Given that music is a temporal phenomena wouldn't response time tests be useful - something akin to grey-to-grey tests in monitors?

[SyncopatedSoul]

Hi I'm new here! Looking for a new DAC I was delighted to find this forum. Very nice find to a place to discuss hi fi from a more scientific standpoint given all the borderline voodoo stuff that is out there.

I want to preface by saying that I am not an electrical engineer or anything. The basis of my questions is my own common sense, so please don't flame me if I messed some of the science up.

So after reading a few DAC reviews and watching a video about what all the measurements mean I was very surprised that all of them are static! Yet music is a rapidly changing phenomena. So I feel a very key important piece of the puzzle is missing in terms of understanding the performance of the measured devices. From a subjective perspective I find this especially important because one of the things I like in a good system is that it feels fast and responsive, which makes the music have more powerful emotional impact especially in moments of change, like when a new instrument kicks in for example. I am aware there is a chance that this experience of responsiveness doesn't come from actual shorter response times, but without a better theory, my best assumption is that it does.

Let's take the multitone test as an example to illustrate what I mean. Given 2 devices that have the same exact multitone chart, isn't it possible for one of them to stabilize from silence to signal faster than the other? Couldn't one have cleaner transition from silence to signal than the other? Couldn't these things be audible and impact the listening experience? (be it in responsiveness or other ways)

What I would have liked to see is a test similar to the grey-to-grey test they do in monitors. That is I would like to see how fast the DAC stabilizes on that multitone signal from silence, and then how long does it take for it to stabilize back on silence once the signal is off. This would be sort of a equivalent to a black to white and then white to black test. Then another test could simulate transitioning between to different multitone configurations similar to a grey-to-grey test in monitors. That way we could have a measure for the response times of different devices. Other tests could test the cleanness of the transitions - did they overshoot? wiggle?

I would love to hear why these tests aren't being done. I thought of a few possible options but would love to hear a professional answer.

1. It is well established that this is light speed fast and that basically all devices have same essentially zero response time.

2. It is hard or impossible to test for some reason.

3. It is deemed unimportant for some reason.

Thanks for any input in advance.
Peace.

 

[ppataki]

I guess you might be looking for an impulse response / step response test
That would show the temporal behavior - I have never seen it with any DACs measured here though

 

[Leporello]

What are the unsolved problems that these tests would be useful for?

 

[Blumlein 88]

Frequency response and impulse response are opposite sides of the same coin. I think impulse response is what would effectively be the test you are thinking about. So if the FR is good, flat and extended, the impulse is good. So that tells you what you need to know in regard to DACs.

 

[BDWoody]

I guess you might be looking for an impulse response / step response test
That would show the temporal behavior - I have never seen it with any DACs measured here though

We get the frequency response, and the impulse response can be derived from that.

If you've got flat at 20kHz, how much faster do you need?

 

[kyuu]

As already stated, frequency response is already temporal in nature. That's not intuitive, which is why this misunderstanding perpetuates. You just have to remember that frequency is a number of cycles over a period of time (1 Hz being one cycle per second).

 

[SyncopatedSoul]

Frequency response and impulse response are opposite sides of the same coin. I think impulse response is what would effectively be the test you are thinking about. So if the FR is good, flat and extended, the impulse is good. So that tells you what you need to know in regard to DACs.

Can you elaborate more, using this review as an example in terms of what test(s) can I see the FR you are talking about and how that corresponds to impulse response? (I mean what is the logical connection)

Topping D50 III Balanced DAC with EQ Review

This is a review and detailed measurements of the Topping D50 III balanced stereo DAC with support for parametric equalization. It was sent to me by the company and costs US $229. Sorry for the quality of the picture/display. It is quite dim compared to my photography light and when I tried to...

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[BDWoody]

Can you elaborate more, using this review as an example in terms of what test(s) can I see the FR you are talking about and how that corresponds to impulse response? (I mean what is the logical connection)

Topping D50 III Balanced DAC with EQ Review

This is a review and detailed measurements of the Topping D50 III balanced stereo DAC with support for parametric equalization. It was sent to me by the company and costs US $229. Sorry for the quality of the picture/display. It is quite dim compared to my photography light and when I tried to...

www.audiosciencereview.com

It's more of a mathematical relationship, as opposed to one that just makes intuitive sense right away.

This thread may help:

Impulse response = frequency response

https://www.stereophile.com/content/dcm-time-frame-tf1000-loudspeaker I came across this today and am curious about what's being stated about impulse and frequency response in their first five paragraphs here. What's said initially seems plausible, but then they seem to drift off point with the...

www.audiosciencereview.com

 

[SyncopatedSoul]

As already stated, frequency response is already temporal in nature. That's not intuitive, which is why this misunderstanding perpetuates. You just have to remember that frequency is a number of cycles over a period of time (1 Hz being one cycle per second).

So I guess my questions is about the "first cycle". I put in quotes because I don't know if that's how you term it. So if I understand correctly what you are saying, it is that given a certain device, the same frequency response for the first and say the 1000 cycle will always be the same?

 

[Blumlein 88]

Can you elaborate more, using this review as an example in terms of what test(s) can I see the FR you are talking about and how that corresponds to impulse response? (I mean what is the logical connection)

Topping D50 III Balanced DAC with EQ Review

This is a review and detailed measurements of the Topping D50 III balanced stereo DAC with support for parametric equalization. It was sent to me by the company and costs US $229. Sorry for the quality of the picture/display. It is quite dim compared to my photography light and when I tried to...

www.audiosciencereview.com

This is over simplified, but may get the point across. Firstly realize even a "static" sine wave is not static. It is a constantly varying value. So the higher the frequency the faster values change. You are wanting to know if a value changes how fast can the DAC respond. Well the fastest it will be asked to change value is at the highest frequency it is capable of reproducing. A 20 khz sine wave has a steeper rate of change for each cycle than a 500 hz sine wave. So if the DAC can respond at the same voltage as at lower frequencies at its highest frequency without distortion or other anomalies then it can respond as fast as it needs to. So even though you have in mind the music goes from soft to loud and back, none of that can happen more quickly than the steepness of the highest frequency the DAC can reproduce at max volume.

From the review this is what to look at:

Now this DAC has selectable filters. The three that are flattest up to the highest frequencies have the fastest possible rates of change. And notice they are ruler flat or very nearly so. So no change in any musical signal can occur faster than the rate of change of a 20 khz max sine wave. Or if this were running at a higher rate like 96 khz, nothing will have a rate of change faster than something a little over 40 khz.

Those filters with an early frequency roll off will impose a slightly lower maximum rate of change. And as the impulse response is related to frequency response you have that frequency roll off. In essence if the FR is good, you don't have to worry about the rate of change.

 

[akamatsu]

Years ago, I stumbled upon an FM broadcast of musicians performing live in the studio. It sounded fantastic! I immediately started scratching my head trying to figure out why it sounded so much better than recorded music. I figured that the difference was timing. Since then, I've experienced nice improvements in vinyl playback by upgrading the power supply to the turntable motor. These upgrades resulted in more accurate and precise spinning of the disc.

 

[kemmler3D]

So I guess my questions is about the "first cycle". I put in quotes because I don't know if that's how you term it. So if I understand correctly what you are saying, it is that given a certain device, the same frequency response for the first and say the 1000 cycle will always be the same?

It turns out that this is basically the case for any normal piece of audio electronics.

It's intuitive to think that the machine needs time to start doing its thing, like a blender needs a fraction of a second to start spinning fast.

What's actually happening is the amp or DAC is constantly outputting a voltage corresponding to its input, whether it is silence or something else. It doesn't need time to "accelerate into motion" because it's always in motion.

If said device is able to reproduce 20KHz accurately, this shows that it is able to "move" as fast as your ear can hear. Mathematically speaking, these "static" tests are 100% convertible to "dynamic" ones and vice-versa.

Sometimes "square wave tests" are used to show transient response using a real signal, but these tend to boil down to the same result as the "static" test and are harder to interpret quantitatively, so not every reviewer does them.

You can see dynamic effects in amps sometimes if there's a momentary high power draw and its capacitors are depleted, but that's pretty easy to measure and would show up in the normal tests. (peak vs. continuous power.)

 

[antcollinet]

So after reading a few DAC reviews and watching a video about what all the measurements mean I was very surprised that all of them are static!

A 20kHz full scale sine is already more dynamic than all music: It goes from max positive to max negative and back again 20,000 times a second. Real music doesn't do this since the levels of high frequencies in music are much lower than a full scale test tone.

But on top of that - here is the time domain wave form of the multi-tone test signal. Also much more dynamic than real music due to the levels of high frequencies being the same as low frequencies. Yet the typical well performing DAC can reproduce it perfectly with inaudible levels of noise and distortion - as shown in the measured test result.

 

[Matt_Holland]

This is over simplified, but may get the point across. Firstly realize even a "static" sine wave is not static. It is a constantly varying value. So the higher the frequency the faster values change. You are wanting to know if a value changes how fast can the DAC respond. Well the fastest it will be asked to change value is at the highest frequency it is capable of reproducing. A 20 khz sine wave has a steeper rate of change for each cycle than a 500 hz sine wave. So if the DAC can respond at the same voltage as at lower frequencies at its highest frequency without distortion or other anomalies then it can respond as fast as it needs to. So even though you have in mind the music goes from soft to loud and back, none of that can happen more quickly than the steepness of the highest frequency the DAC can reproduce at max volume.

This is the best explanation I’ve seen to answer the OP’s question. Nicely put.

@SyncopatedSoul are you also asking if group delay is measurable in DACs which is typically associated with mechanical systems?

 

[tmtomh]

As already stated, frequency response is already temporal in nature. That's not intuitive, which is why this misunderstanding perpetuates. You just have to remember that frequency is a number of cycles over a period of time (1 Hz being one cycle per second).

So many great responses so far in this thread. IMHO this comment most directly captures the conceptual difficuty that, as kyuu says, most folks have (including me before I learned this stuff myself): frequency is speed. Sonic "resolution" is frequency (putting aside for the moment amplitude-related aspects like noise performance).

 

[Matt_Holland]

So many great responses so far in this thread. IMHO this comment most directly captures the conceptual difficuty that, as kyuu says, most folks have (including me before I learned this stuff myself): frequency is speed. Sonic "resolution" is frequency (putting aside for the moment amplitude-related aspects like noise performance).

I think that the logic the OP has used is understandable and commonplace amongst audio enthusiasts. On the negative side, the same logic is used by some audiophile brands to lure people down an illogical, pseudoscientific path that is driven by a faith based emotional response that only certain equipment is capable of delivering a musical/engaging/fast/well timed/rhythmical sound.

A classic example of this is GR Research’s use of the phrase ‘audio smearing’ and the whole MQA thing….

 

[Kal Rubinson]

I figured that the difference was timing.

How did you do that?

 

[GXAlan]

We get the frequency response, and the impulse response can be derived from that.

If you've got flat at 20kHz, how much faster do you need?

Don’t we need phase too? I ask because I think of step response and impulse response as that start and stop question and “pretty flat FR” speakers can look different.

 

[marin.weigel]

Don’t we need phase too? I ask because I think of step response and impulse response as that start and stop question and “pretty flat FR” speakers can look different.

Electronic output stage measurements should not be confused with acoustic measurements of electrodynamic multi-way transducers incorporating complex crossovers.

 

[Mnyb]

A 20kHz full scale sine is already more dynamic than all music: It goes from max positive to max negative and back again 20,000 times a second. Real music doesn't do this since the levels of high frequencies in music are much lower than a full scale test tone.

But on top of that - here is the time domain wave form of the multi-tone test signal. Also much more dynamic than real music due to the levels of high frequencies being the same as low frequencies. Yet the typical well performing DAC can reproduce it perfectly with inaudible levels of noise and distortion - as shown in the measured test result.

View attachment 407719

Yes look at Amir’s DAC tests he often include a multi-tone .

He actually sometimes excludes the fr response other than presenting different filter presets.
As it is boringly predicable with well designed DAC’s it’s there if it’s .

Another conceptual fallacy is to look at these direc filter test pulses you sometimes can see draw the wrong conclusions.