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Considerations for Selecting Layout Density -- Higher speaker density (tighter spacing) provides higher
SPL capability, overcomes ambient noise better and reduces the differences in sound level from location to
location within the space. Lower densities result in fewer speakers and lower system cost, but provide
lower SPL capability and greater variations in level within the space. In a fairly dead room, with low
ambient noise, little or no paging/voice reinforcement, and an SPL requirement within the capability of a
non-overlapped loudspeaker, then an edge-to-edge pattern will often suffice. By contrast, in a room with a
lot of reflective surfaces, high ambient noise and a paging or sound reinforcement requirement, then a
minimum overlap or full overlap is probably indicated. Full overlap should be used for the most critical
high quality sound reinforcement systems.
Budget, of course, may force acceptance of an edge-to-edge or wider spacing when a higher density would
be desirable. In this case, the designer should make the client aware of the potential ramifications of this
choice before the system is installed.
Additional Sound Level (SPL) Due to Speaker Density – Tighter layout densities allow for higher
SPL level due to a greater number of speakers covering each area within the listening space. In
some cases, substantial increases in SPL can be achieved from high densities. The following chart
provides the SPL ADDITION within the listening space.
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Layout Pattern and Density
ADDITIONAL SPL Due
to Pattern & Density
SQUARE PATTERN
Maximum Overlap
+5.2 dB
Minimum Overlap
+2.0 dB
Edge-to-Edge
+0.7 dB
1.4 x Edge-to-Edge
+0.4 dB
2 x Edge-to-Edge
+0.2 dB
HEXAGONAL PATTERN
Maximum Overlap
+5.4 dB
Minimum Overlap
+1.4 dB
Edge-to-Edge
+1.0 dB
1.4 x Edge-to-Edge
+0.5 dB
2 x Edge-to-Edge
+0.3 dB
Level Variation Differences Due to Layout Density – The speaker density affects the amount of
variation of the sound level within the listening space. The tighter the spacing, the more consistent
the sound will be from place to place within the space. The chart below provides a list of the level
variation for each layout pattern and density. While on-axis levels will correspond with the on-axis
SPL computations, the SPL at some off-axis locations will be LOWER by as much as the stated
figure.
For example, in a square pattern installation with edge-to-edge density, if the on-axis Maximum
SPL for Music and Speech (considering distance from the speaker and any additional SPL from
layout density) is computed to be 92 dB, from looking at the chart we can see that there will be
some locations within the listening space that will be 4.4 dB lower in level, or 87.6 dB.