hard filter

[Babak]

Hi,

How can I set a hard filter, e.g. cut off everything below 30 Hz?

If I use the AU LowShelf with a gain of -40 dB @30Hz, also Frequencies above 30 Hz get reduced.

Is there a way just to reduce frequencies bekow 30 Hz without touching the freqiuencies above?

Cheers

Babak

[Sonic Purity]

Hi,

How can I set a hard filter, e.g. cut off everything below 30 Hz?

If I use the AU LowShelf with a gain of -40 dB @30Hz, also Frequencies above 30 Hz get reduced.

Is there a way just to reduce frequencies bekow 30 Hz without touching the freqiuencies above?

Cheers

Babak

In Amadeus II this is easy: use the Filter function under Effects. I am not seeing this function in Amadeus Pro. Hopefully others may know more. Maybe Martin can explain why the Filter function is not in Amadeus Pro (maybe something else which i do not know about superceded it).

[CDJonah_alt]

Try the AU high pass filter and set the cutoff at 30 hz. If you want a
deeper cutoff, you can try using the filter twice.

note that sharp filter cutoffs can create some really strange artifacts.

Chuck

Sonic Purity wrote:

Babak wrote:

Hi,

How can I set a hard filter, e.g. cut off everything below 30 Hz?

If I use the AU LowShelf with a gain of -40 dB @30Hz, also Frequencies above 30 Hz get reduced.

Is there a way just to reduce frequencies bekow 30 Hz without touching the freqiuencies above?

Cheers

Babak

In Amadeus II this is easy: use the Filter function under Effects. I am not seeing this function in Amadeus Pro. Hopefully others may know more. Maybe Martin can explain why the Filter function is not in Amadeus Pro (maybe something else which i do not know about superceded it).

------------------------
))Sonic((




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[Babak]

Hello

Try the AU high pass filter and set the cutoff at 30 hz. If you want a
deeper cutoff, you can try using the filter twice.

note that sharp filter cutoffs can create some really strange artifacts.

Chuck

Babak wrote:

Hi,

How can I set a hard filter, e.g. cut off everything below 30 Hz?

If I use the AU LowShelf with a gain of -40 dB @30Hz, also Frequencies above 30 Hz get reduced.

Is there a way just to reduce frequencies bekow 30 Hz without touching the freqiuencies above?

Cheers

Babak

Thanks for the reply.

I have tried both the HiPass and the Low Shelf filters.

The strange thing is that ith both also frequencies above 30 Hz are affected:

With the HiPass, I get some increase of frequencies aorund 35 Hz.
The Low Shelf also decreases frequencies above 30 Hz.

What artefacts do you mean and why are they created?

Cheers

Babak

[CDJonah_alt]

This is all supposition, but it is probably right.

Most filters actually work in the time domain rather than the frequency
domain. This really means that it doesn't cut off based on a frequency
but by summing and weighting digital values. If, for example you have a
slow square wave and put too sharp a frequency cutoff on the signal, it
will no longer be square but show overshoot (ringing) (I don't think
this is related to the Gibbs phenomenon, but I am not sure, almost
certainly Martin knows). You could take a look at the Wikipedia article
on digital filter -- in that case, they assume you have an analog
converter to create the digital signal, use the filter and then follow
up with a a Digital to analog converter to get back to an ordinary
voltage. It is only the middle stage that you are interested in.

Possibly a better question to ask is: why do you want to sharply cut off
at 30 hz -- an absolute shelf phenomenon?

Chuck

Babak wrote:

Hello

Try the AU high pass filter and set the cutoff at 30 hz. If you want a
deeper cutoff, you can try using the filter twice.

note that sharp filter cutoffs can create some really strange artifacts.

Chuck

Sonic Purity wrote:

Babak wrote:


Thanks for the reply.

I have tried both the HiPass and the Low Shelf filters.

The strange thing is that ith both also frequencies above 30 Hz are affected:

With the HiPass, I get some increase of frequencies aorund 35 Hz.
The Low Shelf also decreases frequencies above 30 Hz.

What artefacts do you mean and why are they created?

Cheers

Babak




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[Babak]

Hi

thanks for the explanation.

Possibly a better question to ask is: why do you want to sharply cut off
at 30 hz -- an absolute shelf phenomenon?

I wanted to show some people that frequencies do matter in orchestral recordings in order to create a sense of space and dynamics.

So I hoped that I could get rid of those frequencies so I could let them compare the sounds

Cheers

Babak

[CDJonah_alt]

When I tried a white noise sample generated via AP, it looked like it
cut the lows about 20 dB, which I would think should be more than enough
to be audible for any purpose. I didn't see "that much" effect above 30
hz. I used the high frequency pass with a 0 db resonance -- with the
superb documentation on these plugins, you should be able to figure out
what the resonance parameter does!

Chuck

Babak wrote:

Hi

thanks for the explanation.

Possibly a better question to ask is: why do you want to sharply cut off
at 30 hz -- an absolute shelf phenomenon?

I wanted to show some people that frquencies do matter in orchestral recordings in order to crrate a sense of space and dynamics.


Cheers

Babak




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--
Charles D. Jonah CDJonah@anl.gov
630-252-3471
Chemistry Division
Argonne National Laboratory
Argonne, IL 60439



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