How much dynamic range is possible in a simple stereo recording?

[esldude]

Hear ye, hear ye, please listen and testify. 

 

With two microphones and a stereo recording how much dynamic range is actually possible? We'll assume using more than two microphones is a treasonous perversion of the stereo medium. 

 

What say ye?  And yes be prepared to defend your opinions.  If you've only anecdotal listening impressions, you're entering a gunfight with a knife.  

 

Is dithered 16 bit digital all anyone needs for distribution of recordings? If not why not?

[esldude]

15 hours ago, Miska said:

 

About 18 - 20 bit worth.

 

 

I think it would be good to preserve original dynamic range of the recordings.

 

 

I picked two hires recordings at random. And for example for these cases 16-bit resolution limits dynamic range compared to original.

 

Here's 2L-111 original 24-bit DXD:

Same dithered to 16-bit:

Keeping the sample rate and using noise shaping the 16-bit would preserve all information though.

 

One DSD256 recording, converted to 88.2 kHz 24-bit PCM:

Same dithered to 16-bit:

 

 

It is not very straightforward to say whether 16-bit is enough because it also depends on sampling rate if you use noise shaping. At high enough sampling rate 1-bit is enough.

What range do you have set for the spectrogram here? As in how many db Range?

[esldude]

I had in mind starting with the event and proceeding thru the chain of recording and reproduction. 

 

I'll assume a two mic recording of no more than 120 db SPL for the recorded event. 

 

A good quiet LDC has a few db self noise.  I'll use 4db as an example.  

 

The sensitivity and range of mic pres would mean you'll need about 25 db of gain so that 120 db SPL puts the ADC near 0 dbFS.  The amplified self noise will sit at 29 db FS.  Leaving you only 91 db of max signal to noise ratio.  This is before counting any ambient noise of the venue which one has to think is going to be at least 30 db which also will be amplified by the microphone preamps.  Meaning you may only have 65 db of signal to noise ratio.  

 

Of course our ears can in the most sensitive range (3-5khz) hear some 15 db into noise.  Plus in that range in ERB units the noise floor is likely some 20-25 db lower.  So we regain some of the range our microphone preamps took away in the range we hear with best sensitivity.  Plus few, few recordings, less than 1% are recorded in this manner, and without compression of any kind.  

 

Either way, dithered 16 bit will get you around 120 db effectively with tpdf dither (more if heavier noise shaping is used).  

[esldude]

6 minutes ago, fas42 said:

 

Yes, it's the 'subjective' dynamics that do it for the hearing - so, how does one correlate that with measurements, and number of bits?

With dither we can get more or less 120 db dynamic range with 16 bit audio.  Do you need more?

 

LP's would lead me to think with the right kinks in the transfer function you don't need that much for subjectively good dynamics. 

 

The use of tasteful compression leads me to the same conclusion. 

[esldude]

We are not talking subjective dynamic range. I want to stick with measured dynamic range. We already know the two don't correlate with each other.

[esldude]

A Lewitt LCT 540 subzero has 132 db of dynamic range. 4db self noise and 136 db max with no padding. It also is a little more sensitive requiring a bit less gain.

[esldude]

31 minutes ago, The_K-Man said:

 

I'm genuine surprised to hear that from someone in an Audiophile forum.  Just remember that there are more than one way to measure the dynamic range of a song.

 

That Sound On Sound article https://www.soundonsound.com/sound-advice/dynamic-range-loudness-war    describes but a few.  Crest factor and PLR(Peak-to-Loudness Ratio) are two of them.

Well for this topic I'm interested in physically possible dynamic range that can be recorded. To keep from mixing subjective range and the various ways of ranking recordings I wish to leave that for another topic.

[esldude]

36 minutes ago, The_K-Man said:

 

You want maximums then. Ok.

 

In purest terms, 16bit = 96dB, 24bit = 144dB, 32bit float = 192dB?  I can't add 2+2, so someone check that last one for me.

So which microphone and recording venue gets us to 144 db?  The answer is none of them. So then the question is how close do we get?

[esldude]

2 hours ago, Miska said:

 

For example Neumann KM183 has A-weighted self-noise of 13 dB and maximum SPL  is 140 dB (0.5% THD). DPA 4006 has A-weighted self-noise of 15 dB and maximum SPL 146 dB. Many of these microphone models have a switchable pad from 10 to 20 dB, so you can roughly shift the dynamic range down by that amount in SPL.

 

But anyway, one way to check is to go through bunch of hires material and see what they have. With my earlier checks and random pick I can say that it is at least more than 16-bit worth.

I couldn't see what in your earlier spectrogram was indicating the difference. Could you explain so I might understand? 

[esldude]

2 hours ago, Miska said:

 

Question was about needed digital resolution, so noise-shaping applies in that scope. Noise shaping also affects analog domain if you measure unlimited bandwidth.

 

 

There's a difference on what is detectable level of discrete tone vs  dynamic range. There's no problem detecting single sine at -120 dB in dithered 16-bit data. But if the signal is white noise at -120 dB level, it is undetectable from the noise floor.

 

 

You can only achieve that with 16-bit if you can move enough of the noise out of audible frequency band, which means you have enough sampling rate to move Nyquist far enough above audible frequency band to make space where to "park" the noise moved away from audible band.

 

For example 16-bit data has fixed total noise level, but it's frequency distribution can be anything you decide. However, if your sample rate is 40 kHz, all your usable bandwidth falls within audible range, so you have no place outside of audible band where to move that quantization noise.

 

My understanding is with dither for 44 and 48 khz rates, you shift noise away from where hearing is most sensitive to areas where our thresholds are higher. So the noise is all in the audible band, but still at levels we'll not hear it. While decreasing noise where we might thereby extending the range effectively for human ears.

[esldude]

2 hours ago, jabbr said:

There are two entirely different questions which are being conflated here:

 

1) what is the maximum dynamic range that can be recorded

vs

2) what is the maximum dynamic range than can be perceived

 

Those are two significantly different discussions. Folks who are purely interested in perception need to understand the intricacies of recording eg noise shaping — @esldude can say if he intends this thread to discuss perception?

Actually I intended to approach #1 first and then proceed to #2.  

 

#2 however wasn't intended to become "which recording sounds more dynamic to me".  Because it is already known what sounds dynamic vs being of greater dynamic range are two different things altogether. 

 

Now some microphones will record cleanly to 155 or 160 db.  For stereo pair recordings that isn't of much significance.  For up close recording of drum sets or guitar amps it is.   From a natural stereo pair recording saying something had a dynamic range of 135 or 140 db wouldn't mean much as the listener at such an event isn't going to sit happily listening at those levels to achieve that.  Which is why I did mention 120 db SPL. 

[esldude]

14 hours ago, Arpiben said:

And what about sensivity or S/N?

For KM183 S/N = 70 dB (/94dBSPL IEC 60268-1).Noise Floor = 24 dBSPL.

Then what about the noise contribution of amplifiers and other analogue equipment before ADC ? Just curious since I have only a rough idea.

You may know, but for others that may not. Microphone S/N specs are not what you might think. They use 94 db SPL as a reference (which is one Pascal) and subtract microphone self noise.

 

As Miska said at higher levels the SNR  as you are used to seeing with electronic gear would be mostly down to highest distortion.

 

Most good mic pre amps contribute so little noise it isn't an issue. But if you used gain in the mic pre amp this gain applies to the noise from the mic or the ambient noise. So the example I used earlier is with a Shure KSM 44A.  With my other gear 25 db of mic pre gain will result in 120 db SPL recording at 0 db fs. The 30 db SPL ambient noise will be 90 db below that 120 db SPL peak level. The self noise of the mic will contribute little being 116 db below peak levels.