Unit 8 - Electroacoustics

Question 1

Column speakers

Answer 1

consist of a cabinet with several loudspeakers mounted vertically above one another.

So long as they are all driven from the same source, the sound radiated from each loudspeaker will interfere with the sound from the others, and the vertical response will be concentrated on the axis, although there may be some secondary lobes.

This is helpful in the common situation where an audience is seated on a horizontal floor. Note that the horizontal response is unaffected by the column effect.

Question 2

Horn loudspeakers

Answer 2

more efficient than normal loudspeakers and also much more directional.

The efficiency arises partly from restricting the area across which sound is spread, and partly because the gradual flare of the horn matches the acoustic impedance of the driver unit, to the impedance of the air more efficiently.

The frequency response of horns is restricted, but they can be useful for speech, particularly outdoors.

Question 3

Line array speaker

Answer 3

Line array speakers were originally introduced for large open air arenas, in an attempt to create a virtual line source to provide a more even coverage over a large area.

The term is now used for a cluster of speakers mounted with the driver units for each frequency band aligned vertically. So they are more like column speakers than line sources. Column speakers are point sources and sound falls off at 6dB for a doubling of distance, rather than 3dB for a true line source.