# Transformer coil (reactor) inductance value in AC (El type)

I want to use one of these inductors (EI type transformer coils with air gap) in series to a speaker (woofer) to filter out high frequencies.

https://www.hammfg.com/electronics/transformers/choke/195-196

simulate this circuit – Schematic created using CircuitLab

Of course this will work inside the loudspeaker in AC and with low average currents and in absence of DC, but the datasheet specifies the inductance "at rated max DC current".

Can I assume in my first-order filter schematic (to determine the frequency response -6dB cut-off curve) the same inductance shown in the datasheet (labelled on the transformer)?

If not, how can I determine the correct inductance value in AC (without DC) of the inductance of a transformer coil whose inductance is specified at "max DC current"?

• I'd suggest that your choice of choke is probably overkill. There are plenty of suppliers of chokes for speaker crossovers. Since you have a question about a specific product, have you asked the manufacturer? – Kartman Jan 21 at 8:59
• Consider the speaker as L instead and this is a 2nd order RLC filter – Tony Stewart EE75 Jan 21 at 9:06
• Assume the speaker as an ideal resistor, and delete the capacitor. I put the capacitor in the scheme to show that there is no DC current in the inductor. Hence it is a normal first order LR filter – Gianluca G Jan 21 at 15:20
• It is not a question regarding a specific product. Most of the reactor inductances are specified at a certain DC current. – Gianluca G Jan 21 at 15:22
• As it's a transformer, you want its inductance to be at least that value, but don't care if it's higher. Using it as an inductor, you'll have to do your own measurements. – user_1818839 Jan 21 at 16:24