I'll only add one comment, because I disagree with and do not accept your position. "Widely considered non-linear distortion" is not "universally accepted". I do not accept that what I said is highly incorrect. My experience is quite the contrary and is not based on speculation, it is based on empirical data.The only reason I decided to post in this thread rather than simply read with amusement was soongsc's post about breakup modes and your reply which based on standard theory and practice was highly incorrect. Break up modes are widely considered non linear distortion essentially because the physical manifestations that cause them are not linear in any real sense. Guessing about lower frequency excitation of upper breakup modes is folly - simply not predictable in any practical sense from one driver to the next since there are way to many contributing variables, some that are exposed as lower order energy storage and some that aren't. In any case, I appreciate your candor in acknowledging the limited scope of usefulness for this exercise in the small signal regime. Given that, I will bow out and not pursue the issue of break up modes in this thread's context any further. Thanks.
Well, make that two comments. A model in software that requires that the response be minimum-phase, at least at a specific signal level, could not accurately generate matching phase from the HBT were it not in actuality minimum-phase. It has always been so in my experience, essentially every time, as the HBT phase nearly perfectly matched the measured phase in the breakup region no matter the driver, woofer or tweeter. At least to within the limits of the measurement software.
Dave
The discussion I added my $.02 to centered around breakup modes - not BL curve non linearity, suspension non linearity, inductance rise, or buzz, rub, etc..... As Michael rightfully points out - breakup modes which have been well documented through laser interferometry for the past 30+ years are clearly not linear phenomena just like the excitation of a tuning fork is not linear. You can strike a tuning fork all day long without exciting resonance at a given level of input force. Exceed a particular input force threshold and the material transitions from high internal energy loss to high internal energy storage and resonance. If one confines analysis to the small signal regime - significant breakup is not a likely possibility.
So please understand the context of my posts. I understand what Michael was trying to say - do you?
a good one !
Michael
Ok, lets talk about cone breakup. If that comes from geometry or deformation can be studied with laser interferometry, sure. I have a Klippel Analyser and access to a laser scanner.
In fact i bought the first Klippel ever made for comercial use Ser.No.100 directly from Wolfgangs lab table way back in the deep east of Germany so i can honestly say that i have more experience with laser methods then most. My practical experience is that when a cone say from aluminum breaks up at 4kHz there is 3rd harmonic distortion at 12kHz. If a crossover, be it analog or digital supresses that peak by 10dB then 3rd harmonic goes down by 10dB too but the RELATIONSHIP between levels in maintained so in a strict sense this does not provide distortion canceation. That 4kHz breakup is simply less exited. fntn, do you think i am to stupid to understand Michael ?
In fact i bought the first Klippel ever made for comercial use Ser.No.100 directly from Wolfgangs lab table way back in the deep east of Germany so i can honestly say that i have more experience with laser methods then most. My practical experience is that when a cone say from aluminum breaks up at 4kHz there is 3rd harmonic distortion at 12kHz. If a crossover, be it analog or digital supresses that peak by 10dB then 3rd harmonic goes down by 10dB too but the RELATIONSHIP between levels in maintained so in a strict sense this does not provide distortion canceation. That 4kHz breakup is simply less exited. fntn, do you think i am to stupid to understand Michael ?
sure - we are at the "cutting edge", aren't we
Hey, thanks ! you seem to be the very first one...
I haven't touched distortion (non linear) in my CMP paper but of course thinking some time about it.
All depends on the measuring techniques used. As CMP systems behave "perfectly steady state" after delay time and before signal shut down, all distortion is happening there: at the time of no-continuous spectral behaviour after time delay and at signal shut down .
Depending on how non linear distortion actually get measured we simply may fail to capture those relevant time slots or get them missed in averaging along signal times where "nothing" happens.
Michael
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Joachim, do you see any foldback in any of these?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I think the method discribed here captures it. As you see there is "nagative time" that separates distortion from the fundamental in the time domain. I learned that from Klippel too. http://www.thinksrs.com/downloads/PDFs/ApplicationNotes/What's new with SR1.pdf
Soon, hard to tell what is the best example but what you see is that at time zero you may only see the top of the mountain range whereas in the timedomain you can see the much wider "foot" of the mountain, so the side frequencies of the peak are shifted upwards and more important downwards.
Soon, hard to tell what is the best example but what you see is that at time zero you may only see the top of the mountain range whereas in the timedomain you can see the much wider "foot" of the mountain, so the side frequencies of the peak are shifted upwards and more important downwards.
It does not seem to really fold back, but rather it's just gradual increase of stored energy till it peaks at the breakup mode. But as you have mentioned, there is a fixed relation between the main signal. So as long as it is there, it's only a matter of how loud you start playing till it's audible. Once it becomes audible, it sound terrible.
I check stored energy with a Blankman windowed burst usually. That gives better resolution over a limited range then a CSD i think. Soon, i try to explain that a peak at say 23kHz can be audible when that resonance is decaying. The decay process shifts the energy into the audible range under unfortunate circumstances.
The nature of material deformation (what diaphragm breakup actually requires and represents) is highly non linear - just like the yield behavior of a piece of steel is highly non linear. One cannot learn the intimate details of materials science with a software simulator alone and name dropping (Prof. K) doesn't save us from our lack of knowledge. Clearly, behavior of the bell and radial modes that are excited in a diaphragm that is undergoing breakup vary with the force applied (voltage drive level) and periodicity of the applied stimulus. If anyone cared to acknowledge that break up distortion is non linear and non causal at the outset because the physical properties of the material are undergoing non linear change, I wouldn't have bothered to comment. Clearly, you didn't acknowledge it and just about the only person who did was Michael. This does not necessarily make you stupid. We all overlook certain aspects of a problem from time to time - particularly when focus is keen on a particular aspect. Very simply put, turning down the gain on a driver with a breakup tendency at a given frequency doesn't solve the underlying problem since you no longer can obtain useful output at that frequency. Obviously, that's what crossovers are for. The method for dealing with the problem is not to adjust behavior on a correctional basis but to completely eliminate it by "turning off" the source of the problem. Nothing has been demonstrated thus far with UE to suggest that this problem (cone breakup) can be "managed" by EQ or phase adjustment any differently than the way a standard crossover would solve it by complete blockage of the signal at that frequency - hence your commentary in the post cited above.
Wait a week or two when I next get to extend my measurement. My question would be how to absorb the breakup at the right time? Properly time inverse command can improve the situation, but to what extent? If drivers can be well behaved, surely it's the best solution; but if EQ can improve the situation further, surely it's welcome.
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fntn, i agree that cone brakeup is unlinear. Did i say it is linear ? If yes i can not remember that i said that. There are options to improve the situation. Talking about tweeters, exotic materials like Beryllium and artificial diamond can be used. That pushes breakup up in frequency. A 1" dome tweeter with Beryllium membrane has the cone breakup at ca.30kHz and a diamond membrane breaks up at 50kHz or higher. Beryllium has also the advantage that it is very light and quite well damped so the breakup peak it not that pronounced. I have samples of Beryllium and Diamond tweeters and they do not sound harsh or metallic at all. Another option is to invert the dome and drive it with a small voicecoil. This makes the dome more stable and gives a wider off axis response. Focal pioneered that and Accuton perfected it with ceramic membranes that have parts of the membrane cut back to damp and spread the breakup. The dome can also being made smaller. A 3/4" aluminum dome breaks up at ca.30kHz. SEAS has a driver like that in the catalog and i use it successfully in commercial speakers. Again it does not sound metallic so i can safely conclude that when the breakup is pushed up high enough it is not an audible problem any more. Some makers have tryed to takle the breakup by using an object in front of the membrane like a ring or plate. Boston acoustics had an elaborated version of that idea with micro tubes in front of the membrane some years ago. The idea is to cancel the peak by mechanical means. I am not particular fond of that idea because the created cavities give rise to delayed enegy themselves and it usually only works over a narrow dispersion window.
If such were the case then the material deformation would be permanent and the radiating diapharm would distort from its original shape and not reture. Additionally, such nonlinear behavior would be evident in that the response of a driver would be highly and obviously dependent upon the level of the input signal, which is easily verified not to be the case. Certainly there are limits to the range over which the driver behaves linearly, and there are nonlinear componets in its behavior, but they are far from the dominant factors. Furthermore, nonlinearity is not a requirement for breakup.
At a molecular level it may be but i agree with John that in praxis nonlinear behavior in the breakup region does not present a dominant problem. Still different membrane materials sound different maybe even after equalisation. I think it is best to simply not to use the breakup region for sound radiation. Even when the brakeup, say in a wideband driver, is well controlled, it usually gives rise to second harmonic distortion and hysteresis
ones the range of pistonic movement is left. I usually prefer a rather deep crossover frequency between midrange and tweeter to avoid that problem. This puts more burden on the tweeter but i found that energy in music is usually rapidly falling over 1kHz.
ones the range of pistonic movement is left. I usually prefer a rather deep crossover frequency between midrange and tweeter to avoid that problem. This puts more burden on the tweeter but i found that energy in music is usually rapidly falling over 1kHz.
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