Handbook for Sound Engineers

1358 Chapter 35

2. Second, it is assumed that the density of discrete
   data points is high enough and the frequency and
   angular dependency of the directivity characteris-
   tics smooth enough so that the true radiation func-
   tion of the spherical wave can be approximated by


3. Third, the use of magnitude-only data, assuming
   that requires that the point of refer-
   ence during the measurement of is chosen in a
   way that the true run-time phase, otherwise
   included with the measurements, can be recon-
   structed by the run-time phase in the model. It
   requires that the source-inherent phase is negligible
   as well,


4. It is assumed that the concerned loudspeaker
   system is a fixed system that cannot be changed by
   the user or when its configuration is changed its

performance data is not affected. The measurement

data is regarded as representative for the whole

range of possible applications and configurations.

5. Finally, for the use of such point sources in compu-
   tations involving geometrical shadowing and ray-
   tracing calculations, the source is regarded as
   located at a single point and is either wholly visible
   (audible) for a receiver or not.

These assumptions have been made especially in the

early 1990s in order to obtain and use loudspeaker direc-

tivity data in a practical manner. Important factors were

the availability and accuracy of measurement platforms

and methods, the storage size of the processed measure-

ment data and the PC performance with regard to

processor speed available to the average user of the data.

However, these assumptions have a set of draw-

backs. That became most evident with the broad use of

Table 35-1. Conventional Loudspeaker Data Formats and EASE GLL Format

EASE SPK EASE XHN GDF ULYSSES UNF CLF EASE GLL

Data Type Simple Data

Table

Simple Data

Table

Simple Data

Table

Simple Data Table Simple Data Table Advanced

Description

Language

Balloon Symmetries Full, Half Full Full, Half, Quarter Full, Half, Quarter Full, Half, Quarter Full, Half, Quarter

Angular Resolution 5° 5° 5° or 10° 5° or 10° 5° or 10° 1° to 90°

Frequency Resolution Octave Octave or Octave or Octave or Octave Any

Complex Data Yes Yes No No No Yes

Individual Transducers No No No No No Yes

Filters No No No No No Yes

Configurable No No No No No Yes

Table 35-2. Measurement Parameters for Typical Balloon Resolutions

Measuring Resolution Measuring

Points

Measuring Time

(for 10 seconds per

measuring point)

Implemented in

2 measuring planes, 15°, symmetrical in both measuring planes 24 | 10 min EASE 1.0

Measurement on sphere surface, 10°, symmetrical in the horizontal plane 325 | 1 h EASE 2.1

ULYSSES 1.0/CLF

Measurement on sphere surface, 10°, no symmetry assumptions 614 | 1½ h CATT-Acoustic/CLF

ODEON

BOSE Modeler

Measurement on sphere surface, 5°, symmetrical in the horizontal plane 1297 | 3½ h CLF

EASE 3.0-4.2

EASE 4.2 DLL/GLL

Measurement on sphere surface, 5°, no symmetry assumptions 2522 | 7 h ULYSSES 2.82/CLF

EASE 3.0-4.2

EASE 4.2 DLL/GLL

Measurement on sphere surface, 2°, no symmetry assumptions 16022 | 2 d MAPP (Meyer)

EASE 4.2 DLL/GLL

2 Transducer measurements on sphere surface, 10°, no symmetry assumptions 1228 3 h EASE 4.2 GLL

EASE 4.2 DLL

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