Driver movement

[dshreter]

I remember a guy here, that post this graph pointing the woofer have problems.
These problems are translate into stuff like ' dullness ', ' never rest ', ' clarity ' to him
This is the woofer from the 2011 R series and he said:
''WTF It never came to a complete hault even when first reflection arrived at 10.3ms - i never saw anything like this except in few car subs that also use two part cone (oval and cone part glued). This must be the dirtiest impulse response in a hifi woofer i measured so far.''

So, this graph what does mean? It's the R300.
''

Is this the impulse response of the driver or an in room mic measurement?

 

[BrokenEnglishGuy]

Is this the impulse response of the driver or an in room mic measurement?

he said this ''
Comparisons are done in two rooms of which one is my own. I decided that modifying is needed before i saw measurements because they didn't sound right - not the other way around. Then i made measurements shown below. Next part of the post isn't reply to you but to others that might be interested. I have no will to prove anything to you ( pics of my room or time line for how long did i listen every one of mentioned loudspeakers) just so that you'd think of something else to write about how and why i should like something i don't.

I'll try to explain with quasi-anechoic measurements why i think their woofers combined with relatively high crossover frequency to midrange (400-500Hz) might be the problem. ''
In comparison, here is 6.5" woofer (used in my DIY three way loudspeaker)''

 

[dshreter]

In Amir's speaker reviews there is sometimes a chart of the cumulative spectral decay. I believe it roughly gives the same and more information in an easier to interpret format.

 

[BrokenEnglishGuy]

In Amir's speaker reviews there is sometimes a chart of the cumulative spectral decay. I believe it roughly gives the same and more information in an easier to interpret format.

For example that guy wrote

''... It needed a bit longer to do get to rest and stopped playing around 4-5ms. Little slower than midrange but that's to be expected. Here is Kef R-2011 woofer (differences in construction are minimal compared to R-2018 woofer)... ''



But time ago i wrote to kef asking if the new woofers allow for higher SPL because the woofer from my R300 doesn't go very loud, Kef wrote to me:

''

Indeed, the R3 bass driver is totally new and different to the R300, so the power handling is greater. The re-design allows for further excursion and extension so requires a larger amplifier to drive it efficiently.

We have also increased the cabinet size, so the overall internal volume is bigger, again, the key reasn why we increased the power handling figures.

With Best


''
Having the R7 i can confirm that, the new woofers can go much louder and cleaner than the previous but i don't have any no impulse measure or any usefull measurement.
Anyway the R3 woofer can pretty loud and cleaner in the 200hz - 400hz, i don't see any problem in that region, but.. no Amir or Erin didn't measure the impulse response from Kef R3.

 

[dshreter]

Having the R7 i can confirm that, the new woofers can go much louder and cleaner than the previous but i don't have any no impulse measure or any usefull measurement.
Anyway the R3 woofer can pretty loud and cleaner in the 200hz - 400hz, i don't see any problem in that region, but.. no Amir or Erin didn't measure the impulse response from Kef R3.

Amir's review does have the cumulative spectral decay for the R3

 

[Shazb0t]

The problem that you have here is that you're trying to theorize how something that you don't understand might affect something else that you don't understand.

Just Google "how does a transducer or loudspeaker work?" Get a basic understanding of how sound is produced and then ask these questions to yourself again.

 

[BrokenEnglishGuy]

Amir's review does have the cumulative spectral decay for the R3

So how does it compares to others '' woofers '' in dampening? the R3 woofer have too much ringing or something?

 

[audio2920]

I sometimes read a thread expecting to know how it ends, but then I find gaps in my knowledge.... so...

Resonances on a waterfall plot (CSD) often have a significant corresponding dip at the 0ms slice, and such resonances don't always show up [as] much in FR, right?

To explain it to myself, I'd always assumed the CSD graph is a windowed (or time sliced) representation of the same impulse response displayed in FR (with a relatively long window). Thus to some extent FR is like "area under the graph" of CSD.

I suspect I'm wrong as I notice sometimes areas on the waterfall sit higher and longer than the rest, yet hardly show up as a peak in FR, even when smoothing looks similar.

Can anyone explain this to me?

 

[RobL]

The first line in the CSD (0ms if scaled back that far) would mirror the FR. The peaks not corresponding to the FR that appear later would be resonances that were excited, perhaps by the other decaying frequencies?

 

[audio2920]

Cool, thanks @RobL, I think I get it now. I'd forgotten that CSD slices are a sliding window with overlap to the slices surrounding them, not sequential slices in time.

Given FR and impulse are interchangeable, presumably a resonance that shows up late in the CSD does contribute to FR, it's just at a low level? (assuming it's within the window used for FR, which it would be for loudspeaker; maybe more questionable for a large room measurement)

 

[audio2design]

Both. You will know how the transducer behaves by measuring it. The result will tell you all you need to know.

If you want to argue further against this, the most basic aspect of wave theory, don’t be offended if I stop replying.

Don't confuse this by using terms like wave theory. This is simply the superposition principle of linear systems.

 

[SIY]

What's needed before any sort of explanation can be understood is a basic grounding in vibrations and waves, including Fourier decomposition superposition, and basic wave equations. Otherwise, the misunderstanding will continue to spiral out of control. This is the book I used as a freshman undergrad, but there are certainly others.

 

[audio2920]

@SIY I just don't have time to read that book I'm afraid.

I do have a science degree in audio engineering, but it was decades ago and I haven't had much cause to think about Fourier transforms in much detail since. Bottom line, I only remember the basics. If my question is too stupid to be asked here, as the more senior member I shall respect your opinion that I am not educated enough to ask questions on ASR.

Anyway, I'm asking: If a resonance shows up late (and maybe long) in the CSD, presumably that content is integrated in the FR plot, so long as it's within the IR window the FT is performed on? Which, it would be in any "normal" sort of loudspeaker measurement.

If that can't be answered, I'll go quietly Thanks.

 

[tvrgeek]

I remember a guy here, that post this graph pointing the woofer have problems.
These problems are translate into stuff like ' dullness ', ' never rest ', ' clarity ' to him
This is the woofer from the 2011 R series and he said:
''WTF It never came to a complete hault even when first reflection arrived at 10.3ms - i never saw anything like this except in few car subs that also use two part cone (oval and cone part glued). This must be the dirtiest impulse response in a hifi woofer i measured so far.''

So, this graph what does mean? It's the R300.
''

It means that the driver is following the laws of physics and any mass on a "spring" will delay start, overshoot and slowly decay. Darn physics again. Mass and all that stuff. To understand the energy to get something moving, you need to do the calculus. Speed, acceleration, jerk. Dt.

But to put up a graph like that and complain it is a problem is not understanding speakers, just as the OP does not understand "speed" and what it means.

So if the question is how to force the driver to follow the signal, then that quickly pushes you into active servo which has not been very suscessful yet. So-so on a few subs. Fortunately, this kind of distortion is not terribly unpleasant as musical instruments behave the same. A well designed driver actually does follow the signal pretty well.

Yup, we knew what we needed in a speaker in the 50's. Anyone can go read the AES papers. We just can't build it yet. No mass, perfectly rigid, totally non-resonant, no reflections or refractions...

 

[BrokenEnglishGuy]

It means that the driver is following the laws of physics and any mass on a "spring" will delay start, overshoot and slowly decay. Darn physics again. Mass and all that stuff. To understand the energy to get something moving, you need to do the calculus. Speed, acceleration, jerk. Dt.

But to put up a graph like that and complain it is a problem is not understanding speakers, just as the OP does not understand "speed" and what it means.

So if the question is how to force the driver to follow the signal, then that quickly pushes you into active servo which has not been very suscessful yet. So-so on a few subs. Fortunately, this kind of distortion is not terribly unpleasant as musical instruments behave the same. A well designed driver actually does follow the signal pretty well.

Yup, we knew what we needed in a speaker in the 50's. Anyone can go read the AES papers. We just can't build it yet. No mass, perfectly rigid, totally non-resonant, no reflections or refractions...

I showed this graph because a member here measure the speaker plus another woofer ( i also posted that spectral decay ), but the second one got better results, i wanted a to know what about that.



Im here to discuss things like:
- Is this well damped ? is any problem in the woofer?
- How it compares to anothers woofers measured here, i showed some examples.

Because the lacks of resonances in the FR, the comulative spectral decay only have small rosonances that doesn't affect the sound quality?, but at what point is bad? having 60dB at 12ms it's fine ?

Or this graph just show the woofer is not well damped? if is not well damped the woofers from FR from R3, then why the FR looks fine?

 

[dshreter]

@SIY I just don't have time to read that book I'm afraid.

I do have a science degree in audio engineering, but it was decades ago and I haven't had much cause to think about Fourier transforms in much detail since. Bottom line, I only remember the basics. If my question is too stupid to be asked here, as the more senior member I shall respect your opinion that I am not educated enough to ask questions on ASR.

Anyway, I'm asking: If a resonance shows up late (and maybe long) in the CSD, presumably that content is integrated in the FR plot, so long as it's within the IR window the FT is performed on? Which, it would be in any "normal" sort of loudspeaker measurement.

If that can't be answered, I'll go quietly Thanks.

Yes it shows up in the FR plot, and you should be able to see a relationship between the two including identifying resonances.

I think in a CSD you can see a combination of harmonic and IMD distortion effects, so a resonance doesn’t necessarily tie back to its own fundamental - it can be noise.

Im not sure what’s wrong with asking a question like this either.

 

[audio2920]

in a CSD you can see a combination of harmonic and IMD distortion effects, so a resonance doesn’t necessarily tie back to its own fundamental - it can be noise

Ah, that makes sense!

I'm not sure if knew that and forgot, or just never had it figured out. Either way, thank you @dshreter ! Appreciated.

 

[SIY]

@SIY I just don't have time to read that book I'm afraid.

The comment wasn't aimed at you, my apologies if you took it that way. So my comments here are a bit more general:

There's a lot of different books on vibrations and waves, that just happened to be the one I used. But without that basic grounding, you're just not going to get any sort of sensible understanding. I absolutely don't mean to be harsh, but it's the reality of the situation- technical learning takes effort and at least a small commitment of time and energy. You can get an answer, but not an understanding, and that will cause even more issues if you try to run with that.

It's not "stupidity" by any means, it's having a basic background to formulate sensible questions and understand the answers. It's like when I was trying to deal with the work my buddies were doing in quantum field theory or gravitation: I just couldn't get it because of my lack of understanding basic things like differential geometry and advanced linear algebra (I will still brain-lock when asked to explain the difference between covariance and contravariance). And I ended up choosing not to spend the time learning that, accepting that these were questions that would be beyond me. Now, one could argue that in my case, it WAS stupidity, but I prefer to believe the alternative. That's my way of trying to encourage you (and everyone here) to make time to review vibrations if you have an interest in acoustics and sound- the understanding you'll get will more than reward the effort. If a dumb chemist like me can work the math, anyone can.

Let me toss out a basic question which you can use to gauge your readiness to deal with understanding waves: imagine a single cycle of a 30 Hz sinewave, that is, it's zero for t<0, and then zero again for t>1/30, and a 30 Hz sin in between (i.e., sin(2pi30t)). What frequencies are present in this waveform?

 

[2M2B]

Yes im a bit confused about the term '' speed '' some audiophiles always talk about things like his speaker is very musical because it's '' fast '' good musical timming and bla bla, but what about the time that the driver takes to stop? That thing is also linked to the frequency/wavelength?
For example, if the driver needs to play a simple slow percusion, when the driver needs to play a simple beat, every time the beat decay if the driver take too long to stop it gonna represent as distortion? because the driver cannot do the wavelength properly so that translate into distortion?

Speed = Micro deforming from it lingering on a bass note because It diaphragm can't cope with doing heavy bass while doing mids/treble if we include full range speakers & Headphones. For 2 way or full range with a woofer none of this matters but in single driver set ups dynamic drivers are not that good. The HD600 distorts when forced to reproduce heavy bass in a fast complex song yet the ER4SR(BA), Sundara(Planar) don't have that problem.

BA drivers = It diaphragm is immune to this when EQ'd or the recording is bass heavy, Cause It really stiff metal foil that loosens up at 10db boost. It why the ER4XR can only muster 4db with back vent despite the fact It can reproduce 12db no problem.

Planar driver = It moves the whole diaphragm as one mass cause of excursion limitations.

Dynamic drivers = It a short cone that uses paper or PET film that lacks any stiffness when forced to output bass they either distort or smear the whole sound.

 

[BrokenEnglishGuy]

I showed this graph because a member here measure the speaker plus another woofer ( i also posted that spectral decay ), but the second one got better results, i wanted a to know what about that.



Im here to discuss things like:
- Is this well damped ? is any problem in the woofer?
- How it compares to anothers woofers measured here, i showed some examples.

Because the lacks of resonances in the FR, the comulative spectral decay only have small rosonances that doesn't affect the sound quality?, but at what point is bad? having 60dB at 12ms it's fine ?

Or this graph just show the woofer is not well damped? if is not well damped the woofers from FR from R3, then why the FR looks fine?

This is the important post