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96khz 192khz

Postby iceman » Wed Feb 19, 2014 1:30 am

hi guys, im wondering are these worthwhile using? or do they just take up more disk space and mean that my interfaces have exciting looking numbers emblazoned on them?
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Re: 96khz 192khz

Postby hollowsun » Wed Feb 19, 2014 2:51 am

iceman wrote:or do they just take up more disk space and mean that my interfaces have exciting looking numbers emblazoned on them?
^^ That
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Re: 96khz 192khz

Postby Jack Ruston » Wed Feb 19, 2014 8:03 am

It depends.

In my experience there's no argument for 192 and in fact smarter people have argued quite convincingly that it causes problems. I suppose if you were really reaching for a reason you could say that it imposes a track count and processing limit that some might find charming. But the idea that bigger numbers means better quality represents a misunderstanding. What it means is more, but not be necessarily better. It's like taking biscuits out of a small box and putting them into a big one in the hope that there will be more biscuits.

96k is a slightly different matter. On the minus side it gives you large files and certainly adds to the processing bill. But it moves one of the tricky parts of converter design, the low pass filtering, well away from what we can hear, which allows a less well designed budget unit to punch above its weight. It's not so much that we need to hear higher frequencies but if we are going to box things in tightly, we need to do it elegantly. 96k also shortens system latency which can be useful in tracking. Some plug ins work better at 96k than at standard rates.

But make no mistake, a very good converter working at standard rate sounds very good. Most records are still made at those rates and many electronic records start off with sources of much lower quality than that.

If you're working with lower track counts, a lot of acoustic instruments or classical recordings there's a good argument for 96. Most pop music with higher track counts, and more processing works very well at 44.1kHz or 48.

Some would argue that the final destination is important. I think that we could well see a future shift towards higher resolution delivery and perhaps there's an argument for using 88.2 or 96 for that reason.

In an ideal world sample rate would be 64kHz.

J
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Re: 96khz 192khz

Postby The Elf » Wed Feb 19, 2014 8:22 am

I do use 96kHz from time to time, since I like how it can affect the low end of some recordings, especially acoustic guitar, piano and small string ensembles. But in general 44.1 is just fine - especially if you're as metal as you suggest! :D
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Re: 96khz 192khz

Postby Ian. » Wed Feb 19, 2014 9:05 am

I don't understand how sampling rates above 44.1 could do anything to make the audio sound better, especially when converters oversample anyway. What is the good argument for 96k with classical recording? Please tell, i'm interested.
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Re: 96khz 192khz

Postby John Willett » Wed Feb 19, 2014 9:15 am

I record classical at 24/96 or 24/88.2 all the time.

These higher rates avoid having the brick-wall filter at 20kHz and any artefacts that can ripple down into the audible frequencies.

I don't bother with 192kHz.
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Re: 96khz 192khz

Postby Jack Ruston » Wed Feb 19, 2014 9:40 am

Yeah, if you use 44.1kHz you're having to filter off at 22.05kHz. But you can't have a 'vertical' filter slope, and steep filters are a tricky business. So the filtering starts to creep down into areas that you can hear. In most rock, pop and electronic we're not concerned with those frequencies anyway. Often we're getting rid of them. But in something like classical where you might have a single pair of mics with extended frequency response and a very 'pure' sonic picture, it makes a difference. And with a stereo recording like that, there's no real downside.

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Re: 96khz 192khz

Postby MarkOne » Wed Feb 19, 2014 10:45 am

The Elf wrote:I do use 96kHz from time to time, since I like how it can affect the low end of some recordings, especially acoustic guitar, piano and small string ensembles. But in general 44.1 is just fine - especially if you're as metal as you suggest! :D

If anyone can point me to a reason that a higher sample rate can effect in any way the low end, I would be happy to read it.
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Re: 96khz 192khz

Postby James Perrett » Wed Feb 19, 2014 11:08 am

The only good reason for using 192kHz is for the times you want to sample signals with a bandwidth of up to 90 kHz or so. I'm not sure that it would ever be needed for normal audio work but there are industrial applications where it would be useful. I've certainly used 96kHz sample rates for recording sonar signals.

96kHz has its uses as Jack already mentioned. In addition, it can be useful when restoring old records as it makes click detection easier - any signal above about 20kHz must be a click (unless you are transcribing a CD-4 quadraphonic disc).
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Re: 96khz 192khz

Postby johnny h » Wed Feb 19, 2014 11:41 am

iceman wrote:hi guys, im wondering are these worthwhile using? or do they just take up more disk space and mean that my interfaces have exciting looking numbers emblazoned on them?
There are certain situations where higher sample rates make a difference but they are mainly due to poor converter design or poor plugin design.
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Re: 96khz 192khz

Postby Hugh Robjohns » Wed Feb 19, 2014 11:44 am

Jack Ruston wrote:I think that we could well see a future shift towards higher resolution delivery and perhaps there's an argument for using 88.2 or 96 for that reason.

In an ideal world sample rate would be 64kHz.

J


I'd go for 60kHz as the ideal -- it works better with all the video rates!

I'd also vote strongly against 'high resolution' delivery formats. The professional recording system should ideally be of higher quality than the delivery format, so that you have wriggle room in post production and can optimise the product for the end consumer. To me, that means 24/96 for recording, and 16/44.1 for delivery.

There is zero point in delivering higher wordlength for the typical home user since they won't have anything that can reproduce the potential dynamic range, and zero point in higher sampler rates since over-sampling delta-sigma converters avoid the potential filtering issues anyway.

From my perspective, 192 and higher rates are a complete waste of time. 96k is useful where you are concerned about high energy, high-frequency content and/or poor converter filtering. High sample rates are useful for some DAW processing, but most modern plug-ins now up-sample internally to deal with that anyway.

But other than that, it's 44.1 for general stuff and 48k if video related, and 96k for anything to be restored or used in sound design (where you might want to slow things down).

H
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Re: 96khz 192khz

Postby Hugh Robjohns » Wed Feb 19, 2014 11:53 am

Jack Ruston wrote:So the filtering starts to creep down into areas that you can hear.

Actually, Jack, it's usually the reverse. The designers keep the pass band maximally flat up to 22kHz or so, and then roll off above that... but because the attenuation slope is not vertical the filter doesn't actually comply with Nyquists requirements, and so some material above half the sample rate is deliberately let through. Most off-the-shelf converter chips only manage 6dB attenuation at the Nyquist frequency! :frown:

Anything that is let through above the half-sample rate will alias back into the audio band, producing anharmonmic distortion, but the presumption is that, in general, there isn't much energy at extreme HF and so the stuff that does get through won't be audible, and therefore most people wont notice most of the time -- but it most definitely a bodge!

However, where you are close-miking sources with a lot of strong HF harmonics and noise -- cymbals, brass and string instruments, etc -- and recording theme at relatively high level, you can get some subtle but perceivable aliasing problems if working at 44.1k. If working in that kind of situation, recording the source at 96kHz can be helpful.

H
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Re: 96khz 192khz

Postby Hugh Robjohns » Wed Feb 19, 2014 11:56 am

MarkOne wrote: If anyone can point me to a reason that a higher sample rate can effect in any way the low end, I would be happy to read it.

This is commonly reported but it most probably a perceptual illusion -- the cleaner top end seems to make the bottom end appear clearer too. Odd... but similar effects have been noted by loudspeaker designers where better tweeters appear to improve the low end!

Our sense of hearing is nothing short of weird!

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Re: 96khz 192khz

Postby The Red Bladder » Wed Feb 19, 2014 12:41 pm

Hugh Robjohns wrote:However, where you are close-miking sources with a lot of strong HF harmonics and noise -- cymbals, brass and string instruments, etc -- and recording theme at relatively high level, you can get some subtle but perceivable aliasing problems if working at 44.1k. If working in that kind of situation, recording the source at 96kHz can be helpful.

Exactly that!

In the good-old/bad-old days when men were men, almost all we worried about was noise and headroom. Then the first ADDA things appeared and we got the most terrible top end, esp. from early ProTools converters. According to Barry at iZ-Technology (Radar) they were poorly clocked and they had not been able to get the filtering (as Hugh describes above) quite right.

When mastering, I could always tell if something had been recorded in ProTools, because the spectrum analyser would stick to the side right at the top end at about 18-20kHz, rather like water to the side of a dirty glass. Somewhere up there, there was a nasty whistle that had to be filtered off.

With the introduction of the better clocked converters in the HD systems and of course others like Apogee and Radar, that nasty and distorted top end disappeared.

But for those of you who like to record at 96kHz, please remember that most studio microphones only go up to about 22kHz anyway. If you really push some of the newer designs, you can get up to nearly 30kHz, but then it is at -40dB or more, compared to the usual 20-20k that they all claim. A good converter at 44/48 is better than something mediocre at 96kHz.

Also, having equipment (desk, pre-amps, etc., etc.) that goes into RF brings its own problems, ranging from gain controls that can act as RF wobblers, to picking up Radio China. For that reason, many bits of kit (some of which even claim F ranges up to 200kHz) are capped all over their longer signal paths to keep the RF out. The customer naïvely likes to see a F range from zero to 200kHz, but for some reason, complains if the gain pot makes funny noises and longer unbalanced lines are able to receive a detailed report on shoe production in the Shaanxi province.

As for video/film compatibility - everybody and their mothers-in-law are batting on about 4K at 60 fps, so a 60kHz sample rate would indeed be ideal.

But then just as soon as we have all settled down at 4K/60fps, no doubt somebody will insist on 8K and 120 fps as being the 'new standard.'

And so we merrily go on!
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Re: 96khz 192khz

Postby Jack Ruston » Wed Feb 19, 2014 12:50 pm

Hugh Robjohns wrote:
Jack Ruston wrote:So the filtering starts to creep down into areas that you can hear.

Actually, Jack, it's usually the reverse. The designers keep the pass band maximally flat up to 22kHz or so, and then roll off above that... but because the attenuation slope is not vertical the filter doesn't actually comply with Nyquists requirements, and so some material above half the sample rate is deliberately let through. Most off-the-shelf converter chips only manage 6dB attenuation at the Nyquist frequency! :frown:

Anything that is let through above the half-sample rate will alias back into the audio band, producing anharmonmic distortion, but the presumption is that, in general, there isn't much energy at extreme HF and so the stuff that does get through won't be audible, and therefore most people wont notice most of the time -- but it most definitely a bodge!

However, where you are close-miking sources with a lot of strong HF harmonics and noise -- cymbals, brass and string instruments, etc -- and recording theme at relatively high level, you can get some subtle but perceivable aliasing problems if working at 44.1k. If working in that kind of situation, recording the source at 96kHz can be helpful.

H

Ah interesting. Thanks Hugh!
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