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shibatch eq...
post Aug 15 2002, 08:47
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i was wondering if anyone has any eq presets for shibatch that they have compiled of adaptations from audio editing applications (eg sound forge, cool edit) or presets catering to their own needs?
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post Aug 18 2002, 12:17
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Originally posted by Joe Bloggs
I thought KikeG said that pre-ringing is not audible What about the variety you get in the brick wall filter for CD?

The only thing you could have heard me saying is that pre-ringing due to brickwall filtering at CD's is not audible.

Ringing in filters happens whenever there is an abrupt discontinuity in the frequency response of the filter. If there is sonic "content" in the original signal at the frequency this discontinuity exists, pre or post ringing will appear. The more abrupt the discontinuity (~ higher slope, or steeper filter), the greater the time-domain ringing.

In CD brickwall filters, the discontinuity happens near 22 KHz. So, if there is any ringing, it will appear at these frequencies. Also, for this ringing to appear, the signal must have content at these frequencies.

Thinking a little bit more about this, in a properly recorded cd signal, there should be no content at these frequencies, because it must have been filtered at the AD stage in order to avoid aliasing. However, this AD pre-filtering can also produce ringing, if there was any content at the filtering frequencies in the original signal. So, if there is any ringing, it is already present in the recorded signal, and (most likely) not produced by the cd player brickwall filter. I say most likely because if the CD player filters at a lower frequency than the AD filter, it will eliminate the AD filter ringing, but will introduce its own. However, I don't think this is likely to be the case. Also, in the case of same synthetic generated signals, there can be no AD stage, then the ringing would happen due to the player filter, but I also think this is not very common, or likely to happen in commercial CD's.

So, there can be ringing in the cd signal, but this ringing will be near 22 KHz, which is inaudible. Also, using a proper not ultra-steep AD filtering, this ringing time duration can be minimized.

Although 22 KHz is not audible, if there are nonlinearities in the playback path at this frequencies, this 22 KHz ringing might intermodulate with other signals and produce intermodulation products which fall into the audible band of frequencies, and in fact "became" audible. However, and as recapitulation, for this intermodulation products to happen and be audible (which is our "final" main concern now), some conditions have to be satisfied:

- There must be signal content in the original signal at 22 KHz. For the ringing to have audible significance, this 22 KHz content must be of relatively high amplitude, and of "transient" type, that is, of very short attack or decay times.

- The AD stage pre-filtering must be quite steep. I believe that with a relatively "soft-edge" filter, the ringing duration and amplitude can be quite minimized. However, I don't know how steep are actually the filters commonly used.

- The playback chain (mostly speakers or headphones) must be able to reproduce this 22 KHz signals, and also be quite nonlinear a this frequencies. I think that good speakers of headphones capable of reproducing such high frequencies are not likely to be very nonlinear. However, I could be wrong.

So, I think that this ringing in CD audio is very, very difficult to be noticeable, and even if it was a real problem, could be effectively adressed using proper AD pre-filtering.

BTW, IIR filters are not phase linear. And if an EQ is not phase linear no self-respecting audiophile will touch it. :diabolic:  

As Frank Klemm explained, for "taste" filtering at audible frequencies, minimum phase filters are preferred, because they show no pre-ringing, only post-ringing, and human ear is very sensitive to pre-ringing, but in comparison almost deaf to post-ringing. Human ear is also quite insensitive to phase distortion, being more insensitive to phase the higher the frecuency.

edit: I've just measured some real world cd players's ringing on an impulse signal, of about 0.5 ms, which is simply below perceptibility of ear.
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Posts in this topic
- ProtectYaNeck36   shibatch eq...   Aug 15 2002, 08:47
- - Joe Bloggs   I have one--it's tailored for improving the FR of ...   Aug 15 2002, 10:09
- - Messer   QUOTE Originally posted by Joe Bloggs BTW, have y...   Aug 15 2002, 12:36
- - Pio2001   Argh ! That transient discussion in the second lin...   Aug 15 2002, 13:04
- - Pio2001   Okay, forget my last sentence, it's completely wro...   Aug 15 2002, 13:12
- - KikeG   A cople of comments: - First, I have have had som...   Aug 16 2002, 03:47
- - Joe Bloggs   QUOTE From http://shibatch.sourceforge.net/ An ac...   Aug 16 2002, 07:02
- - Pio2001   QUOTE Originally posted by KikeG Shibatch SuperEQ...   Aug 16 2002, 11:12
- - KikeG   Joe: From SuperEQ included dsp_supereq.txt file:...   Aug 16 2002, 19:53
- - Pio2001   Using a steep cutoff, there is much time smearing,...   Aug 16 2002, 20:26
- - KikeG   I'd say this is due to SoundForge implementation. ...   Aug 16 2002, 20:55
- - Joe Bloggs   I thought you said that pre-ringing is not audible...   Aug 18 2002, 04:58
- - DSPguru   QUOTE Originally posted by Joe Bloggs IIR filters...   Aug 18 2002, 05:36
- - KikeG   QUOTE Originally posted by Joe Bloggs I thought K...   Aug 18 2002, 12:17
- - Joe Bloggs   Um, what's LTI? Hmm... but can't you say that FIR...   Aug 18 2002, 12:52
- - daniel   QUOTE being more insensitive to phase the higher t...   Aug 18 2002, 13:45
- - Joe Bloggs   QUOTE Originally posted by daniel he's right. Hm...   Aug 18 2002, 17:32
- - Gecko   What about analog equpiment? Especially the filter...   Aug 18 2002, 17:54
- - daniel   QUOTE Do they introduce time smearing or have othe...   Aug 18 2002, 20:54
- - Sachankara   QUOTE Originally posted by Gecko [b] ("Frequenzwei...   Aug 18 2002, 21:16
- - Pio2001   QUOTE Originally posted by daniel he's right. Wh...   Aug 18 2002, 21:59
- - KikeG   QUOTE Originally posted by Joe Bloggs Um, what's ...   Aug 19 2002, 00:01
- - gft   Actually, I have the same question as the original...   Aug 19 2002, 06:33
- - Joe Bloggs   to gft: Why don't you just press 'up' 3 times to r...   Aug 19 2002, 07:00
- - daniel   QUOTE To avoid this, one must use bi-amplification...   Aug 19 2002, 13:08
- - KikeG   I just measured some real world cd players pre-rin...   Sep 12 2002, 00:19
- - Joe Bloggs   ... and what would be your estimate of the amount ...   Sep 12 2002, 08:01

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