GRATEFUL DEAD: WIRED FOR SOUND
A concert artist today performs at the center of an incredible tangle of wires connecting components of a thousand kinds. But even if he knows what they all are, the performer is not likely to discuss graphic equalizers and pink noise during an interview.
Anybody who has seen the Grateful Dead has marvelled at the mysterious mountains of gear they use at their concerts. Because of the sheer amount of this equipment, because of its high quality, and because it is privately owned by the group rather than rented from a sound contractor, GP decided to investigate.
In order to examine the technical side of the Dead's performances, we talked with Rick Turner of Alembic in San Francisco. Besides building sophisticated electronic guitars (see "Casady's Bass," GP, August '72), the craftsmen at Alembic have done extensive work on all the Dead's equipment. Without needing to consult any notes, Turner was able to provide the following information.
What equipment does Jerry Garcia use on stage?
Jerry uses an extensively re-worked Stratocaster, and also one of our Alembic guitars. He plays into a Fender Twin Reverb amp with preamp outpouts going to a McIntosh 2300 amp. This powers three Alembic B-12 speaker cabinets which are stacked on their sides, so that he has a vertical column of speakers extending about eight feet into the air. They're stacked like this because we found that it gives a much wider horizontal spread to the sound, with less spill going up into the rafters.
What about rhythm guitarist Bob Weir?
Bob alternates between a Les Paul, an SG, an ES-335 (all Gibson), and an Alembic. He plays into two rebuilt Twins, one of which powers a pair of Alembic B-12 cabinets, each having two D-120 JBL's in it. He drives his extension speakers with McIntosh 2300 amps.
And bassist Phil Lesh?
Phil has been phasing out his Fender equipment in favor of our preamps and McIntosh 2300 power amps. His bass has two ordinary low-impedance Alembic pickups and one quadraphonic pickup, which puts out a separate signal for each string. Each pickup goes into a separate Alembic preamp module, and from there each of the three signals goes into a 2300. He has six or eight Alembic B-15 cabinets, each containing two D-140 JBL's. Perhaps I should explain that our cabinets are numbered so that A means a cabinet with one speaker, B means two speakers, and so on, and the number indicates the diameter of the speaker. I should also explain that all the equipment I'm discussing is continually being revised as we re-examine what the various components are being used for, and question whether some other hookup can be devised that will do the same thing better.
What is the Dead's P.A. system like?
It varies from month to month, but basically it looks like this: Each of the four singers has a pair of Sennheisen microphones, mounted one above the other about three inches apart. They're hooked up out of phase, and this has the effect of cancelling out the background noise. Any sound that goes equally into both mikes disappears when the two signals are added together, so that all you have left is the sound of the voice, since the singer is only singing into one of them. This eliminates most of the feedback problem, and it also cleans up the sound a great deal. In addition, there are four or five Electra-Voice RE-15's on the drums. Each of the mike signals, and the output from Keith Godchaux's piano, is then split, with half the signal going to the monitor system and half to the P.A.
How is the monitor system set up?
We have an Ampex MX-10 mixer, followed by an Altec Acoustivoicette graphic equalizer. The graphic equalizer has about twenty-five sliding controls, one for each third of an octave all the way up the scale. What we do is feed pink noise into the system from a Hewlett-Packard spectrum analyzer.
What's pink noise?
It's artificially generated sound that has the same audible loudness at all frequencies. This is different from the better-known white noise in that white noise is sound that's generated with equal power all the way up the frequency spectrum, and as a result it gets louder as it gets higher, at the rate of 3 db per octave. Pink noise, on the other hand, has the same volume all the way up. We feed this into the P.A., and then check it with the graphic equalizer to see what kind of peaks and valleys we have in the frequency spectrum of the system. We then adjust the sound with the sliders until it's all equalized. By doing this in every hall they play in, the Dead eliminate any audibility or tone quality problems that might crop up. The power amps for the monitor system are four McIntosh 3500 tube amps, and their output goes to about a dozen A-12 footlight-type monitor speaker cabinets, and as well to some speaker columns on the sides of the stage.
What about the part of the P.A. the audience hears?
This is all controlled from a booth at the back of the hall. It's a stereo system; the speakers on the left and the right sides of the stage are handled completely separately. In the booth there are Ampex mixers, two more Acoustivoicette equalizers, and a Nagra two-track tape machine for recording the concert. Each side of the P.A. has a crossover network for feeding different amps. The crossover has an 18 db per octave slope dropoff, and it splits the signal into four parts. The first is everything below 350 cycles, the second from 350 to 1000 cycles, the third from 1000 to 4000, and the fourth from 4000 up. Each of these then goes to a couple of McIntosh 2300's, and from there as follows: For woofers (below 350 cycles) there are sixteen JBL 2215's on each side of the stage. The low midrange is run through sixteen JBL 120's on each side. The high midrange goes into thirty-two JBL 2105's, which are 5" speakers. And for the highs we have sixteen Electra-Voice T-350 horns.
Who's responsible for all this?
Ram Rod, Dan Healy, and Sparky Razine head the actual equipment crew. It takes them, and about eight other people, four hours or so to set it up. A lot of the original designing was done by Bear. And there's a kind of consulting committee made up of Ron Rickersham, Bob Matthews, John Curl, Peter Quaintence, Bear, and myself. All of us work on it from time to time.
Why use so much gear?
It's not just for volume. Most groups could get three times the volume out of this equipment that the Dead does, but that would be a distorted sound. Not that the Dead are quiet; the sound pressure on stage has been measured at 127 db, and that's loud. But it's all clean sound, not noise. Most independent sound contractors, whose equipment you'll see at a typical rock concert, are much more concerned with economics than with high fidelity. They charge so much to fill a given-sized room with music, and the cheaper they can do it, the more profit they make. The philosophy of the Dead's system, on the other hand, is that since we have the technology to produce a very high quality of sound, we ought to use it. If you care about music, you've got to care about what the audience hears.
(by Jim Aikin, from Guitar Player, July 1973)