# Time Domain measurements?

#### haraldo

##### Active Member
We do not fly to the moon because it is easy, Kennedy.
if it's not hard, it's not worth doing
- Sir Peter Blake, New Zealand, winner of Americas cup 1995

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#### KaiserSoze

##### Addicted to Fun and Learning
I am sorry that my post offended you. That will not happen again. And I had not especially you in mind. That was only a reaction that I see many times

on Threads like this that people do not have basic understanding. When that basic understanding is not there it is mostly impossible to discuss advanced issues.
I should not have replied. And for what it's worth, I did visit that page that you suggested, and it was useful. I read most of it last night, and a couple of other pages on the same subject. There are several active analog solutions that involve op-amps, which are the norm for implementation of active analog filters. But my interest is mainly with passive crossovers. I had previously wondered whether the lattice approach is actually a bridge and this turns out to be case. And there is a phase gradient of course, i.e., frequency-dependent rotation of phase, through which fact I now fully realize that phase rotation can occur without attenuation. But I'm going to have to study this all a lot more to get to where I want to be.

#### DonH56

##### Major Contributor
Technical Expert
Forum Donor
An all-pass implementation typically strives for linear phase and thus constant group delay. That provides optimal pulse integrity -- a pulse coming out looks like the one going in, just delayed. That was my goal for either audio or microwave circuits I designed. You can work it out a myriad of ways, natch.

#### KaiserSoze

##### Addicted to Fun and Learning
"It will somewhat resemble a square wave, but one where the fundamental frequency is the 45 Hz "
So if you take away the fundamental 15 Hz of your example the result clearly does not resemble a square wave.
Okay, but I will say again that it was obvious that the resulting waveform won't be a square wave. Also, "resemble a square wave" isn't exactly the same thing as saying that you'll get another square wave. No matter. I'm still curious to know what you think the overall periodicity will be. If you answer this, you'll be answering a question as opposed to a statement.

#### UliBru

##### Member
Technical Expert
Okay, but I will say again that it was obvious that the resulting waveform won't be a square wave. Also, "resemble a square wave" isn't exactly the same thing as saying that you'll get another square wave. No matter. I'm still curious to know what you think the overall periodicity will be. If you answer this, you'll be answering a question as opposed to a statement.
You also said before:
"What I was trying to say (and believe that I did say in an adequately clear manner) is that if the low-pass filter that is applied is sufficiently steep, that there will be no remnant of the original 15 Hz fundamental in the output waveform, and that the overall periodicity evident in the output waveform will be that of the 3rd harmonic (45 Hz)"

The square wave without the fundametal 15 Hz looks like

Indeed the signal still shows a periodicity of 15 Hz despite there is no 15 Hz sine wave in the signal. That's pretty funny. It may also explain why we perceive a fundamental frequency despite its total absence.

#### haraldo

##### Active Member
@Joachim Gerhard I can´t seem to find an answer to your thoughts onto the following in this thread
How much emphasis do you put on the time coherence of your speakers and why would you drop the absolute phase coherence in a passive x-over?
I guess everything is a compromise and you can´t get everything, so I assume every product is the best compromise possible to do
Looking at step responses from Stereophile on both Virgo and Virgo III they look really very close (and nice) but not fully phase coherent
(I was really close to purchasing the Virgo III, probably a bad choice not to get them)

Would you current passive portrait extended edition look something similar, maybe without the delay between tweeter and mid?

Virgo step response from Stereophile

Virgo III step response from Stereophile

#### ferrellms

##### Member
Everyone is justly raving about the performance of the Kii3 and the D&D 8c.

The Toole school preaches that everything which matters is expressed in the frequency response measurements.

Yet there is a chance that the time-domain performance of these speakers may contribute to the overall results.

https://www.stereophile.com/content/dutch-dutch-8c-active-loudspeaker-system-measurements

https://www.stereophile.com/content/kii-audio-three-loudspeaker-measurements
My Sonarworks 4 correction has a button to select "linear phase". It adds 43msec to the processing time. It seems to have a subtle but real audible effect, slightly clarifying the image and transients. Is this what we are talking about? My room is treated for early reflections.

To my ears, the "linear phase" button smears chocolate icing thickly on the cake.

Is it possible that the lack of early reflections from the Kii, DutchDutch, and my expensive room enable the audibility of the "linear phase"? If so, the measurements could include time numbers for those interested, even though they are not universally considered important.

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#### haraldo

##### Active Member
Everyone is justly raving about the performance of the Kii3 and the D&D 8c.

The Toole school preaches that everything which matters is expressed in the frequency response measurements.

Yet there is a chance that the time-domain performance of these speakers may contribute to the overall results.

https://www.stereophile.com/content/dutch-dutch-8c-active-loudspeaker-system-measurements

https://www.stereophile.com/content/kii-audio-three-loudspeaker-measurements
I'm not raving about them ... I auditioned them and either it's something wrong with me, something wrong with speakers or it was a horrible demo....

I thought they were lifeless, sounded artificial, no magic ..... that was the Kii three BXT (with woofer modules) fed from an Auralic G2.1 streamer.
24 woofers and the bass was lagging, unprecise and inadequate...

I really wonder why anyone would want to buy these speakers

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#### haraldo

##### Active Member
In my opinion time coherence is subtle but important. That is one of the reasons I chose and still love my Thiel CS 3.7 speakers.

Current active speakers can switch this on and off to test. I have listened to a demonstration of a Goldmund system and it was noticeable. Even fixing it with convolution is worth it. After all it is still part of high fidelity to the source.
I agree with you there, and envy your CS 3.7. In lack of a better word, I think there seem to come some sort of artificial "hardness" when you throw the phase coherency out the windows... the best phase coherent speakers just have something special with them that I just don't get with most other products.

I am unsure what I really think about the Dynaudios, they use 1st order electrical crossovers but it's not 1st order acoustical. I think sometimes they cross tweeter very close to Fs , I reckon making the x-over something like 2nd order acoustical.... On Dynaudio Evidence Temptaion tweeter has reversed polarity to midrange...

Dynaudio Evidence Temptation (Stereophile)

Thiel CS 3.7 (Stereophile,)

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#### KaiserSoze

##### Addicted to Fun and Learning
You also said before:
"What I was trying to say (and believe that I did say in an adequately clear manner) is that if the low-pass filter that is applied is sufficiently steep, that there will be no remnant of the original 15 Hz fundamental in the output waveform, and that the overall periodicity evident in the output waveform will be that of the 3rd harmonic (45 Hz)"

The square wave without the fundametal 15 Hz looks like
View attachment 73264

Indeed the signal still shows a periodicity of 15 Hz despite there is no 15 Hz sine wave in the signal. That's pretty funny. It may also explain why we perceive a fundamental frequency despite its total absence.
Verrrry interesting. Yes, I did say that, and after your first (or possibly second) comment in reply, I indicated that I wasn't sure. Your graph appears correct and does indicate that the periodicity remains 1/15 second. It's kind of weird that even though the periodicity is that of a 15 Hz sine wave, there is no spectral energy at that frequency.

#### KaiserSoze

##### Addicted to Fun and Learning
My Sonarworks 4 correction has a button to select "linear phase". It adds 43msec to the processing time. It seems to have a subtle but real audible effect, slightly clarifying the image and transients. Is this what we are talking about? My room is treated for early reflections.

To my ears, the "linear phase" button smears chocolate icing thickly on the cake.

Is it possible that the lack of early reflections from the Kii, DutchDutch, and my expensive room enable the audibility of the "linear phase"? If so, the measurements could include time numbers for those interested, even though they are not universally considered important.
Pardon my butting in, but I just had to throw in a couple of cents worth by saying that while linear phase is presumably of strong advantage somewhere, that with respect to speakers, the relationship between phase and frequency is linear this will in no way avoid phase mismatch among the various frequency components that make up a complex waveform. I'm on the fence with respect to where phase coherency matters (beyond the need for proper summation in the overlap region of a crossover), but if perchance it matters, linear phase isn't going to get it done.

Forum Donor

#### haraldo

##### Active Member
Current active speakers can switch this on and off to test. I have listened to a demonstration of a Goldmund system and it was noticeable. Even fixing it with convolution is worth it. After all it is still part of high fidelity to the source.
I auditioned Sonus Faber Guarneri evolution with and without the Devialet SAM, where the SAM should do phase correction and some supposedly other types of magic. I think through the Devialet it worked best with all the DSP processing turned off, I have no idea what that DSP stuff is doing in this situation but to me it clearly disrupts the musical flow and makes it all become somewhat unnatural to my ears
(Through this specific demo, at least)

So I wonder ... making everything look better and measure more nice can possibly kill the music
There is some part of that DSP processing in this case that "flattens" the music

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#### Matias

##### Major Contributor
Forum Donor
I auditioned Sonus Faber Guarneri evolution with and without the Devialet SAM, where the SAM supposedly is to do phase correction and some supposedly other types of magic. I think through the Devialet it works best with all the DSP processing turned off, I have no idea what that DSP stuff is doing in this situation but to me it clearly disrupts the musical flow and makes it all become unnatural to my ears
(Through this specific demo, at least)

So I wonder ... making everything look better and measure more nice can possibky kill the music
Devialet SAM fixes the bass delay for time alignment, but also extends the bass response while limiting the max excursion to protect the drivers. So listening with/without SAM unfortunately is not time alignment alone, the added bass response will change the perception too.

#### haraldo

##### Active Member
Devialet SAM fixes the bass delay for time alignment, but also extends the bass response while limiting the max excursion to protect the drivers. So listening with/without SAM unfortunately is not time alignment alone, the added bass response will change the perception too.
yeah, when I read about SAM now, that´s what is written there but I seem to remember once there was written that they make the speakers phase coherent in addition, I can´t seem to locate this now, anyway there is multiple things going on there and I don't like it...

#### RayDunzl

##### Major Contributor
Central Scrutinizer
It's kind of weird that even though the periodicity is that of a 15 Hz sine wave, there is no spectral energy at that frequency.
The harmonic waves all have positive (and later negative) going zero crossings aligned at that 15Hz period. They are still adding to make the step up, and subtracting to make the step down, even without the 15hz wave.

Whats missing is a major support for the flat areas of the wave.

---

What's weirder to the eye vs the ear, is that even if the alignment of the harmonic waves is lost, the steady state sound heard is the same.

Square to F9

#### KaiserSoze

##### Addicted to Fun and Learning
The harmonic waves all have positive (and later negative) going zero crossings aligned at that 15Hz period. They are still adding to make the step up, and subtracting to make the step down, even without the 15hz wave.

Whats missing is a major support for the flat areas of the wave.

---

What's weirder to the eye vs the ear, is that even if the alignment of the harmonic waves is lost, the steady state sound heard is the same.

Square to F9

View attachment 73309
The waveform that UliBru provided is correct; it is what you get if you sum together all the terms of the Fourier expansion of a square wave leaving out only the 1st term which has the same period as the square wave itself. To generate what he generated all that need be done is to subtract that single sine wave from the square wave or vice versa, either way. But the catch is that you have to get the amplitude of the sine wave correct.

#### KSTR

##### Addicted to Fun and Learning
What's weirder to the eye vs the ear, is that even if the alignment of the harmonic waves is lost, the steady state sound heard is the same.
This because the waveform is still strictly symmetric. I did tests with a fundamental and a 2nd or 3rd harmonic with varying amounts of start phase offset in 22.5° increments. While the 3rd showed neglegible change of timbre vs. start phase (position of the harmonic on the fundamental) when stepping through the 360° range, the set with the 2rd harmonic shows a slightly wandering timbre.

There are two offsets that have maximum contrast of timbre and those are 180° apart, and there is a second set where the difference is minimal. This set again is 180° apart but rotated by 90° vs the first set. The base offset depends on your playback system and when we have flat zero phase in the range of the frequencies this offset is zero. Inspection shows that for the maximum set the wave-shape is maximally asymmetric and for the minimum set it is symmetric in that flipping the wave is identical to revert it in time.

With a linear-phase highpass (say, a closed box with 2nd inverted phase highpass filter to form a 4th-order linear -phase alignment) and the fundamental close to or left of the tuning frequency the waveshape remains almost fully intact, the fundamental just has reduced amplitude (to the point of being cancelled).

In the waveform this shows up as the flat tops of the square going to a concave sine shape, reducing the fundamental, as shown by @UliBru in https://www.audiosciencereview.com/...ds/time-domain-measurements.12951/post-455827
And when the content has asymmetric waveforms, a linear-phase high-pass target for the acoustical transfer function fully preserves the relationships in the waveform.

The drawback is that we have a pre-ringing with exponential rise, being the mirror image of the post-ringing in the step response which is certainly audible with some signals.

In a crossover, things are different. On-axis we have a flat and zero-phase sum and the ringing cancels out. Canceling also happens in a minimum-phase corssover, just that the off-axis ringing is post-ringing only. The point is that we are just more prone to perceive pre-ringing than post-ringing due to different masking. IMHO linear-phase XO works best with coaxials or symmetrical W-M-T-M-W placement, or beamy transducers/horns.

#### dc655321

##### Addicted to Fun and Learning
Why would I mean amplitude instead of attenuation?
Because the former is the correct term to use - a transfer function can be expressed as a function of amplitude/magnitude and phase.

Now what on earth would motivate you to say, " ... math, which you seem shy of ..."
My comment was inferred from your misuse of terminology, and more directly by this:
my math skills are much too rusty
If you were comfortable with the math, there is an ocean of information at your fingertips regarding signal processing.