Bah Humbug. I'm still PO'd as I thought this was 'my little secret' for the past decade or so.
I guess if you sit on anything to long....
Good work guys.
(This sort of stuff is why you never get to see photos of any of my audio systems and strangers are never allowed near it. One never knows what they might might forget lying around the place.)
There are still some other issues....
I guess if you sit on anything to long....
Good work guys.
(This sort of stuff is why you never get to see photos of any of my audio systems and strangers are never allowed near it. One never knows what they might might forget lying around the place.)
There are still some other issues....
It's not as easy as one thinks, and probably the results will not be exact at the high frequencies. But anyone can draw up a driver cone and surround to see if the modes are in the ball park of drivers of similar size, then jusr start playing around with the patterns. Drawing a physical geometry is probably one of the simpler things.ghpicard said:
Seems to me that it would be reasonably trivial to do some "standard" computer FFT type measurements of "before and after" EnABle showing the waterfall, the impulse response and the harmonic distortion(s). WRT to that it may be very useful to look at the higher order distortions and not just the 2nd and 3rd.
So why not?
_-_-bear
So why not?
_-_-bear
Ideally you would, but quite often not. As briefly shown in an FEA analysis previously posted, high frequency modes consist of many types including concentric and radial. Once you start changing the modes by using different patterns, then the result might show obviouse improvements/differences. I would think the EnABL patterns sort of change the radial modes. Looking through a few thousand mode calculated from FEA really can give one a headache.bear said:
soongsc said:
Ideally you would, but quite often not. As briefly shown in an FEA analysis previously posted, high frequency modes consist of many types including concentric and radial. Once you start changing the modes by using different patterns, then the result might show obviouse improvements/differences. I would think the EnABL patterns sort of change the radial modes. Looking through a few thousand mode calculated from FEA really can give one a headache.
I'll have to see if I have the link at home, I found a reference that indicated that the significant resonances are primarily concentric modes, there's little contribution from radial modes. Also, referring to Klippel, radial modes are IIRC largely attributable to non-uniform distribution of mass concentrically. Manually added mass as done with enabl is guaranteed to be non-uniform distribution. The implication of this is that there will likely be added radial modes to an already good driver from that aspect. Only something such as laser vibrometry will show what's really happening, we can only speculate.
Also, Klippel's paper shows in detail where and how breakup occurs for concentric modes related to the cone/surround junction. These are largely related to the surround movement itself and movement of the cone in close proximity to the surround. It is, again, a function of cone mass/stiffness as well as surround mass/stiffness. The FEA that any DIYer can conduct will be severely limited in accuracy and completeness. It will only scratch the surface, especially since few, if any, driver cones are likely to be perfectly uniform. Some, such as those by KEF, are specifically non-uniform in thickness radially. Then there are all of the profile issues. There's little confidence to be had in DIY efforts at FEA.
Brett said:
Though I am one of the original skeptics of the claimed mechanism in the various threads, I have no doubt that there is a change in the driver acoustic output, it's been measured. The results are consistent with mass/damping/stiffening changes. The problem is in assessing the specifics of the changes. They can be measured. They will not always be good and will be highly driver dependent, as are mods to any driver.
Dave
Dave, I have only seen one, that Dave D linked earlier, the 'mouse-over' comparison and one data point does not an proof make for me. The amount of mass added if I have read it all right is very small and I do not see anything that convinves me of a change yet.dlr said:
For all the wordiness of the proponents, there is a dearth of measured proof that there is a change.
Brett said:
I've made many tests of driver mods myself, I linked to some of them in the original thread IIRC. The amount of mass required to make a significant change varies with every driver. But you are correct that there is a dearth of measurements.
I would suggest that even a single measurement that documents a change in FR is enough to show that it can occur, though that will be academic in that any and all added mass must have some effect, however large or small. The few measurements provided prove nothing absolute of the mechanism nor perceptive changes, but is evidence of altered FR. It's consistent with added mass changes.
Dave
http://www.klippel.de/download/group.asp?group=113
Hi,
There is a now a 97MB zipped file with animated cone vibrations .....
/sreten.
Hi,
There is a now a 97MB zipped file with animated cone vibrations .....
/sreten.
soongsc said:
The paper is at his site. It shows the progression of the breakup at various frequencies. The pdf link is:
Klippel - Cone Vibration
soongsc said:
Thanks for the correction on terminology, the circular modes should contribute little to the acoustic output. Here are relevant quotes from Klippel's paper:
"According to Frankort (edit), the circular vibration components have a negligible effect on the total radiated sound."
"...considering only the circular vibration component can reveal asymmetric vibrations which while not contributing much to the radiated sound nevertheless can introduce distortion due to rubbing of the voice coin in the gap. The reason for these asymmetric vibrations can be a non-symmetric mass distribution of the voice coil or the cone."
The implication from this is that the circular modes are in general not significant unless they introduce distortion due to issues such as voice coil rubbing. Further, this says that unevenly distributed mass (e.g. EnABL) has the possibility of increasing the circular modes of a driver. It would be necessary to use laser vibrometry to assess the vibrational changes, distortion testing could be used for the acoustic impact if done properly and thoroughly.
This is separate from the impact on the radial modes that are also going to be affected. Again, a thorough set of distortion tests would indicate the effects of any added mass. FR tests as presented in this thread are of the most simplistic for total impact. But they are indicative of what is changing, such as the resonances that are altered, primarily radial (since circular is shown to have little impact on the FR) that are shifted (certainly not eliminated) in general as evidenced in the FR. This is why from day one I suggested making a thorough set of distortion tests. So far, there is nothing on that. I doubt that anyone will provide that, even though it's the best that could be provided short of Klippel tests for an analysis of the acoustic impact, DIY or OEM.
One question still remains on FEA. How accurate can DIY efforts into FEA be? Being consistent with an analysis is different than being accurate and complete. Predicted modal vibration of any model would have to be verified. Even so, the impact of those vibrations on the acoustic output would also be necessary for it to be of any use. Read the Klippel paper to see just how involved that would be in a model. It's just not going to happen DIY if accuracy is the goal, as it should be.
Dave
If the circular (bell) modes can contribute to distortion, then certainly effects sound. Whether FEA is accurate enough or not depends on whether it assists in improving a product or not. FEA cannot be exactly like the actual product, because there are lots to be explored and limited investment can be put into research. But if the analysis can correctly identify some issues that results in real product improvement, then it satisfies the requirements.
soongsc said:
If, if, if. A DIY analysis will not be able of correctly identifying issues, it's too limited in capability.
Note again, the distortion indicated would likely be in the area of a rubbing voice coil. This will in almost all cases be a manufacturing defect unless the added mass is significant enough to cause this, hardly the case under discussion. Circular mode impact of enabl or any other DIY will almost undoubtedly not be an issue at all.
To what real product do you refer? Nothing here, we are not manufacturers and it's useless for analysis in the enabl thread. You should start another thread on FEA rather than continue to discuss it here, that's pointless and is little more than a diversion of the topic.
Dave
Any study begins with an educated guess on where to start. It is quite resonable to assume that possibly the EnABL pattern might suppress the bell modes. But currently analysis is being conducted and there is no conclusing yet. Quite interestingly is that what I normally thought to see symmetric mode patterns resulted in only few patterns that are symmetric. Largest deformation mostly occurs on the outer edge of the cone, and is damped significantly by the surround. Analysis is one method to help predict whether the patterns can help or not. I sympathize with your frustration. But things just flow as they can when asking others to help do some work. We all learn as we work along. That's where the fun is.dlr said:
soongsc said:
You missed the point in Klippel's paper altogether. Any bell mode alteration (why assume suppression, why not the more likely addition?) will be inconsequential to the acoustic output of drivers with the enabl tweak.
Any frustration I might have is with the constant reference to FEA that will be total inadequate, in part and in whole, with regard to the patterns because no DIY models with be anywhere close to having the necessary predictive capability. When you can present a predictive model of even a raw OEM driver with verification through measured response, then it may be worth discussion. Until then, it's pointless.
Dave
sreten said:
Hi,
I've seen a paper that did this but cannot find it again.
I have no doubt that it can be done, at least to some reasonable degree of confidence. I have no confidence that it will ever be done by anyone involved in this thread, at least not to any significant level of accuracy. The patterns, also never, ever being consistent from one application to the next, are pretty much out of the question with regard to an accurate model.
Klippel shows an example in the paper at the link I provided, although it is limited in its ability as he notes himself. His is a simpler model using point source modeling of a diaphragm and is only a valid approximate in the far field because of the model method and assumptions. He also indicates how it might be improved by substituting boundary element models. But on top of that, the models must include any diaphragm inhomogeneities before even considering additional inhomogeneities introduced by any pattern, even if it were repeatable, which it is not if applied by hand and not necessary even by machine.
Dave
Prior to the cone vibration module was formally announced, I did put in a wish for one to be able to view the wave front resulting from cone vibration. Don't know whether it will get in there or not. But from the paper, it seems they are possibly looking into it.dlr said:
The journey is just as valuable as the result. But we won't have anything to talk about unless you also have something to show. Well, maybe if you pickup the airfare bill...