Active Speaker

Powered speaker (9K)This is a simple powered loudspeaker that was originally intended to be used as a simple piece of test equipment. It is based around a small full-range loudspeaker that I'd inherited, which originally came from Radio Spares.

The basic idea was to mount it in a diecast aluminium box, treated to make it as acoustically ideal as possible, then add a simple amplifier using active equalisation to make the unit sound acceptable. Originally, the project was intended to be used when servicing audio equipment, but shortly after completion, I finally got around to fitting a pair of phono sockets into the workshop connection panel for doing exactly this. This meant that the unit, which actually sounded quite pleasant, spent most of its time as a bed-side radio.

More recently, I have been using this for its intended purpose on the bench, as since moving house I haven't got around to providing quite the same facilities in the new workshop. However, after around 12 years of reliable service, the mains transformer failed. This prompted me to try some modifications to see if the unit could be improved further, details of which are included here...

In this section...

  • Enclosure - Details of the case that was chosen to house the loudspeaker.
  • Electronics - Circuit design, with detailed explanations of the building blocks.
  • Modifications - Recently, a series of modifications were made to the unit.