Also called a horn. A tube of varying cross section having different terminal areas, which change the acoustic impedance to control the directivity of the sound pattern.
"I just wanted to let you know that I received the restoration of my Doc Severinson album, "Tempestuous Trumpet", and I am thrilled with the quality. What a great job you did!!! This album was from the 1960s. I haven't listened to it in years because I no longer have a record player, and it was never released on CD. I can't stop playing it. It ..."