Cloud Electronics CX2300 - Manual (Page 4)

CX2300 I NSTALLATION AND OPERATION MANUAL 3
Once the crossover frequencies have been determined, an active filter with fixed
frequencies determined by plug-in cards may be preferable for a fixed installation.
2.02 What are the optimum crossover frequencies?
A professional sound system should have a useful response from below 30Hz to above
20kHz but this overall response is a function of the design of the enclosures and the
placement within the building and is beyond the scope of this manual. Wherever possible
refer to the manufacturers specification for details of the crossover frequencies. Where no
specific details are available, there are practical guidelines which can be used to
determine the most suitable crossover frequencies for a particular system.
It is common to find multiples of 38cm and 45cm drivers used in low frequency
enclosures where the upper frequency limit of around 800Hz is dictated by a narrowing of
the dispersion and a loss of definition. The optimum upper limit is around 250Hz.
Where cone drivers are used for mid range purposes, the lower frequency limit should be
no lower than double the resonance of the drive unit and should be compatible with the
upper frequency limit of the bass drivers. The upper limit is again dictated by a narrowing
of the dispersion and loss of definition. For 30cm drive units the upper limit is 1.5kHz and
2kHz for 25cm units.
The high frequency section would normally use horn loaded compression drivers and
manufacturers data would have to be used to determine the most suitable crossover
frequency. A higher frequency than that specified by the manufacturer is often chosen to
improve the reliability of the compression driver's diaphragm. A system compressor/limiter
is also often used to prevent clipping of the power amplifiers output waveform which can
cause premature destruction of the diaphragm(s).
If compression drivers with horns are used to handle the high frequencies, it is common
practice to improve the ultra high frequencies by adding horn loaded tweeters to the same
circuit by using passive filters usually at frequencies above 5kHz.
2.03 Why 3 pole filters ?
When designing the CX2300, we were mindful of the requirement that the unit should
sound good. It is generally accepted that odd order filters sound more musical than their
even order counterparts and our own tests confirm this. The use of third order Butterworth
filters gives a high 18dB/octave roll off which relates to a power reduction of 85% per
octave.