General thoughts:
In part choosing the right type of coil and the wire gauge in relation to sufficient power handling and saturation points (for ferromagnetic cored coils) comes from experience with designing and building speakers.
However, as a general notion, we can say that when a crossover is designed correctly based on the parameters of the drivers used, the requirements for the DCR will dictate what coil type (air core / ferromagnetic core) and what wire gauge is needed.
For air core coils there is of course no core that can saturate, but the when it comes to power handling this is then only determined by wire gauge.
For ferromagnetic cored coils the power handling and the saturation point is determined by core material, density and size, as well as the wire gauge used.
Therefor, as a rule of thumb that will often take the guesswork out of coil selection is that if a crossover is designed correctly the resistance (DCR) of the coils needed for the various sections and positions on the crossover will mean that coil will have sufficient power handling and will not saturate within the limitations of “normal” usage in terms of volume levels.
In most cases if the crossover is correctly designed, the drivers will fail long before a coil would saturate and the loss of inductance would affect the performance of the system.
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.
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.
Why we do not and cannot correctly measure power handling and saturation data:
We have not done any measurements for power handling or saturation point measurements for our induction coils / cores.
The reasons why it is both difficult and also to some degree pointless to measure power handling and saturation point data (for ferromagnetic cored coils) has to do with the complexity of doing such measurements and that the data will not be conclusive enough when it comes to determining if a coil is suitable for a specific crossover position.
When it comes to ferromagnetic cored coils specifically there are several types of core types like laminated steel cores (I-Cores), Toroidal steel tape cores (C-Cores) and Iron powder cores (P-Cores) made from both ferrite and non-ferrite material(s).
The different ferromagnetic core types mentioned above all have different properties and react differently once saturation is reached.
More on the subject of specifically ferrite versus non-ferrite P-Cores can be read HERE.
Below are listed some of the complications we have to factor in when looking at power handling and saturation points:
- 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 or the exact saturation point where a coil would start losing inductance or when audible distortion would occur is therefor not as simple as simply measuring the coil with a steady signal and thereby determining how the coil would perform when used on a passive speaker crossover.