EN 62537:2010

SLOVENSKI STANDARD
01-november-2010
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Interface for loudspeakers with digital input signals based on IEC 60958 (IEC
62537:2010)
Schnittstelle für Lautsprecher mit digitalen Eingangssignalen nach IEC 60958 (IEC
62537:2010)
Interface pour haut-parleurs avec signaux d’entrée numériques basés sur la CEI 60958
(CEI 62537:2010)
Ta slovenski standard je istoveten z: EN 62537:2010
ICS:
33.160.50 Pribor Accessories
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62537
NORME EUROPÉENNE
July 2010
EUROPÄISCHE NORM
ICS 33.160.30; 35.040
English version
Interface for loudspeakers with digital input signals based on IEC 60958
(IEC 62537:2010)
Interface pour haut-parleurs avec signaux Schnittstelle für Lautsprecher mit digitalen
d’entrée numériques basés Eingangssignalen nach IEC 60958
sur la CEI 60958 (IEC 62537:2010)
(CEI 62537:2010)
This European Standard was approved by CENELEC on 2010-07-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62537:2010 E
Foreword
The text of document 100/1433/CDV, future edition 1 of IEC 62537, prepared by IEC TC 100, Audio,
video and multimedia systems and equipment, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 62537 on 2010-07-01.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2011-04-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2013-07-01
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62537:2010 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 62379 series NOTE  Harmonized in EN 62379 series (not modified).
__________
- 3 - EN 62537:2010
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

IEC 60958 Series Digital audio interface EN 60958 Series

IEC 60958-4 - Digital audio interface - EN 60958-4 -
Part 4: Professional applications (TA4)

- 2001 The Complete MIDI 1.0 Detailed - -
Specification v96.1
IEC 62537 ®
Edition 1.0 2010-06
INTERNATIONAL
STANDARD
Interface for loudspeakers with digital input signals based on IEC 60958

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 33.160.30; 35.040 ISBN 978-2-88912-033-8
– 2 – 62537 © IEC:2010(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms, definitions and abbreviations .7
3.1 Terms and definitions .7
3.2 Abbreviations .8
4 General .8
4.1 Feature set.8
4.2 Audio formats .9
5 Control data channel using the U-bit of IEC 60958-4 .9
5.1 General .9
5.2 Formatting.9
5.3 Mode indication .9
5.4 Subchannel usage.10
6 Loudspeaker command set.10
6.1 General .10
6.2 Device identification and configuration .10
6.2.1 Device identification .10
6.2.2 Auto configuration .11
6.3 Parameters .11
6.3.1 Parameter identification.11
6.3.2 Value range.11
6.3.3 Setting a parameter .12
6.3.4 Device addressing .12
6.3.5 Timed parameter setting (optional) .12
6.4 Optional alternative parameter setting through NRPN and/or MIDI controllers .12
6.4.1 General .12
6.4.2 NRPN and MIDI continuous controller association .12
6.5 Control numbers.13
6.5.1 General .13
6.5.2 MIDI channel assignment (control number 0, low resolution, optional) .13
6.5.3 Volume (control number 1, high resolution, mandatory) .14
6.5.4 Volume ramp (control number 2, high resolution, optional) .14
6.5.5 Time delay (control number 3, high resolution, optional) .14
6.5.6 Sample delay (control number 4, high resolution, optional) .14
6.5.7 Volume calibration (control number 5, high resolution, optional) .14
6.5.8 Panning (control number 6, high resolution, optional) .14
6.5.9 Phase left (control number 7, binary, optional).14
6.5.10 Phase right (control number 8, binary, optional).15
6.5.11 Dimming (control number 9, binary, optional).15
6.5.12 Indicator (control number 10, binary, optional).15
6.5.13 High-pass frequency (control number 11, high resolution, optional) .15
6.5.14 High-pass filter in/out (control number 12, binary, optional) .15
6.5.15 Low-pass frequency (control number 13, high resolution, optional) .15
6.5.16 Low-pass filter in/out (control number 14, binary, optional) .15

62537 © IEC:2010(E) – 3 –
6.6 Additional MIDI messages .15
6.6.1 General .15
6.6.2 All off and restore commands (mandatory).16
6.6.3 Program change (optional) .16
7 Power transmission and backward channel (optional) .16
7.1 Power transmission .16
7.2 Backwards data channel.17
7.2.1 General .17
7.2.2 Protocol.17
7.2.3 Simultaneous reception .17
Annex A (informative) Security aspects.18
Annex B (informative) Signal routing.21
Annex C (informative) Application examples .23
Annex D (informative) Implementation using current hardware.25
Bibliography.26

– 4 – 62537 © IEC:2010(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_____________
INTERFACE FOR LOUDSPEAKERS WITH DIGITAL INPUT SIGNALS
BASED ON IEC 60958
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62537 has been prepared by technical area 4: Digital system
interfaces and protocols, of IEC technical committee 100: Audio, video and multimedia
systems and equipment.
The text of this standard is based on the following documents:
CDV Report on voting
100/1433/CDV 100/1700/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

62537 © IEC:2010(E) – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – 62537 © IEC:2010(E)
INTRODUCTION
The IEC 60958 interface allows transmission of 2-channel digital audio with up to 24 bit word
length at 192 kHz sampling rate. This is adequate for loudspeakers, however, there are
additional needs in practice that require standardisation, which go beyond what's currently
defined in IEC 60958. This standard is aimed at fulfilling those needs.
IEC 60958 features a user bit that can form the basis of a control data channel that addresses
those additional requirements. The format of this user bit data channel is based on the
existing MIDI standard.
Beyond the needs given in IEC 60958, the following offers an exemplary, but incomplete list
of of what a digital loudspeaker interface should support:
• Remote control of operating parameters of the loudspeaker.
• Remote power-on of the loudspeaker – preferably without requiring standby power in
the loudspeaker.
• Remote configuration of loudspeaker, for example crossover configuration, or firmware
update.
• Remote supervision of loudspeakers, for example chassis temperature or amplifier
integrity.
• Remote identification of loudspeakers, to allow auto-configuration of the entire system.
• Control of individual or groups of loudspeakers through a single interface.
• Remote control of Audio System through remote control receiver mounted in
loudspeaker enclosure (allowing Audio System to be placed out of sight).
• Extensions to allow for future applications.
NOTE 1 Level and mute control in the loudspeaker is preferred over digital attenuation by the signal source, as
this allows the full audio data word length for the filter network; level should be controlled at the last stage in front
of power amplifiers. In this case, the advantage is that the full audio word length of the given format is available at
any time and at any volume setting. Especially, if a fully digitally constructed crossover network has been
implemented, more precise arithmetical operations can also be made at low volumes. Volume control can thus be
carried out after the crossover network or even after the relevant final amplifier. Even under the most unfavourable
conditions (digital pre-attenuation and analogue gain) the filters and controllers receive the full audio word width
under all operating conditions (ideal state).
NOTE 2 Not all of the listed features are required in all applications. It should therefore be up to the implementer
to select from this standard the parts that are required in his application, and omit the unnecessary features. See
Annex D for application examples.

62537 © IEC:2010(E) – 7 –
INTERFACE FOR LOUDSPEAKERS WITH DIGITAL INPUT SIGNALS
BASED ON IEC 60958
1 Scope
This International Standard specifies the requirements for a digital loudspeaker interface
based on the IEC 60958 series of standards and the MIDI specification. It maximizes flexibility
and value by combining these previously separate standards. Together, the two standards
provide a simple and flexible digital interface for loudspeakers.
Examples for applications of the interface can be found in Annex C of this standard.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60958 (all parts), Digital audio interface
IEC 60958-4, Digital audio interface – Part 4: Professional applications
The Complete MIDI 1.0 Detailed Specification v96.1:2001, (Second edition)
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1.1
digitally interfaced loudspeaker
device that combines a loudspeaker with an amplifier, where the amplifier has a digital audio
input port
NOTE The amplifier and loudspeaker may share a common enclosure, or they may occupy separate enclosures.
The connection between amplifier and loudspeaker and the operating principle of the transducer are left
unspecified and may be analogue. In the context of this standard, the term may be abbreviated as loudspeaker or
speaker when there is no risk of confusion.
3.1.2
phantom power
scheme of transmitting electrical power from a source device to a target device using the
balanced wiring employed for data transfer; in particular, the power is applied between both
balanced signal wires and the ground or shield connection
3.1.3
audio data
data sent to the loudspeaker that is rendered as sound by the loudspeaker
NOTE Typically this data would be in PCM 2’s complement format.

– 8 – 62537 © IEC:2010(E)
3.1.4
control data
data sent to the loudspeaker that controls its operating parameters
3.1.5
controller
source device for control data
3.1.6
solid state relay
assembly of an optically controlled power switch and a LED
3.2 Abbreviations
AES Audio Engineering Society
ASIC Application Specific Integrated Circuit
CODEC Coder / Decoder
CPLD Complex Programmable Logic Device
CRC Cyclic Redundancy Check
DSP Digital Signal Processor
FPGA Field Programmable Gate Array
LED Light Emitting Diode
LSB Least Significant Bit
MIDI Musical Instrument Digital Interface
MSB Most Significant Bit
MSC MIDI Show Control
MTC MIDI Time Code
NRPN Non Registered Parameter Number
PCM Pulse Code Modulation
Sysex System-exclusive
4 General
4.1 Feature set
A digitally interfaced loudspeaker conforming to this standard shall implement the following.
• A control data channel from the controller to the loudspeaker which supports
transmission of MIDI messages. This may be implemented using the U-bit embedded
in the IEC 60958-4 protocol as described in Clause 5.
• A command set as described in Clause 6. A basic command set is mandatory, with
optional commands and manufacturer extensions being supported at the
manufacturer’s discretion.
• Optional: Power transmission from a controller to the loudspeaker, in order to activate
the loudspeaker's power switch. It is sufficient to transmit the power to operate a LED.
The power switch in the loudspeaker may be implemented with a solid state relay. A
phantom supply scheme is used, which employs the balanced interface wiring defined
in IEC 60958-4, see 7.1.
• Optional: A backwards data channel from the loudspeaker to the controller. As this
runs opposite to the signal flow on the IEC 60958 interface, it is implemented as a data
channel riding on the phantom power mentioned above, see 7.2

62537 © IEC:2010(E) – 9 –
4.2 Audio formats
As a configuration setting, the loudspeaker may select from the two subchannels. A mono
loudspeaker shall use the left channel audio data by default, but may optionally be configured
to use the right channel audio data in a manufacturer defined way.
NOTE 1 An optional parameter specifies panning between left and right channels. Speakers that implement this
feature can render an arbitrary mix of the two subchannels.
It is the manufacturer's decision which audio sampling frequencies to support, and whether
single channel double sampling frequency mode is supported. It is highly recommended that
48 kHz two-channel mode with no emphasis be amongst the supported formats.
NOTE 2 The manufacturer should document clearly which formats are supported.
5 Control data channel using the U-bit of IEC 60958-4
5.1 General
In the IEC 60958 interface there is a U-bit for each of the two subchannels, these form two
separate control data channels with a capacity of one bit per sample each.
NOTE Using both together to form a single data channel with twice the capacity would be possible but unwise in
the presence of signal routers, hence the two U-bit channels are kept separate, except when single channel double
frequency mode is used.
5.2 Formatting
The U-channel shall carry data formatted according to the MIDI standard, with the bits being
transmitted in inverted state. That is, a MIDI 1-bit is transmitted as a zero U-bit, and a MIDI
0-bit is transmitted as a one U-bit. This inversion ensures that an unused U-channel (which
carries 0-bits by default) is interpreted by the receiver as an idle line. For each information
byte, 10 bits are transmitted in the usual asynchronous frame format. The 8 data bits of a byte
are framed by a start bit and a stop bit.
NOTE 1 This allows the receiver to detect the start of each byte, and it also allows the transmitter to insert an
arbitrary number of idle bits between each data byte to adjust the bandwidth used.
NOTE 2 If the bits were transmitted in the non-inverted state, an idle U-channel would be seen by the MIDI
receiver as a line with a continuous break condition, which is a sequence of framing errors.
NOTE 3 As the U-bit is transmitted in lockstep with the audio data, it is possible to maintain a defined and sample
accurate reaction time between control data and audio data. One MIDI byte can be transmitted for every 10 sample
periods. Through insertion of idle bits, it is theoretically possible to position MIDI messages in a sample accurate
way.
5.3 Mode indication
The channel status bits shall indicate that the U-channel is carrying MIDI formatted data. The
binary value 0110 in the channel status of the respective subchannel (byte 1, bits 4 to 7) is
used to indicate this usage of the U-bit. This value is currently reserved.
NOTE The necessary amendments need to be added to IEC 60958-4. The amendment does not need to mention
any particular application, such as speakers. The definition allows the transmission of MIDI data for any purpose.
MIDI is a good match with IEC 60958 for several reasons: MIDI is an open-loop protocol that does not need a
backwards channel, although it can take advantage of one, should it be available. The data rate of MIDI is within
the same ballpark as the U-bit data rate in the IEC 60958 series. And MIDI is a general control protocol with a lot
of flexibility for custom extensions, and a lot of support in the industry, for example in the form of hardware and
software products. There are also various ways in which MIDI data can be transported in other interface standards,
such as IEEE 1394, USB or other computer networks.

– 10 – 62537 © IEC:2010(E)
5.4 Subchannel usage
A receiver shall listen to the U-bit channel corresponding to the audio channel it is rendering.
By default this would be the left subchannel. A loudspeaker rendering a mix of both
subchannels shall listen to the U-bit data on the left channel. Transmitters would preferably
send identical data on both U-bit channels, but this is not required.
If the IEC 60958 interface is in single channel double frequency mode, the U-bit channels of
both subframes shall also be combined into one logical data channel, mirroring the situation
for the audio data.
6 Loudspeaker command set
6.1 General
The command set is based on MIDI show control (MSC) commands as defined in the MIDI
standard. Device operating parameters are set using the MSC SET command.
NOTE 1 Since there is no mandatory backwards data channel, the command set avoids backwards
communication from speaker to controller as much as possible. The MIDI protocol shares the same open-loop
philosophy, making it a good candidate for a base protocol.
NOTE 2 MIDI distinguishes between up to 16 devices. MIDI sysex messages, however, do not have this
restriction and can address any number of devices. For example, MIDI Show Control (MSC) can address up to 112
distinct devices and 15 device groups.
NOTE 3 MIDI allows for vendor specific communication through sysex messages, which can be exploited by
individual companies for their own purposes, such as custom features or firmware downloading.
NOTE 4 Attention is drawn to the various features already defined within the MIDI standard, such as MIDI file
dump, which may be beneficial for speaker applications.
A loudspeaker shall support a way of receiving MIDI data. For example, this can be a
standard MIDI port, or an IEC 60958-4 port with MIDI embedded in the U-bit, as described in
Clause 5, or it can be MIDI embedded in a different transport, such as audio or data networks.
NOTE 5 It is strongly recommended to implement speakers in such a way that they are able to accept commands
at any time. Introduction of a dead time after reception of a command greatly complicates the job of a controlling
device. Also, it is practically impossible to define a dead time that suits every application.
NOTE 6 The command set described here is independent of the hardware interface used. Implementing the
command set described here does not imply that the interface described in Clause 5 is used. A speaker is also free
to implement several different interfaces through which it can be controlled concurrently.
NOTE 7 The provision of a backwards data channel is optional. If implemented, the method described in 7.2 can
be used, but this does not preclude other alternatives.
6.2 Device identification and configuration
6.2.1 Device identification
By default, a loudspeaker only needs to respond to MSC commands with the broadcast device
ID (7Fh). It is recommended that a manufacturer provide a means of associating the
loudspeaker with a device id and/or group ID. It is left for the manufacturer to decide how this
is done. Some possibilities are:
• the loudspeaker has its own user interface for configuring this. This can be as simple
as a set of switches, or as sophisticated as a display and associated buttons/knobs;
• the loudspeaker can be configured through manufacturer-specific sysex messages;
• the loudspeaker supports a backwards channel and can identify itself to a controlling
system, which may configure it automatically.
If so configured, a loudspeaker shall respond to messages addressed to its device or group id
in addition to those with the broadcast ID.

62537 © IEC:2010(E) – 11 –
A device by default only amplifies/renders a single audio channel. A stereo speaker/amplifier
hence consists of two devices which can be given separate device IDs. The recommended
way of controlling both channels together is through a common group ID. The same applies to
multichannel formats, where a bundle of channels forming a multichannel speaker can be
grouped together for common control. In this manner, any multichannel format can be
supported using suitable grouping.
NOTE MSC reserves 112 IDs for devices and 15 IDs for groups. This limits the number of devices that can be
controlled individually. It is legal, however, to have several devices with the same device ID. They will react to the
same commands and hence cannot be controlled individually, except possibly using manufacturer-specific
commands. If more devices need to be controlled individually, distinct interfaces will have to be used.
6.2.2 Auto configuration
Auto configuration requires a backchannel to be available. If so, the device shall recognize
and respond to the MIDI identity request message.
The controller may use the response to identify all connected speakers, and make appropriate
decisions as to how to configure them. It is beyond the scope of this document to specify this,
as the process is deemed highly application dependent.
Typically, after collecting the identity request responses, the controller assigns device and
group IDs to all devices that allow this to be done via MIDI sysex messages. Then, each
device will be configured with its initial settings. This can be done through a MIDI dump, or by
recalling a stored configuration, or by sending the appropriate control commands.
The controller may need a description file for each device model in order to be able to
configure it properly. The form and content of such a file is currently undefined and left for
further study.
6.3 Parameters
6.3.1 Parameter identification
The loudspeaker is controlled through a number of parameters that can be set through MIDI
messages. Each parameter has a control number associated with it that serves to identify a
particular parameter. Each parameter also has a value range associated with it that defines
the valid settings for the parameter. Controlling the speaker is done through MIDI messages
that include control numbers and the new value for the identified parameter.
Control numbers for speaker parameters range from 0 to 8 191. The lower half of this range
(0 to 4 095) is reserved for definition by the standard in the initial or future versions. The other
half (4 096 to 8 191) is available for definition by manufacturers.
NOTE For manufacturer defined control numbers, the same number can identify entirely different parameters in
different products. Correctly using those control numbers depends on knowing which product is being addressed.
6.3.2 Value range
There are two different types of parameters with their respective value ranges. One is a low
resolution parameter, whose value range fits within 7 bits, the other is a high resolution
parameter which needs 14 bits. Sometimes, a high resolution parameter can also be used
with reduced resolution, by sending only the most significant 7 bits.
NOTE For binary parameters, the standard MIDI way is to treat them as a low resolution parameter with the
binary value encoded in the most significant bit. That is, values from 0 to 63 represent off, and values from 64 to
127 represent on.
– 12 – 62537 © IEC:2010(E)
6.3.3 Setting a parameter
The standard method of changing a parameter's value is through the MSC SET command.
Optionally, further methods can be provided, in order to increase flexibility and/or efficiency. It
is the decision of the manufacturer whether those additional methods are implemented or not.
The standard method shall always be kept available. Optional methods shall never make the
standard method unavailable. See also 6. 4.
6.3.4 Device addressing
A speaker shall react to MSC SET commands with the command format 16h (amplifier). It
shall also react to the more general formats 10h (sound) and 7Fh (all-types). It may react to
other command formats as appropriate. SET commands with unimplemented/unused control
numbers are ignored.
NOTE 1 Control numbers used with the SET command are usually dependent on the device. The MSC standard
only defines some control numbers for lighting devices, and leaves the control numbers for the other device
classes entirely undefined. This standard proposal takes the liberty and standardises some of these control
numbers for amplifiers (and implicitly for sound devices in general) in the interest of interoperability. Currently
there is no provision made to prevent devices from using these control numbers in different ways, as the MIDI
standard does not reserve any numbers for standardisation.
NOTE 2 A parameter with a given control number exists only once in a device (if it exists at all). Regardless which
interface the commands are received through, regardless of the command format used, and regardless of the
device ID used, it is always the same parameter which is addressed.
6.3.5 Timed parameter setting (optional)
The SET command can optionally carry a time, which specifies when the transition to the new
value shall be complete. If the controlled device doesn't implement the time feature, it ignores
the optional time specification within the SET command. If the time feature is implemented, it
requires MIDI Time Code (MTC) to be sent to the device for time reference. Reception of MTC
is a precondition for the time feature, if the device does not receive MTC it acts as if it didn't
implement the time feature.
NOTE With the optional time feature, it is possible to coordinate the execution of any number of commands on
any number of devices, so that the effects appear simultaneous. Note particularly that the time specifies the end of
a transition, not the start.
6.4 Optional alternative parameter setting through NRPN and/or MIDI controllers
6.4.1 General
This standard defines an optional method to change parameters through NRPNs or through
standard MIDI continuous controllers. This includes a method how individual parameters can
be associated with a controller number or NRPN.
NOTE 1 Being able to control parameters using continuous controller messages can offer advantages when the
speakers are to be controlled with standard MIDI software or hardware. A variety of tools are available which can
emit such continuous controller messages as a result of user interaction, or in an automated way.
NOTE 2 Do not confuse control numbers and controller numbers. The former identify a speaker parameter, the
latter identify a MIDI continuous controller. The association between the two must be explicitly made by the user. A
fixed association between control number and MIDI continuous controller is not recommended.
The MSC SET command allows parameter numbers in the range 0.16 383. The first half of
this range (0.8 191) is used for setting the new value of the parameter with the given control
number. The second half (8 192.16 383) is used for associating the corresponding parameter
with a MIDI continuous control or a MIDI continuous controller.
6.4.2 NRPN and MIDI continuous controller association
A parameter with control number N can be assigned to a MIDI controller or to an NRPN by
sending a SET command with the control number N + 8 192, and sending the NRPN as the
value. As a special case, NRPN numbers below 120 can not be assigned. They refer to

62537 © IEC:2010(E) – 13 –
continuous controller numbers instead. As a special case within the special case, values from
32 to 63 refer to the LSB of double byte controllers, and assign the corresponding MSB, too
(controllers 0 to 31). Values from 1 to 31 are reserved. A value of 0 deletes the assignment of
this control number.
Example: To assign control number 42 to continuous controllers 16&48 (MSB and LSB), send
the following MSC SET command: $F0 $7F $02 $16 $06 $2A $40 $30 $00 $F7
Example: To delete the previous assignment, send: $F0 $7F $02 $16 $06 $2A
$40 $00 $00 $F7
NOTE 1 Assignments are only effective when a MIDI channel has been assigned to the device. Otherwise, the
NRPN assignments are remembered but only become active after a MIDI channel is assigned.
NOTE 2 Controller numbers 6, 38, 96, 97, 98 and 99 (Data entry, data increment, data decrement, NRPN) should
not be assigned if usage of NRPNs is desired. The effect of assigning NRPNs when one of these controllers is
already assigned is undefined.
NOTE 3 Controllers 0 and 32 serve as bank select controllers by default. Assigning to them will make bank select
inaccessible. Do this only if bank select is not required.
NOTE 4 Continuous controllers 120 to 127 are for channel mode control and cannot be assigned.
NOTE 5 Assigning a high resolution parameter to a continuous controller in the range 64 to 119 allows controlling
the MSB of the parameter only. The LSB will be cleared to 0 whenever the continuous controller is set. If you want
the entire parameter to be controllable through continuous controller messages, assign the parameter to a
controller in the range 32 to 63.
NOTE 6 Unassigned continuous controllers or NRPNs have no effect.
NOTE 7 If several devices share a single MIDI channel, assigning different controllers still keeps them individually
controllable.
6.5 Control numbers
6.5.1 General
This subclause specifies the meaning of the standard parameters and their control numbers to
be used with the MSC SET command. The control number for standard parameters are in the
range 0.4 095. The range 4 096.8 191 is reserved for manufacturer specific parameters.
6.5.2 MIDI channel assignment (control number 0, low resolution, optional)
This assigns a MIDI channel (1 to 16) to the device. By default, no MIDI channel is assigned
and the device can only recognize sysex messages. A MIDI channel assignment allows the
device to respond to MIDI commands that are channel-specific.
NOTE 1 The assignment of a MIDI channel is a precondition for NRPN assignment to be effective.
NOTE 2 Assigning the same MIDI channel to multiple devices is perfectly acceptable.
If MIDI channel assignment is implemented, implementation of channel mode messages
should also be considered.
The value given in the SET command is defined like this:
− LSB is ignored and should be set to 0;
− MSB is 0 for deassignment and 16 to 31 for assigning MIDI channels 1 to 16,
respectively.
Other values are reserved and should not be used.

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NOTE 3 Making speakers controllable through MIDI voice messages opens up a large number of possibilities,
because there are many devices which are able to emit channel-based messages. These include: MIDI sequencers,
Hardware controllers, Mixing desks acting as hardware controllers, and more.
6.5.3 Volume (control number 1, high resolution, mandatory)
This sets the loudspeaker volume in dB relative to the calibration level (the calibration level
can optionally be set with a different control number). The control value is a high resolution
value. The MSB encodes the level in increments of 1 dB from −∞ dB up to +27 dB, with 0
meaning −∞ dB (mute), 1 signifying –99 dB, 100 signifying 0 dB and 127 signifying +27 dB.
The optional LSB can specify intermediate values in increments of 1/128 dB.
6.5.4 Volume ramp (control number 2, high resolution, optional)
This sets the duration of a volume ramp. The duration is given in increments of 1 ms, in the
range 0 ms to 16 383 ms. If set to 0, or not implemented, the setting of the volume is
instantaneous. Otherwise the volume change occurs over a period of time given by the
duration, so that the final value is reached as specified by the time given in the volume set
command. If no time is given in the volume set command, the ramp begins immediately.
6.5.5 Time delay (control number 3, high resolution, optional)
This sets the loudspeaker delay. The control value has the format of a delay time in
increments of 1/3rd of a millisecond in the range 0 to 16 383 (0 to 5 461 ms). A loudspeaker is
allowed to limit this to a lower value, at the discretion of the manufacturer.
NOTE The increment of 1/3rd of a millisecond corresponds to approximately 10 cm of travelling distance of a
sound wave in air. If the loudspeaker implements the delay in the digital domain, it will need to convert the delay
into the appropriate number of sample periods, according to the current sampling rate.
6.5.6 Sample delay (control number 4, high resolution, optional)
This sets the loudspeaker delay in increments of one sample period, in the range of
0 to 16 383. This is cumulative with the time delay setting of 6.5.5.
NOTE To form the actual delay, a speaker will typically convert the time delay value to a number of sample
periods according to the current sampling rate, and add the sample delay to form the actual delay coefficient that
gets applied to the audio signal. In order to achieve zero delay, both the time delay and the sa
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