Amplitude and Time, how difficult can it be ?

Rob Sonata · Mar 6, 2017

PeterA said:
Rob, are your referring to Wilson Audio's new WAMM model?

Hi Peter, no I'm not referring to that speaker as I have not heard it (and thus, cannot comment on the results of the design)

However, I do find it encouraging that the company in question is (within their own limits as purely a speaker manufacturer only) taking the matter of time distortion seriously, but I don't think that the methods they are employing can be 100% perfect.

Physical alignment of drive units to compensate for crossover time delays can only succeed for a single point in space (where all the various pathways meet) and, if all the frequencies produced by each driver are subjected to the same amount of group delay for their specific bandwidth.

Now, I don't know the design principles of that particular crossover design but I think it's impossible (within the analogue domain) to ensure that the bandpass filter used to feed a midrange driver (say 500Hz to 3KHz) produces the same amount of time shift equally for all of those frequencies - I'm hoping someone will be able to shine some light on that subject for me ?

Therefore, if the amount of delay is not constant across each individual drivers output, then you are left with a situation where you must take your alignment point at a median frequency within that range.

Surely then, this design approach (with a 5 way speaker) can only produce a perfect time alignment for the 5 median frequencies at one single point in space... therefore, if you move your head backwards or forwards, up or down, then you lose alignment.... maybe ?

Isn't the ideal solution, one that makes sure the wavefront emanating from the speaker is perfectly aligned (vertically in the case of most multi-driver speakers) at the baffle and no matter what distance you are away from the front baffle, all the frequencies are correctly in time.

The manufacturer that I am concerned about produces an entire range of speakers that are perfectly aligned for frequency, amplitude, phase and time - from their tiny little 'desktop' model to their huge award-winning and iconic flagship model.

Rob Sonata · Mar 6, 2017

Whatmore said:
Sanders speakers are time aligned, as too are a couple of Aussie manufacturers- SGR, Kyron, Legend.

I'm sure there are more. Surprised at the claim that only one company does it

I think the Kyron makes use of a digital crossover (possibly by DEQX ?) and Class D amps (N-Core ?) and a loom of various 'speaker' cables - the output from the crossover may well be time aligned, but the output from a Class D amp won't be (there will be a big amount of time distortion between the low and high frequencies)

RayDunzl · Mar 6, 2017

Measuring, I find my panels can throw flat phase to the listening position. Then, the bass cones ramp up in delay as frequency decreases.

Frequency response and phase (unwrapped)

Step response before and after DRC

Measuring a pair of JBL LSR 308 - the phase nearfield is good, but completely whacked by the time the sound gets to the listener, in my opinion, because of reflections - wide dispersion vs narrow dispersion of the panels.

Frequency response and phase (wrapped) at listening position

Step response before and after DRC

The DRC software is AcourateDRC, a lite version of Acourate, fed to a miniDSP OpenDRC-DI (digital in/out)

Whatmore · Mar 6, 2017

Rob Sonata said:
I think the Kyron makes use of a digital crossover (possibly by DEQX ?) and Class D amps (N-Core ?) and a loom of various 'speaker' cables - the output from the crossover may well be time aligned, but the output from a Class D amp won't be (there will be a big amount of time distortion between the low and high frequencies)

How do "speaker" cables differ from speaker cables ?

the sound of Tao · Mar 6, 2017

Fiddle Faddle said:
I am really baffled as to how you came to that conclusion. It is one of the most discussed attributes of good componentry and good reproduction. If you read professional reviews of products it is also much discussed. And just to contradict your statement with one example:

http://www.analogplanet.com/content...udspeaker-reaches-heavens#Gx7iIGF9B3HUlPHC.97

And I may or may not be the exception here, but I rate time domain performance extremely highly - in that for me it is absolutely critical to the quality of a component - almost above all else except the most obvious things.

+1 Not sure there would be too much disagreement that temporal coherence is fundamental to the quality of our experience of music and PRAT (where t=timing) is amongst the most essential and most often discussed critical elements within our pursuit.

Time is certainly one half of the coherence framework and space the other.

Reference to time alignment in speaker design has been relatively common since the 80's. Not sure anyone doing proper audio design would consider discounting the importance of time and much as in comedy, speaker design is allabou t ti ming.

Fiddle Faddle · Mar 6, 2017

the sound of Tao said:
Reference to time alignment in speaker design has been relatively common since the 80's. Not sure anyone doing proper audio design would consider discounting the importance of time and much as in comedy, speaker design is allabou t ti ming.

This has me thinking. What about time alignment in headphone design? I simply cannot use ANY "proper" headphones whatsoever except for ones that use an extremely tiny driver or a balanced armature (examples, my own IE800). The bigger the headphone driver the more unlistenable and incoherent it is to me. And it is not like I lack experience - I have listened to dozens of high end headphones over the years. For example, the famed top of the line Stax system or Sennheiser HD800 / HD800s just don't even sound remotely right at all to me - it is just all incoherent. And it isn't the fact that they are headphones since I do not generally have any problem at all with modern in ear monitors. I can even happily use designs like Westone where they have multiple tiny drivers each covering a certain frequency range and each a slightly different distance from the ear drum in their body shell. But a full range driver design like many if not most of the traditional "desktop" headphones sound awful to me without exception.

I wonder whether that is a time alignment issue, since would I be correct that the extremely close proximity to the ear of a large with respect to the ear) full range driver would result in serious time alignment problems? And at least if you are talking large speakers in a large room, the required (different) distances between drivers and ear is going to be less (in percentage terms of the total distance) than if one large driver were stuck a few cms from the ear drum.

I remember KEF back in the early 90s for example, started bringing out their full range concentric driver and I remember really being impressed with the sound of them. But I don't see this being generally adopted in headphone design. It makes me wonder what I might think of a headphone specifically designed to be perfectly time aligned in the same way Wilson have approached it (so multiple drivers at different distances as is often used in IEM design).

Whatmore · Mar 6, 2017

Rob Sonata said:
The manufacturer that I am concerned about produces an entire range of speakers that are perfectly aligned for frequency, amplitude, phase and time - from their tiny little 'desktop' model to their huge award-winning and iconic flagship model.

The suspense is killing me. Who is it?

the sound of Tao · Mar 6, 2017

FF,
Perhaps there is already some disorientation with headphone listening that focusses you even more on what is coherent since you are audibly being taken out of space. The loss of connection with the real acoustic world, the sounds of your room, natural room reflections and then focused listening just in your head but without any correlating resonance being felt through your body all alters and synthesises even more your total listening perception with much less connection to reality.

Perhaps when you are being taken out of the spatial framework as a reference your brain starts hunting for another familiar reference like the experience of time.

Perhaps also the essential lack of coherent nature throughout the range between different drivers is then heightened... either way just a bit of wild speculatin from this end.

Fiddle Faddle · Mar 6, 2017

I would have thought that myself but it doesn't explain why I have no problem with in ear monitors that have single tiny drivers, armatures or multiple tiny drivers that are actually time aligned. It is only where there is one large driver where I have the problem.

Al M. · Mar 6, 2017

the sound of Tao said:
+1 Not sure there would be too much disagreement that temporal coherence is fundamental to the quality of our experience of music and PRAT (where t=timing) is amongst the most essential and most often discussed critical elements within our pursuit.

Absolutely.

It don't mean a thing
if it ain't got that swing

marty · Mar 6, 2017

RayDunzl said:
Measuring, I find my panels can throw flat phase to the listening position. Then, the bass cones ramp up in delay as frequency decreases.

Frequency response and phase (unwrapped)

View attachment 31414

Step response before and after DRC

View attachment 31415

Measuring a pair of JBL LSR 308 - the phase nearfield is good, but completely whacked by the time the sound gets to the listener, in my opinion, because of reflections - wide dispersion vs narrow dispersion of the panels.

Frequency response and phase (wrapped) at listening position

View attachment 31416

Step response before and after DRC

View attachment 31419

The DRC software is AcourateDRC, a lite version of Acourate, fed to a miniDSP OpenDRC-DI (digital in/out)

I'd like to understand this in greater depth but I'm afraid your explanations are not adequate for me. I just don't know what I'm looking at. Would you be willing to kindly provide a brief description of each curve that I see pictured? Thanks very much.

Stacore · Mar 7, 2017

Rob Sonata said:
Sound is simple, it's just Amplitude and Time (the 'first principles' thing) and yet every audio manufacturer (with the exception of one) seems to ignore the aspect of Time distortion in their products.

Why ?

Not sure if it was already answered but you are very much wrong. The timing errors are called technically phase errors
and are taken into account by every reasonable designer along with amplitude errors. Speakers and time alignment is one example,
signal transformers and their phase behavior is another, NFB (no feedback) is one more, etc etc.

RayDunzl · Mar 7, 2017

marty said:
I'd like to understand this in greater depth but I'm afraid your explanations are not adequate for me. I just don't know what I'm looking at. Would you be willing to kindly provide a brief description of each curve that I see pictured? Thanks very much.

You need an measurement microphone, and software.

I use a UMIK-1 ($100 or so) and Room EQ Wizard (free).

The software sends a tone (known excitation) that slides from low to high frequency to the system, the microphone records the playback from the speakers in the air.

The received "sound" is analyzed in software - what was received is mathematically compared to what was sent, in amplitude and time.

Frequency Response - shows the amplitude of the tone received at each frequency.

Phase - shows how the received sound differs in time compared to what was sent.

Step Response - analyzes the return of the sweep tone and calculates (rather accurately, I might add) how the system would respond to a "step" signal (looks like the front end of a square wave).

---

Other measurements - Impulse Response, Group Delay, time decay, etc., can be performed.

If you add "Room Correction" software/hardware (about $450 in my case), then you modify the signal sent to the equipment to "correct" for problems in frequency and timing, and to adjust for your own preferences.

I'm liking the results, being of scientific bent, others (especially around here) of the touchy-feely persuasion, may object.

Rob Sonata · Mar 7, 2017

Whatmore said:
How do "speaker" cables differ from speaker cables ?

I probably should have called them 'drive unit cables' - I assume that the system uses some kind of multicore cable or a number of individual cables that make up the 'speaker cable' as a whole

Apologies if my use of the inverted commas was upsetting.

Rob Sonata · Mar 7, 2017

Stacore said:
Not sure if it was already answered but you are very much wrong. The timing errors are called technically phase errors
and are taken into account by every reasonable designer along with amplitude errors. Speakers and time alignment is one example,
signal transformers and their phase behavior is another, NFB (no feedback) is one more, etc etc.

I did not mean to insinuate that designers of audio equipment do not take account of phase/time errors and distortion but that most of them (especially in speaker crossover and amplifier design) do not seem to be that concerned about eliminating it.

As mentioned, I know of one manufacturer that produces amplifiers that have a few nano-seconds of delay between the lowest frequency and the highest frequencies in the audible bandwidth.

Now, that is not to say that there are others that are capable of doing this as well, I'm sure members of the audio community can help inform me of such.

I am only asking this question simply because of that fact that time distortion does not exist in our natural environment and when we hear 'real' sound, all of the frequencies in that real sound will reach our ear at the same time.

Surely, we would want that same time coherence to be presented in a system that is reproducing sound.

Whatmore · Mar 7, 2017

Rob Sonata said:
I did not mean to insinuate that designers of audio equipment do not take account of phase/time errors and distortion but that most of them (especially in speaker crossover and amplifier design) do not seem to be that concerned about eliminating it.

As mentioned, I know of one manufacturer that produces amplifiers that have a few nano-seconds of delay between the lowest frequency and the highest frequencies in the audible bandwidth.

Now, that is not to say that there are others that are capable of doing this as well, I'm sure members of the audio community can help inform me of such.

I am only asking this question simply because of that fact that time distortion does not exist in our natural environment and when we hear 'real' sound, all of the frequencies in that real sound will reach our ear at the same time.

Surely, we would want that same time coherence to be presented in a system that is reproducing sound.

Is there any reason why you won't reveal the manufacturer?

Ken Newton · Mar 7, 2017

Rob Sonata said:
...As mentioned, I know of one manufacturer that produces amplifiers that have a few nano-seconds of delay between the lowest frequency and the highest frequencies in the audible bandwidth.

Goldmund/Job?

LL21 · Mar 7, 2017

Ken Newton said:
Goldmund/Job?

I am also going to guess Rob Sonata is recommending Goldmund...but i am also randomly guessing that given Rob's profile he is [possibly] Rob of Sonata Audio? Goldmund, Linn, but also a number others.

I apologize if I have guessed wrong, but as many of here have noted...Rob has kept the suspense running so it was only natural to try for a guess.

I also note this from Sonata Audio's website:

"...Unfortunately, all audio equipment creates unnatural time delays for different frequencies, which your brain recognises as unreal.

Only Goldmund speaker systems produce the most time coherent audio possible and that’s the reason why it instantly sounds more natural...."

microstrip · Mar 7, 2017

Ken Newton said:
Goldmund/Job?

Probably he is referring to Soulution:

"From the input the soulution 711 first buffers the music signal. A high performance correction amplifier is then used to capture and correct any deviations in the signal, very quickly and very precisely. Ultra wideband amplification using no feedback loops follows, a less than 10 nanosecond transit time and level accuracy to within 0.1dB ensuring signal purity."

amirm · Mar 7, 2017

Rob Sonata said:
Surely, we would want that same time coherence to be presented in a system that is reproducing sound.

Only if it doesn't compromise something far more audible and objectionable.

Amplitude and Time, how difficult can it be ?

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