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Public access to copy of this document is provided on the website of Cornell Law School at http://www4.law.cornell.edu/uscode/17/107.html and is here reproduced below: Sec. 107. - Limitations on exclusive rights: Fair Use Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, includ- ing such use by reproduction in copies or phono records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for class- room use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include: 1 - the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes; 2 - the nature of the copyrighted work; 3 - the amount and substantiality of the portion used in relation to the copy- righted work as a whole; and 4 - the effect of the use upon the potential market for or value of the copy- righted work. The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors ♦ PDF Cover Page ♦ ♦ Verso Filler Page ♦ Mic Memo Welcome! This CD holds 22 years of Mic Memo issues — a tremendous database of applications and information on Crown microphones — within a searchable Adobe® Acrobat® pdf file format. Whatever your question, needs, or application, you should be able to find useful tips on this CD. PZM® pioneer Ken Wahrenbrock was the first editor of the PZM Memo, which later became the Crown Mic Memo as Crown developed a full line of microphones. Ken has since passed on. We deeply appreciate his enthusiasm for PZM mics, his willingness to share his knowledge, and his warm spirit. The Mic Memo issues on this CD are arranged in chronological order. To search for a particular topic in this document, use Acrobat Reader’s FIND function. Select the binoculars icon and enter the word or words you are searching for. Turn OFF “Match Case”. Want to know more about stereo applications? Do a search for “stereo”. Click the binoculars "Find again" icon until you find all the places that the word “stereo” was mentioned. Are you interested in applications for the GLM-100? Search for “GLM” or “GLM-100”. All the app notes for this microphone will appear, one at a time. Most of the illustrations in this document were scanned from the published newsletters. They will appear sharper in printouts than they do on screen. I hope you find this compilation an invaluable tool. Bruce Bartlett Mic Memo Editor Layout: Marie Turnock ©2002 Crown Audio, Inc., P.O. Box 1000, Elkhart, Indiana 46515-1000 U.S.A. All rights reserved. Made and printed in the U.S.A. Trademark Notice: Crown, Differoid, PCC, Phase Coherent Cardioid, Pressure Zone Microphone, PZM, and SASS are registered trademarks of Crown International. Other trademarks are the property of their respective owners. Pressure Recording Process and PRP are trademarks of E.M. Long Associates. USING “22 Years of the Crown Mic Memo” Included Software: This CD contains installation software for the latest versions of Adobe Acrobat Reader for Windows and Mac operating systems. Adobe Acrobat Reader is required to access the Mic Memo archive file (in .pdf format) included on this CD. CD Requirements: This CD has been optimized to run in a Windows 32-bit or Mac operating environment with Adobe Acrobat Reader 3.0+ software installed on the local system. THE DOCUMENTS PROVIDED ON THIS CD ARE FOR INFORMATIONAL PURPOSES ONLY. The information contained here represents the view of Crown International on the issues discussed as of the date of publication. Because Crown must respond to change in market conditions, it should not be interpreted to be a commitment on the part of Crown and Crown cannot guarantee the accuracy of any information presented after the date of publication. INFORMATION PROVIDED ON THIS CD IS PROVIDED ‘AS IS’ WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND FREEDOM FROM INFRINGMENT. The user assumes the entire risk as to the accuracy and the use of these documents. These documents may be copied and distributed subject to the following conditions: 1. Each document must be copied without modification and all pages must be included 2. All copies must contain Crown’s copyright notice and any other notices provided therein 3. These documents may not be distributed for profit. Acrobat® Reader: ©1987-2002, Adobe Systems Incorporated. All rights reserved. Adobe and Acrobat are trademarks of Adobe Systems, Inc. First issue, circa summer 1978 Syn-Aud-Con Newsletter DEVELOPMENT OF THE PZM Fig. 1. Prototype built in May 1978 showing a close-up of the capsule mounting Ken Wahrenbrock, a Syn-Aud-Con graduate and a very alert audio investigator, conceived of and built a prototype of the Pressure Zone Microphone, PZM. He used as his model the drawing shown in Tech Topic Vol 5, # 7, and a sub-miniature electret in a configuration that combined complete acoustic integrity with a rugged, practical mounting that allowed extremely versatile placement of the units. During the past year PZM systems have achieved a remarkable acceptance among leading profes- sional audio engineers and members of the entertainment industry. When a microphone receives a rave review by a serious music critic you can be sure it is different. Fig. 2. Pressure Response technique (PRP) Microphone. Drawing from the Syn-Aud-Con Tech Topic The model built by Syn-Aud-Con used an expensive dial vernier adjustment. Wahrenbrock’s prototype used an inexpensive screw. At that time we didn’t know what spacing of the diaphragm from the surface would be ideal. WHY NOT USE FLUSH MOUNTING OF THE MICPOPHONE? A pressure calibrated microphone when flush mounted has its on-axis response essentially in a free field. A sound is said to be in a free field if it is uniform, away from boundaries, and is undisturbed by other sources of sound. A pressure calibrated microphone in a free field has a pronounced rise in its amplitude response at high frequencies because of the undamped resonance of its diaphragm. Fig. 3. Top: Free-field mic response. Bottom: Pressure-response mic response. When placed in a cavity, for example, (a cavity is a pressure sound field) the response becomes uniform with frequency. If a pressure calibrated microphone is flush mounted, then its on-axis re- sponse will not exhibit the high frequency peak noted here. In the PZM system no signal can ever arrive on-axis but can only enter at the sides of the opening between the microphone’s diaphragm and the metal plate. This means that not only does the PZM maintain a “flat” response but that it does so for all angles of incidence in the hemisphere surrounding it. HOW CAN A MICROPHONE SO INEXPENSIVE SOUND SO MUCH CLEANER THAN MICROPHONES LITERALLY 10 TIMES ITS COST? Because all conventional microphones, no matter how skillfully made, no matter how esoteric the materials they are made from, contain a severe acoustic handicap. They receive both direct and reflected sound [actually, they receive direct and reflected sounds at different times.] The PZM always sees the pressure field at the surface of the boundary which is totally free of the anomolies caused by the phase cancellation of direct with reflected sound. Fig. 4. Top: PZM response on a surface. Bottom: Conventional mic response near a surface. PZM: A FUNDAMENTAL ADVANCE IN THE SCIENCE AND ART OF MICROPHONY The 1980s will witness the widespread use of the first really fundamental advance in microphony in fifty years. The tremendous innovations of Wente, Thuras, Olsen, Bauer and others in the late Twen- ties and early Thirties are the basis of every conventional microphone on the market today. Veneklausen’s concept of the “flush-mounted” microphone for stage use, circa the late Sixties, led to a proliferation of useful mounting devices by Shure, EV, and others. Fig. 5. Early PZM model by Ken Wahrenbrock. THE PRP BREAKTHROUGH Ed Long and Ron Wickersham, in studying the behavior of flush-mounted microphones, uncovered a basic error in our thinking. Within a few millimeters of a large surface, sound levels from a pair of equal level signals add coherently because, in close proximity to the surface, the particles are still in phase as they accelerate after being brought to a stop by the boundary.