Granted Patent
Utility
US 4,325,456 · App. 06/196,074
Acoustical transformer for compression-type loudspeaker with an annular diaphragm
Inventor:
Mark Ureda
Patented Case
View Patent ↗
Granted: Apr 20, 1982
Filed: Oct 10, 1980
Inventor
Mark Ureda
Assignee (at issue)
Altec, Inc.
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.