In 1939, Decker was killed in an airplane crash. The company soon began having financial troubles. In 1941, Lansing Manufacturing Company was bought by Altec Service Corporation, after which the name changed to

In 1946, JBL produced their first products, the model D101 15-inch loudspeaker and the model D175 high-frequency driver. The D175 remained in the JBL catalog through the 1970s. Both of these were near-copies of Altec Lansing products. The first original product was the D130, a 15-inch transducer for which a variant remained in production for the next 55 years. The D130 featured a 4-inch (100ámm) flat ribbon wireávoice coiláandáAlnicoáV magnet. Two other products were the 12-inch (300ámm) D131 and the 8-inch (200ámm) D208 cone drivers.

TheáMarquardt Corporationágave the company early manufacturing space and a modest investment. William H. Thomas, the treasurer of Marquardt Corporation, represented Marquardt on Lansing's board of directors. In 1948, Marquardt took over the operation of JBL. In 1949, Marquardt was purchased by General Tire Company. The new company, not interested in the loudspeaker business, severed ties with Lansing. Lansing was reincorporated as James B. Lansing and moved the newly formed company to its first private location, on 2439 Fletcher Drive, Los Angeles.

A key to JBL's early development was Lansing's close business relationship with its primary supplier of Alnico V magnetic material, Robert Arnold of Arnold Engineering. Arnold saw JBL as an opportunity to sell Alnico V magnetic materials into a new market.

Lansing was noted as an innovative engineer but a poor businessman. Decker, his business partner, had died in 1939 in an airplane crash. In the late 1940s, Lansing struggled to pay invoices and ship products. Possibly as a result of deteriorating business conditions and personal issues, he committed suicide on September 4, 1949. The company then passed into the hands of Bill Thomas, JBL's vice president. Lansing had taken out aáUS$10,000álife insurance policy, naming the company as the beneficiary, a decision that allowed Thomas to continue the company after Lansing's death. Soon after, Thomas purchased Mrs. Lansing's one-third interest in the company and became the sole owner. Thomas is credited with revitalizing the company and spearheading a period of strong growth for the two decades following the founding of JBL.[3]

Early products included the model 375 high-frequency driver and the 075 ultra-high frequency (UHF) ring-radiator driver. The ring-radiator drivers are also known as because of their distinctive shape. The 375 was a re-invention of the Western Electric 594 driver but with an Alnico V magnet and a four-inch voice coil. The 375 shared the same basic magnet structure as the D-130 woofer. JBL engineers Ed May andáBart N. Locanthiácreated these designs. Two products from that era, the Hartsfield and theáParagon, continue to be highly desired on the collectors' market. The JBL 4320 series studio monitor was introduced through Capitol Records in Hollywood and became the standard monitor worldwide for its parent company, EMI. JBL's introduction to rock and roll music came via the adoption of the D130 loudspeaker