Air cored single wire, multi-strand (litz) and foil-based induction coils:
Our Air Core Wire Coils, Litz Wire Wax Coils, Cross Coils and Wax Coils are all either made without a core or with a neutral wooden core.
These coil types can generally be used across the board for all positions on the crossover, however from certain technical or cost related perspectives, it may not make sense to use air core coils for certain crossover positions.
Ferromagnetic cored coils:
Inductors with ferromagnetic cores tend to become saturated as the current increases.
Air core induction coils, however, have no core to saturate, and therefore are independent of electrical currents.
Any induction coil made with a ferromagnetic core will always have a certain level of audible distortion / noise.
The cores material and construction will dictate how profound this distortion / noise will be.
I will also depend on the driver used, the crossover design, and filter order.
Ferro-magnetic cored inductors can largely be used for bass and lower mid-range sections of the crossover without any audible distortion or interference, or as rule of thumb for positions below 1.2 kHz.
Wire/Foil Gauges:
The gauge/thickness of wire or foil will influence both the resistance of the coil (DCR) and the power handling of the coil.
Using a thicker gauge of wire or foil can also add more dynamic headroom.
The wider the surface is of the conductive material for a coil, the more freely the electrons can travel, which makes Litz wire and foil-based coils superior compared to single strand wire-based coils.
Coil power handling:
The reason why it is difficult to exactly determine the exact power handling data for a specific coil (gauge/core type and size) has to do with the complexity of doing such measurements, below are listed some of these complications:
- Are we talking 4Ω or 8Ω impedance when measuring?
- At what frequency are we measuring?
- At what amplifier output voltage / amperage are we measuring?
Music consists of a very wide range of signals across the frequency response range.
How a specific coil will perform in a crossover will therefore depend on the music type played and volume levels over extended play time, etc.
To measure the exact wattage load where a coil would start losing inductance, a core saturates or when audible distortion would occur is therefor complicated.
It will often be possible to get advice or share experiences with audio experts and DIY audio enthusiasts alike, who have a lot of hands-on experience with coil selection. Such advice or experience sharing can usually be found in online articles or via online audio forums.
In many cases it is also a matter of personal preference, budget, and philosophy which coils could or should be used and if any theoretical or measured potential “issue” is in fact audible to the human ear.
If you want to go down the route of getting a better idea of what a coils overall power handling would be, a setup will have to be made, where you use a white noise test signal.,
It would simulate/represent the full power bandwidth energy area in the audible band (20-20kHz) run through the coil during such a test.
Another thing to note is that even if you make a test using a white noise signal, the results may not translate into something that you can physically hear for your specific speaker design