Re: testing design???
If they follow through, then it will be a step forward. I agree that the test conditions, hardware, software, mic hardware, mic positioning, environment and any other pertinent data should be described. Software settings, such as (if MLS) window time markers, window type used, smoothing or not, etc., are needed. The most difficult and therefore the most extensively described tests will be those for distortion, because there are so many tests that can be made, both in type and number of each. I suggest reviewing Mark K's site carefully, possibly using a similar test regimen. Documenting the tests is critical. Ensuring repeatability is also a must, since there will be before/after comparisons.
At this point, we should just wait and see what is forthcoming. Until then, that should not be criticized. I'll give the benefit of the doubt for the time being.
The caveat is that all of the above has to do with measured changes. Changes in perception will not necessarily be quanitifiable reliably. None of what would be included in the above will in any way cast any light on the debate about the mechanism, either.
Dave
auplater said:
Anyone care to share the testing protocol / design / method that will be used for all these tests? No? I thought not... there probably isn't much of one in existence....
Not much discussion here about what would be useful experiments to run. Just alot of diffuse talk of "we'll test on axis, off axis, characterization (whatever that means). What tests will be run? How will the results be evaluated? Will any kind of explanation of errors in the tests, their limitations, how to present the data, number of trials, what variables will be examined? Or are we just gonna get more extraneous data of dubious merit to hash through again as if it represents the holy grail? Do any of the testers have any sort of understanding of treatment combinations, confidence intervals, alpha error, that sort of thing?
Otherwise, why bother doing the tests? The results will be no better than subjective anecdotal evidence as far as determining what (if anything) is going on unless there is some serious planning involved on how to do them and how to interpret the results.
John L.
If they follow through, then it will be a step forward. I agree that the test conditions, hardware, software, mic hardware, mic positioning, environment and any other pertinent data should be described. Software settings, such as (if MLS) window time markers, window type used, smoothing or not, etc., are needed. The most difficult and therefore the most extensively described tests will be those for distortion, because there are so many tests that can be made, both in type and number of each. I suggest reviewing Mark K's site carefully, possibly using a similar test regimen. Documenting the tests is critical. Ensuring repeatability is also a must, since there will be before/after comparisons.
At this point, we should just wait and see what is forthcoming. Until then, that should not be criticized. I'll give the benefit of the doubt for the time being.
The caveat is that all of the above has to do with measured changes. Changes in perception will not necessarily be quanitifiable reliably. None of what would be included in the above will in any way cast any light on the debate about the mechanism, either.
Dave
Re: Re: testing design???
typical cheap shot.. I thought this was gonna be the technical side... count me out
Seriously Dude, there's no negative attitude here... I'd just like to see an honest set of data presented that meets certain standards set beyond the usual pablum presented in the lay press...
Attempts to portray me as a "nattering nabob of negativism" are just an attempt to shoot the messenger. If you don't understand that the data that will be generated is of limited value to those beyond the subjective DIY aspect of audio, then what can I say??
I've already pointed several references to, for instance, ANOVA designs for screening. You should google it. Might have a transcendent moment wrt what's being attempted.
John L.
Daygloworange said:
typical cheap shot.. I thought this was gonna be the technical side... count me out
Seriously Dude, there's no negative attitude here... I'd just like to see an honest set of data presented that meets certain standards set beyond the usual pablum presented in the lay press...
Attempts to portray me as a "nattering nabob of negativism" are just an attempt to shoot the messenger. If you don't understand that the data that will be generated is of limited value to those beyond the subjective DIY aspect of audio, then what can I say??
I've already pointed several references to, for instance, ANOVA designs for screening. You should google it. Might have a transcendent moment wrt what's being attempted.
John L.
Re: Re: Waterfals and such
IMO these plots are only tools that engineers can use to help find what needs fixing. The same way we get fixed by a doctor.
The CSD plots that John posted do not show enough difference to determine which is clearly better. It it true that different CSDs don't tell how a driver will sound, neither can SPLs if they are similarly closely matche.dlr said:
IMO these plots are only tools that engineers can use to help find what needs fixing. The same way we get fixed by a doctor.
Re: Re: Re: Waterfals and such
The graphs to which I refer are the two used for demonstration, one being that of an "acousically perfect" driver, with any FR anomilies buried down 40db or more. These two were in no way "closely matched". Absent any other data, the second one is clearly the better. But you make my point, the whole problem with using a single CSD as definitive for being able to determine the sound of the driver is just plain not possible.
The link is
Driver comparison demonstration
DAve
soongsc said:
The graphs to which I refer are the two used for demonstration, one being that of an "acousically perfect" driver, with any FR anomilies buried down 40db or more. These two were in no way "closely matched". Absent any other data, the second one is clearly the better. But you make my point, the whole problem with using a single CSD as definitive for being able to determine the sound of the driver is just plain not possible.
The link is
Driver comparison demonstration
DAve
Re: Re: Re: testing design???
No John, just a little sarcasm, that's all. I could levy the same accusation towards your speculatory criticism of the upcoming tests.
I'm one of those guys who wants to see better data as well. Don't paint me as placebo plagued subjectivist.
I did try and involve discussion about suggestions regarding testing, and all I got was " cricket,... cricket....".
BTW, I read this post of yours the other day, but didn't have the time to respond. I have been thinking the exact same things you have, in regards to boundary layers. I have to agree with you.
I also don't see there being any laminar flow (worth discussing) over a speaker cone, so why would we even discuss boundary layer?
In a nutshell, (although it's not my field) I don't think that EnABL does anything in the "air" at all.
If it did, man, I could think of about 100 different areas I'd be investigating applying the EnABL treatment to, other than speaker cones....
Cheers
auplater said:
No John, just a little sarcasm, that's all. I could levy the same accusation towards your speculatory criticism of the upcoming tests.
I'm one of those guys who wants to see better data as well. Don't paint me as placebo plagued subjectivist.
I did try and involve discussion about suggestions regarding testing, and all I got was " cricket,... cricket....".
BTW, I read this post of yours the other day, but didn't have the time to respond. I have been thinking the exact same things you have, in regards to boundary layers. I have to agree with you.
I also don't see there being any laminar flow (worth discussing) over a speaker cone, so why would we even discuss boundary layer?
In a nutshell, (although it's not my field) I don't think that EnABL does anything in the "air" at all.
If it did, man, I could think of about 100 different areas I'd be investigating applying the EnABL treatment to, other than speaker cones....
Cheers
Re: Re: Re: Re: testing design???
Well, not really. I said from day one of my involvement that a full set of on- and off-axis and distortion tests are required to begin to characterize a driver. I thought it unnecessary to repeat myself. The critters making noise came right after I said that, berating me for saying so. Looking back, that was January 4th. It's now March 21st. 2-1/2 months and 1800+ additional posts to make a start in that direction.
My first day posting
Dave
Daygloworange said:
Well, not really. I said from day one of my involvement that a full set of on- and off-axis and distortion tests are required to begin to characterize a driver. I thought it unnecessary to repeat myself. The critters making noise came right after I said that, berating me for saying so. Looking back, that was January 4th. It's now March 21st. 2-1/2 months and 1800+ additional posts to make a start in that direction.
My first day posting
Dave
Yeah Dave, you have been vocal many times about what measurements you feel would be needed for proper evaluation.
I know you and others get a lot of flack for your posts, I've got no problem with hard questions, and challenges being asked. I'm the same way.
I enjoy all the contributions made by JohnK, John L, yourself, et al..
I watch for those kinds of posts, as I'm a naturally inquisitive mind. I enjoy speculation as much as anyone else, but quickly want to see concrete proof as well.
I enjoy speculating, then seeing how close my guesses are to the truth.
It's been mentioned before, let's face it, there aren't any lives at stake here, it's just a hobby.
Cheers
I know you and others get a lot of flack for your posts, I've got no problem with hard questions, and challenges being asked. I'm the same way.
I enjoy all the contributions made by JohnK, John L, yourself, et al..
I watch for those kinds of posts, as I'm a naturally inquisitive mind. I enjoy speculation as much as anyone else, but quickly want to see concrete proof as well.
I enjoy speculating, then seeing how close my guesses are to the truth.
It's been mentioned before, let's face it, there aren't any lives at stake here, it's just a hobby.
Cheers
Not a nattering nabob of negativitism? C'mon John. If you can't see how this is at least cynical, then I don't see the value of your posts. This is a truly unfair comment. Ask the question and await an answer. Otherwise you're simply stating your negative opinion. You and others have asked for objectivity. Let's give it in return, hey? Ask for clarification but don't assume (subjectively) the answer...
Carl
methods
ya know, I've been asking about methods for awhile now...
Only Dave (dlr) has indicated any deference to the difficulties involved.
Why do you suppose that is?
It might be nice if one of the testers asked something like "how many trials do you think would it take to establish statistical significance"
http://en.wikipedia.org/wiki/Statistical_significance
Several have even indicated that testing is already underway... yet, no one has stated what the details of the tests are, what is expected to be determined, anything. Just repeated statements of "if you have more stringent criteria, be my guest to organize a detailed experiment on your own and present the data." I'm not the one making the claims of doing an experiment, hence I have to wonder what the agenda is, if no one is offering any sort of experimental protocol. Just blind faith that "trust us, we'll do it right"... so, good luck with that.
John L.
Carlp said:
ya know, I've been asking about methods for awhile now...
Only Dave (dlr) has indicated any deference to the difficulties involved.
Why do you suppose that is?
It might be nice if one of the testers asked something like "how many trials do you think would it take to establish statistical significance"
http://en.wikipedia.org/wiki/Statistical_significance
Several have even indicated that testing is already underway... yet, no one has stated what the details of the tests are, what is expected to be determined, anything. Just repeated statements of "if you have more stringent criteria, be my guest to organize a detailed experiment on your own and present the data." I'm not the one making the claims of doing an experiment, hence I have to wonder what the agenda is, if no one is offering any sort of experimental protocol. Just blind faith that "trust us, we'll do it right"... so, good luck with that.
John L.
Jeez...
Is there anything in the literature that reports upon the effect of the change of material with distance from the voice coil?... This with regards to the radiated signal?
...Another way...What is the effect upon a radiated signal when it transitions from a cone (of any material) to a surround (pleated, rolled, rubber, fabric or otherwise)?
Bud's EnABL can be considered more fully after that is understood.
Is there anything in the literature that reports upon the effect of the change of material with distance from the voice coil?... This with regards to the radiated signal?
...Another way...What is the effect upon a radiated signal when it transitions from a cone (of any material) to a surround (pleated, rolled, rubber, fabric or otherwise)?
Bud's EnABL can be considered more fully after that is understood.
Re: Jeez...
The first question can be found, I'm sure, but in essence each material has a different energy transfer function when in contact with air. That would probably be found in some table or materials reference book. However, if the change is small in relation to the entire surface, whatever impact it will have on the integrated (vector sum) signal output from the driver will be small as well. The total response either measured by a mic or heard by an ear at some distance x from the driver is the integrated output of the driver. A small change in the output at any area on the surface will result in a correspondingly small change in the response at point x.
The second question is easy in concept, though the verbal description is not. A surround serves two functions.
One, it supports the cone for the range of movement desired of the cone. Two, it is also designed to terminate the cone mechanically such that the transverse wave is fully damped.
One is simple, Two is not. In fact, number two is never fully effective. This is easily seen in many drivers and is manifested in a frequency response glitch anywhere from around 800-1500Hz based primarily on the distance from former attachment point to the surround, although this is affected to some degree by the speed of sound in the cone material used.
Number Two is very often also manifested in an impedance glitch in the same frequency region, though not always because the reflected wave does not always modulate the voice coil enough for there to be a significant change in electrical impedance of the driver motor.
John k's description in the old thread of what happens describes it through the graph he created. These old posts that directly address issues are being forgotten.
As the initial transverse wave moves outward from the former attachment point (it's really not the coil moving the cone, it's the former, the latter being moved by the coil), part of the energy is transferred into the compression (acoustic) wave and the rest continues through the cone (let's ignore the cone material internal damping for simplicity). When the transverse wave reaches the surround, it damps (absorbs) a large part of it. At some frequencies, it probably damps it almost completely. That part not damped is reflected back into the cone and there is a transverse wave then moving from surround to former. Nothing here that has not been known for decades.
This reverse wave (as I'll call it) does the same thing as the initial, forward wave. Part of the energy is imparted into the air adding to the acoustic response and the rest continues in the cone. If it is not all transferred into the acoustic wave or damped internally in the cone, it arrives back at the former. The former has little damping properties at all, so two things occur.
One, it modulates the former. This means that it tries to move the former. Since the former is moving as a consequence of the original electrical signal applied to the coil, this reflected wave modulation is acting on the former in some time-delayed fashion. The result depends on the phase of the reflected signal as it relates to the original signal in the former. If it is in-phase at some frequency, it will reinforce that frequency and a peak will result in the acoustic output (frequency response). It if is out-of-phase at some frequency, it will be destructive interference and a dip will result in the acoustic output. At frequencies not precisely at those points, there will be varying amounts of either constructive or destructive interference. Over much of that range, the effects will be barely noticeable, if at all. This is why the FR anomolies seen in the 800-1500Hz range or so have a peak, then a dip, then a taper back to nominal.
This reflected transverse wave then moves back in the direction of the initial wave. Until all of the energy in the initial wave is either transferred into the acoustic wave or is damped entirely, it keeps going back and forth from former to surround to former. This is how significant resonances occur at the primary impedance mismatch.
There is usually not an FR anomolie associated with the surround mismatch at the higher frequencies. This is, I believe, due to the higher effectiveness of the surround in terminating the cone at these frequencies. Simply put, it damps these frequencies very effectively. Many driver materials also damp these frequencies more effectively as well, so there is much less energy that reaches the surround as frequency increases.
The problem that occurs above the primary frequency mismatch is that the cone itself, always at some level of bending (all are bending wave drivers to some degree as john k pointed out to me), will radiate some energy out-of-phase with earlier energy transferred into the acoustic wave output. The cone profile (geometry) is a compromise of material and shape, designed to achieve some optimal target output bandwidth. The material changes the speed of sound in the cone (transverse wave), so the geometry is designed to keep the vector sum of all output points of the cone as much in-phase as possible for the bandwidth target. Softer materials flex (bend, thus damp) more at higher frequencies. Soft materials start to radiate as a ring rather than a cone as frequency increases. This helps keep the radiated energy closer to being in-phase.
When the radiated sound is not close enough in phase, FR anomolies arise. Hard cones have little flex and little damping, so when the frequency is at some well-defined point, the out-of-phase radiation is worse than for soft materials. The cone may actually be in breakup at first. That is, there are no internal cone resonances created at that point. The out-of-phase issue arises solely from the differing vector outputs at the various points on the cone. Change the geometry and some frequencies could be brought nearly perfectly into phase. However, others would then be more out-of-phase, so there's a huge tradeoff to be made related between geometry and this phase issue.
Going back to the surround question, it cannot act on these higher frequencies by itself, since it can only either damp or reflect energy that arrives at the surround. Plus, when the driver is truly in breakup, that is, it is flexing with insufficient damping in way that creates large constructive or destructive energy resonances internally in the cone, the surround has almost no effect at all for those frequencies for which the cone does not move at the surround interface. Since the surround does not move, these could be considered as significant or maybe fundamental bending wave frequencies, I suppose. This is a function of the cone alone. They are a bending modes of the driver that is almost exclusively an isolated characteristic of the cone material and shape. The surround, any surround, will have almost no effect on these.
Simple to visualize, difficult to put into words.
Dave
Ed LaFontaine said:
The first question can be found, I'm sure, but in essence each material has a different energy transfer function when in contact with air. That would probably be found in some table or materials reference book. However, if the change is small in relation to the entire surface, whatever impact it will have on the integrated (vector sum) signal output from the driver will be small as well. The total response either measured by a mic or heard by an ear at some distance x from the driver is the integrated output of the driver. A small change in the output at any area on the surface will result in a correspondingly small change in the response at point x.
The second question is easy in concept, though the verbal description is not. A surround serves two functions.
One, it supports the cone for the range of movement desired of the cone. Two, it is also designed to terminate the cone mechanically such that the transverse wave is fully damped.
One is simple, Two is not. In fact, number two is never fully effective. This is easily seen in many drivers and is manifested in a frequency response glitch anywhere from around 800-1500Hz based primarily on the distance from former attachment point to the surround, although this is affected to some degree by the speed of sound in the cone material used.
Number Two is very often also manifested in an impedance glitch in the same frequency region, though not always because the reflected wave does not always modulate the voice coil enough for there to be a significant change in electrical impedance of the driver motor.
John k's description in the old thread of what happens describes it through the graph he created. These old posts that directly address issues are being forgotten.
As the initial transverse wave moves outward from the former attachment point (it's really not the coil moving the cone, it's the former, the latter being moved by the coil), part of the energy is transferred into the compression (acoustic) wave and the rest continues through the cone (let's ignore the cone material internal damping for simplicity). When the transverse wave reaches the surround, it damps (absorbs) a large part of it. At some frequencies, it probably damps it almost completely. That part not damped is reflected back into the cone and there is a transverse wave then moving from surround to former. Nothing here that has not been known for decades.
This reverse wave (as I'll call it) does the same thing as the initial, forward wave. Part of the energy is imparted into the air adding to the acoustic response and the rest continues in the cone. If it is not all transferred into the acoustic wave or damped internally in the cone, it arrives back at the former. The former has little damping properties at all, so two things occur.
One, it modulates the former. This means that it tries to move the former. Since the former is moving as a consequence of the original electrical signal applied to the coil, this reflected wave modulation is acting on the former in some time-delayed fashion. The result depends on the phase of the reflected signal as it relates to the original signal in the former. If it is in-phase at some frequency, it will reinforce that frequency and a peak will result in the acoustic output (frequency response). It if is out-of-phase at some frequency, it will be destructive interference and a dip will result in the acoustic output. At frequencies not precisely at those points, there will be varying amounts of either constructive or destructive interference. Over much of that range, the effects will be barely noticeable, if at all. This is why the FR anomolies seen in the 800-1500Hz range or so have a peak, then a dip, then a taper back to nominal.
This reflected transverse wave then moves back in the direction of the initial wave. Until all of the energy in the initial wave is either transferred into the acoustic wave or is damped entirely, it keeps going back and forth from former to surround to former. This is how significant resonances occur at the primary impedance mismatch.
There is usually not an FR anomolie associated with the surround mismatch at the higher frequencies. This is, I believe, due to the higher effectiveness of the surround in terminating the cone at these frequencies. Simply put, it damps these frequencies very effectively. Many driver materials also damp these frequencies more effectively as well, so there is much less energy that reaches the surround as frequency increases.
The problem that occurs above the primary frequency mismatch is that the cone itself, always at some level of bending (all are bending wave drivers to some degree as john k pointed out to me), will radiate some energy out-of-phase with earlier energy transferred into the acoustic wave output. The cone profile (geometry) is a compromise of material and shape, designed to achieve some optimal target output bandwidth. The material changes the speed of sound in the cone (transverse wave), so the geometry is designed to keep the vector sum of all output points of the cone as much in-phase as possible for the bandwidth target. Softer materials flex (bend, thus damp) more at higher frequencies. Soft materials start to radiate as a ring rather than a cone as frequency increases. This helps keep the radiated energy closer to being in-phase.
When the radiated sound is not close enough in phase, FR anomolies arise. Hard cones have little flex and little damping, so when the frequency is at some well-defined point, the out-of-phase radiation is worse than for soft materials. The cone may actually be in breakup at first. That is, there are no internal cone resonances created at that point. The out-of-phase issue arises solely from the differing vector outputs at the various points on the cone. Change the geometry and some frequencies could be brought nearly perfectly into phase. However, others would then be more out-of-phase, so there's a huge tradeoff to be made related between geometry and this phase issue.
Going back to the surround question, it cannot act on these higher frequencies by itself, since it can only either damp or reflect energy that arrives at the surround. Plus, when the driver is truly in breakup, that is, it is flexing with insufficient damping in way that creates large constructive or destructive energy resonances internally in the cone, the surround has almost no effect at all for those frequencies for which the cone does not move at the surround interface. Since the surround does not move, these could be considered as significant or maybe fundamental bending wave frequencies, I suppose. This is a function of the cone alone. They are a bending modes of the driver that is almost exclusively an isolated characteristic of the cone material and shape. The surround, any surround, will have almost no effect on these.
Simple to visualize, difficult to put into words.
Dave
I don't have any intension of becoming deeply involved in this discussion. I've said pretty much all I have to offer. But I do want to make a few comments about the direction the thread is taking. First, Bud's opening remarks.
So Bud agrees that Newton’s Law's are all that is required: The time rate of change in momentum of a body or object is equal to the sum of all forces acting on it and the a direction of the vector of the resultant sum. Commonly express as F = ma. And, for every action there is an equally and opposite reaction. All that is left is to ask how these laws apply. Frankly, it is pretty straight forward.
The second point Bud makes is that this all gives him grief. "It doesn't make sense." Well to me the tone of this isn't particularly open minded. It seems to be more along the lines to get you all to think like he is; that Enable must be doing something very different. In any event, something not making sense doesn't mean it's the wrong explanation. It makes perfect sense. It just doesn't make sense to Bud.
If you recall, back in the old thread I posted something to the effect of looking at the cone vibration in a vacuum. Well, low and behold, it turns out that somebody has done just that, and more. (I’ll actually do research the topic rather than just talk about it). They took a driver and placed it in a large sealed enclosure and made laser scans of the cone surface velocity when the enclosure was at normal atmospheric pressure, and at several reduced pressures. The intent was to see how the air mass load on the driver affected the cone motion. The results were of interest because they indicated that as the pressure was reduced, changing the effective cone mass, the magnitude and pattern of cone vibration changed. With regard to frequency response which was also measured, a shift in the frequency and magnitude of breakup resonances was observed, very similar to that which has been observed in pre and post treated driver measurements reported in the old thread. The connection between the two is that in both cases the effective cone mass was altered by a small fraction; in one case by introducing additional mass at specific locations on the cone, in the other by uniformly reducing the air mass load over the cones surface. Very different means of changing effective mass, but very similar results.
Bud's third paragraph is purely a subjective comment, again, intending to lead you away for the simple explanation... And then, HOW....
The point is that there is no progress being made here, and I don’t think will be. I read about all the new tests. Well, they are not new tests; they are the same old tests being carried out on new sets of drivers. What do you expect to see? And while I agree with dlr that a full compliment of on and off axis measurements are needed, the off axis measurements should not have impact on what enable does or doesn't do unless the altered cone results in a significant change in the directivity of the driver. I say this because only the on axis (or direct) response is "pure" in the time domain. Anything off axis reaches the ear after it has been diffracted, reflected, absorbed, transmitted, dissipated, scattered.... and so on by the surroundings.
If this is to be understood that there are only 3 things that need to be considered: the cone vibrates differently and energy transfer to the air remains the same, the energy transfer is altered while the cone vibration is unchanged, both effects are at work.
One thing is for certain: the cone must vibrate differently. That is a requirement of adding material to the cone. The second thing is that there is not change in the way energy is transferred to the air. The laws of physics remains the laws of physics and no matter how you look at it, sound is a result of motion of air and the mechanism of how the air is set in motion doesn't change. It is excited by the motion of the cone surface.
One problem that sometimes makes thing look different is that we look back to existing theory to explain how something works. The problem is that these theories often have assumption built into them. We talk about the wave equation in acoustics and we forget to realize several important thing. The acoustic wave equation for fluids is a very simplified model of how waves propagate and are generated in a fluid. There are many simplifications. Most of these have to do with the magnitude of the velocity and pressure changes resulting from acoustic excitation. If these variations become too large the acoustic approximations loose accuracy and eventually become invalid. We wouldn’t use the acoustic wave equation to describe how shock wave propagate, for example. However, one thing we do know is that the radiated SPL form a driver before and after treatment is not significantly altered on the average. Thus, if the acoustic assumptions are valid pretreatment they are also valid post treatment.
How would we verify that these assumptions are valid? Easy, since they are magnitude related we look at the result for differing play back levels. If we observe that the effect of enable is independent of play back level then we can be pretty sure that the acoustic assumptions are valid. If we observe a level dependence then they might be being stretched. But it really doesn't matter because these are just assumptions made to allow us to treat the problem in a simpler manner which we might be able to solve mathematically. In reality, we have a much deeper mathematical understanding of how a fluid behaves and the acoustic approximations just let us say we can forget about certain contributions from certain sources. But in the real world, all these contributions are always present. It's always just an application of Newton’s Law, F = ma. Remember, F is the sum of all forces acting on the object (in this case the air in contact with the cone surface) and if there are 5 contributions to that force and three of them are very large compared to the other two, like 1000 time larger, then the total force contribution of the smaller two is like 2/3000 (-60dB) and can be ignored in a mathematical model, perhaps. But those small forces will always be present in reality.
Finally, the idea that any "model" that is capable of predicting the subjective performance change (good or bad) of pre and post treated drivers at this time is ridiculous, at least as Bud sees it. Not because it is necessarily beyond predictive capability but because to do so requires a correlation be developed between some objective result and the subjective result. To date, all the differences in objective results have been declared insufficient to develop such a correlation by proponents of Enable, rightly or wrongly. Thus there is little point in even attempting to develop such a predictive capability because the developer has no idea what he is being asked to predict.
John k...
P.S. To moderator. You will note that I have posted under a different user ID. I re-registered as a new user. The reason being that I attemped to change my email address and the reactivation required failed no matter how tried to do it. I kept getting Web address invalid. I have asked this be corrected both by posting to the administrative section and by direct email to the webmaster but AFAIK the problem has not been corrected. Could you please look into this?
BudP said:
So Bud agrees that Newton’s Law's are all that is required: The time rate of change in momentum of a body or object is equal to the sum of all forces acting on it and the a direction of the vector of the resultant sum. Commonly express as F = ma. And, for every action there is an equally and opposite reaction. All that is left is to ask how these laws apply. Frankly, it is pretty straight forward.
The second point Bud makes is that this all gives him grief. "It doesn't make sense." Well to me the tone of this isn't particularly open minded. It seems to be more along the lines to get you all to think like he is; that Enable must be doing something very different. In any event, something not making sense doesn't mean it's the wrong explanation. It makes perfect sense. It just doesn't make sense to Bud.
If you recall, back in the old thread I posted something to the effect of looking at the cone vibration in a vacuum. Well, low and behold, it turns out that somebody has done just that, and more. (I’ll actually do research the topic rather than just talk about it). They took a driver and placed it in a large sealed enclosure and made laser scans of the cone surface velocity when the enclosure was at normal atmospheric pressure, and at several reduced pressures. The intent was to see how the air mass load on the driver affected the cone motion. The results were of interest because they indicated that as the pressure was reduced, changing the effective cone mass, the magnitude and pattern of cone vibration changed. With regard to frequency response which was also measured, a shift in the frequency and magnitude of breakup resonances was observed, very similar to that which has been observed in pre and post treated driver measurements reported in the old thread. The connection between the two is that in both cases the effective cone mass was altered by a small fraction; in one case by introducing additional mass at specific locations on the cone, in the other by uniformly reducing the air mass load over the cones surface. Very different means of changing effective mass, but very similar results.
Bud's third paragraph is purely a subjective comment, again, intending to lead you away for the simple explanation... And then, HOW....
The point is that there is no progress being made here, and I don’t think will be. I read about all the new tests. Well, they are not new tests; they are the same old tests being carried out on new sets of drivers. What do you expect to see? And while I agree with dlr that a full compliment of on and off axis measurements are needed, the off axis measurements should not have impact on what enable does or doesn't do unless the altered cone results in a significant change in the directivity of the driver. I say this because only the on axis (or direct) response is "pure" in the time domain. Anything off axis reaches the ear after it has been diffracted, reflected, absorbed, transmitted, dissipated, scattered.... and so on by the surroundings.
If this is to be understood that there are only 3 things that need to be considered: the cone vibrates differently and energy transfer to the air remains the same, the energy transfer is altered while the cone vibration is unchanged, both effects are at work.
One thing is for certain: the cone must vibrate differently. That is a requirement of adding material to the cone. The second thing is that there is not change in the way energy is transferred to the air. The laws of physics remains the laws of physics and no matter how you look at it, sound is a result of motion of air and the mechanism of how the air is set in motion doesn't change. It is excited by the motion of the cone surface.
One problem that sometimes makes thing look different is that we look back to existing theory to explain how something works. The problem is that these theories often have assumption built into them. We talk about the wave equation in acoustics and we forget to realize several important thing. The acoustic wave equation for fluids is a very simplified model of how waves propagate and are generated in a fluid. There are many simplifications. Most of these have to do with the magnitude of the velocity and pressure changes resulting from acoustic excitation. If these variations become too large the acoustic approximations loose accuracy and eventually become invalid. We wouldn’t use the acoustic wave equation to describe how shock wave propagate, for example. However, one thing we do know is that the radiated SPL form a driver before and after treatment is not significantly altered on the average. Thus, if the acoustic assumptions are valid pretreatment they are also valid post treatment.
How would we verify that these assumptions are valid? Easy, since they are magnitude related we look at the result for differing play back levels. If we observe that the effect of enable is independent of play back level then we can be pretty sure that the acoustic assumptions are valid. If we observe a level dependence then they might be being stretched. But it really doesn't matter because these are just assumptions made to allow us to treat the problem in a simpler manner which we might be able to solve mathematically. In reality, we have a much deeper mathematical understanding of how a fluid behaves and the acoustic approximations just let us say we can forget about certain contributions from certain sources. But in the real world, all these contributions are always present. It's always just an application of Newton’s Law, F = ma. Remember, F is the sum of all forces acting on the object (in this case the air in contact with the cone surface) and if there are 5 contributions to that force and three of them are very large compared to the other two, like 1000 time larger, then the total force contribution of the smaller two is like 2/3000 (-60dB) and can be ignored in a mathematical model, perhaps. But those small forces will always be present in reality.
Finally, the idea that any "model" that is capable of predicting the subjective performance change (good or bad) of pre and post treated drivers at this time is ridiculous, at least as Bud sees it. Not because it is necessarily beyond predictive capability but because to do so requires a correlation be developed between some objective result and the subjective result. To date, all the differences in objective results have been declared insufficient to develop such a correlation by proponents of Enable, rightly or wrongly. Thus there is little point in even attempting to develop such a predictive capability because the developer has no idea what he is being asked to predict.
John k...
P.S. To moderator. You will note that I have posted under a different user ID. I re-registered as a new user. The reason being that I attemped to change my email address and the reactivation required failed no matter how tried to do it. I kept getting Web address invalid. I have asked this be corrected both by posting to the administrative section and by direct email to the webmaster but AFAIK the problem has not been corrected. Could you please look into this?
Re: methods
There's no collusion going on here John.
Perhaps I left things a bit ambiguous. I said the process is underway. Actually, the drivers are simply enroute to Al at RAW Acoustics.
Al mentioned to me what he has in mind (due to my short term memory lapses, I won't paraphrase), and he plans on being quite methodical and thorough.
This is a side project for him, and the other parties, and not a priority. It will take some time for him to do these tests are document everything.
In my mind, I also tended to think that on axis FR, distortion, CSD, and power responses would be the most telling.
I've also often wondered about air density due to elevation. How a driver might perform under different atomospheric conditions such as barometric pressure, temperature and humidity.
There are a number of components in any musical event. The first few milliseconds are quite complex. Noise, amplitude ramp, formant, frequency, and pitch, harmonics, inharmonics are the main source components.
The initial "excitation" of a musical note from an acoustic instrument (for example, a stringed instrument) involves an "attack". That transient usually contains a lot of "noise" as the string goes into excitation, and before it settles into a steady state mode of vibration.
A snare drum for example, is mostly random noise on top of the fundamental pitch of the drum.
I know for a fact that a lot of audio designers have very limited knowledge of how musical instruments actually make sound. In all fairness though, there aren't enough hours in a day for one person to amass the knowledge of all things.
That's the one thing I find really interesting about the audio forums. The sharing of ideas and knowledge.
Cheers
auplater said:
There's no collusion going on here John.
Perhaps I left things a bit ambiguous. I said the process is underway. Actually, the drivers are simply enroute to Al at RAW Acoustics.
Al mentioned to me what he has in mind (due to my short term memory lapses, I won't paraphrase), and he plans on being quite methodical and thorough.
This is a side project for him, and the other parties, and not a priority. It will take some time for him to do these tests are document everything.
In my mind, I also tended to think that on axis FR, distortion, CSD, and power responses would be the most telling.
I've also often wondered about air density due to elevation. How a driver might perform under different atomospheric conditions such as barometric pressure, temperature and humidity.
There are a number of components in any musical event. The first few milliseconds are quite complex. Noise, amplitude ramp, formant, frequency, and pitch, harmonics, inharmonics are the main source components.
The initial "excitation" of a musical note from an acoustic instrument (for example, a stringed instrument) involves an "attack". That transient usually contains a lot of "noise" as the string goes into excitation, and before it settles into a steady state mode of vibration.
A snare drum for example, is mostly random noise on top of the fundamental pitch of the drum.
I know for a fact that a lot of audio designers have very limited knowledge of how musical instruments actually make sound. In all fairness though, there aren't enough hours in a day for one person to amass the knowledge of all things.
That's the one thing I find really interesting about the audio forums. The sharing of ideas and knowledge.
Cheers
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