Test & measurement
The Toroidal Coil from Jantzen Audio is wrapped around a toroidal sandwiched steel core and has very little resistance, allowing it to transfer much power without overheating. Shrink foil is being used to reduce the microphonic impact. A crossover setup was used to quantify the power handling in watt RMS at 8Ω impedance. The maximum wattage corresponds to the highest wattage load a C-Coil can bear until the inductance is affected.
Because of their unique properties, Toroidal Coils are the ideal inductors for the bass section of individual crossover designs where high power handling and low resistance are desired. The C-Coil is intended for use in the bass section of passive speaker crossovers and should not be used in the mid-range or tweeter sections.
The audio industry has long preferred toroidal coils due to the decreased distortion and fringing effects, which they claimed resulted in a smoother sound.
The critical advantage of toroidal coils is that the form of the centre reduces magnetic flux escape. Also, the core is a closed-loop with no ends or corners from which the flux escape. Because of the lower losses, there is less electromagnetic interference (EMI) and more efficiency.
The windings can be scattered around the core, allowing for greater use of the core material, the improved coupling between individual windings, and increased performance. The closed-loop also generates a stronger magnetic field, resulting in improved inductance and Q factor.
This higher efficiency generally means that a toroidal coil can generate more power proportionally to its size. This is utilised in mains power transformer applications.
The most noticeable distinction between toroidal coils and other coils is their ring-shaped form, as previously mentioned. This is due to the core material's different form. The wire is repeatedly pulled through the centre hole and rewound around the outside of ring-shaped cores.
The wire is wound around a bobbin in most coils, typically cube or rectangular. This bobbin has a series of cores that pass across the middle and along the perimeter. A specialised manufacturing process is necessary due to the coil's unique shape.