# Subwoofer low-pass crossover (4ohm 80hz) inductor core & bobbin

**URL:** <https://forum.digikey.com/t/subwoofer-low-pass-crossover-4ohm-80hz-inductor-core-bobbin/32347>\
**Category:** Passives\
**Tags:** magnetics-transformer-inductor-components, ferrite-cores, bobbins-coil-formers-mounts-hardware\
**Created:** [June 25, 2023, 3:54pm UTC](https://forum.digikey.com/t/subwoofer-low-pass-crossover-4ohm-80hz-inductor-core-bobbin/32347 "2023-06-25T15:54:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![newyorknick](https://sea2.discourse-cdn.com/digikey/user_avatar/forum.digikey.com/newyorknick/32/37533_2.png) [@newyorknick](https://forum.digikey.com/u/newyorknick)\
**Post date:** [June 25, 2023, 3:54pm UTC](https://forum.digikey.com/t/subwoofer-low-pass-crossover-4ohm-80hz-inductor-core-bobbin/32347/1 "2023-06-25T15:54:34Z")

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Need help finding a core & bobbin that would work for a custom inductor that im building for a 4 ohm passive subwoofer crossover that will be crossed over at 80hz. I am using 16 AWG enameled copper wire. I’m getting a little lost with all the options. This is a pilot test and will be making these in bulk if the results are what I expect.

I’ve seen a number of high end manufacturers use toroidal cores so if that is feasible or better given my requirements I’m all ears. Im new(ish) to this so any and all suggestions / improvements are welcome!

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**Author:** ![Karl\_1696](https://avatars.discourse-cdn.com/v4/letter/k/9de0a6/32.png) [@Karl\_1696](https://forum.digikey.com/u/Karl_1696)\
**Post date:** [June 26, 2023, 1:01pm UTC](https://forum.digikey.com/t/subwoofer-low-pass-crossover-4ohm-80hz-inductor-core-bobbin/32347/2 "2023-06-26T13:01:39Z")

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Hello,

About the best I can do is give you links to our bobbins and cores.

> **[Magnetics - Transformer, Inductor Components | Bobbins (Coil Formers),...](https://www.digikey.com/en/products/filter/bobbins-coil-formers-mounts-hardware/935?s=N4IgTCBcDaIEYHs5wJYDsQF0C%2BQ)**
>
> Bobbins (Coil Formers), Mounts, Hardware are in stock at DigiKey. Order Now! Magnetics - Transformer, Inductor Components ship same day

> **[Magnetics - Transformer, Inductor Components | Ferrite Cores | Digi-Key...](https://www.digikey.com/en/products/filter/ferrite-cores/936?s=N4IgjCBcoLQExVAYygFwE4FcCmAaEA9lANogCsIAugL74wCciIKkGO%2BRkpENtICXEKgLoCASwAmAQwA2AAiQjsVakA)**
>
> Ferrite Cores are in stock at DigiKey. Order Now! Magnetics - Transformer, Inductor Components ship same day

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<div class="post-metadata">

**Author:** ![rick\_1976](https://sea2.discourse-cdn.com/digikey/user_avatar/forum.digikey.com/rick_1976/32/1571_2.png) [@rick\_1976](https://forum.digikey.com/u/rick_1976)\
**Post date:** [June 26, 2023, 5:52pm UTC](https://forum.digikey.com/t/subwoofer-low-pass-crossover-4ohm-80hz-inductor-core-bobbin/32347/3 "2023-06-26T17:52:44Z")

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As a starting point, understand that the inductance factor AL given for a core typically has units of nanohenries per turn squared. A core with a listed AL of 1 will offer roughly 1nH of inductance with 1 turn, 4nH with 2 turns, 9nH with 3 turns, etc.

After this, there is some product N\*i (N=# of turns, i = current through winding) that will cause a given core to reach saturation and lose its ability to behave as a proper inductor, the upshot of which is that larger inductances and higher peak current values result in a need for a physically larger core.

Core materials can introduce non-linearities and sensitivities to factors such as temperature however, so it is not uncommon for applications desiring stability to use a non-magnetic core (air core) to avoid these.

There’s a brief article [here](https://media.monolithicpower.com/mps_cms_document/2/0/2020-en-wechat-how-to-avoid-inductor-saturation-in-your-power-supply-design_r1.0.pdf) that might be useful, and I’d recommend Wurth’s _Trilogy of Magnetics_ available [here](https://www.digikey.com/en/products/detail/w%C3%BCrth-elektronik/744006/2345473) and elsewhere as a thorough resource for study on topics relating to magnetic components.