by BERT WHYTE
LAST MONTH I described the old Brooklyn Paramount theatre, which was to be the locale for a four channel recording of its newly restored 26-rank "mighty Wurlitzer" organ. Now I'll cover the details of that recording.
It becomes quickly apparent when you decide to make a four-channel recording that it takes a lot of heavy equipment, and there is almost always a scarcity of eager, strong-bodied young men to lug the stuff. I guess over the years I've been spoiled by the superb facilities available to me on "location recording." First there was the famous Mercury recording truck, which Bob Fine had equipped to cover virtually any recording contingency, and in which, in relative comfort, I made some of the earliest stereo recordings.
Then there was my Everest recording truck, which was equipped for every kind of recording including six-channel 35-mm magnetic film. This truck used to accompany me as "personal baggage" on the S.S. United States, or the Queen Elizabeth. We would disembark at Southampton, drive to London, and thence to Walthamstow Town Hall, where British Customs would open the sealed truck and in fairly short order we would be set up to record. Ah, those were the days! Now I'm older and fatter, and definitely not kindly disposed to the more athletic side of location recording. Nevertheless, once you. have been infected with "recording fever," there is no turning back, and it is astonishing in retrospect what kind of personal effort and sacrifices one will make for the sake of a recording! To make this four-channel stereo recording I used an altogether remarkable tape machine ... the Ampex 440-4. This is the workhorse of many professional recording studios, where they are installed in consoles. My unit had the tape transport and four-channel electronics mounted in separate portable ( transportable would be a better term) cases. The 440 transport follows traditional Ampex design, considerably updated and advanced in this latest version. All elements are extremely rugged, designed for heavy duty.
The transport is solenoid operated, of course, and the pushbutton controls have a reassuringly solid feel and respond instantly to your touch. The 440 I have operates at 7.5 and 15 ips, and speed change is electric at the flick of a switch.
Switches also handle equalization for both tape speeds, as well as tensioning for reel size. With this unit you can use up to 1031-inch reels, but you can also mix reel sizes--7-inch on one side, and 103E on the other and vice versa. Unlike previous Ampex professional recorders, the 440 accepts both quarter-inch and half-inch tape. Neat trick, and here is how they do it ... the tape guides at the supply and take-up sides of the recorder, have an ingenious spring-loaded mechanism, which when pulled up and given a half turn, gives guidance for quarter-inch in one position and half-inch in the other position. Next, the entire head structure is interchangeable. The heads are contained in a cast housing, the base of which has been precision milled and fitted with three machined guide pins. This mates with a milled area on the heavy top plate, and the pins fit into perfectly aligned holes in the plate. The leads from the heads terminate in a flat Fiberglas board and are connected to a series of pins. The pins plug into female receptacles which are mounted at the back end of the milled area on the top plate. With this arrangement, one can choose many different mono and stereo head configurations for use with either quarter- or half-inch tape. The four record/playback amplifiers are completely independent and can be connected to the heads in a variety of ways. Currently I have a three-channel half-inch head ( there are thousands of three-channel half-inch productions in the vaults, and if one has the right connections . . . ) and a four-channel half-inch head. I also used a quarter-inch four-channel head for a while, one of the first of this type built by Ampex. The precision fitting of head assembly to base plate, makes possible head interchange without alignment. You can check the alignment, of course, and thus far it has been on the nose! The head assembly also contains a scrape flutter filter ( with provision for a second filter if desired ) and for the first time on an Ampex professional machine, automatic tape lifters.
Actually the lifters come up through the top plate and into the head assembly.
Now here is another clever bit . . . the lifters pull the tape away from the heads in the fast forward or rewind modes .. . but not completely. Thus a certain level of "monkey chatter" can still be heard and the trained recording engineer is able to use this sound to locate various parts of the program on the tape. The 440 electronics are all solid-state, have large, legible VU meters, the usual input and output pots, and switches to select between record, playback, and "sel sync." The sel sync feature permits totally synchronous recording, by circuit switching which changes a record head into a playback head in multiple-track "layer-on layer" recording. Sound-on-sound and sound-with-sound recording with amateur tape machines always suffers from the approximate tenth of a second lag between the record and playback heads.
For this organ recording, I used the 440 with the four-channel half-inch heads, mainly in the interests of signal-to-noise ratio. This really came about, because the 440, in common with all professional machines, uses Cannon XLR input and output plugs. These mate splendidly with the professional Dolby A301, which is similarly equipped.
Trouble is, I didn't have a pair of Dolby A301s. My Dolby "B" Type units have RCA pin jacks and I just didn't have the time to make up cables with XLR on one end and RCA pin on the other end. I have since rectified this situation, and now can do "state-of-the-art" four-channel stereo plus Dolby recording. The Ampex 440 is found mostly in professional studios and as such, are usually set up for a line input from a mixing console.
Thus in the portable versions if you want to record with microphones, you must use a plug-in pre-amplifier, which goes into an accessory receptacle on the rear of the record/playback amplifiers. This is okay, but it doesn't afford the flexibility of a mixer like the Ampex AM-10, which accepts multiple mikes and can also split mikes between channels. Since I was recording four-channel stereo, two mixers were necessary. With this Ampex 440 unit and the mixers, one can handle almost any kind of "remote" or "location" recording.
In a huge place like this theatre, you need miles of mike cable, especially in a hall where your recording equipment is not necessarily in a place of your choosing. In surveying the theatre for mike placement, I thought I had found a good solution to this problem. As I told you last month, Long Island University uses the theatre as a gymnasium. They had ripped out about half the old orchestra seats and installed in their place a basketball court. Powerful lights are installed over the court, about 40 feet high, and strung on wires across the width of the theatre from the organ pipe chambers on each side. The chambers begin roughly 35 feet from the floor. I figured I would hang my primary left- and right-channel mikes from these lighting support wires.
In order to change bulbs when they burn out, there is a "cherry picker"-an elevating platform-on the premises, and with this gizmo I thought I had it made.
Alas, none of the custodians would undertake to run the "cherry picker." Now even with Star mike stands and booms, you can't get higher than about 20 feet.
And they are heavy. And I didn't have any. Momentarily thwarted, we spotted a pile of commercial-type folding tables off to one side, and with the aid of some agile types we placed tables one on top of another, at a pre-determined spot on each side of the theatre near the pipe chambers, and when we had built up the "table platforms" as high as we dared, we gingerly put one of my lightweight PIC mike stands on top. This precarious assembly put my mikes about 30 feet high. The mikes used for the front channels were the new Electro-Voice RE-55 omni-directional dynamics. They are rugged, highly sensitive mikes with a flat wide-range response, and a particularly good bottom end. While I decry the practice of placing mikes fairly close to the pipes, which usually reduces the spatial characteristics, it is important to get your mikes level with the pipe chambers.
When they are level and you adjust the closeness of the mikes to the pipes, so that you get the important high frequencies without short-changing the acoustic perspective, you've got the beginnings of a good balance. Incidentally, the reverberation time in the theatre was no more than 1.5 to 1.7 secs, but the hall has great brilliance and liveness. The left and right rear mikes were Electro-Voice RE 15 cardioid dynamics. They were placed on regular mike stands about 12 feet high and a certain width apart, and a certain distance from the front mikes.
The "dead" side of the cardioids were placed to the rear. This four-channel stereo recording utilized a special technique, and thereby hangs a tale.
Some of you old-timers may remember a very early stereo recording called "Sounds In The Round." It was a rather spectacular recording demonstrating the spatial and directional aspects of stereo.
The recording was brilliantly engineered by Bob Jordan and Jim Cunningham. Jim has always been in the forefront of stereo experimentation, and today he is research director for the Eight Track Recording Co. of Chicago. About four years ago, after much experimentation and research in multi-dimensional recording techniques and psychoacoustics, Jim developed a unique four-channel stereo recording technique. A great deal of this technique is based on fairly complex factors, but in essence here is how it works . . . Research has shown that the human brain cannot integrate sounds lasting much longer than 33 milliseconds, with possibly 50 milliseconds right on the ragged edge.
Sounds longer than this confuse the brain and thus we hear various orders of reflections. Working with this information, Jim Cunningham devised a four-channel stereo set-up, in which the primary mikes are placed in more or less normal position near the orchestra, depending on the hall acoustics. The secondary mikes he places preferably at 33 feet and no more than 50 feet to the rear of the primary mikes. This distance is based on the velocity of sound-approximately 1 foot in 1 millisecond-hence 33 ms equals 33 feet. The width between the primary and secondary mikes is dependent on many factors, such as size and shape of hall, reverberation time, size of performing group, and so on. But in general, Jim's experiments have led him to conclude that whenever practicable, the width between the mikes should be kept to the 33 to 50-foot maximum. Further tests have revealed that Jim's technique doesn't work as well in a very reverberant hall.
In many situations, it may be necessary to use cardioid mikes for front and rear channels, with the rear cardioids presenting their "dead" side to the rear of the hall.
Ampex 440-4
Having made his four-channel stereo recording in this fashion, Jim plays back the recording quite differently from the usual set-up of speakers in front of, and to the rear of the auditor. The front speakers remain in their normal position, but the "secondary" speakers are placed from ;í to 3í the distance between your seat and the front speakers, they are placed at the extreme sides of the room, and they are angled in towards you.
I made the recording of the Brooklyn Paramount organ with the Cunningham technique. The primary ( front) mikes were a little less than 50 feet apart, the secondary (rear) mikes were about 30 feet to the rear of the front mikes and about 35 feet apart. The liveness of the hall, led me to use the omni-directional mikes in front and the cardioids in the rear.
How does the Cunningham recording compare with the four-channel stereo we have heard up to now? In my opinion, and the opinion of others who have heard it, this is the most convincingly natural sound yet. It is absolutely spectacular.
You play the two front channels and the sound is that of a good high-quality stereo recording. You switch in the secondary channels and the effect is stunning and dramatic. The effect is not at all subtle. Your whole listening room opens up, a great stage seems to appear before you. The effect is totally natural too. Obviously, there is no danger of overbalancing rear speakers and hearing discrete instruments behind you, as is too often the case with current four-channel sound. In making the recording, the rear channels were about 6 dB lower than the front. In adjusting the playback level of the secondary speakers, you strive for a balance which complements the front speakers, and this seems to be at quite a bit higher level than you would ever use for the rear channels in the surround techniques. What about pop music with the Cunningham technique? It works well here too, providing that the recording is made properly and played back with Jim's special set-up. However, a Cunningham pop recording can be played in "surround" style if desired, and without any degradation of the sound. It is equally important to emphasize that the playback of currently available four-channel stereo music will not give you the Cunningham sound. To hear this fabulous new sound, it must be recorded and played back in accordance with his prescribed techniques.
Where can you hear Cunningham four channel stereo? That is a bit of a problem right now. I will be demonstrating some of it at the Westbury and Newton Hi-Fi Shows, but the trouble is that by the time you read this the shows will be over. It may be that some of the more venturesome hi-fi sales rooms will want to demonstrate this sound. The overall point to remember is that a great deal of experimenting lies ahead with all types of four-channel sound. Both the Cunningham and the "surround" four-channel sound have their respective merits. Then there is the thorny problem of speaker placement in living rooms. Decor and personal taste have to be a big factor here. Fortunately, if you are contemplating the purchase of a four-channel stereo tape recorder, it is comforting to know that Cunningham, or "surround" or any other kind of four-channel stereo that is likely to appear, can be played with equal facility on the same machine.
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It has been brought to my attention that a few columns ago, I made a real goof. In writing about the RCA Quad Eight, I wondered why the time of the cartridges would be cut down from 80 to 40 minutes. I even mentioned a few sentences earlier, that in Quad Eight the first set of four channels would end and the player shift to the second set of four channels. Worse still, I recorded and sequenced the four programs on each of the first hundred or so cartridges for RCA. So I certainly know how the process works. In fact, about a year ago I wrote an elaborate article in Audio about 8-track cartridge sequencing. I'll have to attribute my boo-boo on the time aspects of Quad Eight to too many gin-and tonics, or some such thing when I was writing the column, Sorry about that.
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Progress is being made on the Dolby front. Ampex Stereo Tapes, biggest producer of open-reel, cartridge, and cassette tapes, has announced it will be producing "Dolbyized" cassettes. First items will be some London operas, with Tosca and Norma heading the list. Ampex expects to be in production of the Dolby cassettes by October 1st of this year.
The company has said it will produce "Dolbyized" cassettes "whenever practicable" from most of their production, but obviously such items as historical and childrens' tapes would be excluded.
Now that the ball is rolling on cassettes, how about some "Dolbyized" open-reel tapes for all the quality conscious audiophiles who read this magazine?
(Audio magazine, Nov. 1970; Bert Whyte)
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