Simple passive low pass filter - Need Help Please

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Hi guys recently started doing some small scale portable and homemade audio systems , like a 2.1 home system using PSU and car Stereo and 2.1 using a 2.1 amp + MP3 decoding board(with USB,SD,AUX and bluetooth input) , portable stereo using old (but good) USB speakers with battery and have a few other projects in mind to do soon. Currently Im thinking of a 2.1 portable - so far im thinking 2xPAM8403 2x3W 5v amps , 1 for left/right and 1 for the woofer , but I have noo idea how to make a filter for the woofer and thats what I need help with to make. It has to be something small , best would be that I could use the lfet and right channels from the second amp for the woofer , can anyone explain to me what I have to do to make something like that ?
 
im thinking 2xPAM8403 2x3W 5v amps , 1 for left/right and 1 for the woofer , but I have noo idea how to make a filter for the woofer

You can use a 10k series resistor from each input, and connect the output ends of the resistors together.
Then filter this mono signal with either a simple passive RC filter, or an active second order op amp filter.
For example, a series 15k resistor and a shunt 0.1uF capacitor would give an 80Hz rolloff (including the 10k parts).
Do you have a level control on the bass amp? If not, you can add one after the RC filter.
This would need to be figured into the frequency calaculation
 
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You can use a series resistor from each input, and connect the output ends of the resistors together.
Then filter this mono signal with either a simple passive RC filter, or an active second order op amp filter.
Do you have a level control on the bass amp? If not, you can add one after the filter.

oook but how to I calculate what values I need for the resistors and capacitor ?
 
You can use a 10k series resistor from each input, and connect the output ends of the resistors together.
Then filter this mono signal with either a simple passive RC filter, or an active second order op amp filter.
For example, a series 15k resistor and a shunt 0.1uF capacitor would give an 80Hz rolloff (including the 10k parts).
Do you have a level control on the bass amp? If not, you can add one after the RC filter.
This would need to be figured into the frequency calaculation

So something like this >
An externally hosted image should be here but it was not working when we last tested it.
?
 
Well this is what I (with some help ) have come up with
FA8P3VVIL5J3WZ2.png
 
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