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Old 02-22-2017, 04:16 AM   #1
phonofranz
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Default ReaEQ's low pass filter changes with sampling rate

Just noticed this today on a mastering session involving ReaEQ.

I switched sampling rate from 48KHz to 96KHz (for other reasons) and heard sound becoming duller. Than I found that Low Pass filters in ReaEQ change steepness with samplerate. This is clear on the graph AND soundwise.


http://forum.cockos.com/attachment.p...1&d=1487761894

http://forum.cockos.com/attachment.p...1&d=1487761900


Is this an expected behaviour?
Attached Images
File Type: jpg Reaeq LP at 48KHz.jpg (40.6 KB, 307 views)
File Type: jpg Reaeq LP at 96KHz.jpg (39.2 KB, 314 views)
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Old 02-22-2017, 05:17 AM   #2
schwa
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For filters that affect frequencies near the Nyquist frequency, in other words exactly the situation you are describing, yes this is expected behavior.
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Old 02-22-2017, 05:31 AM   #3
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Thank you Schwa. After you answered I've tried with some third party plugins and they show same behaviour. Difference is subtle until you use a steep filter, where the effect is dramatic.
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Old 02-22-2017, 06:01 AM   #4
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Oversampling would solve this. You can try with Meldaproduction EQ which has oversampling.
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Old 02-22-2017, 06:33 AM   #5
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+1 for oversampling in ReaEQ
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Old 02-22-2017, 11:01 AM   #6
Dannii
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Quote:
Originally Posted by EvilDragon View Post
+1 for oversampling in ReaEQ
Another +1 to this long standing FR.
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Old 02-22-2017, 11:22 AM   #7
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if you work at 96Khz you shouldn't need oversampling, should you? I want to understand why schwa said it is the expected behaviour, and to understand why oversampling would solve this.

@phonofranz, duller when it is at 96Khz? based on your images, I think it would be duller at 48Khz.
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Old 02-22-2017, 12:43 PM   #8
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A low pass filter @ 15kHz has relatively little effect if the sample rate is 48kHz; at that sample rate the maximum theoretical frequency that can be represented at all is 24k so the filter just doesn't have much to work with. At 96kHz, a 15kHz filter has a much more significant effect. Oversampling would cause the 48k signal to be processed more like the 96k signal. Oversampling the 96k signal would be overkill.
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Old 02-26-2017, 07:28 AM   #9
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Quote:
Originally Posted by EvilDragon View Post
+1 for oversampling in ReaEQ
Thankfully there are hundreds of other EQ's on the market which have oversampling already.
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