User manual AEA COLES 4038 STUDIO RIBBON MICROPHONE

[. . . ] Allen Avenue, Pasadena, CA 91104 Phone: (626) 798-9128 / Fax: (626) 798-2378 E-mail: stereoms@compuserve. com COLES 4038 STUDIO RIBBON MICROPHONE USERÕS GUIDE By Ron Streicher and Wes Dooley QUICK START I F YOU CAN'T WAIT TO USE YOUR NEW COLES 4038, PLEASE READ THESE PRECAUTIONS FIRST SO YOU DON'T ACCIDENTALLY TRASH YOUR NEW TOY. 1 . KEEP YOUR 4038 COVERED BY THE SUPPLIED PLASTIC BAG WHEN NOT ACTUALLY BEING USED. THIS KEEPS THE STRONG MAGNET INSIDE THE 4038 FROM ATTRACTING "TRAMP" IRON PARTICLES WHICH POLLUTE THE INSIDE OF THE MIC. THIS ALSO PROTECTS THE VERY THIN (. 6 micron) AND FAST ALUMINUM RIBBON INSIDE THE 4038 FROM BEING STRETCHED IF THE MIC CASE LID SNAPS SHUT OR IF THE MIC'S STAND IS MOVED TOO QUICKLY ACROSS THE STUDIO. [. . . ] Thus it is a good idea to watch polarity in microphones, cables, electronics and speakers. ). As the sound source moves from the central axis, the differential pressure Coles 4038 UserÕs Guide November, 1997 © Page 6 on the ribbon decreases, as will the electrical output. Thus it is easy to understand why a well designed bi-directional microphone has almost no output from sounds arriving from an angle of 90¡ off-axis: these sound waves strike the ribbon edgewise and exert equal pressure on both the front and rear surfaces of the diaphragm. The result is that there is no difference in the pressure exerted on the two surfaces of the ribbon; hence there is no motion, and no output signal is generated. The term velocity or pressure gradient is often used when describing ribbon microphones, because as noted above, as a sound wave passes the ribbon, minute differences in air pressure are created between the front and rear surfaces of this diaphragm. The classic ribbon microphones were the first to have a directional pattern, what we call a figure-of-eight or bidirectional polar response pattern. Earlier microphones were omnidirectional pressure microphones and responded only to the variations in the absolute air pressure of a sound wave without any particular regard to the sound's direction or distance of origin. Ribbon (velocity or pressure gradient) microphones have a well defined figure-of-eight directional pattern and their bass frequency response varies depending on whether the sound source is near or far. This bass boost proximity effect is characteristic of all directional mics. DESIGN OF THE COLES 4038 MICROPHONE ÒThe BBC-Marconi Type A microphone, believed to be the first of this type to be manufactured in Great Britain, was produced in 1934 É The performance of this microphone is still good, even by modern standards, but the instrument is bulky and there has long been a demand É for a smaller version giving an equal or better performance. Ó With these criteria as the goal, the engineering division of the BBC went about designing a new microphone to meet the growing demands of their FM radio and television production departments. The end result was the BBCÕs model PGS bi-directional ribbon microphone. But along the way, the additional problems of extended frequency response, ribbon fragility, and susceptibility to wind noise, were carefully addressed. The 4038 is first mentioned in print in December of 1955 in the excellent BBC monograph by D. The 4038 has a smooth response from 30 Hz to above 15 KHz, exhibiting an ideal 6 dB per octave roll-off at high frequencies. A symmetrical polar response in the vertical direction was achieved through the unique shape of the microphone housing which is designed to function as an acoustic lens. Its Coles 4038 UserÕs Guide November, 1997 © Page 7 standard electrical output impedance of 300 ohms remains nearly constant throughout the audio passband. Special attention was paid to reducing hum pickup through the use of a shielded toroidal output transformer and starquad style wiring around the ribbon itself. The 4038's ribbon diaphragm has a very low mass and high internal damping, so transient response is exceptional. The ribbon is made of a special beaten aluminum and is about one third the thickness of ribbons used in the RCA 44s and 77s. The BBC PGS and STC 4038 design team developed a ribbon corrugation pattern that did not quickly lose it's tension. In constructing the 4038, particular attention was given to special internal protection for the ribbon which greatly reduces its susceptibility to damage from either mechanical shock or excessive wind velocity Ñ problems to which earlier ribbon microphones such as the RCA 44 were particularly vulnerable. The practical benefit for 4038 users is that they rarely have to re-ribbon the mics unless damaged by external forces. ÒCARE and FEEDINGÓ of RIBBON MICROPHONES Although the Coles 4038 has been designed to withstand the normal rigors of the recording studio, as with any precision device certain precautions should be taken when handling and using it. The first (and this should be the most obvious but, alas, is not) is that the microphoneÕs greatest enemy is a strong air current. [. . . ] This warranty is transferable but you must retain the original invoice for proof of purchase. Damage resulting from modification, unauthorized service, repair, or abuse is not covered by this warranty. AEA shall be the sole determinant of what constitutes Òabuse. Ó (Exposure to rough handling, wind, excessive low frequency SPL, moisture or liquids, and microphone power such as phantom or "T" are some examples of abuse. ) Coles 4038 UserÕs Guide November, 1997 © Page 11 SPECIFICATIONS of the COLES 4038 P o l a r r e s p o n s e : Bi-directional (cosine, figure-of-eight) I m p e d a n c e : 300-ohm is standard; also 30-ohm by special order F r e q u e n c y r e s p o n s e : 30 Hz to 15, 000 Hz (see spec. sheet curve) S e n s i t i v i t y :-65dB re: 1 Volt/dyne/cm2 D i s t o r t i o n : Inversely related to frequency. [. . . ]