AJinFLA said:
What we typically see presented as FR is a very gross measurement of a more-or-less steady state event. We are measuring what the event looks like on the surface. How is an event that is happening 30-50 dB down going to show up on that gross characterization of the event.
It is like saying that a 10k resistor has a significant effect on what the volt-meter reads when it is paralleled with a 1 ohm resistor.
dave
As has already been pointed out, that's what distortion measurements can easily do. It also doesn't matter how low in level the change exists, down 1, 10 or 100db, it is unequivocally a change in the frequency response or in other words, as described by john k in his post, a change in the acoustic wave described in scenario 1, CV or cone vibration, given that it is unlikely to be a change in the transfer function. Of course change does not necessarily mean elimination or even control.
I still am puzzled by all of the discussion of changes occuring 30-50db down or with no change in frequency response, yet all empirical evidence (as opposed to anecdotal) presented to support changes uses standard frequency response measurements, SPL and/or CSD, taken from an MLS measurement system.
The other aspect as yet unanswered is that claims are made of dramatic changes in perceived response, yet the claim includes statements of no FR change or that it is 30-50db down. I dare say that any significant, scientific peer-reviewed studies of a listeners ability to sense changes at these low levels do not fall into the realm of dramatic. Dramatic also isn't much of a quantitative term, but it's used to try to provide quantitative (as in big) changes.
It is not a gross measurement, if done correctly it is a direct, accurate measurement within the limits of the measurement system that will show variations before/after. Non-linear issues such as motor influences are found with distortion measurements. If the changes are 30-50db down as you claim, they will still show up as distortion. If it's not distortion, but a change in FR that only changes -30db or -50db, it's still a change in frequency response, still measurable and within the limitations of current measurement systems.
It's also possible to extract the step response from the impulse response. This is most definitely not a steady-state measurement. There's nothing exceptional in any of this.
There is still a lot of inconsistency and/or contradiction that has yet to be addressed.
Dave
MaVo said:
This may it come as a surprise to You but thats how speakers do operate most of the time !
planet10 said:
That would be my point. If they are 30 or 50 dB down then this has very little to do with damping standing waves. A change of -40dB would be a 1% reduction in the amplitude of the standing wave. We have absolutely no problems measuring -40dB either. We can routinely run THD sweeps on drives and see distortion figures well below 1%. You can do very careful measurement before and after on a given driver and look at the difference signal. Frankly I would say that in general it would be more difficult to hear a change of that order than measure it.
If the differences in the basic FR are in the -30 to -50 dB range then I would presume you can readily identify which of to identical drivers you are listening to since even a well matched pair of drivers will typical exhibit differences in response on the order of +/- 1dB? Or the differences in playback level of the order of 0.08dB? (1 = 0 dB, 1.01 = 0.08 dB).
Meaning no disrespect to anyone here, I just don't believe in the “I can hear it but it can't be measured school any more”. I once did. But over the years I found that whether it be cables, speaker wires, or what very, if I heard a difference I could concoct a very reasonable experiment which showed the difference in some form. Sometimes the difference is more evident in a CSD than an FR or maybe in an impulse. But when I looked at, for example speaker cables, I didn't just measure the impedance or what ever. I would place the cables in my system and the look at the content of the signal applied at the speaker. I never, not once, found a case where I heard a difference where there wasn't a corresponding difference in measurement of the electrical signal applied to the speaker. Quite to the contrary, they were times where small differences in the measurements were noted but no discernable audible difference was observed.
There is also the idea of nonlinearity. This is a real possibility. An acrylic coating will have some visco-elastic properties will exhibit nonlinear behavior. But again, that doesn't mean that exotic measurements are required. We can get hung up on the fact that the transformation of an impulse to FR or CSD is only valid for a linear system. That is true, but not really important. What is important is that and FFt of an impulse for the system is unique and repeatable. If the system is nonlinear but stable, the FFt of an impulse of given amplitude, while not a 100% accurate representation of the FR, remains unique.
Let me stop being long winded. If you take a measurement of a system what is important is that the measurement is unique and repeatable. If I take a measurement it doesn't matter if it’s an accurate representation of the FR or anything else if what we are looking for are differences. All that matters is that if repeated, is the result the same. If we can establish that, then when we change something in the system the difference between the measurement of the original system and the modified system will reveal the effect of the change
My thoughts/prejudices regarding FR stem not from loudspeakers, but from amplifiers and phono cartridges. I don't know of many people who use FR as a gauge of anything unless there are gross anomalies involved. Absent those, they(FR's) are pretty useless in judging some obvious differences in sound between these devices...you can also throw in THD as being useless when comparing SS to SS amps.
Mongo don't know better
I'm going to start with an assumption that much of this testing we are talking about is done with pink noise or some other variety of "homogeneous" signal.
Please consider test signals in comparison to the material we actually listen to. I submit there are significant differences in dynamic range and portions of the frequency band which are or are not being used at any one time. In music, there are signals at many levels that sum to provide the listening experience.
How is the variety of levels represented in the test signal? How is a driver's ability to ferret out "low level detail" represented in any test result?
I'm going to start with an assumption that much of this testing we are talking about is done with pink noise or some other variety of "homogeneous" signal.
Please consider test signals in comparison to the material we actually listen to. I submit there are significant differences in dynamic range and portions of the frequency band which are or are not being used at any one time. In music, there are signals at many levels that sum to provide the listening experience.
How is the variety of levels represented in the test signal? How is a driver's ability to ferret out "low level detail" represented in any test result?
dlr said:
Are you sure. To accurately characterize what is happening i hypothesize that you would need to piggy-back a stimulus on your main stimulus that is 30-50 dB down and then concern yourself only with what is happening to the piggybacked part of the stimulus. By gross i mean that in all the tests i have seen we are only examining what is happening to the primary stimulus in the absence on any piggy backed stimulus.
Prepare to have your perceptions shaken. this is why i say this technology is paradigm changing, and that anyone who hasn't experienced it does not have the frame of reference to understand it.
In any discussion where someone is trying to explain the unexplainable there are bound to be holes you can drive a truck thru. It is like trying to explain colour to someone who is blind.
We thank you for pointing these out so that we can stretch our brains to try to do a better job.
dave
john k... said:
Please see my response to Mr Ralphs.
If the standing waves at -40 dB are masking information that is present in the signal then the removal of the masking can have significant effects on the sonic presentation. The ability of our ear-brain to detect stuff this low level is the difference between survivial & being eaten by a wild beast. Some 2-4 thousand years of civilaization has not changed that.
Again, i say, until such time as you have exposed yourself to the technology you do not have a frame of reference on which to analytically evaluate what is happening.
To echo pedroskova's comments about amplifiers... if the only tool you have is a hammer, then everything gets treated like a nail.
A paradigm shift is required, and the start to that is experiencing the technology. To that end Chris today suggested a road trip for a treated & an untreated pair of mFonkens. As soon as customers leave me with enuff drivers to do this we will get it happening. Until then you'll have to come up to the mountain, or be at one of the events where we bring the demo Fonkens (next one Jan 26 in Vancouver)
dave
PS: I'm sure we would see similar discussions to this one when Einstein was trying to get the point across about relativity... at least we all have the opportunity for direct experience (if only we are willing)
MJL21193 said:
In his day, Einstein was often called -- in today's parlance -- a snake oil salesman.
They used to say the same things about guys suggesting that black holes exist (we still only have indirect proof of that one)
dave
Post #1344 & #1386
Beyond the Ariel posts #2202 & #2203
Your middle name is obviously contradiction.
Strange how a PhD chemist would have that to say to a PhD in acoustics eh?
cheers,
AJ
pedroskova said:
pedroskova said:
Beyond the Ariel posts #2202 & #2203
gedlee said:
pedroskova said:
Your middle name is obviously contradiction.
Strange how a PhD chemist would have that to say to a PhD in acoustics eh?
cheers,
AJ
Fonken Eh's....
only available in Canada you say? Pity! The model Eh, Fonken Eh I like the sound of that, has a good Canadian ring to it. Fonken Eh, Fonken good.
only available in Canada you say? Pity! The model Eh, Fonken Eh I like the sound of that, has a good Canadian ring to it. Fonken Eh, Fonken good.
Re: Fonken Eh's....
Coined as a contraction of Fostex + Onken, as in "Hey Dave, what about the FE127E in the mini-Onken?" (originally intended for the CSS FR125)
'frankly my dear, I'd rather be....'
Moray, you should know that we Islanders sometimes consider ourselves as distant cousins to mainland canucks, eh?
moray james said:
Coined as a contraction of Fostex + Onken, as in "Hey Dave, what about the FE127E in the mini-Onken?" (originally intended for the CSS FR125)
'frankly my dear, I'd rather be....'
Moray, you should know that we Islanders sometimes consider ourselves as distant cousins to mainland canucks, eh?
Me not v clever ...
But it is obvious to me my enabl'd combo speaker is significantly outperforming itself with it's new paint-job. I can sit and listen to long tracks of music now - and enjoy them. And I couldn't do that before!
It "sounds" like it is following the musical waveform better. (I'm pretty sure sine waves would be just as enjoyable before/after, but David Bowie's "Heroes" is both different and better).
Presumably we could get a small piece of complex waveform, play it and record the result. Then mathematically measure some parameter which quantifies the difference between the two.
Some sort of r.m.s. of the differences between waveforms.
Do any of the tests that have been done approximate this very simple idea?
But it is obvious to me my enabl'd combo speaker is significantly outperforming itself with it's new paint-job. I can sit and listen to long tracks of music now - and enjoy them. And I couldn't do that before!
It "sounds" like it is following the musical waveform better. (I'm pretty sure sine waves would be just as enjoyable before/after, but David Bowie's "Heroes" is both different and better).
Presumably we could get a small piece of complex waveform, play it and record the result. Then mathematically measure some parameter which quantifies the difference between the two.
Some sort of r.m.s. of the differences between waveforms.
Do any of the tests that have been done approximate this very simple idea?
planet10 said:
Yes, that is fine, but ask yourself what would happen if, at the frequency of the standing wave, the driver was stimulated by a 0dB input signal. As I said, a standing wave is a resonance. As such its decay characteristics can be categorized by its Q. So let’s say that the resonance peak is 5dB above the input level. So if the wave has amplitude of -40dB below the nominal signal level the content of the nominal signal at the standing wave frequency would be -45dB. Now take the nominal signal and raise the amplitude of the content at the standing wave frequency to 0dB. The result would be an obvious 5dB peak in the response at the standing wave frequency. If that peak wasn't there when the input level is at 0db then it would be there at -45 either. What you are sort of suggesting is that the standing wave is only a small signal phenomenon. And that the Enable (or what ever treatment used to damp the standing wave) only alters the small single response. For the standing wave to be only a small signal phenomena the driver would have to be highly nonlinear. If that were the case the problems with sound reproduction would be a lot more severe that. Anyway, we are still talking about damping of a standing wave. So what needs to be investigated is the behavior at that frequency. Nothing is preventing us from looking at the behavior at different amplitude levels.
But also remember that damping of standing wave in the underlying premise put fourth by Bud. Maybe that is a red herring. Maybe standing waves have nothing to do with it? Hey, I'm just string the pot here. Food for thought. I don't have any real interest in the process unless it is shown to have some effect in the pistonic range of driver operation.
Re: Fonken Eh's....
There is also a Fonken tour happening,, so far Lethbridge, Medicine Hat, then Calgary...
dave
moray james said:
There is also a Fonken tour happening,, so far Lethbridge, Medicine Hat, then Calgary...
dave
And i submit that is you heard the technology that would change to a very real interest in seeing/explaining what is happening. We need people like you with your experience & perspective pounding on this problem. But until you hear it, you have no idea what the problem is.
dave
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