Janine Elliot checks out the multi-driver Optoma HEM4 In Ear Monitors costing a penny short of £250.
“The use of Knowels™ drivers is paramount to the success of this series of monitors. Their history goes back to 1946, set up by Hugh Knowles in the USA and originally making microphones, speakers for TVs, and hearing aids. Balanced armature drivers have actually been around since the 1920s primarily in headphones used with crystal radios, though they were then much bigger with the diaphragm round-shaped, like the soundbox on a wind-up phonograph. In the simplest of terms these modern rectangular shaped balanced armature receivers have a coil inside which due to inducing a magnetic field when playing audio through it moves one end of a “U” shaped metal unit which has a magnet attached….”