Master Thread: Are measurements Everything or Nothing?

[Geert]

i also noticed "digital" sq without ever listening to tubeamps/vinyls x) you are talking about a "whole" other group, "retro-listeners" i would call them


well i was googling a little, because i got curious how multitones are actually produced with just "one" sinewave, kinda interesting topic and it got me thinking
"noise"... how is it embedded in the sinewave we see/hear? or other phrase, how will actual noise influence the "main" sinewave? could it be that noise has some influence of the perception of the maintone, even at points where we cant set noise apart from the main signal? (and measurements just working fine)
curious what you think, this would actually explain a lot, even on a scientific way
it would also explain powercables/usb filters etc effects, because even a tiny bit noisereduction could make a difference
it would also explain why more "precise" speaker (studio monitors for example) show this way more obvious, because they are "so" precise that they also influenced more by it

also, the thing we cant measure is: the actual sound-sinewave in the air (like the actual sinewave "midair") we just can measure it through a mic again and i really think our ears/brain are to specific things way more sensitive then mics that essentially just measure "volumes" (because "altered" soundwaves could hit the mic and the mic is essetially generating a sinewave by its own and maybe "filtering" things that way?

You should write a science fiction book.

 

[Plcamp]

I will go out on a limb and say the person you responded to didn't understand even half the acronyms. I have designed electronics, amps, etc formally for decades and I was unsure of what acronyms you were using at times and some details because of that seemed wrong. Like I said it came across as bafflegab.

I easily understood half of them. But that doesn’t matter anyway.

It gave me something to think about that I had not (out of band noise). I appreciated it.

Just so you know.

Regarding J Crowe’s method, well I had not seen before a “many tone” IMD test that revealed a kind of noise floor like that, and I found it interesting that the noise floor tracks linearly with volume.

 

[tvrgeek]

I would say you should define them for the person you responded to who looking at their other posts had no clue what you were talking about. I guarantee there are many of here who probably more knowledgeable about amplifier design who were reading that and going WTF? When you add in missing words and wrong words (IE irreverent where irrelevant should have been used) , it becomes unreadable especially when you are using acronyms for which there are no real standards or discussing in the context where multiple things are in play (speakers and amps per se) and an acronym could have multiple meanings.




I am going to save this in case I ever teach a course again. This tends towards the baffle them with BS category especially with the miswording and grammar errors that destroy readability.

So, you can't say what you did not understand? Any you say you built amplifiers? I am confused at that.

What acronym would you like me to explain? If you built an amp, you would know what a CCS, CM, IPS, VAS, Miller, 2-pole, or DP compensation is. I hope you know what a LTP is and what degeneration means. If someone would like to learn, I have several times suggested the basic reading from Bob Cordell and Douglas Self. Marshall Leach was more the math fundamentals, where the others are practical implementations.

Or I could say " It's magic and I know best" Would that make you happy? I don't believe in magic and sure as hell don't know best.

I know there are differences that can be measured and some topology that influences them. I know how they influence and are influenced by the load. I know I can hear them at any level I can afford. I am not saying I can hear in all cases I can't afford.

4 or 8 Ohm resistive load is not the best at defining an amplifier performance, but unless it is a powered speaker so the load is defined you are kind of stuck. It is unrealistic to have a "typical " load as no load is typical. I have modeled approximations of different speakers in Spice and it can have an order of magnitude effect on the THD. I use that knowledge in my crossover designs. I commend Amirm for always doing 4 Ohms as well as 8. It is informative if you understand how class AB amplifiers work. Not perfect, but reasonable. I do not know enough about class D to know the interaction.

If there is a repeatable subjective difference, there is an objective difference. The question is how to identify and quantify it.

 

[Killingbeans]

"noise"... how is it embedded in the sinewave we see/hear? or other phrase, how will actual noise influence the "main" sinewave?

could it be that noise has some influence of the perception of the maintone, even at points where we cant set noise apart from the main signal? (and measurements just working fine)

What would make us unable to set the noise apart from the main signal?

also, the thing we cant measure is: the actual sound-sinewave in the air (like the actual sinewave "midair") we just can measure it through a mic again and i really think our ears/brain are to specific things way more sensitive then mics that essentially just measure "volumes" (because "altered" soundwaves could hit the mic and the mic is essetially generating a sinewave by its own and maybe "filtering" things that way?

A mic doesn't fabricate sine waves. It reacts to a value in air preasure at any given point in time. Those continuous values gives you the signal.

So no, it does measure the actual sound waves "midair", as you said youself. There's no interpretation, intelligence or magic involved.

A mic does however have a bandwidth and a frequency response. That's why you need a mic with an associated specific calibration file if you want to do 'flat' measurements.

EDIT: And yes, any mic also both distorts and makes noise, but that's the least of your worries when entering the realm of acoustics. Thankfully we can just look at the electrical source itself and forget about all that dirt

 

[Plcamp]

This is all pretty much known, hence why distortion measurements at multiple increasing SPLs swept by frequency but I like to see more IMD stimulus to induce Doppler.

One thing I am wondering. When a speaker is playing a multitone test signal, and exhibiting sideband IM distortion products, does the voice coil current also show the same IM products? To what degree are the IM products of a speaker driver even visible to the amp trying to control the driver…does the amp matter?

Hope this question makes sense.

 

[Deleted member 23982]

What would make us unable to set the noise apart from the main signal?

i meant by ear, so at a point where the noise is "inaudible" but essentially still "messing" with the main sinewave, which could become audible even if we dont hear the "noise" directly, this would atleast explain why "audiophiles" are always talking about "overall sound change"

A mic doesn't fabricate sine waves. It reacts to a value in air preasure at any given point in time. Those continuous values gives you the signal.

So no, it does measure the actual sound waves "midair", as you said youself. There's no interpretation, intelligence or magic involved.

no i know but no transducer or what its called is perfect, couldnt the "mass" of the mic membrane actually "filter" something out? so essentially smooth a noisy sinewave again?


also we thrief for "realistic" sound but speakers/headphones dont quite reach this state no matter what we do, isnt the "noisy" sinewave (electrical and by the actual speaker outputting soundwaves) essentially what sets it apart from "natural sounds" ? (beside distortion and other things but i guess you could call them "noise" too) i mean many talk about dacs outputing "perfect" sinewaves that are same to eachother (or does this just get explained with, "noise isnt audible anymore" ?)

if we are purely scientific speaking this is pretty much the only explanation that can explain "audiophiles" subjectiv expierences (yea sure, placebo is a option too....) IF we are at a point where everything is measurable
maybe everything important is measurable, we just dont aknowledge the influence by it eg "inaudible"

 

[audio2design]

I knew exactly what you meant tvrgeek as I speak DIYaudio, but it may surprise you that people who design amplifiers for money when the speak will say long term pair and current mirror and constant current source, not all the acronyms which are usually used by DiY trying to fit in. But then they are probably more likely to say emitter coupled pair or differential pair ...

 

[Jimbob54]

i meant by ear, so at a point where the noise is "inaudible" but essentially still "messing" with the main sinewave, which could become audible even if we dont hear the "noise" directly, this would atleast explain why "audiophiles" are always talking about "overall sound change"


no i know but no transducer or what its called is perfect, couldnt the "mass" of the mic membrane actually "filter" something out? so essentially smooth a noisy sinewave again?


also we thrief for "realistic" sound but speakers/headphones dont quite reach this state no matter what we do, isnt the "noisy" sinewave (electrical and by the actual speaker outputting soundwaves) essentially what sets it apart from "natural sounds" ? (beside distortion and other things but i guess you could call them "noise" too) i mean many talk about dacs outputing "perfect" sinewaves that are same to eachother (or does this just get explained with, "noise isnt audible anymore" ?)

if we are purely scientific speaking this is pretty much the only explanation that can explain "audiophiles" subjectiv expierences (yea sure, placebo is a option too....) IF we are at a point where everything is measurable
maybe everything important is measurable, we just dont aknowledge the influence by it eg "inaudible"

 

[DWI]

It's you demonstrating serious lack of understanding. Do you really believe the more objective orientated people on this forum spend their money on the best measuring equipment without considering it has the features they need and it fits in their interior?

Consumer audio stores sell products that they think their customers want in their homes. If it is a product that is designed with studio monitor performance, like D&D, Kii, ATC or some KEF products, then fine. I've never seen Genelec in a consumer audio store. That tells me all I need to know about its value as a consumer product. They did bring out a consumer range some years ago, but it seems to have been almost completely ignored. But it's a free world, mostly, and you can put in your home what you want.

 

[tvrgeek]

But for

What would make us unable to set the noise apart from the main signal?



A mic doesn't fabricate sine waves. It reacts to a value in air preasure at any given point in time. Those continuous values gives you the signal.

So no, it does measure the actual sound waves "midair", as you said youself. There's no interpretation, intelligence or magic involved.

A mic does however have a bandwidth and a frequency response. That's why you need a mic with an associated specific calibration file if you want to do 'flat' measurements.

EDIT: And yes, any mic also both distorts and makes noise, but that's the least of your worries when entering the realm of acoustics. Thankfully we can just look at the electrical source itself and forget about all that dirt

Other than measuring, who wants a flat mic? Isn't that usually a choice of the recording engineer to work with the musician for a specific sound? Long live old AKG tube mics.

I believe noise is overrated for speakers. More of an issue with cans. I forget the level, but I can hear by blood flow louder than the background of my amps. We do get low noise floor almost for free with good designs. But wait now, Is noise masking actually significant? If all the distortion is significantly below the noise, and the noise is low enough, then will we hear no specific character of the amp/DAC/whatever? Say, we have THD below 120 dB and a 100dB SNR. Do we hear any distortion? Is Johnson our savior?

 

[Deleted member 23982]

you just dont understood then my english isnt perfect but not that bad...

 

[Jimbob54]

you just dont understood then my english isnt perfect but not that bad...

I don't think it's your English that's the problem at all.

 

[Killingbeans]

i meant by ear, so at a point where the noise is "inaudible" but essentially still "messing" with the main sinewave, which could become audible even if we dont hear the "noise" directly, this would atleast explain why "audiophiles" are always talking about "overall sound change"

Like @audio2design says, that might be possible in specific non-music experiments. But once you turn to music, things like the masking effect steam-roll it completely. An "overall sound change" is more likely to be caused by the amount of sleep you got last night or the food you had for dinner.. or how the weather is affecting your mood. And the list goes on and on.

no i know but no transducer or what its called is perfect, couldnt the "mass" of the mic membrane actually "filter" something out? so essentially smooth a noisy sinewave again?

Again, that's bandwidth you're describing. Keep the audible spectrum within that bandwidth, and you're golden.

Besides, if you invented a mic that removed noise like that, every sound engineer on the planet would give their first born to get one

also we thrief for "realistic" sound but speakers/headphones dont quite reach this state no matter what we do, isnt the "noisy" sinewave (electrical and by the actual speaker outputting soundwaves) essentially what sets it apart from "natural sounds" ?

Acoustics and SPL is by far the biggest contributors to realism, IMO. That's also why perfect audio reproduction is a pipe dream.

A bit of noise has little to no effect on the illusion. Just look at how people still enjoy vinyl playback.

 

[tuga]

Other than measuring, who wants a flat mic? Isn't that usually a choice of the recording engineer to work with the musician for a specific sound?

It depends on whether the recording is of the documental type, like the recording of a live classical music performance, or a capture for a multi-track mix production, like most pop/rock music.

 

[rdenney]

What would make us unable to set the noise apart from the main signal?



A mic doesn't fabricate sine waves. It reacts to a value in air preasure at any given point in time. Those continuous values gives you the signal.

So no, it does measure the actual sound waves "midair", as you said youself. There's no interpretation, intelligence or magic involved.

A mic does however have a bandwidth and a frequency response. That's why you need a mic with an associated specific calibration file if you want to do 'flat' measurements.

EDIT: And yes, any mic also both distorts and makes noise, but that's the least of your worries when entering the realm of acoustics. Thankfully we can just look at the electrical source itself and forget about all that dirt

Agreed, but I want to address the issue of music and sine waves.

A microphone doesn't fabricate sine waves, but it certainly produces them. Everything "musical" we see on a scope is a superposition of sine waves, once we filter out the highest frequencies needed to describe (near) instantaneous change transients. (And the microphone membrane does that.) What's left is sine waves, though there may be a lot of them piled up to create the total signal. Even a square wave is simply a superposition of sine waves.

People don't understand root mean square. RMS can be applied to any waveform numerically. Applying it to a single-frequency sine wave is simple math, but using numerical methods, any waveform can be averaged using RMS--it's just the square root of the average of a series of squared values. With digitized music, calculating the RMS is simple.

The importance of RMS is simply this: It is the DC equivalent of AC when calculating the heat it produces in a resistor.

Noise is just random sine waves superimposed on the signal. It may be at a much higher frequency (as shown in the trace above) or not. It's just any component of the waveform that is not intended signal that originated somewhere else. When the air handler in my house is running, I get a spike at 120 Hz in my REW measurements--not high frequency at all. And there is significant low-frequency noise caused by vinyl roar. The 100K Nobel pot in my preamp creates a floor of resistor noise. Noise can be at any frequency, which is why it's hard to filter out. Noise way above the audio passband is easy to get rid of.

Rick "not the same thing as distortion" Denney

 

[Geert]

But it's a free world, mostly, and you can put in your home what you want.

Yes, did anyone on this forum say you can't? Otherwise I don't understand your rant against these evil objectivists.

 

[Geert]

Noise is just random sine waves superimposed on the signal. It may be at a much higher frequency (as shown in the trace above)

I was just listening to a song with a snare played with brushes, which is like white noise. Nothing mystically happend to the sound of the other instruments or vocals

 

[Deleted member 23982]

I was just listening to a song with a snare played with brushes, which is like white noise. Nothing mystically happend to the sound of the other instruments or vocals

well while i get your analogy i can actually hear a difference between vocal only and same vocals on heavly "polluted" rock tracks or whatever, same with piano only vs multiple instruments, tho it isnt a night/day difference, marginal but considering the amplitude of "that" noise you are probably right that "normal noise" cant have such a effect to this extend i was talking about unless there are some "different mechanism" for general noise

one of the reason why i think good setups are specially benefical for rock/metal or to put it another way, they sound extra worse on bad setups...

 

[tvrgeek]

I knew exactly what you meant tvrgeek as I speak DIYaudio, but it may surprise you that people who design amplifiers for money when the speak will say long term pair and current mirror and constant current source, not all the acronyms which are usually used by DiY trying to fit in. But then they are probably more likely to say emitter coupled pair or differential pair ...

Oh, so you do understand, just trying to be important. I actually talked to a lot of professional fulltime amplifier designers, and yes, they used acronyms.

 

[Geert]

well while i get your analogy i can actually hear a difference between vocal only and same vocals on heavly "polluted" rock tracks or whatever, same with piano only vs multiple instruments

Sure you can, because the other instruments are competing with the vocal for bandwidth and dynamic range limited by the recording media. It's the art of music production and mixing to effectively deal with this as good as possible.