ISO 26432-2:2008

Digital source processing - Part 2: Digital cinema (D-cinema) low frequency effects (LFE) channel audio characteristics

ISO 26432-2:2008 addresses the interoperability of equipment from the standpoint of the frequency response of filters used in the playback or monitor path in the theatre low frequency effects (LFE) channel for digital cinema. This response curve will create standardization of these filters without specifying their design.

Procédé de source numérique — Partie 2: Caractéristiques sonores de chaîne des effets basse fréquence du cinéma D

General Information

• Status: Published
• Publication Date: 08-Jul-2008
• ICS: 37.060.99 - Other standards related to cinematography
• Technical Committee: ISO/TC 36 - Cinematography
• Drafting Committee: ISO/TC 36 - Cinematography
• Current Stage: 9093 - International Standard confirmed
• Start Date: 10-Jul-2023
• Completion Date: 13-Dec-2025

Overview

ISO 26432-2:2008 - "Digital source processing - Part 2: Digital cinema (D‑cinema) low frequency effects (LFE) channel audio characteristics" defines standardized electrical frequency‑response characteristics for the LFE playback or monitor path in D‑cinema environments. The standard specifies a response curve (turnover frequency, slope and allowable deviations) to ensure interoperability of cinema playback equipment without mandating specific filter designs.

Key topics and requirements

• Turnover frequency

  • Defined as the point where the filter response is –3 dB from the passband reference.
  • Required turnover frequency: 125 Hz (± 5 Hz).

• Filter slope / Reference response

  • The LFE filter slope follows the Reference Filter Frequency Response Table (see values below). The standard prescribes the response curve rather than a circuit topology or implementation.

• Passband deviation

  • Allowed deviation within the passband: ± 1 dB.

• Reference Filter Frequency Response Table (specified points)

  • 25 Hz: 0 dB
  • 31.5 Hz: 0 dB
  • 40 Hz: 0 dB
  • 50 Hz: 0 dB
  • 63 Hz: 0 dB
  • 80 Hz: 0 dB
  • 100 Hz: 0 dB
  • 125 Hz: −3 dB
  • 160 Hz: −45 dB
  • 200 Hz: −102 dB

Applications and practical value

ISO 26432-2 is practical for anyone responsible for producing, delivering or reproducing low‑frequency audio in theatrical digital cinema:

• Cinema equipment manufacturers - to design LFE playback filters that are interoperable with industry playback chains.
• Theatre audio system integrators and calibrators - to verify and tune monitor or playback LFE response to the standardized curve.
• Post‑production and sound designers - to understand playback expectations for LFE content and ensure mixes translate correctly in D‑cinema playback.
• Quality assurance and compliance testing - for verifying that playback/monitor chains meet specified passband flatness and turnover tolerances.
• Standards bodies and facility spec writers - for inclusion in procurement or certification criteria for D‑cinema systems.

Adopting this standard reduces variability in the low‑frequency channel across venues, improving consistency of audience experience and simplifying system integration and certification.

Related standards

• SMPTE EG 432‑2‑2006 (original engineering guideline adopted into ISO 26432‑2)
• SMPTE 202M‑1998 - Motion‑Pictures: Dubbing Theaters, Review Rooms and Indoor Theaters - B‑Chain Electroacoustic Response
• SMPTE RP 200‑2002 - Relative and Absolute Sound Pressure Levels for Motion‑Picture Multichannel Sound Systems

Keywords: ISO 26432-2, D‑cinema, digital cinema, LFE, low frequency effects, turnover frequency, filter slope, reference filter response, audio interoperability.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 26432-2
First edition
2008-07-15
Digital source processing —
Part 2:
Digital cinema (D-cinema) low frequency
effects (LFE) channel audio
characteristics
Procédé de source numérique —
Partie 2: Caractéristiques sonores de chaîne des effets basse
fréquence du cinéma D
Reference number
©
ISO 2008
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 26432-2 was prepared by the Society of Motion Picture and Television Engineers (as
SMPTE EG 432-2-2006) and was adopted, under a special “fast-track procedure”, by Technical Committee
ISO/TC 36, Cinematography, in parallel with its approval by the ISO member bodies.
ISO 26432 consists of the following parts, under the general title Digital source processing:
⎯ Part 2: Digital cinema (D-cinema) low frequency effects (LFE) channel audio characteristics

EG 432-2-2006
SMPTE ENGINEERING GUIDELINE
Digital Source Processing —
D-Cinema Low Frequency Effects (LFE)

Channel Audio Characteristics
Page 1 of 3 pages
Table of Contents
Foreword .
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