# [PD] lop~ and hip~ difference equations

Joe White white.joe4 at gmail.com
Fri Feb 19 14:58:17 CET 2016

```These should be the coefficients for implementing hip~ with rpole~ and
rzero~

Fc - cutoff frequency
Fs - sampling frequency

a = 1 - (Fc * 2 * pi / Fs) // 0 <= a <= 1
b = (a + 1) / 2

w[n] = x[n] + a[n] * w[n-1]

y[n] = b[n] * (w[n] - x[n-1])

On 19 February 2016 at 10:34, Dario Sanfilippo <sanfilippo.dario at gmail.com>
wrote:

>
> You're right, Joe. I was actually referring to hip~ when talking about the
> impulse response, indeed hip~ is one-pole and one-zero. It might be good to
> specify it in the help file.
>
> What formula would you use for the coefficients of rpole~ and rzero~ to
> implement it?
>
> Cheers,
> Dario
>
>
>
> On 18 February 2016 at 20:27, Alexandre Torres Porres <porres at gmail.com>
> wrote:
>
>> let me share some patches too.
>>
>> as said: lop~ is not the same as rpole~ but is possible to be implemented
>> using rpole~, hip~ can be implemented with rpole~ and rzero~
>>
>> my patches show the difference equations and all, they're in portuguese,
>> and part of my computer music class examples available here
>>
>> cheers
>>
>> 2016-02-18 14:32 GMT-02:00 Joe White <white.joe4 at gmail.com>:
>>
>>> Hey Dario,
>>>
>>> [lop~] can be implemented with just an [rpole~], did you make sure to
>>> set the coefficients correctly? I've attached an example patch to implement
>>> [lop~].
>>>
>>> [hip~] is an [rpole~] and [rzero~] in series. You can find the
>>> coefficients in the source code.
>>>
>>> Cheers,
>>> Joe
>>>
>>> On 18 February 2016 at 14:59, Dario Sanfilippo <
>>> sanfilippo.dario at gmail.com> wrote:
>>>
>>>> Hello, list.
>>>>
>>>> Do you know what the difference equations of [lop~] and [hip~] are?
>>>>
>>>> Just hoping that one of you has a quick answer, otherwise I'll try
>>>> figuring it out by looking at the code.
>>>>
>>>> Anyway, they don't seem to be the same as [rpole~] as the impulse
>>>> response is different.
>>>>
>>>> Thanks,
>>>> Dario
>>>>
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>>>
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>
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