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5) If both loudspeakers are full-range devices, the addition of the down-fill device will
affect the long-throw response by increasing level in the LF region. This is usually
beneficial since the overall array will provide greater LF levels, producing a more
balanced system and better LF polar characteristics. However, this means that the
final low-frequency EQ must be done with all devices on.
Note: Below 250 Hz, treat all components of the array as one device with the
same EQ filters.
This proven procedure provides very good, consistent results for this common arrangement.
Signal Processing
Loudspeakers shown in this array guide are described in their most passive
configuration; the number of DSP channels required and amplifier recommendations
shown for each array type reflect this.
A separate DSP channel is required for the downfill loudspeakers. With the exception of
the AM4315, the low-frequency section of a three-way system or separate LF enclosure
will require an additional DSP channel, as will the subwoofers.
DSP signals for each individual array may be paralleled symmetrically. For instance,
where two loudspeakers are side by side horizontally, there is no benefit to providing
independent DSP. Level differences may be done at the amplifier if required.
Loudspeaker DSP settings may be found on the JBL web site. For the crossover
between the subwoofers and the low-frequency section, a 24 dB/octave L-R crossover
slope on each side is recommended. Also, it is good practice to use as a minimum an 18
dB/octave high-pass on the system with the corner frequency somewhere between the –
10dB and –3dB down point of the loudspeaker reproducing the lowest frequency. Refer
to the loudspeaker specifications for this data.
Low Frequency Pattern Control
Most of the arrays described in this guide have integral to them low-frequency devices
that are arranged to provide improved directivity. No special DSP techniques are
required to realize these benefits.
It is generally better to arrange LF devices vertically rather than horizontally, as the
vertical arrangement tends to collapse the vertical polar pattern, which is beneficial in
keeping energy off of the stage and projecting it into the room. Where it is important to
limit the LF energy on the stage and to gain additional level and impact, look for solutions
that stack two or more LF drivers vertically.
To further explore low-frequency arraying please refer to the following JBL white papers:
1) Basic PD5322 and PD5122 Array Applications; Technical Notes Volume 1,
Number 32.
2) F
orward Steered Arrays in Precision Directivity
Speaker Systems; Technical
Notes Volume 1, Number 28
.
