Measurements and the Correlation of What We Hear

[DonH50]

Haha! This thread is tempting to jump into. I'm out of town this week, then there is the RMAF next, but I'll think about how to implement the NPR test in audio amplifiers when I get back.

Typical distortion figures for loudspeakers (which vary WILDLY depending on how you measure them) range from about 5% to over 50%. I've measured non-servo subwoofers to go up to 50% even below their distortion spl. The graphs look like a big smiley face, very high at low spl's (which I figure is caused by air not transmitting enough) to very high at large spl's (which I figure is air being pushed aside by the rapidly moving cone). The elasticity of air makes measurement of distortion very difficult for loudspeakers.

Very interesting, Gary. I can think of lots of reasons why speakers distort at high levels, but high distortion at low levels does not make sense to me. I admit I do not have a lot of loudspeaker theory to fall back on... In an amp, we tend to measure SINAD, and high noise and low levels causes a bathtub'ish curve. Not sure why you'd get the same in a loudspeaker, unless measurement and/or (pre)amp noise floor is in the picture at low levels. I suppose mic self-noise could also enter into it if the SPL is very low. The only other thing that comes to mind is mechanical hysteresis causing distortion with low drive levels. I am sure I am leaving out something, many somethings...

 

[fas42]

I tried building a switch box to rapidly switch between cables, but the difference inserting that switch box was greater than the difference between the two cables.

Again, the big problem with audio: the setup to measure what's going on causes more variation and disturbance than what you're trying to measure. Scientists have to constantly fight this problem, and audio is not some magical universe immune from this consideration.

Which is why ears are sometimes best ...

Frank

 

[mep]

I am somehow unsettled to see how some of us are bending around incredible loops to come up with the notion that something that exists (a stimulus which creates a perception) can't be measured ..i sincerely would have not thought this line of reasoning ..well.. reasonable but .. we are audiophiles ... we believe in stranger things ...
I will answer Gary post later .. It seems at first reading to belong in the "we-can-hear-it-but-can't-measure-it" category ... I disagree with that line of thought...

Frantz-Again, I'm not saying that what we hear can't be measured, I'm saying we haven't figured out yet how to measure what we hear with any correlation beyond gross problems which show up readily in the measurements that are commonly taken. And that my friend is a huge difference.

Gary professionaly designs both speakers and amplifiers, and he hasn't figured it out yet either. No manufacturer that I'm aware of provides measurements of their new and improved gear in order to convince audiophiles through measurements why their new product is better. All we get is audiophile hype via audiophile adjectives. Lots of people say that the OEMs are taking lots of measurements and I'm sure they are. They just don't share them with us and we can all speculate as to why. At the end of the day, we have tons of marketing hype and precious few measurements. And that is why I am mildly amused when people proclaim how much they love measurements they don't really have.

Mark

 

[mep]

I'm going to give a concrete example of what audiophiles have to deal with from OEMs when making a purchasing decision. Here is what ARC has to say about why the REF-5 is better than the REF-3:

"The REF3 was a sonic breakthrough when it was introduced in 2004 and it has remained at the top tier of preamplifiers since, which is why the REF5 will stun listeners by its enormous advancement in sound quality. The REF5 possesses great bandwidth and resolving power combined with a purity and naturalness that is uncanny – grain and electronic artifacts are simply absent. Bass impact, depth and control are startling, while music ebbs and flows with a dynamic life that is rarely experienced outside the concert hall. While differences in recordings are immediately apparent, the REF5 connects you to the intent of the musicians and the soul of the performance, drawing you in. Music emerges from a totally black background because the REF5 – defying its vacuum-tube architecture – is utterly quiet. Only by hearing it for yourself will you fully appreciate the sonic advancements unveiled by the REF5."

I bolded the parts I want to emphasize that I have no idea how you would measure these claims.


Switching gears, below I have listed the salient specifications of the REF-5 and the REF-40:

REF 5 FREQUENCY RESPONSE: +0 -3dB 0.2Hz to 200kHz at rated output. (BALANCED, 200k ohms load.)

REF 40
Frequency Response
+0 -3dB 0.2Hz to 200kHz at rated output.
(Balanced, 200k ohms load.)

REF 5 DISTORTION: Less than .01% at 2V RMS Balanced output.

REF 40 Distortion
Less than .0006% at 2V RMS Balanced output.

REF 5 GAIN: Main output (SE or BAL input): 12dB Balanced output, 6dB Single Ended output. Tape output: 0dB. (Processor input: 0dB Balanced.)

REF 40 Gain
Main output (SE or BAL input): 12dB Balanced output


REF 5 INPUT IMPEDANCE: 120K ohms Balanced, 300K ohms SE, Inputs (7): CD, TUNER, VIDEO, PHONO, AUX1, AUX2, PROCESSOR. (XLR and RCA connectors).

REF 40 Input Impedance
120K ohms Balanced, 600K ohms SE, Inputs (7): CD, TUNER, VIDEO, PHONO, AUX 1, AUX2, PROCESSOR, (XLR and RCA connectors.)

REF 5 OUTPUT IMPEDANCE: 600 ohms Balanced, 300 ohms SE main (2), 20K ohms minimum load and 2000pF maximum capacitance. Outputs (3): 2 main, 1 tape (XLR and RCA connectors).

REF 40 Output Impedance
600 ohms Balanced, 300 ohms SE main (2), 20k ohms minimum load and 2000pF maximum capacitance. Outputs (3): 2 main, 1 tape (XLR and RCA connectors).

REF 5 MAXIMUM INPUT: 20V RMS maximum Balanced, (10V RMS SE).

REF 40 MAXIMUM INPUT: 20V RMS maximum Balanced, (10V RMS SE).

REF 5 RATED OUTPUTS: 2V RMS (1V RMS SE) into 200K ohm balanced load (maximum balanced output capability is 30V RMS at less than 0.5% THD at 1kHz).

REF 40 Rated Outputs 2V RMS (1V RMS SE) into 200K ohm balanced load (maximum balanced output capability is 30V RMS at less than 0.5% THD at 1kHz).

REF 5 CROSSTALK: -80DB or better at 1kHz and 10kHz.

REF 40 Crosstalk: -80dB or better at 1kHz

REF 5 CONTROLS: Volume (104 steps), Select Input. Push Buttons: Power, Proc, BAL/SE, Mono, Invert, Mute.

REF 40 Controls: Volume (104 steps), Select Input. Push Buttons:
Power, Proc, Bal/SE, Mono, Invert, Mute.

REF 3 POWER SUPPLIES: Electronically regulated low and high voltage supplies. Automatic 40 sec. warm-up/brown-out mute. Line regulation better than .01%.

REF 40 Power Supplies
Electronically regulated low and high voltage supplies. Automatic 40 sec. warm-up/brown-out mute. Line regulation better than .01%.

REF 5 NOISE: 1.7uV RMS residual IHF weighted balanced equivalent input noise with volume at 1 (109dB below 2V RMS output.)

REF 40 Noise: 1.7uV RMS residual IHF weighted balanced equivalent input
noise with volume at 1 (109dB below 2V RMS output.)


The biggest difference I can see between these two preamps is the distortion measurement. .01% for the REF-5 vice .0006% for the REF-40. ARC failed to mention what type of distortion they were measuring though. The other difference is the REF-40 has twice the number of line stage tubes and one more 6550 in the power supply. The input impedance for single-ended inputs is also twice as high with the REF-40 in comparison with the REF-5.

Is the distortion specification enough to explain why the REF-40 sounds better than the REF-5?

 

[FrantzM]

mep

read this last post and I have absolutely NO experience with these preamps ... The assumption you made however is that the REF 5 "sounds better" ... To paraphrase Steve does it sound really better or does it sound different? I am by the wa y not saying that it does not .. I am pondering and if there aren't any objective metrics by which something could be said to be better .. then it seems to be a matter of preference .. I would however quickly add that there is a statistical convergence of sorts .. Audiophiles will never take what is produced by a Bose Wave Radio as better than anything the audiophile industry has ever produced ... DBT, level-matched , etc... as for preferences once a gear is seen or kown to be in a system ... opinion tend go in expected directions ... I have seen audiophiles , myself included hear things... with the right amount of suggestions ...
I am not saying by the way that the REF-5 would not sound better to me than the REF-4 and I do also admit that there is not much one can get from the usual measurements about how a given component sounds. I know that if they sound different under the exact, same conditions they have to measure differently in some parameters .. at least one parameter. To me your thread would point toward developing new protocols of measurements not about the non-validity of the scientific method.
The notion measurements suppose that of adequacy.Measuring just the weight of food will not tell you much about their suitability to consumption, even less about their taste .. You need more and eventually you need to taste them with your own mouth to produce an opinion ...

 

[Phelonious Ponk]

I'm going to give a concrete example of what audiophiles have to deal with from OEMs when making a purchasing decision. Here is what ARC has to say about why the REF-5 is better than the REF-3:

"The REF3 was a sonic breakthrough when it was introduced in 2004 and it has remained at the top tier of preamplifiers since, which is why the REF5 will stun listeners by its enormous advancement in sound quality. The REF5 possesses great bandwidth and resolving power combined with a purity and naturalness that is uncanny – grain and electronic artifacts are simply absent. Bass impact, depth and control are startling, while music ebbs and flows with a dynamic life that is rarely experienced outside the concert hall. While differences in recordings are immediately apparent, the REF5 connects you to the intent of the musicians and the soul of the performance, drawing you in. Music emerges from a totally black background because the REF5 – defying its vacuum-tube architecture – is utterly quiet. Only by hearing it for yourself will you fully appreciate the sonic advancements unveiled by the REF5."

I bolded the parts I want to emphasize that I have no idea how you would measure these claims

.

Of course not. Performance is measurable though, to your point, often left unmeasured. This kind of bloated, self-congratulatory puffery is not verifiable by any means. Immeasurable indeed. Deliberately so. Personally, my first measure of a component is the philosophy, the goals, the character of the company that makes it. Anyone capable of that paragraph would never make it to the consideration set. YMMV.

By the way, your specs refer to a Ref 5 and a Ref 40, not Ref 3. I'm confused.

Tim

 

[fas42]

possesses great bandwidth and resolving power combined with a purity and naturalness that is uncanny – grain and electronic artifacts are simply absent. Bass impact, depth and control are startling, while music ebbs and flows with a dynamic life that is rarely experienced outside the concert hall. While differences in recordings are immediately apparent, the REF5 connects you to the intent of the musicians and the soul of the performance, drawing you in. Music emerges from a totally black background because the REF5 – defying its vacuum-tube architecture – is utterly quiet. Only by hearing it for yourself will you fully appreciate the sonic advancements unveiled by the REF5."

The biggest difference I can see between these two preamps is the distortion measurement. .01% for the REF-5 vice .0006% for the REF-40. ARC failed to mention what type of distortion they were measuring though.

The language is poetic, but I could easily imagine someone using it to describe what happens when you reduce low level, high frequency distortion by a major amount. The distortion figures imply quite strongly that they have done that, so they may indeed be justified in describing it so. Of course, it would be handy if they gave more details in terms of figures but I guess that's not going to suck in too many more customers with cash in hand ...

But, as Tim said, I'm confused here about what spec links with what ..

Frank

 

[Orb]

Don,

As distortion in loudspeakers is most times orders of magnitude higher than that of amplifiers we could imagine an experiment : measure the distortion of a typical loudspeaker and modify an amplifier to have the same distortion figures as this speaker and electronically equalize to compensate for FR. Then play it through a loudspeaker with very low distortion - e.g. Quad ESL63 . Would it sound like the original loudspeaker? Tests should be made in anechoic conditions, to avoid the contribution of the dispersion patterns.

Another aspect to add with speakers beyond distortion is that of resonance, which changes the characteristics of the timbre (Toole has a paper or two on timbre with resonance, and how it can relate to speakers).
Again the only way to measure accurately how it changes the sound of what we hear is to look at the complex waveform in the format I gave a little while ago; fundamental tone with each individual partial and showing their energy-amplitude against time (so we get the attack-sustain-decay) of the instruments note or chord.

It may seem I am being a bit pedantic, but it needs to be considered this thread is about correlating measurements to what we hear, which IMO many of the post focuses are directed slightly off tangent - still fun to read and participate but not necessarily completely helpful in this specific debate.


Cheers
Orb

 

[MylesBAstor]

mep

read this last post and I have absolutely NO experience with these preamps ... The assumption you made however is that the REF 5 "sounds better" ... To paraphrase Steve does it sound really better or does it sound different? I am by the wa y not saying that it does not .. I am pondering and if there aren't any objective metrics by which something could be said to be better .. then it seems to be a matter of preference .. I would however quickly add that there is a statistical convergence of sorts .. Audiophiles will never take what is produced by a Bose Wave Radio as better than anything the audiophile industry has ever produced ... DBT, level-matched , etc... as for preferences once a gear is seen or kown to be in a system ... opinion tend go in expected directions ... I have seen audiophiles , myself included hear things... with the right amount of suggestions ...
I am not saying by the way that the REF-5 would not sound better to me than the REF-4 and I do also admit that there is not much one can get from the usual measurements about how a given component sounds. I know that if they sound different under the exact, same conditions they have to measure differently in some parameters .. at least one parameter. To me your thread would point toward developing new protocols of measurements not about the non-validity of the scientific method.
The notion measurements suppose that of adequacy.Measuring just the weight of food will not tell you much about their suitability to consumption, even less about their taste .. You need more and eventually you need to taste them with your own mouth to produce an opinion ...

Can't sounding different = better? I'm sure that ARC thinks the new model sound better and different than their older models, yet maintaining the co's signature sound philosophy. After all, the equipment will never sound like live music and all designs, like it or no, have to involve certain mutually exclusive tradeoffs.

 

[FrantzM]

Can't sounding different = better? I'm sure that ARC thinks the new model sound better and different than their older models, yet maintaining the co's signature sound philosophy. After all, the equipment will never sound like live music and all designs, like it or no, have to involve certain mutually exclusive tradeoffs.

Myles

What a manufacturer thinks of its product or proclaims to think could be very different from what you, I or other people may think. I know this will not change, not now anyway as there continue to be a gap between what we perceive and what we have been measuring but it is not, I repeat likely for the last time a gap that can't be bridged, reduced or eliminated altogether as we seem to be very close to in video...
I would also consider the value of the statistical results from trained listeners as it relates to preference as a step toward devising better measurements or measurement protocols. Trained listeners of which I believe audiophiles are a subset (albeit their training could ameliorated, by exposure to certain tools). The Harman Group seems to be further along than many (most) manufacturers in this direction. I think we will see more of this in the future...

 

[MylesBAstor]

Myles

What a manufacturer thinks of its product or proclaims to think could be very different from what you, I or other people may think. I know this will not change, not now anyway as there continue to be a gap between what we perceive and what we have been measuring but it is not, I repeat likely for the last time a gap that can't be bridged, reduced or eliminated altogether as we seem to be very close to in video...
I would also consider the value of the statistical results from trained listeners as it relates to preference as a step toward devising better measurements or measurement protocols. Trained listeners of which I believe audiophiles are a subset (albeit their training could ameliorated, by exposure to certain tools). The Harman Group seems to be further along than many (most) manufacturers in this direction. I think we will see more of this in the future...

I tihink part of the discprepancy in some cases is due to the fact that the designer has a better set-up for evaluation than many of his customers. Not to mention, they've obviously fine tuned the system with their electronics. Now speakers are a different story and many use multiple amps to check out their product.

 

[microstrip]

I'm going to give a concrete example of what audiophiles have to deal with from OEMs when making a purchasing decision. Here is what ARC has to say about why the REF-5 is better than the REF-3:
(...)
The biggest difference I can see between these two preamps is the distortion measurement. .01% for the REF-5 vice .0006% for the REF-40. ARC failed to mention what type of distortion they were measuring though. The other difference is the REF-40 has twice the number of line stage tubes and one more 6550 in the power supply. The input impedance for single-ended inputs is also twice as high with the REF-40 in comparison with the REF-5.

Is the distortion specification enough to explain why the REF-40 sounds better than the REF-5?

Mep,
The difference should be heard, not seen ...

 

[RogerD]

I'm going to give a concrete example of what audiophiles have to deal with from OEMs when making a purchasing decision. Here is what ARC has to say about why the REF-5 is better than the REF-3:

"The REF3 was a sonic breakthrough when it was introduced in 2004 and it has remained at the top tier of preamplifiers since, which is why the REF5 will stun listeners by its enormous advancement in sound quality. The REF5 possesses great bandwidth and resolving power combined with a purity and naturalness that is uncanny – grain and electronic artifacts are simply absent. Bass impact, depth and control are startling, while music ebbs and flows with a dynamic life that is rarely experienced outside the concert hall. While differences in recordings are immediately apparent, the REF5 connects you to the intent of the musicians and the soul of the performance, drawing you in. Music emerges from a totally black background because the REF5 – defying its vacuum-tube architecture – is utterly quiet. Only by hearing it for yourself will you fully appreciate the sonic advancements unveiled by the REF5."

Marks reference to ARC and their REF-5 preamp I found interesting. So I pulled out my manual on my amplifiers and wanted to see how that was marketed and their explanation hoping to find something I could understand and make sense of. What I found was different than ARC's approach and maybe the few technical audio people can explain the scientific jargon used. All I can say is the 1x10 to the -12 impressed this non scientific person.

"FHT allows the iterative analysis of circuit behavior in response to dynamic and spectral pseudo random stimulation. It quantifies and analyses the effects of such things as dielectrics, dissipation, inductance, hysteresis , differential nodal transfer characteristics, and group distortion effects with resolution to 1x10-12

The result is a level of accuracy and integrity that would otherwise be unobtainable with conventional design / testing methodologies. - agtron inc."

btw this is what I mean when i say audio has to benefit from technology and computer modeling.

 

[Phelonious Ponk]

"FHT allows the iterative analysis of circuit behavior in response to dynamic and spectral pseudo random stimulation. It quantifies and analyses the effects of such things as dielectrics, dissipation, inductance, hysteresis , differential nodal transfer characteristics, and group distortion effects with resolution to 1x10-12

The result is a level of accuracy and integrity that would otherwise be unobtainable with conventional design / testing methodologies. - agtron inc."

What's FHT?

Tim

 

[RogerD]

Also I was giving some thought about the ability of measuring circuits and audio devices to 1x10-12 degree. I can tell you that that HP distortion analyzer just is going to be useless in determining the quality of this particular amplifier.

I purchased these amplifiers in Feb of 1994 and I'm sure these methodologies are more common now.

For those of you who are measurement biased maybe this is confirmation if this level of measurement is being used to produce a cutting edge design that is better than what was available just X years ago. Maybe published figures are useless to the consumer to some degree. Listening might be the most important thing. IM or THD is it obsolete?

 

[RogerD]

What's FHT?

Tim

"FHT is the name for high-resolution,time domain circuit modeling"

I would have to ask the designer to be sure,but this was the only explanation given in the manual.

 

[mep]

mep

read this last post and I have absolutely NO experience with these preamps ... The assumption you made however is that the REF 5 "sounds better" ...

Frantz-I have no experience with either of these preamps either so I'm not making an assumption that one is better than the other. ARC is telling you/us that the 5 is way better than the 3 via marketing hype. And maybe the 5 does sound way better than the 3. Let's say the audiophile adjective marketing hype (AAMH)is true. What measurements would possibly correlate to the AAMH?

 

[mep]

.
By the way, your specs refer to a Ref 5 and a Ref 40, not Ref 3. I'm confused.
Tim

Don't be confused. The REF-3 specifications are no longer on ARC's website so I used another ARC example with two of their current model preamps that have specifications (no measurements) posted on their website. The point to this was that the REF-40 is way more expensive than the REF-5 and as much better as the REF-5 was supposed to sound in comparison to the REF-3, I'm sure there is another magnitude of mo' better with the REF-40 over the REF-5. And I guess it's not entirely true that the REF-40 is still a current model because it was a limited edition run and they are sold out. The argument remains the same though. Look at the specs and tell me why the REF-40 should sound better outside of the one obvious distortion spec even though ARC doesn't even tell you what type of distortion they measured.

 

[mep]

It may seem I am being a bit pedantic, but it needs to be considered this thread is about correlating measurements to what we hear, which IMO many of the post focuses are directed slightly off tangent - still fun to read and participate but not necessarily completely helpful in this specific debate.


Cheers
Orb

I agree.

 

[Phelonious Ponk]

I obviously can't tell you why it should be better, because, evidently ARC's communication discipline, perhaps their measurment discipline was about the magnitude of mo' bettah. I could get more meaningful measurements on a Yamaha AV receiver. But I'm not sure I get your point. Are you saying measurements are meaningless because the high end has mostly abandoned them? Or they abandoned them because they were meaningless?

Personally I'd guess that all but a few very wacky high-end companies that are little more than glorified DIY shops are still measuring plenty. I don't know how they would develop repeatable improvements and duplicable products without them, frankly. I think what they have abandoned is the communication of those measurements, and have done so because it is convenient. Why convenient? Because 1) most of their target market doesn't want to be bothered with them and would much rather have, and believe, the magnitude of the mo' better hyperbole and 2) because good comprehensive measurements close far too much of the gap between a $10k amp and a $1k receiver.

Tim