Since 1989 Josephson Engineering has provided specialized microphones for acoustic instrumentation, studio, stage and field recording to critical users worldwide. In recent years, several other microphone companies have learned of our capabilities, and have contracted with us to supply them with custom made microphones and microphone capsules under their own brand. Two of the more critical of these are Manley Laboratories, for whom we make a dual large diaphragm capsule for their Gold Reference mics, and Groove Tubes, for whom we manufactured both the Series 2 and Series 3 microphone capsules until they became part of Alesis. We also make and have supplied instrumentation microphones to Meyer Sound and their customers for use with the SIM-II acoustic measurement system, Crown/Techron for use with their TEF analyzers, and SysID Labs for use with the acoustic measurement system developed by Bell Laboratories. Over the years we have also developed microphone elements and arrays for a wide variety of consumer and industrial products and government systems.
A wide variety of standard, semi-custom and custom microphone capsules based on DC polarized air condenser technology, and complete microphones are available from Josephson. Our proprietary diaphragm conditioning technology allows for many different combinations of frequency response, polar patterns and output level to be realized without some of the limitations of earlier designs. Old designs can also be reproduced faithfully or incorporated to meet new requirements.
Research and Development Facilities
Josephson Engineering is located in Santa Cruz, California, just west of the "Silicon Valley" town of San Jose where it was founded in 1989. In the Josephson shop, there are complete design and modeling facilities for the evaluation of capsule and electronic designs. Two main test setups are in daily operation; one is a computer controlled synchronous dual FFT analyzer based on proprietary software, the Ariel Labs DSP-16 system and Bell Labs' SysID analysis program. A range of instrumentation standard microphones from 1/8 to 1 inch diameter are used for references. This setup can be moved into the larger space or outdoors for low frequency testing. The other test setup is based on an Eckel anechoic chamber of 15 cubic meters volume, which is effective from about 200 Hz upward. Two Brüel & Kjaer automatic frequency response recorders, one functional to 20 kHz and the other to 200 kHz, are driven by reference mics in the chamber. A B&K polar plotting turntable and ancillary amplifiers and signal processing equipment are used for directional measurements. The automatic response recorders also support electrostatic calibration of the reference microphones to assure consistency between NIST-traceable checks of those mics done by an outside facility.
The machine shop includes a wide assortment of hand and machine tools including a lathe, milling machines, saws, grinders, presses and measurement equipment. Much of the specialized prototype equipment is built on tooling that was made in-house. Several computers are used to assist design, test and calibration processes. Mechanical design of all parts is controlled using an electronic archive of Autocad drawings, while circuits are drawn and circuit boards laid out using the Orcad system.
Subcontractors for Production
Josephson Engineering has immediate access to some of the most qualified precision machine shops, circuit board fabricators and assembly contractors in the world. The accuracy requirements for microphone manufacture are quite familiar to these companies which have been working in aerospace, semiconductor, microwave and magnetic memory system fabrication for the past 75 years in this area. Competition between shops is often on the basis of performance and precision, exceeding customer requirements, rather than on price, which is fairly uniform for similar work. This allows us to pick the most suitable contractor for the manufacture of each part. Most of these contractors are within a few km of the research and test lab, but others may be thousands of km away. We're constantly reviewing the technologies we use -- for instance, for many years the most qualified lab for vacuum metallization of polymer material was in Europe, so we worked with them to produce much of the raw material for our gold metallized polymer diaphragms, but in the past ten years we've had better results with an American supplier to the aerospace industry who can more precisely meet our requirements. The best low-noise field effect transistors are made for us by one company in Japan.
Advanced Technology Key to Design Flexibility
Years of research were put into the process that became the Josephson Engineering microphone diaphragm technique before it was made commercially available. Key to this approach is our ability to control stiffness (compliance) and tension of the diaphragm separately and independently. In conventional metal and plastic diaphragm microphones, one of those parameters usually determines the other. Many early attempts brought to market by other companies have been less than successful due to migration of the polymer chains in the tensioned film structure, resulting in reduced diaphragm tension, changes in output level and frequency response, and eventual failure of the microphone element. Original capsules using Josephson diaphragm technology have been returned to the lab for testing after 20 years in regular field use. They have shown only minor changes in response, if in fact there were any changes at all. >
Some old processes however cannot be improved upon very much. The precision assembly of backplate and its surrounding insulators is still lapped either by hand and with a precision optical lapping machine using a proprietary abrasive slurry. This allows manufacturing and environmental variations to be removed before the completed microphone capsule is assembled.
Open to New Ideas
Many traditional microphone makers have convinced themselves (and many of their customers) that they can define the one correct approach to any given microphone application. It's hard to maintain this point of view, when one considers the many varieties of sounds and musical preferences that exist. Microphones might be thought of as tools for performance, like musical instruments or artists' brushes. Since the electro-acoustical reproduction process is still based on capturing variations in pressure and pressure gradient at a few discrete places, rather than the recreation of an entire ambient sound field (which seems to be impossible at the moment), we accept the belief that accuracy is in the ear of the listener. Instead of trying to bring laboratory analysis to the concert hall or living room, we prefer to think instead of the possibility that the aural scene is invoked fluently to the listener; this may require precisely accurate pressure transducers with frequency response flat within tenths of a decibel, to frequencies far beyond conventional hearing, or it may require different pickups of gradient and time domain behavior that aren't so simple to capture. We concentrate on mastery of the design and manufacture of complete microphones and microphone elements to meet the preferences of the listener, and we're always open to new ideas on how best to do that. Some of these developments are well protected in the finished microphones as trade secrets and several others are now the subject of US patent applications. The Josephson OEM microphone program is designed to lend our expertise to your product, so that you can use our technology to address the needs of critical listeners in your market.
Partial Listing of Research/Development and Production Equipment