Meyer Sound M'elodie, Operating Instructions Manual

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CHAPTER 5

HOW LINE ARRAYS WORK

Line arrays achieve directivity through constructive 
and destructive interference. For example, consider 
one loudspeaker with a single 12-inch cone radiator in 
an enclosure. The loudspeaker’s directivity varies with 
frequency: When the wavelengths being reproduced 
are larger than the driver at low frequencies, it is 
omnidirectional; as the frequency increases (and the 
wavelength is comparable to the size of the driver), 
directivity narrows. Above about 2 kHz, it becomes too 
beamy for most applications, which is why practical system 
designs employ crossovers and multiple elements to 
achieve controlled directivity across the audio band.

Stacking two of these loudspeakers one atop the other 
and driving both with the same signal results in a different 
radiation pattern. At common points on-axis, there is 
constructive interference, and sound pressure increases by 
6 dB relative to a single unit. At other points off-axis, path 
length differences produce cancellation, resulting in a lower 
sound pressure level. In fact, if you drive both units with 
a sine wave, there will be points where the cancellation is 
complete, which can be shown in an anechoic chamber. 
This is destructive interference, sometimes referred to as 
combing.

A typical line array comprises a line of loudspeakers 
carefully spaced so that constructive interference occurs 
on-axis of the array, and destructive interference (combing) 
is aimed to the sides. While combing has traditionally been 
considered undesirable, line arrays use combing to positive 
effect: to control the directivity.

M’ELODIE CURVILINEAR ARRAY

The M’elodie loudspeaker employs a combination of drivers 
to enable you to optimize both coverage and directivity in 
a M’elodie line array system. To achieve optimal results, it 
is important to understand how these components work 
together.

High Frequencies

For high frequencies, M’elodie uses a very precise Constant 
Q horn — developed using Meyer Sound’s anechoic 
chamber — which provides a consistent beamwidth of 
coverage in the horizontal plane. 

In the horizontal pattern of an array of M’elodies, these 
horns work to produce a wide 100-degree coverage; in the 
vertical, however, Meyer Sound’s REM technology provides 
narrow coverage in order to:

■ 

Minimize destructive interference between adjacent 
elements

■ 

Promote coupling to throw longer distances

As more elements are arrayed in a vertical column, they 
project mid- and high-frequency energy more effectively 
through coupling. The amount of energy can then be 
controlled using the relative splay between the elements:

■ 

Wide angles:

 Curving a line array can aid in covering a 

broader vertical area.

■ 

Narrow angles:

 Straightening a line array provides a 

longer throw and coverage that more closely matches 
that of the mid-low frequencies. 

Mid to Low Frequencies

For the mid to low frequencies, line arrays must be coupled 
together to narrow their vertical coverage and project mid 
and low energy to the far field. The directional control of 
the array depends on the length of the array (number of 
elements). 

Directional control is achieved when the length of the array 
is similar or larger than the wavelength of the frequencies 
being reproduced by the array. As frequencies get lower 
and wavelengths get longer, the number of cabinets has a 
critical effect on the directional control. The number of array 
elements is very important: the more M’elodie loudspeakers 
used, the more directional the vertical beamwidth becomes 
at the lower frequencies. However, at low frequencies the 
splay angle between cabinets has little effect since the total 
length is not modified substantially.

CHAPTER 5: LINE ARRAYS AND SYSTEM INTEGRATION