Importance of impulse response

[fineMen]

... time for the transient to silent fast.

Simply put nope. What is "silent"? To the ear or to some instrument of which kind? Again, there is too much 'signal'-thinking involved. One cannot and will never replicate a 'signal' because that is distorted, lost, what have You, in the production process. Even in the listening process, two ears left right with mutual cross talk, even with a single speaker. Speaker in front, stereo at the sides, anybody?

Real science is still on the way to understand human hearing. But the audiophile knows it all: the graphics in the magazine shall look edgy right. Because of the science (as the audiophile understands it).

In order to optimize hearing aids (!) for really demanding people science concluded that a phase rotation giving about a few milli seconds of a group delay equivalent wasn't objectional for any (!) hearing task. Science specifies it more in that even 10..20ms in the bass below 100Hz or so is not the least perceptible, let alone objectionable, while in the mids around 1kHz we have the most critical band. Here best is to keep group delay below 2ms. And that again is for perceptibility alone. Not that it changes the quality of the sound in any way--it means the same to the human mind, its only just a bit not quite the very same.

The audiophile jumps up yelling "Not the same signal, fraud!" Right, but the sound means the same to the human mind. If that does not please the audiophile, he should change his mind one or the other way.

Anyway, there are nearly no (!) speakers around that break the limits stated above. We are good, isn't it terrible?!

 

[kemmler3D]

that short time period cannot encapsulate a 20Hz frequency.

Intuitively, no, but technically, yes it does, somehow. Truthfully I also struggle to conceptualize the physical nature of this. What does that look like in the motion of your sub's cone? It's producing 20hz for 0.6ms or something? It's sort of hard to mentally square it with what the time domain signal looks like. But technically you do need all frequencies including bass to produce a true impulse.

Real world impulses really do contain bass frequencies despite the low duration. Look at a spectrogram of a hard cymbal strike. We hear mostly treble but the bass is there. What bakes my noodle is that implies a (say) 20hz vibration lasting for way less than 0.05 seconds.

 

[fineMen]

Intuitively, no, but technically, yes it does, somehow. Truthfully I also struggle to conceptualize the physical nature of this. What does that look like in the motion of your sub's cone? It's producing 20hz for 0.6ms or something? It's sort of hard to mentally square it with what the time domain signal ...

You really love to doubt your very stereo equipment, don't You? It is scientifically proven, that it occurs that people enjoy their costly investment the most if they tend to accept its performence. There is a strong correlation in just believing the correctness and enjoyment for the sake of musical expression.

But conversely, if You are a scientifically minded sceptic, what about attending a real concert? Sit (literally) on the player's grand piano and let her explain what spectrum of different interpretations of a simple (not so) Schubert song might do to you personally. You should be sure she likes you, but that's easy, as the true music lover the common audiophile is?

All other comment given by you speaks of a person, listening to music as an artform, as an unconscious machine that has to be tricked, go figure! And that is you, really? Is it really so, that the true empowered, entitled, golden ears audiophile has to shut-down his mind to actually realize the purpose of his stereo / 5.1 / 7.1 / 7.2 ... ?

Just think about it, for maybe 0.6 milliseconds. Funny, right?

 

[kemmler3D]

You really love to doubt your very stereo equipment, don't You? It is scientifically proven, that it occurs that people enjoy their costly investment the most if they tend to accept its performence. There is a strong correlation in just believing the correctness and enjoyment for the sake of musical expression.

But conversely, if You are a scientifically minded sceptic, what about attending a real concert? Sit (literally) on the player's grand piano and let her explain what spectrum of different interpretations of a simple (not so) Schubert song might do to you personally. You should be sure she likes you, but that's easy, as the true music lover the common audiophile is?

All other comment given by you speaks of a person, listening to music as an artform, as an unconscious machine that has to be tricked, go figure! And that is you, really? Is it really so, that the true empowered, entitled, golden ears audiophile has to shut-down his mind to actually realize the purpose of his stereo / 5.1 / 7.1 / 7.2 ... ?

Just think about it, for maybe 0.6 milliseconds. Funny, right?

Sorry, it's not clear that you understood my comment. I'm interested in the physical correspondence between an ideal impulse and the motion of a low frequency transducer reproducing that signal. I am interested in this for its own sake, it has no impact on my enjoyment of recorded music either way.

 

[antcollinet]

You really love to doubt your very stereo equipment, don't You? It is scientifically proven, that it occurs that people enjoy their costly investment the most if they tend to accept its performence. There is a strong correlation in just believing the correctness and enjoyment for the sake of musical expression.

But conversely, if You are a scientifically minded sceptic, what about attending a real concert? Sit (literally) on the player's grand piano and let her explain what spectrum of different interpretations of a simple (not so) Schubert song might do to you personally. You should be sure she likes you, but that's easy, as the true music lover the common audiophile is?

All other comment given by you speaks of a person, listening to music as an artform, as an unconscious machine that has to be tricked, go figure! And that is you, really? Is it really so, that the true empowered, entitled, golden ears audiophile has to shut-down his mind to actually realize the purpose of his stereo / 5.1 / 7.1 / 7.2 ... ?

Just think about it, for maybe 0.6 milliseconds. Funny, right?

Say what now???

 

[fluid]

Intuitively, no, but technically, yes it does, somehow. Truthfully I also struggle to conceptualize the physical nature of this. What does that look like in the motion of your sub's cone? It's producing 20hz for 0.6ms or something? It's sort of hard to mentally square it with what the time domain signal looks like. But technically you do need all frequencies including bass to produce a true impulse.

Real world impulses really do contain bass frequencies despite the low duration. Look at a spectrogram of a hard cymbal strike. We hear mostly treble but the bass is there. What bakes my noodle is that implies a (say) 20hz vibration lasting for way less than 0.05 seconds.

I probably didn't explain very well and unintuitive is right. The uncertainty principle, the time frequency trade off applies to how the information is represented. A Dirac pulse is a single cycle of every frequency so the very short impulse can contain the 20Hz information within it and the wider the bandwidth the shorter the time has to be. Bob McCarthy, as quoted before "Time bandwidth product is the relationship between the length of the time record and the bandwidth. The relationship is reciprocal, therefore the combined value is always one. A short time record creates a wide bandwidth, while a long time record creates a narrow bandwidth."

You can either see it with high frequency resolution, high time resolution or some combination of the two. So when you filter the impulse to only show the low frequencies the time period increases but so does the frequency resolution.

Take the sampling rate as an example, the Dirac pulse is represented as the change between 0 to 100% from one sample to the next and back again. If the same data is sampled at 8KHz or 96KHz it will change the bandwidth and make the 96K version shorter.

My only real point is that Impulse responses are a great way of representing the signal but looking at them raw without being processed can be misleading.

 

[fineMen]

Say what now???

So guys, could you imagine, that I design your car, autonomous driving included? Should I apply standards as used here? I won't.

I probably didn't explain very well an ... a single cycle of every frequency ... a great way of ... signal but ... misleading.

I do design your car, actually. 'nough said.

 

[RayDunzl]

What does that look like in the motion of your sub's cone? It's producing 20hz for 0.6ms or something?

Well, there's this:

Using REW, and de-selecting "Plot responses normalized", and filtering the frequency bands, as the frequency band specified is decreased, the amplitude of the impulse graphed also decreases so as to all but disappear.

(If plotted with normalization, the bands are all shown with the same peak size.)

 

[kongwee]

Simply put nope. What is "silent"? To the ear or to some instrument of which kind? Again, there is too much 'signal'-thinking involved. One cannot and will never replicate a 'signal' because that is distorted, lost, what have You, in the production process. Even in the listening process, two ears left right with mutual cross talk, even with a single speaker. Speaker in front, stereo at the sides, anybody?

Do you really listen to music? Orchestra has silent from staccato hits. Rock band like to have a staccato hits to end their song. You need to end the transit fast to feel the hits. How are you gonna explain in science to make the loudspeaker silent as it should?

The spectral decay is much more useful to visualise that than the impulse response, here for example of a well controlled loudspeaker
View attachment 245542
and here from a less well controlled one
View attachment 245541

Correct, spectral decay is more useful than impulse respond to see the overall performance of loudspeaker.

Another grin...

Black - "perfect" impulse from above
Red - impulse from preamp out, playing a 20-20k sweep
Blue - impulse from 20-20k sweep file generated by REW and imported and measured

View attachment 245477

Looks like the DAC/Preamp (red) did a pretty good job of mimicking the stimulus (blue).

I wonder what this says about reading impulse response graphs?

I believe you can listen from -450 to 450us. It is not a really a sweep as our ears can perceived. If we take -450us to 450us as a full cycle. it is around 1kHz. It should be much higher physically in sound. You can generate it as a sound clip and measure it through sound meter to the actual frequency that our ear perceived.

 

[kemmler3D]

Well, there's this:

Using REW, and de-selecting "Plot responses normalized", and filtering the frequency bands, as the frequency band specified is decreased, the amplitude of the impulse graphed also decreases so as to all but disappear.

(If plotted with normalization, the bands are all shown with the same peak size.)

View attachment 245624

View attachment 245625

View attachment 245627

Hmm, this makes total sense. If I am thinking about this right, of course no one transducer is producing a perfect impulse or some kind of wacky micro-fractional waveform. Rather, once all the frequencies are summed (acoustically) the impulse signal would emerge in the same way it does in these charts...? Makes sense, I think. Thanks!

 

[fluid]

I do design your car, actually. 'nough said.

Please stop chopping quotes together to try and change their meaning. I imagine they don't let you design the audio system for the car though do they?

 

[kimmosto]

One problem with timing visualization especially as step response is Y axis scaling. Maximum should be average (at mid) or maximum dBSPL in Pa to see how much pressure drops compared to ideal or minimum phase version.
This is quite extreme example having sealed "sub" with 4th order XO at 80 Hz, 8th order XO at 380 Hz and 8th order XO at 3 kHz. Pressure loss in leading edge of ideal "slam" is about 8 dB.

Delay and phase in frequency domain

 

[Ra1zel]

Well thankfully the year is 2022 and one does not have to limit himself, you can make a speaker that has great "optimized" spinorama, flat magnitude, smooth directivity we have all that "easily" now, yet you can also optimize the step, ETC, impulse without much trouble and guess what, throw a low THD/IMD drivers and (virtually) inert cabinets while we are at it.

Almost 300 posts about importance of time domain in speakers when you can just make a speaker and try for yourself. Experiment what minimum phase speaker does for you and whether it's worth it, it's not rocket science. Right now good spinorama is what sells so most manufacturers don't care much about other stuff, we'll have to wait for definitve resarch on timing behavior and it's relevance to experienced sound quality.

Anyway good thread and a major learning opportunity, some valuable posts by many (excluding fineMen)

I imagine they don't let you design the audio system for the car though do they?

I at least hope they don't let him

 

[fineMen]

Anyway good thread and a major learning opportunity, some valuable posts by many (excluding fineMen)

Especially regarding @fineMen this is a not an evaluable logical statement. Some, not all post were valuable. From what part do you exclude those by @fineMen? Excluded from the valuable, or excluded from the less worth posts?

You see, there is logic in conversation, and I really don't get the logic in discussing an impulse response comparing visualizations on paper as a graph, or the relevance for stereo.

I could not convince the panel, that a visual examination is worthless. Same with auditory examination, because neither the production of a recording would be able to preserve "that", whatever that means, nor does listening via speakers of any provenience provide an undistorted transmission channel for "that" in the signal. I said, "multiple microphones used" and I said, "crosstalk between ears".

There was never a counter argument.

I argue that my contributions are accounted to the less-worthy camp. It may be because I already know that stuff you are learning here. I struggle with the presentation, because it gives the best opportunity to get it just wrong.

 

[Plcamp]

Then what difference does a perfect impulse, or rather flat phase, bring to the sound?
To my ears, cleaner stronger transients are easiest to hear.
I'd say improvements to timbre, rhythm, and overall clarity/definition also occur.

I think this is true but I don’t trust myself to judge it.

With a Minidsp it should be trivial set up equivalent amplitude response with differing phase responses on the preset channels and rapidly back and forth swap between them, so I might try that.

 

[MAB]

So guys, could you imagine, that I design your car, autonomous driving included? Should I apply standards as used here? I won't.

I do design your car, actually. 'nough said.

OMG! It’s Elon Musk! Guys, Musk is an ASR member!!! This is so exciting.

 

[fineMen]

OMG! It’s Elon Musk! Guys, Musk is an ASR member!!! This is so exciting.

Something else, long-winded again, adding to post #274. Latest when a loudspeaker is to be evaluated by direct audition, the relative phase of a set of frequencies doesn't only determine the relative phase of the excitation in the cochlea of the (two!) ears.
First that group (hence the name: group delay) of frequencies undergoes the electro-dynamic conversion. That is an inherently non-linear process So it might be, that the phase also determines the amplitude dependent variable conversion rate, commonly known as harmonic and intermodulation distortion
I argue that at least for the widely used and ever beloved two-way speakers some high frequency package is affected by the current actual position of the membrane/motor and its speed. The latter is determined by the bass, more specific by the relative phase of bass and high frequency package.

A simplified example: define the group delay, the arrival time of the h/f package as 0, then in one case bass is delayed by say 10ms, but in the other case by 15ms. That means that given an additional low frequency of 50Hz the h/f package could sit on the peak of the excursion of the membrane, while in the other case it would sit on just it's rest position.

With an DIY home brew audition, it would take a lot of volume in the bass to "hear something", hence high excursion is needed, and figure the rest out yourselves.

You may mark this contribution for later, good luck!

 

[MAB]

I do design your car, actually. 'nough said.

No.

BTW. Taking people’s word out of context is not OK. But you do much worse, you rearrange the words they say, and that is unethical.
This is you rearranging someone’s post:

fluid said:
I probably didn't explain very well an ... a single cycle of every frequency ... a great way of ... signal but ... misleading.

It’s like you’re writing a ransom note with someone else’s words. You do this often. You should stop.

 

[Ra1zel]

You may mark this contribution for later, good luck!

Sorry man but I can't get anything out of that incoherent rambling.

People are talking about one thing and you do your own thing. It's like trying to communicate with text generator AI... then again those are getting quite advanced.

 

[fluid]

Sorry man but I can't get anything out of that incoherent rambling.

I think he means that group delay of a specific time could coincidence with the excursion of the cone creating more distortion.