Headphones

Quad has said little about the construction of the ERA-1, so I took a peek inside. The motor comprises what looks to be a single-sided isodynamic diaphragm with seven plated neodymium bar magnets arrayed in opposition either side (neodymium has to be plated to prevent corrosion). Each facing pair will have like poles facing the diaphragm, with the next pair along having the same arrangement but using the opposite pole. This creates a squashed magnetic field which between each pair of magnets is roughly coplanar with the translucent plastic diaphragm. Exactly what plastic Quad uses hasn't been stated but, as you'd expect, the sinuous planar 'voice coil' appears to be of aluminium. Four tracks run parallel to each other, having seven folds that create eight straight sections of track in the gaps either side of the seven magnet pairs. Unlike most isodynamic tweeters, there is no fibrous damping in contact with the diaphragm to quell resonances, but fine fibre meshes on the outside faces of both magnet arrays provide acoustic resistance. KH