User manual AEA AEA LD2020 WINKIE-BLINKIE STEREO SCOPE

Audio Engineering Associates · STUDIO RIBBON MICS · PHASE DISPLAYS · M/S STEREO · TALL STANDS · MIC POSITIONERS "Tools to make Great Recordings Easier" AEA LD 2020 "Winkie Blinkie" Stereo Scope User Guide What is Stereo? How do you monitor the "stereoness" of your program signal? This has been pondered by audio engineers since the pioneering days of stereo in the 1930's. At the heart of this question lies another: What exactly is stereo? Surely it is more than just two channels of audio... The word stereophonics was derived by combining two Greek words: stereo, which means solid, and implicates three spatial dimensions (depth, breadth, and height), and phonics, which means the science of sound."1 Thus, stereo as we know it, is a sonic illusion representing three-dimensional space. While in current practice stereo is generated and conveyed to the listener via two signals, it is the technical nature of these two signals (or channels) which defines the sonic image. The human hearing process relies on two fundamental criteria for spatial recognition: intensity and phase. The brain interprets the minute differences in intensity and phase (i.e. time of arrival) of a sound as it reaches each of our two ears, and uses these differences to determine the direction and distance of the source of the sound. To make successful stereo, it is necessary to capture, preserve, and reproduce these significant differences. There are many techniques employed by recording engineers to create stereophonic illusions, and there are numerous texts where the interested reader can find articles detailing these methods. "Accurate stereo imaging is the foundation for the art of stereo recording. Experience with the basic techniques and knowledge of their attributes are essential for anyone working in stereo formats. The art of recording lies in manipulating illusions. The science of recording involves the tools and techniques used to create these illusions." 2 The LD 2020 Stereoscope from Audio Engineering Associates is a new and useful tool to aid the conscientious engineer in the pursuit of good stereo imaging. With its simple, easy to read display for monitoring intensity and phase, these two critical electrical fundamentals can be maintained in the proper relationships to provide a successful and pleasing sonic illusion. 1029 N. Allen Ave., Pasadena, CA 91104 www.wesdooley.com Phone: (626) 798-9128 Fax: (626) 798-2378 Stereo waveform display Given that stereo is comprised of two signals, each can be defined by a vector -- a line having magnitude and direction. Further, each of these signals represents an event in time which, as discussed above, has two properties: intensity and phase. An oscilloscope is a complex test instrument ideal to observe these, for it shows signals on two axes: intensity and time (another way of describing phase). The vertical axis of the display indicates intensity, and the horizontal axis, time. Most commonly, the waveform of the signal is shown on the 'scope screen. However, it can also be used to display the two channels of a stereo signal; by convention, the left channel is shown on the vertical axis and the right channel on the horizontal axis. [Refer to Figures-1a and b] When these two signals are equal and displayed together, the result is shown in Figure-1c; because the two channels are equal and in phase, this also is a classic monophonic signal. If the two signals are equal but 180° out-of-phase the result is shown in Figure-1d. This is another "classic" case, but is one to be avoided whenever possible, because if transmitted in mono, the signals will cancel each other, and no output will result. Because stereo involves sound signals in "real space" the elements of intensity and phase are generally not equal between the two channels: usually there will be some difference in one or both of these characteristics. Phase differences will appear as a divergence from the simple lines shown, for example Figure-1e, which shows still equal signals, but with a phase difference of 90° between them. Once the signal intensities also begin to differ, the display becomes more scrambled, and the familiar Lissajous figures result, as shown in Figures 1-f, g, and h. Note that the directional tendencies of these still bear a resemblance to the in-phase, out-of-phase, and random-phase displays shown earlier. By watching this stereo display, the engineer can easily and quickly "see" the characteristics of the sonic image: whether it is narrow or wide; in or out of phase; properly balanced or weighted to one side or the other. The AEA LD2020 Stereoscope As noted earlier, an oscilloscope is commonly used to display stereo signals. However, a 'scope is often too bulky, heavy, or expensive to be used conveniently in the production environment. Audio Engineering Associates has developed the LD 2020 Stereoscope to meet this need. This portable, battery-operable package, weighing in at less than one pound, is specifically designed to provide a visual monitor of stereo signals. With a minimum of controls and a 400 LED matrix display, it is easy to setup and use any time, anywhere. Two balanced 1/4" jacks and two Sensitivity controls receive the stereo signals. The pushbutton Battery/External power switch selects the powering option, and the L-R/PANorama pushbutton determines the display mode. That's all there is to it. To setup the display, first generate a monophonic signal at "normal" operating level on both channels of your signal source. Connect the outputs to the two inputs of the LD 2020 and turn the unit on. Use the Sensitivity controls to adjust the size of the display; for best results, these controls should be set about equally. You are now ready to begin monitoring stereo signals. In the L-R mode, the signals will be displayed as shown in Figure-1. However, for a more intuitive interpretation of the way stereo is heard, we have incorporated a PANorama mode. As can be seen in Figure-2, a Left-only signal slopes to the left, a Right-only signal slopes to the right, and a monophonic, in-phase signal is a vertical line. Because the stereo program follows these same directions, you have an instant and easy to understand view of your stereo program content. Placement of elements, channel balance, and control of width are obvious, and any out-of-phase problems immediately become evident. Once you have viewed your signal via the LD 2020's PANorama mode, you'll probably never want to go back to a regular 'scope display again. Specifications Inputs: Impedance: Sensitivity: Powering: Battery life: Dimensions: Weight: Supplied with: 1/4" balanced, TRS jacks >20K-ohms 120mV for full-scale deflection at maximum gain Internal 9V battery (Duracell MN-1604 or equivalent) External 6--15 VDC power supply, 50 mA Greater than eight hours (Duracell battery) 7 1/2" (h) x 4" (w) x 1 1/4" (d) Approx. 14 ounces (with battery) 120 VAC power supply Operations Manual Notes: 1 The New Stereo Soundbook, 2nd Ed. R. Streicher and F.A. Everest. AEA. 1998, pg. 1.1 2 "Basic Stereo Microphone Perspectives -- A Review." R. Streicher and W. Dooley. JAES vol 33, no. 7/8, 1985 July/August, pp. 548. This user's guide is the second edition. We would appreciate your comments, whether positive or negative, about this manual and about our products. This user's guide is the second edition. We would appreciate your comments, whether positive or negative, about this manual and about our products. Other Products by Audio Engineering Associates: RCA Working Reproduction Microphones and replacement parts AEA R44C Microphone A Reengineered version of the classic RCA 44 Long Ribbon. AEA R77C - A Reengineered version of the RCA 77 Variable Response. Modular Microphone Positioning System Stereo Microphone Bars Decca Tree Arrays M/S Stereo Processors MS 38 MKII MS 38 Lite Modular Studio Microphone Stands and Booms Since 1981 we've acted as the US agent for Coles Electroacoustics, manufacturers of the 4038 studio ribbon microphone and the 4104B, a "lip" mic for voice-over work in high noise environments. We sell and service the mics and stock spare parts. In North America we represent CB Electronics, a leading worldwide supplier of machine control equipment to the sound-for-film industry. Their products specialize in professional control of and translation between bi-phase, 9-pin serial and time code machines. Their new SR line provides low cost multiple machine remote controls for RS-422, Sony, and Tascam DA88 protocol machines. Our Audio Test Department buys, sells, trades, and rents new and used audio test gear. Audio Precision, B&K, Hewlett Packard, Galaxy, Goldline, Neutrik, and Amber are among the lines we maintain in stock for audio measurements of Level, Polarity, Phase, THD and IMD distortion, W&F, SPL, and spectrum RTA. "Tools to make Great Recordings Easier" Audio Engineering Associates 1029 N. Allen Ave. Pasadena, CA 91104 Phone: (626) 798-9128 STUDIO RIBBON MICS PHASE DISPLAYS · M/S STEREO · TALL STANDS · MIC POSITIONERS · · Fax: (626) 798-2378 www.wesdooley.com