What objective measurements qualify as "High Fidelity"?

[Axo1989]

The thread appears to be juddering over a few semantic rough patches.

If we consider a primary purpose of an audio reproduction system as reproducing audio recordings, then fidelity to the recorded signal is relevant. Another primary purpose is providing enjoyment, so said fidelity may be modified for that purpose, obviously.

Reference to live performance or original sound event is semi-relevant, depending on the material to be reproduced. For much studio-produced sonic collage there is no single original event. For synthetic sources there is no original sound apart from some means of generating and transducing it audibly.

Reproducing a recording in a physical space is to some degree dependant on characteristics of the space, so fidelity of reproduction, or pleasure therefrom, are subject to that. We have arguments about equipment (most especially loudspeakers) and about spaces (reflective or otherwise) and related preferences that may be congruent with or orthogonal to fidelity (variously conceptualised). Plenty to work with.

 

[richard12511]

I believe THX has “standards” that they set for many technologies. For example, with loudspeakers they measure on axis FR, off axis, distortion, and output. They have several tiers(compact, ultra, dominos), and each higher tier has lower tolerances for those above metrics.

 

[DanielT]

I saw that DIN 45500 was brought up in the thread.

Speaking of standards. For subwoofers, you might think that you set criteria such as at frequency X then minimum Y % distortion at Z SPL to get an ok. Which would require HiFi manufacturers to agree to use a mini level, standard for subwoofers but there seems to be little interest in that.
Polk argued for this, but I don't know what happened to that standard:

Subwoofer Shopping Made Easier With The CEA 2010 Standard

Subwoofer Performance: How to Know When You Have It (or Why Inches and Watts Tell You Nothing of Value Whatsoever)?

www.ecoustics.com

This was interesting. There seems to be a need to:
Trade Regulation Rule Relating to Power Output Claims for Amplifiers Utilized in Home Entertainment Products
Posted by the Federal Trade Commission on Dec 18, 2020

Regulations.gov

www.regulations.gov

 

[Killingbeans]

My experiences with ASR and certain new technology makes me think it would be like pulling teeth

No doubt. There would be tons of disagreement and painful compromises to be made, but the end result would possibly be worth it.

It has pretty much worked for the computer industry, and I don't see why it shouldn't for hi-fi... other than an abundance of emotions making things volatile

But you have a situation where newer better technology deviates from accuracy. I have seen this debate numerous times here on ASR

The committee would first have to agree on a definition of "accuracy" (more teeth to be pulled). Easy to do with electronics, but a nightmare when acoustics and DSP get involved.

Anything deviating from that definition would be classified as a gimmick, and automatically be disqualified from being part of the standard.

I do not share your optimism

I don't blame you

No matter how I look at it? If I look at it from the perspective of an Olympic sprinter and that 0.1% being the difference between gold and silver and the subsequent money made off endorsements I’d say doing ten times as much work paid off big time.

Diminishing returns are subjective.

I get what you're saying, but no.

A point of diminishing returns is a point of diminishing returns, no matter how you look at it. You can litterally make a graph and put a finger on it.

Whether pushing beyond that point is worth it, is a completely different matter.

The hi-fi industry is largely built upon the idea that even the smallest deviations from perfection makes the auditory experience pure agony.

In reality it doesn't take much to reach the point where enjoyment dwarfs any nuisance to such an extent, that any further "improvement" becomes nothing but wankery.

But then again, what's left of a hobby if you don't have wankery?

Although, from what I can tell, the hobby has taken it to an extreme and has mostly evolved into something that doesn't really care about reality.

Things that give real and substantial improvements are largely ignored. Things that dick around far beyond the point of diminishing returns get a lot of resources. And things that do absolutely nothing other than triggering the placebo effect get the vast majority. A result is a result, no matter whether it's imaginary or not.

IMO, that's the main reason why we'll probably never see standards being implemented and followed. It would remove all of the silliness that constitutes most of the fun.

 

[Vacceo]

Even that doesn't work, in my opinion. Have you ever spent time choosing a recording space, positioning the musicians in it, choosing mics and positioning them? It's very instructive to do so. Tiny differences have significant effects and big differences change everything. So what is the sound source and how does it qualify as a reference? And given that none of the resulting recordings you could make are what any listener actually heard, it's clear the recording itself is an artifice involving all manner of choices, most of which were made for reasons that we can only guess at.


The signal is not the source you described in the previous paragraph, it is the output of an artificial recording process.

And it's not the only reference we have. We also have test signals. Using only those we are able to build systems that will please most people.

A film is also artificial and the point of watching a film is not "taking the director's seat".

What you have is the film, or the record, and that's the only element that you can apply fidelity to.

 

[Multicore]

The thread appears to be juddering over a few semantic rough patches.

If we consider a primary purpose of an audio reproduction system as reproducing audio recordings, then fidelity to the recorded signal is relevant.

Ok, let's do semantics.

My argument has been that fidelity isn't a useful technical concept in a scientific approach to engineering components and systems, i.e. that trying for define it technically and formally relate it to our usual objective measures doesn't help with the engineering and we will get in a muddle if we try.

What then is the nature of the relevance?

Another primary purpose is providing enjoyment, so said fidelity may be modified for that purpose, obviously.

Modified fidelity. New to me. It's different from both infidelity and fidelity?

 

[Multicore]

What you have is the film, or the record, and that's the only element that you can apply fidelity to.

Test input and output signals also work and are commonly used in the engineering of both audio and visual equipment and systems.

But even if the film, or the record, were the only element that you can apply fidelity to, it doesn't follow that it is useful to try to do that.

 

[Vacceo]

Test input and output signals also work and are commonly used in the engineering of both audio and visual equipment and systems.

But even if the film, or the record, were the only element that you can apply fidelity to, it doesn't follow that it is useful to try to do that.

Test signals can also follow fidelity: how well the gear reproduces them without alteration. Gear is agnostic to what it is fed.

 

[Jim Taylor]

My argument has been that fidelity isn't a useful technical concept in a scientific approach to engineering components and systems, i.e. that trying for define it technically and formally relate it to our usual objective measures doesn't help with the engineering and we will get in a muddle if we try.

That's like saying that accuracy is not a useful technical concept in a scientific approach to engineering target rifles. Say what?

Perhaps the term "fidelity" is being used several different ways here. As far as electronics goes, my definition of fidelity is, "What goes in is what comes out, only at a higher level of power."

But even if the film, or the record, were the only element that you can apply fidelity to, it doesn't follow that it is useful to try to do that.

Why not?

 

[Vacceo]

That's like saying that accuracy is not a useful technical concept in a scientific approach to engineering target rifles. Say what?

Perhaps the term "fidelity" is being used several different ways here. As far as electronics goes, my definition of fidelity is, "What goes in is what comes out, only at a higher level of power."

I´d add that, since that is physically impossible, those changes should hopefully not be audible.

 

[terryforsythe]

Thank you everyone for your input!

If qualifying as "high fidelity" is objective, there should be objective specifications to which measurements can be compared to make that determination. Without such specifications, we are left with subjectivity to make the determination. E.g., one person may deem 80 dB SNR to be adequate for high fidelity, while another person may deem 120 dB SNR to be the minimum.

As noted, I think that what qualifies as high fidelity is subjective. Nonetheless, for those with a differing opinion, please articulate what objective measurement threshold levels qualify equipment as being high fidelity. Below I took a stab at it, but please feel free to change these initial values and/or add other objective measurement specifications you deem to be important.

Electronics (e.g., amplifiers and DACs)

1. Signal-to-noise ratio (SNR): 120 dB min.
2. Total harmonic distortion (THD): -120 dB max.
3. SINAD - Not important so long as SNR and THD meet thresholds
4. Intermodulation distortion (IMD): -120 dB max
5. Stereo separation: -90 dB min.
6. Frequency response: 20 Hz - 20 kHz +/- 0.1 dB throughout operational power output range

Speakers and speaker/subwoofer combinations

1. On-axis frequency response: 20 Hz - 20 kHz +/- 1.5 dB @ 1W/1m
2. Horizontal off-axis frequency response: -6 dB +/- 1.5 dB 500 Hz - 15 kHz @ 1W/1m @ a specific angle that is greater than 50 degrees
2. Vertical off-axis frequency response: -3 dB +/- 1.5 dB 500 Hz - 15 kHz @ 1W/1m @ a specific angle that is greater than 20 degrees
3. THD: 0.5% max 100 Hz - 20 kHz @ 96 dB; 1.0% max 40 Hz - 100 Hz @ 96 dB; 3.0% max 20 Hz - 40 Hz @ 96 dB
4. Dynamic range (compression): 0.5 dB max 20 Hz - 20 kHz comparing 102 dB to 76 dB @ 1m
5. Closed baffle or open baffle: Not important so long as above specifications are met.

System

1. In-room frequency response: 20 Hz - 20 kHz +/- 2 dB from target curve* @ 86 dB @ listening position using 1/12 octave smoothing (equalization probably necessary for most rooms)
* Target curve would not have bass boost, but otherwise would be similar to Harman curve

 

[terryforsythe]

I guess we are taking fidelity to mean accuracy or resolution. And this accuracy is to the original recording. So therefore anything that deviates from this is not strictly "highest fidelity". This would include altered frequency response, I would assume. My 2c.

Every acoustic reproduction system, without exception, will deviate from the original recording. E.g., I never have seen a speaker measure 20 - 20 kHz +/- 0 dB at 0.00% THD, not to mention room impact. So, that means no system with current technology is "highest fidelity".

 

[terryforsythe]

It's interesting to note that for the "electronics" metrics you listed, you mostly chose steady-state, frequency domain measurements. What about burst measurements or time domain measurements, and related test signals? These are mostly lacking from the gamut of FFT-based frequency domain stuff that you can find.

Please add burst measurement and time domain measurements you believe should be applicable, and the threshold levels those should be for high fidelity.

 

[terryforsythe]

This covers it pretty well.

From the video:

We have a threshold level for SNR.

Now, we need the rest.

 

[Multicore]

Why not?

Because it may be that fidelity is not an especially important measure of fitness for purpose or of value or of utility relative to others.

 

[Jim Taylor]

Because it may be that fidelity is not an especially important measure of fitness for purpose or of value or of utility relative to others.

If that were true, wouldn't we still be listening to wax cylinders?

Jim

 

[Multicore]

If that were true, wouldn't we still be listening to wax cylinders?

In previous posts, e.g. this, I said that I think that the idea of fidelity as a vague expression of aspirations was probably useful in the past but that it is now obsolete.

 

[sergeauckland]

Thank you everyone for your input!

If qualifying as "high fidelity" is objective, there should be objective specifications to which measurements can be compared to make that determination. Without such specifications, we are left with subjectivity to make the determination. E.g., one person may deem 80 dB SNR to be adequate for high fidelity, while another person may deem 120 dB SNR to be the minimum.

As noted, I think that what qualifies as high fidelity is subjective. Nonetheless, for those with a differing opinion, please articulate what objective measurement threshold levels qualify equipment as being high fidelity. Below I took a stab at it, but please feel free to change these initial values and/or add other objective measurement specifications you deem to be important.

Electronics (e.g., amplifiers and DACs)

1. Signal-to-noise ratio (SNR): 120 dB min.
2. Total harmonic distortion (THD): -120 dB max.
3. SINAD - Not important so long as SNR and THD meet thresholds
4. Intermodulation distortion (IMD): -120 dB max
5. Stereo separation: -90 dB min.
6. Frequency response: 20 Hz - 20 kHz +/- 0.1 dB throughout operational power output range

Speakers and speaker/subwoofer combinations

1. On-axis frequency response: 20 Hz - 20 kHz +/- 1.5 dB @ 1W/1m
2. Horizontal off-axis frequency response: -6 dB +/- 1.5 dB 500 Hz - 15 kHz @ 1W/1m @ a specific angle that is greater than 50 degrees
2. Vertical off-axis frequency response: -3 dB +/- 1.5 dB 500 Hz - 15 kHz @ 1W/1m @ a specific angle that is greater than 20 degrees
3. THD: 0.5% max 100 Hz - 20 kHz @ 96 dB; 1.0% max 40 Hz - 100 Hz @ 96 dB; 3.0% max 20 Hz - 40 Hz @ 96 dB
4. Dynamic range (compression): 0.5 dB max 20 Hz - 20 kHz comparing 102 dB to 76 dB @ 1m
5. Closed baffle or open baffle: Not important so long as above specifications are met.

System

1. In-room frequency response: 20 Hz - 20 kHz +/- 2 dB from target curve* @ 86 dB @ listening position using 1/12 octave smoothing (equalization probably necessary for most rooms)
* Target curve would not have bass boost, but otherwise would be similar to Harman curve

Whilst the above for electronics may be the SOTA , they are ludicrously excessive as a minimum standard for Hifi. THD of -60dB is perfectly adequate for transparency, and a S/N ratio of 80dB more than acceptable. Stereo separation of 20 -25dB is good enough for stereo, and a 20-20kHz response of 1dB sufficient, even 3dB wouldn't be audible at the frequency extremes.

It might be useful to do some blind listening tests to see just how tolerant we are.

S

 

[egellings]

As I see it, fidelity is a useless concept for our purposes and has been for decades. It was a useful marketing term back in the day but as an engineering goal I can't see how to use it.

All recorded music is artifice. So fidelity to what?

If there actually was a recording of a band or orchestra playing all together, then fidelity could have meaning. You'd want the sound of the band, room artifacts, warts & all. If the music was spliced together from individual musicians playing at different times, then there'd be no homogenized performance to accurately reproduce. Fidelity in that case would be fidelity to the producer's idea of whatever mix that sounds good.

 

[kemmler3D]

Yes. And we have ways to express and to measure that ability. We don't need to involve fidelity to do it. Trying to relate fidelity to the objective measures that have proven their value confuses matters. That's why I think the concept isn't useful.

I generally take "fidelity" to mean the same thing as "minimal distortion", but I appreciate that you put a deeper or more philosophical concept behind the word. I don't anymore because it involves too many opinions. More specifically, aiming for "fidelity" to a certain experience is a faulty premise. "You can't step into the same river twice," etc.