|  IP: Logged

 |  IP: Logged

Does anyone else have data or publications that document what was used?

 |  IP: Logged

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

The need, as I see it (not necessarily Ray) comes from the fact that the modern cinema processor is tuned to the ISO 2969 curve. This is a response that the historical systems did not have. If a film is mixed to an old speaker in an old room, without EQ (or sound "warping" units), it will not sound normal in a modern theatre. This is putting aside all of the differences due to the reverberation and acoustics of the theatre.

The idea of the "academy" filter in processors like the CP-100 and CP-200 is to superimpose an old theatre response on top of the new tuning in such a manner that is will be the ideal, average, response.

As Mark accurately points out, in the 50's-60's the reponse of theatre was pretty much a funtion of the reponse of the speaker as it interacted with the room. Such is not the case with an "EQed" system, starting with the CP-100 onwards.

Within the past year, I installed a Panastereo CSP-1200/4600 system. As delivered, the magnetic tracks do not receive any filtering since none are specified anywhere. One of the test films we ran was Ben-Hur in 70mm 6-track (panned dialgue and everything). To my ears, it was way too bright sounding. You could hear everytime a track was cut in and out. The hiss level and hum level would change. Certainly, this was not to be heard. Applying a bit of Bass and Treble cut would move it into acceptable. Having run many conventional films on a CP-200 and not having the same sort of problems (including Ben-Hur), I investigated the academy curve issue for magnetic films. Thus far, there are none that we have found. Certainly, until some definitive documentation states to the contrary (and I want documentation that all of the studios followed it) there is some room for interpretation and opinion here.

Steve

 |  IP: Logged

 |  IP: Logged

Being "flat" on the recording is relative...what room did they listen to it in? If the highs seemed a bit wanting, they would have tried to emphasise them...likewise on the bass.

Steve

SOUND RECORDING: RECORDING SYSTEMS: MAGNETIC FILM (page 694)
"The frequency response of a magnetic channel is maintained flat from 50 to 12,000 Hz (+/- 1/2 dB), so that second, third, fourth and even fifth generation transfers can be made without any major alteration to the frequency content. It is also essential that strict control of azimuth is maintained to facilitate world-wide exchange of recorded material.

"The standard reference film to which all 35mm magnetic recorders are aligned is the RCFM, available from the Society of Motion Picture and Television Engineers. It is an original recording of three 200 mil tracks on fully coated film, containing a series of spot frequencies from 50 to 12,000 Hz. Each film is individually calibrated and correction factors are provided."

SOUND RECORDING: MULTI-TRACK SYSTEMS: RECORDING REQUIREMENTS (page 704)
"Since the final prints delivered to cinemas carry a magnetic stripe track with a frequency response of 50 to 12,000 Hz, high and low pass filters are not required."

"5.6 RESPONSE

The electrical frequency characteristic of each channel will eventually be standardized but for the time being it will be satisfactory to state that the overall characteristic from recording through reproduction shall be flat from 50 to 8000 cycles with tolerances as shown in Fig. 9A.

The relative response of the channels is more important than absolute or average response. The tolerances or permissible variations between channels is shown as Fig. 9B. This measurement must be made with a suitable test film because the recording characteristic will have pre-equalization of approximately 6 dB at 60 cycles and 3 dB at 8000 cycles, both of which are useful to reduce hum and noise difficulties. The amplifier system, if measured independently, will have a frequency characteristic with a slope of 6 dB per octave (6 dB decrease in signal for each doubling of frequency) except as this characteristic may be modified to take into account the low frequency pre-equalization and high frequency losses.

FIG. 9a & 9b

The mid-band channel gains must be adjusted to within 1 dB between the lowest and highest channel.

Intimate contact between the magnetic track and the pickup head surface is very important for high frequency reproduction, and any factor, such as distorted film, low film tension or an accumulation of dirt or oxide on the head surface -all of which tend to destroy good contact-must be observed and minimized. Clean the surface with a soft rag or wooden stick. Azimuth should be adjusted for maximum output"

Of course, the differences in track width and transport speed would be factors in arriving at the final specifications.

The ANSI/SMPTE 202M standard specifies a N curve for non wide range installations.
Compared to the X curve the N curve rolls off 7 dB at 10 kHz.
The CP 200 build in filter follows the N and X curve difference within +0/-1.5 dB.

 |  IP: Logged

 |  IP: Logged