Cycling '74

Did you know you can make a high-pass filter using a low-pass filter?

Did You Know #5: High Pass Filters

atch the entire Did You Know series on our Youtube playlist

Watch the entire Did You Know series on our Youtube playlist!

Make a high-pass filter using a low-pass filter.

week-5

This is definitely a fun trick in the DSP world. Be aware, however, that you will not get the same rolloff as a highpass filter with matching coefficients for most filters (except for onepole~ or a biquad~ using only poles), so if you want a highpass with a steep rolloff, use a cascade of biquad~'s. If memory serves, the subtraction works on the poles of the filter, which is why in the attached demo this works with a cascade of onepole~s, but not with a cascade of biquad~s.

This is definitely a fun trick in the DSP world.  Be aware, however, that you will not get the same rolloff as a highpass filter with matching coefficients for most filters (except for onepole~ or a biquad~ using only poles), so if you want a highpass with a steep rolloff, use a cascade of biquad~'s.  If memory serves, the subtraction works on the poles of the filter, which is why in the attached demo this works with a cascade of onepole~s, but not with a cascade of biquad~s.

any idea how can i generate filters in max msp using external co-efficient that i got from MATLAB, basically i am looking forward to build an Linear Phase Fir Filter in max msp. Is this possible

Hi
any idea how can i generate filters in max msp using external co-efficient that i got from MATLAB, basically i am looking forward to build an Linear Phase Fir Filter in max msp. Is this possible


did you look into filterdesign ? and filtercoeff~ ?

yeah i looked, but i guess i can only make IIR filters from filter design tool. I found this the following patch from a msp tutorial where i can put my filter co-efficient and see the response but i cant actually use it to filter my audio signal.

Hi,
yeah i looked, but i guess i can only make IIR filters from filter design tool. I found this the following patch from a msp tutorial where i can put my filter co-efficient and see the response but i cant actually use it to filter my audio signal.


hm it seems not simple indeed ! i thought it would be simple !... By any chance, did you look into buffir~ ?

ok actually, if i understand correctly, buffir~ is the object you need. i'll give it a try

thanks for the quick replies. I am looking into the example patch of buffir~ since yeastarday. i cant seem it to figure out how it is actually working. I understood i will need a buffer to save my impulse response in order to use the buffir~ object. but i cant go any further. it would be great if you give it a try. i am stuck in the office with this one.

hi,
thanks for the quick replies. I am looking into the example patch of buffir~ since yeastarday. i cant seem it to figure out how it is actually working. I understood i will need a buffer to save my impulse response in order to  use the  buffir~ object. but i cant go any further. it would be great if you give it a try. i am stuck in the office with this one.


okay, here's what i got after tryiing using that buffir~. No idea if it's the expected result tbh...

thanks again a lot, just give me sometime to look around it. i will get back to you as soon i find if its giving the expected results or not.

Week 5: High- and Low-pass Filters