Low pass filter on car speakers

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mk2mark2
Posts: 2
Joined: Wed Mar 10, 2021 7:18 pm

Low pass filter on car speakers

#1 Post by mk2mark2 »

Hey guys,

I used to have an account on here some time ago (over 10 years I think), I bought and built a few plans and just remembered what a great community this was as I was dealing with an issue with a car stereo.

Hopefully things are still going well here, glad to see everything still up and running!

So quick question for you guys, I'm updating the stereo in an old bmw 6 series and I'm trying to figure out the front speakers. I'm sure it's a simple fix, but it's kicking my ass!


What I know is that there's a woofer and a tweeter, and what I believe to be a low pass filter built onto the woofer. Here's a diagram that I've traced out: https://i.imgur.com/5ct7McN.png I'm assuming the coil of wire is an inductor.

I can get the woofer and the tweeter to work separately but I can't seem to crack the code to get them both to work, so any help there will be much appreciated.

Here's a few photos of the speaker if that helps: https://imgur.com/a/0Slr1Lt

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Bill Fitzmaurice
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Joined: Tue May 02, 2006 5:59 pm

Re: Low pass filter on car speakers

#2 Post by Bill Fitzmaurice »

I'm not sure what that picture shows. It appears that someone wrapped magnet wire around the magnet, in what could only be a disastrous attempt at making a filter inductor. Most car stereos use a simple 1st order filter on the tweeter, usually a cheap NPE capacitor, and no filtering of the midrange. This is what I added to my BMW to make things right.

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mk2mark2
Posts: 2
Joined: Wed Mar 10, 2021 7:18 pm

Re: Low pass filter on car speakers

#3 Post by mk2mark2 »

Thanks Bill.

These are the stock speakers that came with the BMW, they sounded great in the car, but changing the headunit meant changing all the wiring too.

That's a good idea to just forgo the filter built onto the speakers and use my own crossover.

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