JBL Bi-Radial Studio Monitors 4430 & 4435 (1981)
At JBL, we’ve been investigating the relationship between on and off axis frequency response for several years. The result is a new generation of studio monitors that provide falte response over an exceptionally wide range of horizontal and vertical angles. The sweet-spot and its traditional restrictions are essentially eliminated.
Link for PDF: JBL Bi-Radial Studio Monitors 4430 & 4435 (1981)
https://aboutprosound.com/wp-content/uploads/2022/09/JBL-4430-4435-Biradial-Studio-Monitors-1981.pdf