BSS Audio FDS-310 Owner's Manual - Manual (Page 20)

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14.0 How to Equalise CD Horns
Todays 'Constant Directivity' (CD) horns and drivers can be used in 2-way
systems with comparatively low crossover frequencies.
Even so, the laws of physics dictate that the very high efficiency attained
cannot be kept up all the way to 20kHz. In addition, the CD horns control of
dispersion further 'thins out' the SPL at higher frequencies. As a result,
response falls off progressively above 4kHz, and more rapidly above 20kHz.
In the FDS-310, optional equalisation has been fitted to compensate for the
effect and provide a more level acoustic response (see Figure 14.1).
When 'STEREO 2-WAY' operation is selected, CD horn equalisation can be
individually setup on both CH.1 and CH.2 HIGH outputs.
When set to 'MONO 3-WAY' mode, the CD horn equalisation can be setup on
the HIGH output (Output 4). The equalisation for output 2, even if selected, is
automatically defeated when in 3-way mode. This means the FDS-310 can be
switched from 2 to 3-way operation with any combination of horn EQ
installed, without complications.
Horn EQ selected
OUTPUT 2
OUTPUT 4
OUTPUT 2 & 4
OUTPUT 2
OUTPUT 4
OUTPUT 2 & 4
Equalising CD Horns
Output status:
2-way Operation
EQ on CH.1 HIGH only.
EQ on CH.2 HIGH only.
EQ in stereo (CH.1 & CH.2).
3-way Operation
No EQ.
EQ on 'HIGH RANGE' only.
EQ on 'HIGH RANGE' only
Fig 14.1 CD Horn EQ
Response
Refer to section 22.3 for information on activating the equalisation.