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Linear phase pre-ringing: Does it effect all frequencies?
Old 2 weeks ago
  #1
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Linear phase pre-ringing: Does it effect all frequencies?

Hey

So if i do a low mid range, narrow Q cut with a linear phase EQ, and it introduces some pre-ringing, will the pre-ringing only affect the frequency that i cut, or will the pre-ringing apply to the entire frequency spectrum?
Old 2 weeks ago
  #2
Quote:
Originally Posted by bojobojo View Post
Hey

So if i do a low mid range, narrow Q cut with a linear phase EQ, and it introduces some pre-ringing, will the pre-ringing only affect the frequency that i cut, or will the pre-ringing apply to the entire frequency spectrum?
Maybe not answering your question but have you seen this video...

https://www.youtube.com/watch?v=efKabAQQsPQ
Old 2 weeks ago
  #3
Here for the gear
 

yeah its an amazing video, but it unfortunately doesn't answer my question
Old 2 weeks ago
  #4
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FabienTDR's Avatar
 

Verified Member
No, only the affected content (if there is any) will contain pre/post ring artefacts.

For example, in case of a AD/DA or SRC Nyquist filter, the filtered part, i.e. the part that gets removed by the filter is fully outside the audible band, so no pre-ringing can will leak below 20kHz, and thus, remain fully inaudible. That's why they can use incredibly steep filter of several thousand dB/oct and still sound great.

Or a different example. If you have a linear phase lowpass in the middle of the audible band, say cutoff at 800Hz, then all content above 800Hz will be by affected by the filter. Artefacts will be very obvious.

More precisely, only the stop band of a linear phase filter gets smeared, with linear phase, the pass band does exactly what it says: It passes the signal unchanged (just note that a smooth filter has a very large stop-band, often reaching into the audible area).
Old 2 weeks ago
  #5
Gear Addict
 

What I understand as pre-ringing is the part of the impulse response that comes before the signal (middle point of the IR in linear phase filters). This happens at a specific frequency, that is, peak frequency with bell filters and corner frequency with low-pass filters, and the amplitude decreases with time depending on Q, slope, etc. So from the two options "the pre-ringing only affects the frequency that you cut" is much closer to the truth.

Also, say, you have signal that's bandwidth-limited to 0-11khz. If you add a filter above that frequency, the output will basically phase-cancel with the original signal. Filtering corresponds to multiplication in the frequency domain, so this is a way of saying "0*x = 0".

Edit: Basically what FabienTDR said.
Old 2 weeks ago
  #6
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very helpful, thank you
Old 1 week ago
  #7
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Alexey Lukin's Avatar
 

Verified Member
Ringing happens when transient input signals exist at the frequencies where the filter's frequency response has sharp variations.

Example:
  1. A snare drum is filtered with a notch filter at 500 Hz → ringing (because transient energy is passing through the filter's action region)
  2. A bass guitar is passed through the LP filter cutting at 15 kHz → no ringing (because frequency ranges do not overlap)
  3. A sustained tone is filtered with a notch filter of the matching frequency → no ringing (because there's no transients)
  4. A hi-hat is filtered with a gentle shelving EQ → no ringing (because the frequency response does not have sharp variations)
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