THE CASE FOR OPEN REEL TAPE --What it comes down to is technical specifications.
By Craig Stark
What it most often comes down to is signal-to-noise ratio and frequency response.
IT will hardly come as news even to the minimally informed audiophile that the recording and playback facilities offered by a reasonably good cassette deck these days meet the needs of most music listeners very well indeed. Therefore, if you are even thinking about buying an open-reel tape deck, chances are that at least some of your requirements are, in one way or another, rather special.
What this most often comes down to is a question of technical specifications, particularly signal-to-noise ratio and frequency response. These are discussed in some detail in the accompanying box, but they can also be summarized briefly by recalling a couple of simple facts. First, the wider track widths and higher tape speeds of open reel pull more tape past the recorder's tape heads in a given period of time. All else being equal, that means a better signal-to-noise ratio for open-reel. Second, while frequency response at slow tape (cassette) speeds can be extended for small signal levels, the slower the tape speed the poorer the tape system's high-frequency response at large signal levels. Thus, while cassettes are undoubtedly satisfactory for most home music purposes, if you set your tape standards high enough, only open-reel will do. It's not just for editing convenience alone that professionals record at 15 or sometimes 30 inches per second (ips) on tracks approximately four times as wide as those of the 1 7/8-ips cassette! Why Open-reel? Beyond the critical questions of frequency response and SIN, there is also that of recording flexibility, another key attraction of open-reel. Simplicity of operation is no doubt a virtue the cassette format can legitimately boast of, but this simplicity means that you must forgo a great many choices offered by open-reel, and some of them may be important to you. Take, for example, the following:
Speed and Running Time. All cassettes operate at a fixed tape speed of ips. There are home open-reel recorders available, on the other hand, that run at two, three, or even four or five different tape speeds: 15, 7 1/2, 3 3/4, 1 7/8, and 15/16 ips. And each of these speeds has its special virtues. For re cording live music, 7 1/2 ips is the mini mum speed I would recommend, and if you're looking to make a master tape for even quasi-professional purposes (a high-school glee-club concert that will be turned into a limited-edition LP, for example), I strongly recommend 15 ips.
The 3 3/4-ips speed will do a more than adequate job for most off-the-air or disc-copy dubbing (though I still stick to 7 1/2 if the material is musically demanding), and it is perfect for back ground music such as you might wish to play at a party.
The 3 3/4-ips (and slower) open-reel speeds bring the factor of uninterrupted running time into the picture. The thinnest cassette usually recommended for high-quality, reliable operation is the C-90, which gives you a maximum of 45 minutes per side. At 3 3/4 ips, a 1-mil open-reel tape (again, the thinnest recommended) on a standard 7-inch reel gives you an uninterrupted running time of 96 minutes, and double that time if your recorder can accommodate the larger, 10 1/2-inch reel size. Open reel operation at 1 7/8 ips (or even 15/16 ips) can double or quadruple the 3 3/4-ips running times. (It should be pointed out that cassettes generally provide better performance at 1 7/8 ips than open-reel machines, but for undemanding applications, such as speech, open-reel offers enormous storage capacity on a single reel).
Track Formats. Any cassette, mono or stereo, can be played on any cassette deck. That's simplicity, but it's also restriction. If you have a regular home quarter-track stereo open-reel deck, for example, and want to record a lot of monophonic material (from old discs of a non-stereo FM station, for example), you can utilize each of the open-reel deck's four tracks, separately. You can't do that with cassettes.
Further, if you buy an open-reel deck you can choose either a half-track or a quarter-track stereo format. The former, preferred by the pros, records two wide tracks over the entire width of the tape at a single pass (there is no "side 2," as with quarter-track). This greatly simplifies any subsequent editing, yields a slightly better signal-to noise ratio, and minimizes some of the dropouts near the tape edge that some times afflict quarter-track (both open-reel and cassette). On the other hand, most home open-reel decks are in the quarter-track format, as are most pre recorded open-reel tapes. To give you full freedom of choice, some open-reel decks are available in either half-track or quarter-track as the main format but with a fourth, playback-only, head in the other configuration, so you can play either type of tape.
Multitracking and Four-channel.
While quadraphonic sound did not exactly take the country by storm, it still has many adherents and, so far as tape is concerned, the discrete four-channel open-reel recorder is the way to go.
The chief interest of many purchasers of four-channel open-reel decks today, however, is not quadraphony, but exploring the "multitrack" techniques used in making virtually all popular and many classical releases. (See the article "Semi-pro Recording" on page 54.) Multitracking is a technique in which almost every separate performer in a musical performance is recorded individually on his own "track," some times in isolation from the other per formers, so that his part can be processed on its own and then balanced ("mixed") with the other performers' contributions at the recordist's leisure.
OPEN REEL ...
"If there's a touch of the recording engineer in your makeup, you'll tend to regard the 'chore' of threading up tapes as an almost symbolic ritual...." The technique differs from the so called "sound-on-sound" process (a standard capability of almost all three-head open-reel decks) in significant ways. Sound-on-sound involves constant recording of already-taped material as transfers are made from one track to another, and in the end any material "mixed" by the sound-on-sound process winds up on a single track. Multitrack techniques permit the same sort of sequential recording in assembling a performance part by part, but they also allow all the parts to be kept separate-at least up to the full track capacity of the recorder. Furthermore, the existence of the parts on to tally separate tracks makes a stereo mix possible.
To create a multitrack recording in which different parts are added at different times, a way must be found to synchronize any new material with the tracks already recorded. With multi track tape machines this is accomplished by switching the record-head gaps serving already recorded tracks into a temporary playback mode. The performer adding the new material can then listen to previous contributions and play or sing along while being re corded on any of the unused tracks.
The fact that the record head is being used for both playback and recording maintains the synchronization.
Though the playback fidelity of the record head may not be ideal, it is of little concern, for the only need is to keep the parts in synchronization with each other, not separated by the time it takes the tape to travel between the record and playback heads. The names given to this synchronizing facility vary with the machine manufacturer; some call it "Sel-Sync," others "Quadra-Sync," others "Simul-Sync." But it is a feature found on most four-channel open-reel machines today. If you're an active recordist or a member of a musical group trying to "get the act together" before going into a professional studio, a four-channel deck with multitrack facilities will be of real interest.
The Price-tag Approach
Whether you're interested in the higher quality of open-reel and its creative possibilities, or just a replacement deck that will enable you to play your library of open-reel tapes, sooner or later you'll have to try to narrow the field of available machines. Unlike the case with cassette machines, the absolute number of possibilities is reason ably limited, and many shoppers will find that the high cost of open-reel decks will limit even that number severely. In the low and low-to-middle price brackets (below about $350) cassettes have taken over almost completely, and almost 40 percent of the open-reel models listed in the 1978 edition of STEREO REVIEW'S Tape Recording & Buying Guide are in the $1,000-and-up range.
$450 and under. If you're a new comer to tape, this is the price class in which it is most difficult to choose be tween the open-reel and cassette for mats. On the other hand, if you have a library of older open-reel tapes and are on a tightish budget, you may find a perfectly suitable machine. Akai's 4000DS Mark II is probably the least expensive machine in the group ($299.95), and it is available (for $379.95) with built-in Dolby. Other offerings bear the mark of Sony, Toshiba, or Philips. Subject to some variation, machines in this class will offer three heads, a single-motor transport with mechanical controls, a wow-and flutter percentage in the 0.1 to 0.15 percent range, and a signal-to-noise ratio in the area of 50 to 55 dB. Frequency response may be somewhat limited on some models. Seven-inch reels will be the maximum size, and most decks will offer 71/2- and 3 3/4-ips operation, with an additional 1 3/4-ips speed occasionally available.
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OPEN-REEL AND A TECHNICAL COMPARISON
ONE question that puzzles many audiophiles (and annoys some others) is how a $300 cassette deck can boast the same performance specifications as a professional open-reel mastering recorder that costs ten times as much. Part of the answer, of course, may lie in the optimism of some copywriter at the cassette ma chine's advertising agency or in the conservatism of the open-reel ma chine's engineering department. But another part of the answer all too of ten lies in the use of differing measurement techniques and standards.
The average consumer, for example, can hardly be expected to know that a "wrms" wow-and-flutter specification (almost universally used for cassettes) is almost certain to produce a number that is 30 to 50 percent "better" than a "DIN peak weighted" measurement made on the same deck. (Professionals use the DIN specification almost universally, but, confusingly, some consumer open-reel decks use the one, some the other, and neither is likely to specify which standard is being applied.) Straightening out the whole tangled mess of specifications (even assuming the numbers given are always honest) describing open-reel and cassette tape decks in the space of a single article would be a task for Aquinas, who I am not. But I would like to address myself to two comparative specifications that often confuse audiophiles into thinking that there's no "real" difference between open-reel and cassette formats. These "specs" are frequency response and signal-to noise ratio.
At one time or another, everyone has heard a tape played back at half (or double) the speed at which it was recorded. The audible effect is to shift the frequency we hear down (or up) by an octave. What this proves technically, however, is that it is not the frequencies themselves that are recorded on the tape at all. What is recorded is a magnetic pattern that repeats itself at fixed intervals along the tape. The distance between repetitions of the magnetic pattern is called the "wavelength" of the signal. At a 15-ips tape speed, a 15,000-Hz tone has a wavelength of one thousandth of an inch, or one "mil." At 7 1/2 ips the same tone must be compressed into half the distance along the tape, so the wavelength be comes 0.5 mil. At 3 3/4 ips, the wave length of that tone is down to 0.25 mil, and, at the cassette speed of 1 7/8 ips, the distance between each of the repeating magnetic patterns is only 0.125 mil (125 millionths of an inch).
Unfortunately, when magnetic wavelengths become very short, losses in the record-playback process increase substantially. To offset these losses at slow tape speeds, the high frequencies are considerably boosted before they are applied to the tape. (This process is called "re cord equalization.") There is, how ever, a limit to how much short-wavelength signal can be stored on the tape, and if we try to exceed this "saturation" point, the more we in crease the input to the tape, the less we actually get back from it.
From this it can be seen that the "frequency response" of a tape sys tem depends very much on the level of the signal fed into it. Customarily, the frequency response of cassettes (and 3 3/4-ips open-reel) is measured at a level 20 dB below the nominal "0 VU" point-a level that would not cause most VU meters to show any input at all. Frequency response at 7 1/2 ips is usually checked at-10 VU, and, at 15 ips, at 0 VU. Under these differing test conditions, some cassette decks can achieve flat frequency response out to 20,000 Hz, and at 7 1/2 ips, open-reel response customarily extends far beyond the audible frequency range.
However, the accompanying figure shows what happens to frequency response when a "0 VU" input is used, even allowing for a higher "0" level at the faster speeds. The top three curves are taken from an excellent audiophile open-reel deck using best-quality tape. The fourth curve (1% ps) is derived from one of the best cassette decks on the market using "state-of-the-art" tape. In each case, bias and equalization were adjusted so that at low input levels the frequency response was ±2 dB at 20,000 Hz. As you can see, the higher open-reel speeds buy both more high-frequency headroom and the ability to put more signal on the tape even at lower frequencies.
This brings up the vexed question of signal-to-noise ratios. Here again, a variety of measuring techniques is used in the equipment industry, making direct comparisons of the numbers reported impossible. To give you some idea of the relative capability of the cassette versus the open-reel medium I measured weighted (CCIR/ARM) signal-to-noise ratios, all referred to the same 3 percent distortion point, for the same tapes and speeds shown in the figure. They came out as follows: 15 ips, 68.7 dB; 7 1/2 ips, 69.1 dB; 3 1/4 ips, 65.8 dB; 1 7/8 ips, 55.7 dB. (This was without Dolby noise reduction.)
-C. S.
--- FREQUENCY IN (CYCLES PER SECOND)
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$500 to $700. A rather large number of decks, from most of the major manufacturers, is available in this "bread-and-butter" class. Three heads (occasionally four) and three-motor transports are now the rule, some using directly driven capstans rather than belt-drive linkages. While 7-inch reels still predominate (together with a 7 1/2 ips top speed), Pioneer and Teac offer models that accommodate the large 10 1/2-inch reels. Wow-and-flutter figures are typically in the 0.05 to 0.07 percent range, signal-to-noise ratios have improved (55 to 65 dB), and frequency response is generally well above 20,000 Hz at the highest machine speed. Pioneer and Akai offer auto-reversing models, and Sony has two four-channel decks (though without multitrack synchronizing) in this range. Here, too, are to be found Teac's popular A-2300SX (available for $100 more with built-in Dolby), as well as the lowest-price model in the Tandberg line.
$700 to $1,000. Decks in this price class are moving very close to professional caliber, and nearly every feature you could want (10 1/2-inch reels with four-channel synchronizing, for exam ple) can be found from several manufacturers. The renowned Revox A77 (and its updated version, the B77) are here, too, though you must go a little higher in price if you want them with built-in Dolby. Wow-and-flutter figures drop as low as 0.04 percent, signal-to noise ratios rise as high as 67 dB, and many of the machines have switching to permit the use of various types of re cording tape. Decks in this class are, as their prices suggest, designed for the really serious tape enthusiast.
$1,000 and up. Shoppers looking for open-reel decks in this price range are really looking for lower-price versions of professional mastering recorders. All the "studio touches," such as servo-controlled reel tensions (and even, on the Technics RS-1500US, an iso-loop drive), are to be found here.
The top-of-the-line models of almost every manufacturer are represented, and most offer relative ease in accommodating not only top-quality consumer tapes, but the advanced studio mastering tapes as well. In essence, if you're ready to spend this much, you presumably expect to do a fair amount of live recording, and you no doubt al ready know more about the subtleties of tape-deck design than a general article such as this can cover! To return to the basic question: Is it to be open-reel rather than cassette for you? If there's a touch of the recording engineer as well as of the music lover in your make-up, it probably is, and you'll tend to regard the "chore" of threading up tapes not as an obstacle, but as an almost symbolic ritual dutifully ob served to insure that you'll get the best sound your equipment is capable of.
That might sound just a little like Walter Mitty's dreams of grandeur, but there are far worse dreams one might entertain.
Also see:
CASSETTE TAPE PROGRESS--An expert looks at where technology is taking us, ROBERT DONADIO
Source: Stereo Review (USA magazine)