Does analog media force a dynamic on music? or Does Analog Media increase the dynamics? Impact of Brickwall limiter.

[Jean.Francois]

Hi,
Previously in the dynamics of music, we saw the difference between the dynamics of the medium and the dynamics of the music, as well as the effects of dynamic compression on the music in terms of distortion.
Today, we will discuss another aspect, the impact of dynamics on tape or vinyl recording.
The subject seems simple, we transfer the digital file to tape or vinyl and it is reproduced with little or no modifications.
To do this, we will use a test master file that includes the same musical sample with a different DR ranging from DR19 to DR7 as shown in the graph below :



This master file is burned on vinyl and played on a turntable. We then obtain the following result:



We notice that the variation is only from DR17 to DR10. In particular for the low DR, we notice that we do not go below the DR10.
To better represent this phenomenon, here is a synthesis curve which presents on the horizontal axis the DR value of the master from DR7 to DR19, and on the vertical axis the DR result after the playback of the vinyl cut with this master:



We can see that the vinyl does not go below DR10 in this example. This increase is therefore a distortion generated during the cutting and playback process compared to the original master.
Why this result? Vinyl is analog and it uses electromagnetic and mechanical means that give it a specific functioning. This operation is not compatible with certain digital treatments like the use of the Brickwall limiter which strongly distorts the signal in the digital world.
To go further in this test, the same operation is carried out with a magnetic tape on which we record the reference master. On playback, we obtain the same phenomenon as shown by the synthesis curve grouping the vinyl and the tape:


What can we conclude :

• Analog media have their own characteristics that must be respected to obtain a faithful reproduction on these media. Therefore, a specific master is needed for these media.
• The use of brickwall limiters generates distortion, and if you burn a vinyl or record a tape from this type of digital master, you generate distortion again. It's a double punishment by accumulating distortion twice. So it's anything but high fidelity.
• Measuring the DR on analog media is possible, but it does not always allow you to deduce the DR of the master that was originally used.

Find the whole test with more details on its realization and the measurements here.

Jean-François

 

[MaxwellsEq]

Very interesting. I'm not completely surprised.

 

[Jim Shaw]

Interesting, especially as we are pressed to describe the defacto appeal of vinyl. I will follow this discussion. I don't have the time or energy to read the research about vinyl's limitations vs. good digital. But I'm interested to learn from other competent individuals' grounded research.

Just, please, no audiodolt upchuck like "vinyl sounds better, harrumph."

 

[DVDdoug]

They didn't say how this experiment was done. Were they in control of the vinyl mastering & cutting and do they know if it used the same or different master?

It's a little easier to get ahold of a tape recorder but they don't say how they did it. When I was doing home recording in the analog days, it was common to go occasionally "into the red" to optimize the signal-to-noise ratio. Tape tends to soft-clip and the tape record/playback further smooths the clipping so it makes a pretty good limiter (minimal harmonic distortion). I suspect pro studios also occasionally went into the red but over time tape improved and there was more headroom so depending on how the machine was calibrated, they may have been able to go well over 0dB without clipping/limiting.

All of these formats should be capable of handling the full dynamic range of regular music except at very low levels (or silence) where analog noise becomes a problem. The noise doesn't usually affect the measurement of program dynamics but it does affect the measurement of the equipment or storage/transmission channel. (When I was playing a records, a lot of my records and clicks & pops that weren't exactly "low level" but they didn't affect dynamic range of the music.

If "DR" is the crest factor (peak-to-average ratio) it's a poor representation of perceived dynamic range (or musical "dynamic contrast"). There is no perfect way to measure dynamic contrast because there are long-term and short-tern dynamics and everything in-between. But IMO, EBU R128 loudness range ("LRA") is better because it tries to measure the range (or a range) of perceived loudness.

MP3 compression (file compression unrelated to dynamic compression) also distorts the wave shape, making some peaks higher and some lower, for a "better" DR calculation. But these short-term peaks don't contribute to perceived loudness so it doesn't change the sound of the dynamics. I've ripped lots of CDs to MP3 and many of the MP3s peak over 0dB. (MP3 can go over 0dB whereas CDs cannot.) I believe this phenomenon is exaggerated with "artificially limited" (or clipped) material.

 

[Jim Taylor]

I want to be perfectly clear about one thing; I'm just an old man who watched people cut many years ago.

Which lathe did you use to cut a vinyl master?

Long ago, there were oodles of filters on a lathe to protect from overcutting ... and more importantly, overheating. Not only that, but the mastering that I saw involved controlling the low frequencies by hand, to reduce the obviousness of groove noise. I was told (and I believed the person telling me) that some more expensive and more complicated lathes could be set to do this automatically. It appears that some of that may be occurring on your charts, no?

I apologize if all this incoherent rambling from the time of the dinosaurs has no bearing on your post. I just thought your conclusions were a bit odd, considering the methods employed in lacquer or vinyl cutting to protect the equipment rather than the recording.

Jim

 

[Jean.Francois]

I detail more in the complete article the course of the test.
For the vinyl cutting it's a direct cut and the magneto used is a Teac 3440. We have the control of the master as well for the tape as for the vinyl cutting.
We use only one master which includes the 8 extracts with different DR.
The level is not pushed to red, to not have the natural compression of the tape.

The problem is for the weak dynamics with the use of a brickwall limiter. We notice that the tape or the vinyl does not support a weak DR and transforms the signal and regenerates the signal and thus the dynamics.
It is the digital processing of the brickwall limiter that does not pass on a vinyl or tape support.
It must be said that it is a treatment that generates a very strong distortion of the signal.

The protection mechanisms of the vinyl cut do not produce this phenomenon, which is also found on the tape.

This means that if actual records are cut from a compressed master, the analog functioning of the vinyl (or tape) is not respected and the increase in dynamics generated is only additional distortion.
And I'm not sure, with the vinyl craze, that everything is done properly for all vinyls.

Unlike MP3, which produces a digital phenomenon, for vinyl and tape, it is an analog phenomenon.

Concerning the measurement, whether with DR or LUFS with True Peak, it only changes the representative values per type of measurement, but does not change the curves and conclusions.

 

[Cbdb2]

So your saying tape and vinyl are dynamic range expanders/compressors with a ratio dependant on the compression of the original signal? Can you explain the mechanism? What are the time constants, where do they come from? Hard to believe they would be the same for tape and vinyl when they are such different processes. Would like to see what happens with DR test signals that show the compression/expansion parameters.

 

[Waxx]

So your saying tape and vinyl are dynamic range expanders/compressors with a ratio dependant on the compression of the original signal? Can you explain the mechanism? What are the time constants, where do they come from? Hard to believe they would be the same for tape and vinyl when they are such different processes. Would like to see what happens with DR test signals that show the compression/expansion parameters.

It's not the tape or vinyl that expands or compresses, it's that that physical format can't deal with music that is so compressed that there is no dynamic range anymore, because of physical limitations of the format. Both tape and vinyl need a dynamic range of at least 10dB before they run into physical limits.

So the mastering engineer can't limit that hard for those formats, and keeps more dynamic range in his mastering. While for digital 0dB digital range is in theory also possible with the format. It will sound like shit, but technically it can be done and some push it that far these days...

I personally also think that is what attrackt many music lovers and audiophiles (not the same) to vinyl. Digital can do that also, but the bussiness doesn't do it (at least the mainstream). Change that and more people will go digital only... For me it's more that attrackt me to the sound of vinyl, but for many it isn't. It's the fact that vinyl forces the label to leave more dynamic range in the music that makes it sound better than digital.

 

[SSS]

Hi,
Previously in the dynamics of music, we saw the difference between the dynamics of the medium and the dynamics of the music, as well as the effects of dynamic compression on the music in terms of distortion.
Today, we will discuss another aspect, the impact of dynamics on tape or vinyl recording.
The subject seems simple, we transfer the digital file to tape or vinyl and it is reproduced with little or no modifications.
To do this, we will use a test master file that includes the same musical sample with a different DR ranging from DR19 to DR7 as shown in the graph below :



This master file is burned on vinyl and played on a turntable. We then obtain the following result:



We notice that the variation is only from DR17 to DR10. In particular for the low DR, we notice that we do not go below the DR10.
To better represent this phenomenon, here is a synthesis curve which presents on the horizontal axis the DR value of the master from DR7 to DR19, and on the vertical axis the DR result after the playback of the vinyl cut with this master:



We can see that the vinyl does not go below DR10 in this example. This increase is therefore a distortion generated during the cutting and playback process compared to the original master.
Why this result? Vinyl is analog and it uses electromagnetic and mechanical means that give it a specific functioning. This operation is not compatible with certain digital treatments like the use of the Brickwall limiter which strongly distorts the signal in the digital world.
To go further in this test, the same operation is carried out with a magnetic tape on which we record the reference master. On playback, we obtain the same phenomenon as shown by the synthesis curve grouping the vinyl and the tape:


What can we conclude :

• Analog media have their own characteristics that must be respected to obtain a faithful reproduction on these media. Therefore, a specific master is needed for these media.
• The use of brickwall limiters generates distortion, and if you burn a vinyl or record a tape from this type of digital master, you generate distortion again. It's a double punishment by accumulating distortion twice. So it's anything but high fidelity.
• Measuring the DR on analog media is possible, but it does not always allow you to deduce the DR of the master that was originally used.

Find the whole test with more details on its realization and the measurements here.

Jean-François

Lot of good work done. Looking to your definition of dynamic range for me it is somekind arbitrary. Why should the signal RMS compared to signal peaks define dynamic or dynamic range? For me dynamic range is the gap between acceptable noise level and peak signal with a defined allowed distortion value, as for tape it was 3% THD. And for music signal the maximum signal value to the lowest signal value. Both tape and music are not interrelated. On a media with high dynamic range music with low dynamic range can be recorded. Your conclusion that recordings have to act regarding the media like vinyl and tape are right. Both media have inherent limitations and distortion mechanisms. For vinyl already known since 70 years as one can read in technical articles of that time.

 

[KSTR]

Why should the signal RMS compared to signal peaks define dynamic or dynamic range?

Exactly.
Peak to RMS is completely non-representative for actual dynamic range.

Take a squeezed-to-death recording and pass it through a phase-shifter allpass (similar to the allpass function of most speakers). While perceived dynamics and general timbre do not change (or only very little), peaks now can come out at up to 3(!!) times the previous full-scale value, so an increase of 9dB in simple DR metrics, not matching perception.

As for the vinyl stuff, any small amount of EQ will change peaks as well, and vinyl most often contains additional high-pass filter which alone is enough to change momentary peak samples. On top of that you have RIAA EQ tolerances and, not to forget, a potentially even peaking HF response. This is what I think we see in the original post, though gross distortion can also lead to increased peaks.

Proper DR algorithms that match perception a bit better set short-term RMS (like 50ms window) in relation to long-term RMS (like 1 second window) which makes phase shifts and minor EQ irrelevant and also require the hot spots to be relevant, using histogram tolerance limits so that "single high DR events" are discarded. Like when you have track that has been compressed to death but mastered at a low level (say -10dBFS) to have one split-second of a burst that hits full-scale. This this is the same DR overall and the histogram would show such. Additionally, bandwidth should be restricted to reasonable ranges.

All in all, proper DR metering that correlates to perception is anything from trivial.

 

[Cbdb2]

It's not the tape or vinyl that expands or compresses, it's that that physical format can't deal with music that is so compressed that there is no dynamic range anymore, because of physical limitations of the format. Both tape and vinyl need a dynamic range of at least 10dB before they run into physical limits.

So the mastering engineer can't limit that hard for those formats, and keeps more dynamic range in his mastering. While for digital 0dB digital range is in theory also possible with the format. It will sound like shit, but technically it can be done and some push it that far these days...

I personally also think that is what attrackt many music lovers and audiophiles (not the same) to vinyl. Digital can do that also, but the bussiness doesn't do it (at least the mainstream). Change that and more people will go digital only... For me it's more that attrackt me to the sound of vinyl, but for many it isn't. It's the fact that vinyl forces the label to leave more dynamic range in the music that makes it sound better than digital.

So analog can't properly reproduce a heavily distorted electric guitar? Or anything else (I can give you lots of examples) with no dynamic range? How does it do that?

 

[KSTR]

I would think the cooling for the master foil cutting head is not prepared to deal with compressed-to-death material at max volume...
EDIT: RIAA Equalisation make things worse here.

 

[Cbdb2]

Why? And if that realy is a problem a proper mastering engineer would turn the level down. And what about tape?

 

[Jean.Francois]

So your saying tape and vinyl are dynamic range expanders/compressors with a ratio dependant on the compression of the original signal? Can you explain the mechanism? What are the time constants, where do they come from? Hard to believe they would be the same for tape and vinyl when they are such different processes. Would like to see what happens with DR test signals that show the compression/expansion parameters.

The common point between vinyl and tape is that there is a phase rotation in both. This phase rotation partly explains the result for small DR values, but the transfer curve for vinyl and tape is more complex and behaves differently for higher DRs.
The curve below represents the impact of a phase rotation on the same initial file in comparison with vinyl: