In this way a large mass of air is moved at once which doesn't require very high pressures from any individual speaker.Ī major improvement in the quality of the vocal sound is due to the use of differential microphones. The speaker cones are arranged together as close as possible so that the whole surface of the cluster acts as one working surface. Each type of speaker is designed to have the same horizontal and vertical angle of dispersion so that all frequencies are heard equally well. The vocal low range speakers are arranged in a column. The center cluster of the vocal system, consisting of high and midrange speakers, is curved so as to disperse sound cylindrically there is not much vertical dispersion, and horizontal dispersion is ideally between 140 and 180 degrees. The signal in each band is then separately amplified by MacIntosh 2300 amps fed to JBL 15 inch, 12 inch or 5 inch speakers or Electrovoice tweeters. From there the combined signal goes to a Crossover which divides the frequency range into four band (High, Upper Mid, Lower Mid, Low). THE VOCAL SYSTEM - The signals from each of the vocal microphones are brought together by a Differential Summing Amp, where phase purity can be regulated and hence the transparency of the sound maintained. A sound system could get the same volume from half as much power, but it wouldn't have the quality. The whole system operates on 26,400 Watts of continuous (RMS) power, producing in the open air quite an acceptable sound at a quarter of a mile and a fine sound up to five or six hundred feet, where it begins to be distorted by wind. This separation is designed to produce an undistorted sound, a clean sound in which qualities like 'transparency', 'brilliance', 'presence', and 'clarity' are substantial musical dimensions. Thus the vocals, piano, drums, lead guitar, rhythm guitar and bass each have their own channel(s) of amplification. No two musical 'voices' go through the same system. The sound system is actually a combination of six individual systems, each being electronically separate and having a specific purpose and function. Each musician has control of his own local sound environment, being able to adjust his stage monitors of other instruments as well as his own instrument. Each microphone has a volume control on it, enabling the band to mix the vocal sound from the stage. With the new set-up there is no need for a mixing console to adjust the various sound levels. With the speakers behind them, in integral array with the instrument speakers, the band is in a much better position to hear what the audience hears, and to adjust accordingly. They have monitors, but these are not very effective, nor are the echoes which ricochet around the hall. It creates a blind spot for people sitting in potentially good seats, and the musicians themselves don't really know how they sound. Conventionally, vocal systems occupy the front corners of the stage. The system is unusual in that all the speakers are arrayed behind the musicians. This is a technical report from the standpoint of the ideas on sound reproduction incorporated into its design, and with a description of its sub-systems. Recently there have been major changes made in the Dead's sound system, bringing it a big step closer to the ancient ideal of the perfect sound system*.
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