferably, the intermediate passage provides a smooth transition that is substantially free from steps, sharp corners, breaks or facets, and acts to smoothly funnel airflow from the rectangular inlet to the round outlet. The intermediate passage preferably includes transitional surfaces that connect adjacent walls of the duct. Each transitional surface preferably provides a single smooth continuously curved surface connecting a side wall and an adjacent end wall along the intermediate passage. The smooth transition of the intermediate passage and the use of transitional surfaces as just described reduces turbulence and noise within the duct connector and results in greater fan or blower efficiency.