Steel laminate cores don't distort so readily. If you are winding your own, buy the smallest value in the type you want (usually 1mH), and add turns to it.
If you go air core, PVC rings suffice....
The faces are 3/8" lexan. The face has a groove for 2.0" diameter PVC center hubs to be used. I have another face made for 1.5" PVC. Wire pictured is 18awg with Blue (dry oil) polyurethane coated enamel. Zip ties are Thomas and Betts steel-barbed ties.
If you go air core, PVC rings suffice....
The faces are 3/8" lexan. The face has a groove for 2.0" diameter PVC center hubs to be used. I have another face made for 1.5" PVC. Wire pictured is 18awg with Blue (dry oil) polyurethane coated enamel. Zip ties are Thomas and Betts steel-barbed ties.
Amazing work, Sir! I like how neatly tied it is.
I’ve only wound smaller values in air cores, and in this case I need about 5.3-5.5mH and a very low DCR. Do you know of a good source for 10g or even 8g copper wire?
1- you will want a machine to wind at those gauges or you will be very sore afterwards.
2- once you get above 16awg in size, the amount of copper length required will get long fast. I had a 5 pound spool of 14awg, and only got about a pair of 3.5mH total. Up 2 sizes and double the length means you may need 20# of wire.
3- If you can find it, the internet will have it. BAE wire is where I purchased my last lot of spools.
4- estimate is 1.5" thick bobbin, and about 6" diameter, and that may be on the small side.
2- once you get above 16awg in size, the amount of copper length required will get long fast. I had a 5 pound spool of 14awg, and only got about a pair of 3.5mH total. Up 2 sizes and double the length means you may need 20# of wire.
3- If you can find it, the internet will have it. BAE wire is where I purchased my last lot of spools.
4- estimate is 1.5" thick bobbin, and about 6" diameter, and that may be on the small side.
It poses some serious challenges, based on my modelling using Wheeler’s formula for square cross-section geometry. I will stay the course with cored types for this large inductance.
Have you any experience with c-coil inductors?
Have you any experience with c-coil inductors?
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You can use this software for calculating coils.
https://coil32.net/download-coil64-for-windows.html
You can choose square or circular cores, single layer, multilayer etc.
Prefer laminated iron core over ferrite/powered iron for a matter of size.
Saturation of iron starts around 1.3T while ferrite starts at 0.3T.
You'll need a much smaller cross-section area using iron.
Things to check when using iron core:
1. Maximum peak current that the cross-section area handles around saturation.
Example: If you need 100W @ 4ohm, you have 5Arms or 7Apeak.
Choose a section area that start to saturate well above, let's say, at minimum 10A, for example.
2. Always use air gap (EI, toroid etc) or open magnetic circuit (rod, only E etc) so as to limit the effective permeability to around 10 to 15.
The lower, the better THD, but less gain.
A value of 10 is a good balance between cooper reduction compared to the air core and low THD.
3. As for any coil, calculate DCR and check heat dissipation
https://coil32.net/download-coil64-for-windows.html
You can choose square or circular cores, single layer, multilayer etc.
Prefer laminated iron core over ferrite/powered iron for a matter of size.
Saturation of iron starts around 1.3T while ferrite starts at 0.3T.
You'll need a much smaller cross-section area using iron.
Things to check when using iron core:
1. Maximum peak current that the cross-section area handles around saturation.
Example: If you need 100W @ 4ohm, you have 5Arms or 7Apeak.
Choose a section area that start to saturate well above, let's say, at minimum 10A, for example.
2. Always use air gap (EI, toroid etc) or open magnetic circuit (rod, only E etc) so as to limit the effective permeability to around 10 to 15.
The lower, the better THD, but less gain.
A value of 10 is a good balance between cooper reduction compared to the air core and low THD.
3. As for any coil, calculate DCR and check heat dissipation
I have used a C-coil in a few designs now. Seriously low DCR, and that equates to some extra slam in the bass. Sometimes you want that.
Sure, single parameter doesn't define a good speaker.
C-coils you mean the 2xC core?
If yes, they are good, cause you can control the gap in between the two C's engineer it as you want.
Like this?
C-coils you mean the 2xC core?
If yes, they are good, cause you can control the gap in between the two C's engineer it as you want.
Like this?
The point is lack of information about saturation current and effective permeability.
They seam to be more focussed on DCR and power.
They seam to be more focussed on DCR and power.
Thank you all for the great replies.
Jantzen needs a table of reference for distortion pertaining to the c-coil, and I suspect the trade-off for their very low resistance may be increased distortion.
My use case is a third-order low pass in the 500Hz region, 12” 4.7 Ohms DC woofer in a 3-way studio monitor. Most of the listening is at well under 1W, although I would like the woofer section to avoid unnecessary distortion during dynamics or spirited listening. No PA levels though.
Jantzen needs a table of reference for distortion pertaining to the c-coil, and I suspect the trade-off for their very low resistance may be increased distortion.
My use case is a third-order low pass in the 500Hz region, 12” 4.7 Ohms DC woofer in a 3-way studio monitor. Most of the listening is at well under 1W, although I would like the woofer section to avoid unnecessary distortion during dynamics or spirited listening. No PA levels though.
You need to check the effective permeability or THD of these C-Cores, cause high effective permeability can distort even below 1W, cause signal will be affected by the hysteresis and natural non linearity of iron all along the BxH curve.
In your case, using very low power, saturation will not be a problem if you take cores designed for 200W, 400W and this information is available from vendors.
So even if they push their cores to 400W and touches the saturation region, with 10W, 20W, 50W you will be far away from that region.
From off the shelf inductors, maybe with the cheap I-cores (<US$10.00 Dayton, for example) there will be more probability of lower distortion.
Cause for I-cores (just a rod core), we know that the magnetic circuit is not even closed, so effective permeability cannot be high and linearity will be good at low power levels. You get that good balance.
In your case, using very low power, saturation will not be a problem if you take cores designed for 200W, 400W and this information is available from vendors.
So even if they push their cores to 400W and touches the saturation region, with 10W, 20W, 50W you will be far away from that region.
From off the shelf inductors, maybe with the cheap I-cores (<US$10.00 Dayton, for example) there will be more probability of lower distortion.
Cause for I-cores (just a rod core), we know that the magnetic circuit is not even closed, so effective permeability cannot be high and linearity will be good at low power levels. You get that good balance.
I have some doubt they would be willing to divulge even harmless data like this, but I could ask. I found a couple tests of various crossover inductors including c-coils. Surprisingly, the c-coils faired well in the tests compared to quality I-cores from Erse/US Coils and Madisound, but as you say, there could be a low-power non linearity.
https://www.mtg-designs.com/tips-tricks-tests/inductor-testing/inductor-testing-part1
https://www.htguide.com/forum/missi...-of-inductor-types-on-distortion-performance=
Erse/US Coils Super Q 5.6 mH in 12 AWG (0.117 Ohm) is an option at the moment. Since the harmonics of their I-core laminate inductors are quite low, it looks like the woofer should mask them.
https://www.mtg-designs.com/tips-tricks-tests/inductor-testing/inductor-testing-part1
https://www.htguide.com/forum/missi...-of-inductor-types-on-distortion-performance=
Erse/US Coils Super Q 5.6 mH in 12 AWG (0.117 Ohm) is an option at the moment. Since the harmonics of their I-core laminate inductors are quite low, it looks like the woofer should mask them.
I want to thank each of you for your valuable input and help. 👍
Another question:
What is the acceptable spacing between an air core inductor of about 5mH for a woofer section and the other inductors in a crossover for the midrange and tweeter (second order filters)? I may choose to use laminated steel types in the woofer section if this poses a problem.
Another question:
What is the acceptable spacing between an air core inductor of about 5mH for a woofer section and the other inductors in a crossover for the midrange and tweeter (second order filters)? I may choose to use laminated steel types in the woofer section if this poses a problem.