JBL VLA Compact User manual

VLA Compact Line Array (VLA-C) Calculator

V1.1.2

INTRODUCTION

Welcome to the JBL VLA Compact (VLA-C) Line Array Calculator. We hope you will find it to be a useful
simulation software tool that will enable you to obtain even higher levels of performance from your VLA
Compact loudspeaker system.

Installing VLA Compact Calculator

Before installing the VLA-C Calculator, uninstall all previous versions using the Windows
to Add/Remove programs. After un-installing older versions, unzip the VLA-C Calculator distribution file
and then run the “setup.exe” program. Your computer will need to have the latest version of Microsoft
.NET 4 (the installer will download this automatically if your computer requires an update). JBL’s VLA-C
Calculator requires a PC with Windows XP or newer. Recommended screen resolution is 1024 x 768
(minimum).

ACOUSTICAL MAPPING TAB

The Acoustical Mapping tab allows for definition of the following parameters:

• Units (metric or imperial)

• Air absorption parameters (temperature and humidity) under “Options”

• Room dimensions in XY coordinates (X = distance, Y=elevation) or distance/angle

• Array location and elevation

• Number of enclosures

• Enclosure type

• Inter-enclosure angles

• Array site angle

• Enclosure: gain, delay, EQ (graphic or parametric, plus whether front or rear facing for VLA-

C125S subwoofers)

The following acoustical prediction results are displayed:

• SPL Mapping (selectable individual frequencies from 20 Hz – 10 kHz)

• 0 dB Isobars (up to 4 frequencies simultaneously)

• SPL Attenuation (up to 4 frequencies simultaneously)

• Frequency response (up to 6 probe locations)

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Control Panel

Parameter definition and acoustical predictions are discussed in more detail in the following.

Units:

Selected the desired units by clicking on either ft/lb or m/kg. Values are updated accordingly.

Air Parameters (through the “Options” tab):

Enter the desired Temperature (°F or °C) and % Humidity. The VLA-C Calculator calculates atmospheric
attenuation based on ISO 9613-1.

DEFINING THE AUDIENCE PLANES

Select “Coord (X,Y) or “Dist/Angle” to toggle between plane definition modes.

Coord (X,Y) Mode:

Audience listening planes can be entered graphically (see: Graphical Adjustment of Planes) or manually
in the “Room Dimensions” cells in terms of XY coordinates (X = distance/range, Y = elevation/height). In
the example below, the origin is set at the intersection between floor level (Y=0) and the downstage
edge (X=0). Always take into account the audience listening level (ear height) when defining audience
planes. For seated audiences, ear level is 4 ft (1.2 m) and for standing audiences approx 6 ft (1.8 m).

Distance/Angle Mode:

Planes can be entered in terms of distance and angle, allowing measurements to be taken on-sight with
a laser rangefinder and inclinometer. The rangefinder/inclinometer location should first be defined in
terms of XY coordinates (a yellow cursor is displayed in the Acoustical Mapping window to show its
location). For the example below, the rangefinder/inclinometer is tripod-mounted on the stage with XY
coordinates = (0,6). It is also possible to left-click, drag-and-drop to move the rangefinder location in the
Acoustical Mapping plot window, as desired.

Distance Measurement:

Angle Measurement:

DEFINING ARRAYS

Arrays can be defined on either Acoustical Mapping or Array Configuration pages. Up to 24 enclosures*
can be defined along with enclosure: type, EQ, gain, delay; array sight angle (equivalent to Box #1
angle); and inter-enclosure angles (adjustment via nudge buttons).

By default, four VLA-C265 enclosures are loaded with 1.5 degree inter-enclosure angles:

* Exact suspension limits depend on enclosure type(s), array size, array shape, overall array orientation and the
selected array frame attachment configuration. Always refer to warning indications on the Array Configuration
page. Overhead suspension of loudspeaker systems should be undertaken only by trained and qualified personnel.
JBL Professional is not responsible for the use, misuse or misapplication of these products.

SELECTING INTER-ENCLOSURE ANGLES

Once the vertical section of the audience profile has been defined, the goal in selecting the number of
enclosures and angles between enclosures is to ensure that the audience is covered from front to rear
of the defined audience profile with equal spacing between enclosure site angle impacts (rays) over the
audience profile. Note: for long throw applications, reduced enclosure impact spacing may be desirable
for the upper enclosures of the array. Once coverage and enclosure site angle spacing is correct, further
optimization can be performed by applying circuit level gain shading and frequency tapering
(equalization on a circuit basis using shelving eq filters available in the JBL Line Array Control Panel
through the EQ button).

The “Get Me Started” feature implemented provides a useful starting point for further manual
optimization. Provided that a sufficient number of enclosures is specified to cover the audience from

front to rear, the Get Me Started feature will determine inter-enclosure angles that provide equal site
angle impact spacing:

BEFORE “GET ME STARTED”

AFTER “GET ME STARTED”

Gain can be adjusted in 0.5 dB steps and delay in 0.022 millisecond (ms) increments. Note: Delay
adjustment is recommended for Electronic Delay Steering (EDS) of subwoofer arrays only -- Delays are
pre-defined and linked for VLA-C265 and VLA-C2100 enclosures.

FILTER EQ

The frequency response of a line array is determined by many factors including the array size (number of
boxes), array curvature, and the listening distance. JBL factory presets were designed to create an
appropriate tonal balance starting point for the array conditions described above. Since the number of

presets that can be created by a manufacturer is not infinite, user adjustment of certain DSP parameters
is necessary to create the desired tonal balance for a given array and application. This EQ was designed
to help system engineers quickly and easily manipulate the tonal balance of an array.

This EQ consists of 5 adjustable DSP filters, each with a specific intended purpose. Some of these filters are
grouped across the entire array (global adjustments), some filters are circuit group specific, and some filters have
frequency centers and Q values that are linked but have adjustable circuit gain. Below is a description of how these
filters work:

Array Size Compensation: Filter 1 is intended for correcting LF/MF build up created by an array that is longer than
the intended preset. LF adjustments should be applied to all cabinets within the array, therefore filter 1 is a global
filter (affecting all enclosures in the array).

Atmospheric Absorption Compensation: Filter 2 is intended to compensate for atmospheric conditions due to
large variations in temperature and humidity that can have an impact on the overall HF energy. This filter is applied
globally (to all the enclosures in the array) and can be used to quickly brighten or darken an array. It can also be
used for artistic preference reasons to adjust overall system tonal balance.

HF Throw Distance Compensation: Filter 3 along with Gain shading is intended to correct for distance offsets
between different sections of an array. The Type, Frequency and Q are linked across the entire array but the gain is
adjustable per circuit (ie, per enclosure individual or set of enclosures that are on the same amplifier channel). This
filter can be used to reduce HF energy close to an array and increase HF energy to areas further away where air
absorption has a bigger impact.

User PEQ 1 & 2: Filters 4 and 5 are User PEQs that can be applied to individual circuit groups (ie, per enclosure
individual or set of enclosures that are on the same amplifier channel). Frequency centers and Q are not linked
across circuits and, for this reason, it is recommended that User PEQ 1 & 2 are used for frequencies above 1kHz
with moderate gain changes only.