Comments on NagraMaster

Compiled by
Peter V. Meiselmann  C.A.S.

 

               Having recorded over 30 feature films on a Nagra IV-S TC with 15ips NagraMaster equalization, I sometimes still run into repeated problems with various post-production facilities here in Hollywood.

               One acquires quickly a reputation of being ‘esoteric’ or ‘non- standard’ – which implies ‘problematic’, only because a lot of post houses are unfamiliar with a not so widely used Nagra standard: NagraMaster. They have problems transferring tapes correctly, unless they own a Nagra IV-S TC or Nagra T-Audio.

                Immediately the producer and the director hear that there is something wrong with either the production sound mixer or his equipment or that he does not really know what he is doing.
                Nevertheless, superior sound quality is not only a personal preference and commitment. It gives the sound recordist the justification to claim a long deserved recognition within the various creative processes of making a film.

                Recording on NagraMaster is admittedly also a political issue. You have to convince production that running at 15ips is worth the extra expense in tape stock.  On the other hand, tape stock is the least expensive link in the production chain and as humiliating it is to have to argue about it, it is well worth the effort.

                The following compilation of statements should clear up some of the confusion about NagraMaster equalization, (it is not a ‘master tape’ that was recorded on a Nagra), and remind Nagra users and post production people of an existing and superior recording  equalization.

DAN DUGAN of Dan Dugan Sound Design. 
                                                                          San Francisco.

               Most Nagra users ignore the second 15ips position on the IV-S speed switch labeled ‘NagraMaster’. NagraMaster is a special equalization which gives a greatly improved signal-to-noise ratio at 15ips compared to the NAB standard. With current high-level tapes like Quantegy 480 it compares favorably with DAT recording.

                Recording at the standard dialogue speed of 7.5ips requires a substantial treble boost (preemphasis) inside the recording amplifier. This is to compensate for losses in the recording process. This treble boost reduces the high-frequency headroom. It is possible to record all the way up to +4 modulation at lower frequencies, but by the time you are up to 10 kHz, the boost has hit the ceiling, so though the frequency response is flat at low and moderate signal levels, high treble levels will saturate.

                  The maximum recorded level at 10kHz with today’s tapes is 5-10dB lower than the low-frequency maximum. This is no problem with voices or classical music, because the peak energy spectrum of these sources also roll off at higher frequencies. Also at 7.5ips there is no complementary roll off in the playback, as there is in the RIAA disk equalization, for example, so an overall phase shift with frequency, called group delay, is an inherent sonic limitation of 7.5ips recording.

                   At 15ips no treble boost is needed. Indeed, with today’s tapes, a small amount of treble roll off is required. This makes the 15ips NAB record EQ good for recording hot cymbals or synthesizers, or treble-rich sound effects like hissing steam, that would have to be turned down to avoid treble saturation at 7.5ips. Not having the pre-emphasis at 15ips also means much less group delay.  

                  Kudelski’s trick with NagraMaster EQ is to use the 7.5ips treble boost for recording at 15ips. Then a complementary treble roll off is used in playback to restore flat frequency response. This makes a dramatic decrease in the tape noise level, and furthermore, shapes the noise spectrum to a velvety hush rather than an intrusive hiss. This has to be heard to be appreciated. Since the preemphasis and playback rolloff are complementary, the group delay (phase shift with frequency) stays low. NagraMaster is more like digital than any other analogue system.

                    There are two disadvantages to using NagraMaster.
First, you have to be aware of the possibility of high-frequency saturation due to the preemphasis. This is not a problem if you are used to recording at 7.5ips. The preemphasis is the same, so the same recording level habits will serve.

                    The second problem is confusion at the transfer house. You have to make sure that everybody down the line knows how to handle NagraMaster before you use it for a project. NagraMaster tapes must be transferred either from a Nagra (IV-S or T-Audio), or from a standard NAB machine followed by a NagraMaster rolloff EQ. Recordists "in the know" about NagraMaster have achieved spectacular results. Nelson Stoll used it for 'The Black Stallion' and
'Dune'. Steve Powell used NagraMaster EQ for the series 'Midnight
Caller'.

                      Several years ago we were faced with doing transfers from NagraMaster tapes to 35mm dailies. Since we had no machine capable of dealing with NagraMaster equalization, I developed a simple, passive equalizer that is placed between the output if the ¼" tape machine (Otari, Studer, MIC, Ampex, Fostex, etc.) and either the transfer machine or the transfer room board. (= NagraMaster Box).
                       Since then we have done many projects that required NagraMaster equalization.

                       The recording is a straight analog path without any noise reduction to degrade the signal. For ease and simplicity this format can not be equaled. Using the NagraMaster format in production yields superior analog performance and sound quality on a robust and common format.
                      
                        While DAT is convenient, it leaves a lot to be desired in the quality of the sound and dependability of the transport. For high quality production sound NagraMaster is the obvious choice.

AGAMEMNON ANDRIANOS. Production Sound 
                                                         Mixer. San Rafael.

                         I used NagraMaster on my latest picture 'The Absent Minded Professor' starring Robin Williams. Robin Williams never does a take the same way twice and very often would add or enhance his performance with vast changes in level or action. NagraMaster gave me the cushion needed to capture his spontaneity on the tracks.

                        The greater dynamic range of NagraMaster allows you to under-record a little, providing greater headroom for sudden level changes, from screams to whispers. You can record with confidence and tape noise is exceptional for quiet scenes.

                        NagraMaster allows for a quieter recording, measuring about 5dB better signal-to-noise ratio than 15ips NAB. However, it sounds better than that due to the frequency spectrum of the tape noise. It has a smoother or velvet like quality that is less irritable or intrusive to the recording.

                        NagraMaster is the best recording EQ for ¼" tape that is available on all Nagra IV-S machines. For analog recording it gives you a knockout punch to digital (DAT) or Dolby noise reduction.

NELSON STOLL. Nelson Stoll Audio Services,
                                 San Francisco.

                         I have been using NagraMaster for twenty years to record the sound for most of my feature films, such as 'Dune',
'Basic Instinct', 'Mrs. Doubtfire', including Francis Ford Coppola's latest feature 'The Rainmaker'.

                          NagraMaster provides a 5dB improvement in signal-to-noise ratio over 15ips NAB and subjectively sounds like more as the spectrum of the noise level is less audible. The recordings yield much greater low level detail and the overall noise level is quite a bit lower.

                           Tape stocks have improved quite a bit since Kudelski first implemented NagraMaster and a higher recording flux level can be applied overall to further improve the dynamic range.

                            For general work I recommend a record flux level of 560nW/m for 0dB on the Nagra meter. This yields over 75dB signal-to-noise with about 0.7% THD ‘A’ weighted for maximum level. When the Nagra limiter is used properly, the practical dynamic range is closer to 80dB.

                            At this flux level, print through can be audible if there is no background noise when recording high level transients using certain tape stocks. The signal-to-print of recent stocks has improved to make this a less common problem.

                             Of course, there is no free lunch. The trade off is high frequency headroom, which is about 5dB less than with 15ips NAB. The limiting of high frequencies can be heard on a fully modulated recording of breaking glass, cymbals or any other event that contains excessive high frequencies, but for virtually all dialogue and effects recordings for film that compromise is not a problem.

TOM KNOX, former Product Specialist, Nagra USA.

                             The world of Film Production Sound and Music Mastering finds itself faced with a variety of disk, DAT, and at least a half dozen other workable recording formats. With modern digital audio equipment design so strongly driven by the personal computer industry, we find ourselves constantly seeking more bits, higher sampling frequencies, faster access, better data reduction algorithms and fatter storage devices. Does all the marketing pressure to use the latest-greatest 'stuff' make the work of production sound, mixing and transfer any easier, more reliable or sonically superior or more affordable?

                              Many of our cohorts in the Music Production business continue to bulk at the sonic quality of today's best digital audio recording systems. The choice of mastering their prize CD's continues to be 1/2 inch, 30ips analog recording. Warmth, openness and lack of harshness characterize the analog format and satisfy these critical listeners.

                             When Nagra engineers designed the 2-track, 1/4inch analog recorders, Nagra IV-S and Nagra-T Audio, they realized that current analog recording standards (NAB and CCIR) were not taking full advantage of available technology and tape media. Consequently NagraMaster was born and is now a standard feature on all Nagra IV-S and Nagra-T Audio machines.  Nagra's quality analog electronics, anti-distortion circuits, plus modern tape formulations make NagraMaster a recording format that rivals or exceeds the best that 16-bit / 48kHz RDAT has to offer.

                             For transfer facilities not using the Nagra-T or Nagra IV-S TC, a NagraMaster box is simply connected in the audio path at the output of the playback machine. The sound mixer is urged to record independent 1KHz and 10KHz reference tones at the head of each reel to verify alignment of the playback chain.
Of course, a test reel recording is recommended before production begins, particularly if those persons involved have not used NagraMaster previously.

NAGRA News. June 1997.

 
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