Has anybody measured the resolution of vinyl records?

[Motrek]

I don't know anything about vinyl but I find this an interesting topic of conversation that comes up sometimes. I've googled for the answer but can't find anything quantitative about it.

This should be a fairly straightforward experiment to run. Get multiple presses of a record, put them on a turntable, and record them using high resolution/high frequency recording hardware. Compare the recordings somehow. (The comparison could be a little complicated and mathematical but still seems very doable to me.)

To control for the recording hardware, you could record the same song being played multiple times from the same digital source.

 

[slipperybidness]

Hmmm.

The term resolution kind of loses meaning when working in the analog domain.

I get what you are saying, but I'm not sure that this is applicable.

 

[Motrek]

Hmmm.

The term resolution kind of loses meaning when working in the analog domain.

I get what you are saying, but I'm not sure that this is applicable.

Not at all. The word "resolution" simply refers to the resolving power of something, i.e., what's the smallest detail that a thing can accurately resolve.

This is a no-brainer to understand and quantify when talking about digital things. With analog things, it requires measurement.

Imagine a tiny little 0.033 millisecond (30 kHz) blip in your sound wave. I can easily imagine that such a small physical feature can not be reliably reproduced on a record given today's physical materials and pressing equipment. Thus, the resolution of a record (in this hypothetical example) is less than 30 kHz.

 

[Motrek]

In fact, it occurs to me that audio resolution could be tested in basically the same way as photographic resolution.

With cameras, a test image is used with e.g. gradually converging lines. You look at the point where the lines blur together in your picture and that tells you the resolving power of your camera/lens.

Similarly, all we would need to do is have a record made that has two sounds on it:

1) A solid tone. We can look at a recording of the tone and see how much variation there is in the peaks and that will give us the number of "bits" of accuracy in the signal.

2) A tone that increases in frequency. We look at the recording of this and see where the signal no longer resembles a sine wave and that will give us the maximum frequency that can be represented on a record.

So all we need is somebody who knows how to press such a record. Or maybe this has all been done already.

 

[Speedskater]

Past experiments have shown that the resolution is about equivalent to a 14 or 15 bit digital recording.
While with a new record, high frequency response may exceed a 48kHz digital recording. But at those high frequencies, many phono cartridge/pre-amp combinations have very messy or peaky response. And then there is loss of those high frequencies after just a few playings.

 

[Motrek]

Past experiments have shown that the resolution is about equivalent to a 14 or 15 bit digital recording.
While with a new record, high frequency response may exceed a 48kHz digital recording. But at those high frequencies, many phono cartridge/pre-amp combinations have very messy or peaky response. And then there is loss of those high frequencies after just a few playings.

Great info!

Re: 14/15 bits, I assume this is 7/7.5 bits per stereo channel?

Also, do you know what the "typical" frequency resolution of a record would be, i.e., after some "typical" number of spins? (Whatever people think that might be.)

 

[rojo]

Interesting reading:

Vinyl vs. CD parts 1 - 5
Vinyl vs. CD parts 6 - 9

 

[Rickster71]

Too bad resolution wasn't the only issue with vinyl.
The problems are the pops & clicks.
Spending all that money and having sound like someone is eating a bowl of Rice Krispies.

 

[Swerd]

Before digital sound recording, analog sound quality was inferred from it's dynamic range, the ratio of sound from the loudest passages divided by the quietest passages. Vinyl records were often said to have a maximum theoretical dynamic range of as much as 78 dB. But in the real world, this number was more like 70 dB or less. Things like tape recording speed and magnetic tape particle density, as well as the inherent noise level in vinyl grooves tended to limit how low you could reduce the background noise level, thus limiting the dynamic range. The upper limit was created by the decision to run the turntable speed at 33.3 RPM and keep the recorded music to roughly 20 minutes per side. Efforts were made to increase this range, such as with DBX noise reduction. But it never took off at a consumer level.

Rather than estimate the number of bits in an analog recording, it might be easier to compare the dynamic range available from a CD once it's converted to analog. I don't remember clearly, but I remember a number close to 90 or 95 dB, a dynamic range much greater than 70 dB.

 

[Swerd]

A few minutes with Google, and I found this: http://wiki.hydrogenaud.io/index.php?title=Myths_(Vinyl)

Myth: Vinyl has greater resolution than DC because its dynamic range is higher than for CD at the most audible frequencies
The dynamic range of vinyl, when evaluated as the ratio of a peak sinusoidal amplitude to the peak noise density at that sine wave frequency, is somewhere around 80 dB. Under theoretically ideal conditions, this could perhaps improve to 120 dB. The dynamic range of CDs, when evaluated on a frequency-dependent basis and performed with proper dithering and oversampling, is somewhere around 150 dB. Under no legitimate circumstances will the dynamic range of vinyl ever exceed the dynamic range of CD, under any frequency, given the wide performance gap and the physical limitations of vinyl playback. More discussion at Hydrogenaudio.

 

[Motrek]

A few minutes with Google, and I found this: http://wiki.hydrogenaud.io/index.php?title=Myths_(Vinyl)

Myth: Vinyl has greater resolution than DC because its dynamic range is higher than for CD at the most audible frequencies
The dynamic range of vinyl, when evaluated as the ratio of a peak sinusoidal amplitude to the peak noise density at that sine wave frequency, is somewhere around 80 dB. Under theoretically ideal conditions, this could perhaps improve to 120 dB. ...

I found this too and my knee-jerk reaction to it was that this doesn't give much information about the accuracy of the signal. But I guess it does, because to have a quiet signal, it has to be accurate (and not messed up with noise and/or manufacturing tolerance issues).

So that seems like a good measure of amplitude resolution but not time-domain of course.

 

[Swerd]

Another Google hit: http://wiki.audacityteam.org/wiki/Bit_Depth
scroll down a little more than ½ way

Bit Depth of Various Sources
Figures vary a little for analog sources, depending on quality of equipment and recording. Some figures were measured using above average quality domestic hifi equipment (where applicable), and will be typical for professional recordings played on good domestic equipment. Other figures were obtained from audio engineers' written material.

CD

• Standard audio CDs (cda): the digital recording format is 16-bit, but a fair bit of the source material is of much lower dynamic range. Also high dynamic range source material is often deliberately compressed, so the resulting real dynamic range is well below 16-bit in many cases. Some CD recordings do have 16 bits of dynamic range, but far from all.
• Other file types on data CDs: Resolution depends on the file format and audio content, and can vary widely.

Cassette

• Ferric: 6 bit
• Chrome: 6 bit
• Metal:

• Some home recordings have less dynamic range
• Low quality equipment or recordings will generally have less dynamic range.
• A 1970s portable cassette player recording live via microphone, with plenty of hiss, a little motor noise and low sound quality, yielded just 2.5 bit depth for the whole record & play cycle.

Vinyl and shellac

• 16 rpm (broadcast record):
• 33 rpm 12" (album): 9 - 10 bit
• 45 rpm 7" (single):
• 45 rpm 12" (12" single): 10 bit
• 33 rpm 7" (EP double single):
• 45 rpm flexible single (paper thin plastic film):
• 78 rpm (shellac):
• 78 rpm aluminium disc (home recordings):

Note that 33 rpm 12" compilation albums that have 10 tracks recorded per side usually have noticeably reduced dynamic range. This is needed to achieve the extended play time.

FM Radio

• Single measurement only: 4.5 bit. Exact bit depth is dependant on signal strength and tuner specs.

 

[Swerd]

To summarize

33 RPM vinyl – as high as 70 dB dynamic range, estimated to be as low as 9-10 bits, or as high as 14-15 bits (anyone have a reference for this?)

Standard CD – 16 bits, as high as 90-95 dB dynamic range

 

[highfigh]

In fact, it occurs to me that audio resolution could be tested in basically the same way as photographic resolution.

With cameras, a test image is used with e.g. gradually converging lines. You look at the point where the lines blur together in your picture and that tells you the resolving power of your camera/lens.

Similarly, all we would need to do is have a record made that has two sounds on it:

1) A solid tone. We can look at a recording of the tone and see how much variation there is in the peaks and that will give us the number of "bits" of accuracy in the signal.

2) A tone that increases in frequency. We look at the recording of this and see where the signal no longer resembles a sine wave and that will give us the maximum frequency that can be represented on a record.

So all we need is somebody who knows how to press such a record. Or maybe this has all been done already.

Call this company- they master for vinyl-
http://www.chicagomasteringservice.com/vinyl.html

 

[3db]

Not at all. The word "resolution" simply refers to the resolving power of something, i.e., what's the smallest detail that a thing can accurately resolve.

This is a no-brainer to understand and quantify when talking about digital things. With analog things, it requires measurement.

Imagine a tiny little 0.033 millisecond (30 kHz) blip in your sound wave. I can easily imagine that such a small physical feature can not be reliably reproduced on a record given today's physical materials and pressing equipment. Thus, the resolution of a record (in this hypothetical example) is less than 30 kHz.

Actually, vinyls upper limit is around 70KHz.... but there's no point going that far as cartridges have a problem going that high.

 

[highfigh]

Actually, vinyls upper limit is around 70KHz.... but there's no point going that far as cartridges have a problem going that high.

79KHz is hard, but several are rated to 45-50KHZ.

 

[Swerd]

Two points about ultra-high frequency performance of vinyl playback:

Ultra-high frequency performance is not the same as resolution of detail in recorded sound.

There is no cutoff filter for high frequency in vinyl playback systems as there is in CD playback. However you cannot assume this translates to something audible, much less a benefit. First, recording microphones used in studios do not perform any where near that high a frequency. So there is no signal in that range. Next, no audio playback system performs that high. And finally, we really do not hear that high.

 

[highfigh]

Two points about ultra-high frequency performance of vinyl playback:

Ultra-high frequency performance is not the same as resolution of detail in recorded sound.

There is no cutoff filter for high frequency in vinyl playback systems as there is in CD playback. However you cannot assume this translates to something audible, much less a benefit. First, recording microphones used in studios do not perform any where near that high a frequency. So there is no signal in that range. Next, no audio playback system performs that high. And finally, we really do not hear that high.

If someone drives with the windows open and the factory stereo cranked for a long time, I doubt 15KHz would be possible an that would be for a young person. However, if the album has a lot of clean high frequency content with a lot of harmonics from cymbals, etc, chopping the frequency response at 20KHz might be noticeable (noting that the highest fundamental frequency from most musical instruments doesn't exceed 4KHz, piano and piccolo are about 3950Hz) if the playback response was switched between 20-20KHz and 20-40KHz.

 

[3db]

Two points about ultra-high frequency performance of vinyl playback:

Ultra-high frequency performance is not the same as resolution of detail in recorded sound.

There is no cutoff filter for high frequency in vinyl playback systems as there is in CD playback. However you cannot assume this translates to something audible, much less a benefit. First, recording microphones used in studios do not perform any where near that high a frequency. So there is no signal in that range. Next, no audio playback system performs that high. And finally, we really do not hear that high.

Agreed. I only mentioned this because of the misconception that vinyl is limited in frequency response which it isn't.

 

[highfigh]

Agreed. I only mentioned this because of the misconception that vinyl is limited in frequency response which it isn't.

You mean strictly limited by some requirement specific to the format as opposed to an inherent physical limitation, right? They do limit the upper response, somewhat, due to the heat buildup and need to cool the cutter head. Limiting/filtering is cheaper than cooling.