Order of Hi Pass + Low Pass filters?

Jan 18, 2012 at 11:02pm

Order of Hi Pass + Low Pass filters?

Hello I have a Low pass filter + Hi pass filter in my patch, each controlled by a single pot (dial) in an attempt to mimic a typical EQ section on a mixing desk. Anyway my question is would the signal chain go:

Signal>HI pass> Lo Pass> Out (or Vice Versa)

>HI Pass
OR Signal > Out
>Lo Pass

Hope the question is clear enough, thanks!

#61325
Jan 18, 2012 at 11:11pm

Typically these are shelving filters with fixed frequencies, but however, if i understand your question,
The Lowpass-highpass or Highpass-Lowpass
really shouldn’t make an audible difference, does it? But i think you can easily search the web for cicuit plans of any mixer.
I don’t understand
“>HI Pass
OR Signal > Out
>Lo Pass”

Are you thinking about patching them serial/parallel?
in the typical mixer, they are serial.

Cheers!

#221070
Jan 18, 2012 at 11:32pm

Hi thanks or the reply, yeah wasn’t the best worded question sorry about that, my diagrams could do with a bit of work but yeh it was whether they are serial or paralell, thanks!

#221071
Jan 19, 2012 at 2:16am

Actually, since the typical bands of those filters don’t cross, it also doesn’t matter if they are serial or parallel :)

#221072
Jan 19, 2012 at 4:18am

they need to be in series otherwise they just wont work
the exception to this is band pass which are generally in parallel

#221073
Jan 19, 2012 at 4:44am

oops sorry youre right, serial

#221074
Jan 19, 2012 at 4:51am

sorry but wouldn’t they work if they are shelving filters and turning the knobs is adjusting the gain? Clearly, their efficiency would be decreased a lot, but they would do *some* attenuation of the corresponding frequencies, no? And with bandpass you mean the mid attenuation? why is that parallel?

#221075
Jan 19, 2012 at 11:04am

if a hp filter is in parallel with a low pass, then the frequencies you want filtered out by the high pass (low frequencies) will be passed by the low pass and vice-versa, so everything gets passed. It will have an effect on the sound, but not as generally intended as indicated by the names “high-” and “low-pass”. tHis also applies to notch filters– they should be done in series

The converse is true for band pass filters, and therefore they should be aligned in parallel

#221076
Jan 19, 2012 at 4:59pm

This is not answering your question exactly, but if you want to create an EQ you will probably have more luck with the cross~ object which is purpose built for frequency splitting while every day use high / low / band pass filters are not :)

#221077

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