Actually, he shows it affects just 1 coil also...sorry, distracted by the neighbor's dog barking!...
Look through the thing from Troels; this shows what everyone is talking about very clearly, even having 1 coil upside down from the other. The main point I was making is that DISTANCE and orientation DO affect the mutual coupling GREATLY!
I does, but need to look a the circumstances. If it is connected in series with woofer then using 4+4 is a bad idea because of increased Re.
Single air core 8mH coils (1.6mm wire, D=50mm, L=30) will have Re=0.766 Ohm. 2 4mH coils (1.6 mm wire, D=50 mm, L=30) will have Re= 0.531 Ohm each so for the same inductance 2 coils will have 0.3 Ohm higher resistance. If anyone in a right mind will use air cored 8mH inductor
With cored coils differences will be smaller like 2 4mH with combined Re 0.44 Ohms when single 8mH coil will have Re of 0.305 Ohm
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The point I was trying to make to Dean was that putting two 4mH coils in series does not necessarily result in 8mH - it depends how you wire them together etc. Better to use a single 8mH coil as you said.
Exactly this is the reason that most of the time if I use large cored coils (like ERSE Super Q) I ending up splitting crossovers to two or on one occasion three different boards.
OK, well, now we have it all in agreement. Yes, we all made good points; we just didn't get it ALL fully explained to one another. Toroids would be the best shape if I remember correctly that help minimize "stray" inductance.
http://www.jantzen-audio.com/wp-content/uploads/2020/04/C-Coil.pdf
Although in the past, closed-core inductors and transformers often used cores with a square shape, the use of toroidal-shaped cores has increased greatly because of their superior electrical performance. The advantage of the toroidal shape is that, due to its symmetry, the amount of magnetic flux that escapes outside the core (leakage flux) is low, therefore it is more efficient and thus radiates less electromagnetic interference (EMI).
the above from Wiki...
What is a Toroid Inductor?
A toroid inductor, wild used in electronic circuits, is an insulated coil that is wire wound on a ring-shaped form which is made of different materials, such as, powdered iron, ferrite or another material. A toroid inductor is mostly used at large inductances are required. Toroid inductors have more inductance per turn and can carry more current than solenoids with a core of similar material and size.
the above from "coilmaster"...
http://www.jantzen-audio.com/wp-content/uploads/2020/04/C-Coil.pdf
Although in the past, closed-core inductors and transformers often used cores with a square shape, the use of toroidal-shaped cores has increased greatly because of their superior electrical performance. The advantage of the toroidal shape is that, due to its symmetry, the amount of magnetic flux that escapes outside the core (leakage flux) is low, therefore it is more efficient and thus radiates less electromagnetic interference (EMI).
the above from Wiki...
What is a Toroid Inductor?
A toroid inductor, wild used in electronic circuits, is an insulated coil that is wire wound on a ring-shaped form which is made of different materials, such as, powdered iron, ferrite or another material. A toroid inductor is mostly used at large inductances are required. Toroid inductors have more inductance per turn and can carry more current than solenoids with a core of similar material and size.
the above from "coilmaster"...
It doesn't matter how you wire them if they are properly oriented and far apart enough. If you are referring to the scenario when coils stuck together, it totally makes sense as two replacing a single one, connecting them in the same winding direction is crucial and do the geometry and coil size it is possible to have 4 different inductance values
And orientation applies in both the physical and the electrical sense.
We are in agreement regarding winding direction being crucial.
The total inductance for cumulatively coupled series inductors is different from that of differentially coupled series inductors, and in neither case would 4mH plus 4mH equal 8mH.
Obviously, if the two series inductors are magnetically isolated from each other, no such coupling effects will occur.
Well, for me, the whole point is to learn from each other. I am amazed sometimes how much detail I DO remember on certain subjects; others, I completely forget everything I ever knew and have to "re-learn".
Heat index above 100 deg. F (>> 38 C !!!) in the middle of USA; time for a cold beer!!!
Cheers!
Heat index above 100 deg. F (>> 38 C !!!) in the middle of USA; time for a cold beer!!!
Cheers!
Also it will have to lowest Re possible but it unless Re, usually in a range of 20-50 mOhm is absolutely critical I would't use it as it have the highest distortions of all cored inductors
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