# DSP1124P - how to create a LPF?



## drummerbod (Jun 28, 2010)

Trying to get the BFD to create a LPF but not succeeding.

I've used 4 filters but can't seem to kill anything over 100Hz fully. I can still hear upto 1KHz and maybe higher.

Anyone done this successfully? If so... what settings did they use. I'm trying for a 80Hz crossover effectively without using more than 4 filters.


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## Wayne A. Pflughaupt (Apr 13, 2006)

A low- or high-pass filter is an infinite slope – i.e., response continually drops beyond the turnover frequency. 

For instance let’s take the case of the filter you’re trying to create at 80 Hz. A true LPF filter with a 24 dB/octave slope, response will drop 24 dB for each octave beyond 80 Hz. So, at 1000 Hz response would be about 90 dB down.

You simply can’t affect this with an equalizer’s bandpass filters.

Regards,
Wayne


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## drummerbod (Jun 28, 2010)

Thanks - thought not. I couldn't see how to do it.

Looks like I will have to buy or make a LPF.


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