ATC's approach to tweeter design is unique in the marketplace. By incorporating a secondary suspension component the moving assembly is naturally constrained to travel only in the axial direction. The result is a design that suppresses rocking modes and ensures lower distortion levels. The additional stability that this approach provides over more conventional tweeter construction negates the need for ferro-fluid (usually required for cooling, damping, etc). As a consequence, the magnetic gap can be made smaller allowing ATC tweeters to not only perform optimally, for longer, but also offer improved power handling over conventional designs.
While this unique tweeter topology offers superior performance, the resultant increased moving mass and overall complexity must be offset and overcome by the perfect alignment of all components. Consequently manufacturing and assembly demands exceptional care and accuracy - a level of capability that ATC excels at.
The standard SH25-76 and its ultimate 'S' spec stablemate approach these engineering challenges in different but equally successful ways. The standard tweeter has a novel and lighter moving mass bracing component, while the 'S' spec driver has an exceptionally powerful motor assembly that, when combined with the optimally stiff and lightweight coil former, delivers vanishing low levels of odd harmonic distortion and a well controlled extended frequency response beyond the limit of human hearing.
The additional stability over other designs negates the use of ferro-fluid, so ATC tweeters perform at their best for longer, and the magnetic gap can be made smaller, further improving power handling.
Each tweeter motor assembly employs a magnetically annealed top plate and huge N48M Neodymium ring magnet, the geometry of which has been individually optimised using finite element analysis to ensure the best possible performance. Achieving an incredibly high flux density of over 2.0T in the magnetic gap, the magnet assembly of the SH25-76S is fully saturated and therefore free from the effects of flux modulation in the surrounding metalwork, lowering odd harmonic distortion to below -70dB across the operating band. The high levels of flux density in the gap combined with a short coil long gap configuration result in a linear and extended frequency response beyond 20kHz.
