Influence of inductor types on distortion performance

[Zvu]

Cedric from JustDIYit started it so i wanted to verify it for myself.

I used next coils for the test and i compared it to raw woofer measurement. All measurements are normalized because of different Rdc of coils, mic 0.5m from woofer, about 90dB at 1 meter.

3mH - air coil
3mH - EI transformer laminate coil
7.5mH - Jantzen C-core toroidal coil
7.5mH - air coil

First, raw woofer measurements. Not much really, quite average performance for around 90dB at 1m.

https://i.postimg.cc/pd5PD8nM/woofer-raw-response.png

3mH air coil

https://i.postimg.cc/WzwNdvqD/3m-H-air-core-coil.png

3mH EI laminate transformer coil

https://i.postimg.cc/FHRrHwrR/3m-H-EI-laminate-core-coil.png

7.5mH air core coil

https://i.postimg.cc/dtJQzLgG/7-5m-H-air-core-coil.png

7.5mH Jantzen C-core coil

https://i.postimg.cc/Jz21DK0Q/7-5m-H-Jantzen.png

So, in retrospective, Jantzen C coil measures really well so it is quite worth it. If you are buying woofers with very low distortion and you pay good money for it, don't ruin it with laminate or ferrite cored coils. Air core coils are the best but not practical if trying to keep low Rdc and over 3.5mH inductance.

[Zvu]

Does anyone have Dayton audio iron core coils and is willing to test it this way ? Or ERSE laminate coils ?

It would be great to see how do they perform and are they perhaps worth using. It might be that these are just made of some lousy alloy.

Maybe not all laminates are created equal ?

[HiFiCompass]

Does anyone have Dayton audio iron core coils and is willing to test it this way ? Or ERSE laminate coils ?

It would be great to see how do they perform and are they perhaps worth using. It might be that these are just made of some lousy alloy.

Maybe not all laminates are created equal ?

I measured some laminated cores "Sledgehammer" and they were quite good:

https://hificompass.com/en/projects/experiment/test-couple-iron-core-inductors

[chrisn]

I'm surprised there was such difference! I've not seen EI brand, I also wonder if different brands vary much.

[tcpip]

When you're adding these coils for the testing, then they are acting as low pass filters and the cone excursion at higher frequencies is reducing.

Is it possible that there is less distortion with the larger-value coils simply because the cone is moving less at higher frequencies due to their sharper rolloffs?

[Zvu]

It is one of the reasons i am showing normalised measurements. Anyway, distortion in 3mH and 7.5mH air core coils don't differ very much up to 400Hz.

EI is not a brand but a type of core for large chokes. Core can be toroidal, I core or EI core and so on.

There are few clips for ERSE and measurements of their coils on the tube. Depending on material used for cores (and maybe shape of the coils) measurements differ substantially.

https://www.youtube.com/watch?v=ETJa9o9ZCwg

https://www.youtube.com/watch?v=sxJBK4JIYJk

[Dave Bullet]

When you're adding these coils for the testing, then they are acting as low pass filters and the cone excursion at higher frequencies is reducing.

Is it possible that there is less distortion with the larger-value coils simply because the cone is moving less at higher frequencies due to their sharper rolloffs?

The coils at the values tested would not have any effect on excursion apart from introducing DCR which was compensated for. Excursion above the cutoff would be negligble anyway

[Evil Twin]

If you wish to test cores accurately, test with a passive load and an audio analyzer.

Yes, there are significant differences.

And the coils will not suppress harmonics in a driver when used in a crossover.

An easy way to evaluate your crossover is to test the raw driver as Zvu has done, and then with the built crossover. If the distortion rises in the driver passband, you have a problem with your crossover components.

Air core coils should not introduce any flux level related distortion- merely insertion losses. there is no magnetic material with nonlinearity to generate distortion.

[Zvu]

I measured some laminated cores "Sledgehammer" and they were quite good:

https://hificompass.com/en/projects/...core-inductors

I thought that Sledgehammer were product of Dayton but i see now they are Madisound's.

Does anyone have Dayton steel laminate (still the price leader) and is willing to share some measurements ?

I will buy and measure it eventually but i'd hate to see they don't measure well and i end up with strangely shaped paper holders - again. If anyone has it and would like to save me some time and money for shipping and parts (and make few sweeps for the benefit of all of us) i appeal to them (: