Alley may be paved, or unpaved, and a blind alley is a cul-de-sac. Modern urban developments may also provide a service road to allow for waste collection, or rear access for fire engines and parking. Because of geography, steps (stairs) are the predominant form of alley in hilly cities and towns. This includes Quebec City in Canada and in the United States Pittsburgh (see Steps of Pittsburgh), Cincinnati (see Steps of Cincinnati), Minneapolis, Seattle, and San Francisco as well as Hong Kong, Genoa and Rome. Some alleys are roofed because they are within buildings, such as the traboules of Lyon, or
Power Alley Power Alley Power Alley is a term used in audio engineering to denote the line between subwoofers where output from each subwoofer is in phase and is noticeably louder. Subwoofers placed at each side of the stage will typically cancel unpredictably everywhere in the listening area except along the center line between the speakers. Because of this, placing subwoofer cabinets together tends to give a smoother response to each member of the audience. This is explained in detail in "The Power Alley ". Centering the subwoofers between the high end cabinets tends to minimize the timing error throughout the listening