Billy Vee Sound Systems

Loudspeakers: Aktiv and Passive

Loudspeaker Technologies explained

For a long time the loudspeaker was regarded as the most important part of the music reproduction chain. This all changed in the mid 1970's when it was realised that the most important part of the Hi-Fi system is the source. 'Garbage in equals garbage out!' With the development of better sources, the loudspeaker technologies and materials have become more elaborate in order to unveil the ever increasing details that modern audio equipment can resolve.

Loudspeaker drivers and filter networks.

Loudspeakers generally have more than one drive unit. This is because no single driver can handle the entire frequency range that needs to be produced and as such the frequencies need to be filtered for each driver. This filter network is called the Crossover. This filter network can either be Passive, takes its power to work from the musical signal produced by the amplifier, or Aktiv where the the crossover is several magnitudes smaller and get its power to work from a power supply which is powered by the mains electricity.

NB. If a loudspeaker has a mains input, this does not make it 'Aktiv' it is just powered. Aktiv is something entirely different.

Passive Loudspeakers.

Due to the very nature of its location, between the power amp and drive units, the power being fed to the passive crossover is sometimes up to +/-30 amps. The crossover components need to be large in both size and value. Passive crossovers are normally fitted within the loudspeaker cabinet as there are no adjustments that can be made to them.

The values of the components are large as are the distortion values and as a result the amplifier has to overcome the load of the crossover before the loudspeaker can start to perform. We all notice this as a point on the volume where all of a sudden the music springs into life.

Aktiv Loudspeakers.

Aktiv loudspeakers use the same drive units as their passive counterparts, but they are driven in a totally different way. The crossover network gets its power from a dedicated power supply and as such the components are much smaller in value. Also unlike their passive counterparts, the Aktiv crossover goes between the pre and power amplifiers. This has two major advantages. Firstly, the amplifier is connected directly to the drive unit and can therefore exert more control over its movement. Secondly, the amplifier is limited to the frequency range of the drive unit to which it is attached. This results in more power being available for the transient response of the music signal and thirdly, each frequency band can be adjusted to help compensate for some room acoustics. There are two types of Aktiv loudspeaker, those with the power amplifiers built into the cabinet of the loudspeaker and those where all the electronics are external to the cabinet. The latter gives more flexibilty in choice of electronics and greater flexiblitiy for upgrading the system by changing each component part.