"Originally Posted by Sonce View Post
the Clippel Controlled Sound system is measuring the driver impedance (z=u/i in the real time), then converting it to the woofer parameters - as an input in the Audio Signal Processing unit"
I think Sonce now has a better explanation of the Klippel system than in his or her earliest posts, although attention to repeated mis-spelling of "Clippel" might be nice.
As far as MFB, "driver impedance" means back-EMF because nothing else about the impedance is changing much in relation to sound output. So that is just a misleading way of saying its vintage back-EMF feedback.
The "voltage" bit is just to linearize the amp and has nothing to do with MFB.
So, there appears to be nothing new about the Klippel system?
B.
the Clippel Controlled Sound system is measuring the driver impedance (z=u/i in the real time), then converting it to the woofer parameters - as an input in the Audio Signal Processing unit"
I think Sonce now has a better explanation of the Klippel system than in his or her earliest posts, although attention to repeated mis-spelling of "Clippel" might be nice.
As far as MFB, "driver impedance" means back-EMF because nothing else about the impedance is changing much in relation to sound output. So that is just a misleading way of saying its vintage back-EMF feedback.
The "voltage" bit is just to linearize the amp and has nothing to do with MFB.
So, there appears to be nothing new about the Klippel system?
B.
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I quoted my old post, so my understanding of the Klippel system is the same as before and is not changed.
Impedance is changing with temperature (high wattage input) and the resonant frequency may be changed due to the ageing process.
As I wrote before, the voltage sensing is for measuring impedance and has nothing to do with the amplifier. Did you check how CLIO and ARTA are measuring impedance? Here is the explanation again:
Pay attention where the amplifier is located and note the absence of negative feedback loop - it is inside that amplifier.Then, compare it to the Fig. 2 from here:
Klippel Controlled Sound (KCS) - Controlled Sound Technology for Nonlinear Compensation of Loudspeakers | audioXpress[/QUOTE]
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Don't know much about the Klippel system other than the videos on Youtube, but to me it looks like an adaptive software, eg. AI of sorts that learns the speaker and then there is just DSP to introduce a "fix" or multitude of fixes. There was many things it can learn and fix, including limiting, counteracting suspension stiffness and voice coil offset, BL asymmetry with DC etc. Many "small things" to make a speaker sound better, reduce distortion. Then, there seems to be also the EQ thingie as well, so one can tailor Fs and Qts. MFB with brain.
We use these cable:
MOGAMI® - Ultraflexible Miniature Cables
Looks thick in the picture but there is a silicone sleeve to prevent flexing at the connection points. It's the same cable as used in the Grimm sub.
Oh wow good to hear there are cheaper options nowadays. The ACH-01 was very nice, but also pretty expensive. For one or two pieces it was doable, but it wasn't feasible for production.
Why would you need 4 sensors though, wouldn't single DOF be enough? What kind of sensors are being used? I didn't even know Murata made sensors that could measure such high accelerations! Or are you perhaps using the shock sensors similar to the starbass modules from Piratelogic? They are afaik NRND by murata (Shock Sensors|Sensors|Product Search|Murata Manufacturing Co., Ltd.).
If you can't talk about it I can understand due to IP.
I guess the linearity is improved when you average 4 of them, also that you reduce (eliminate?) 2nd harmonic as well.
It would be interesting to put the sensor on a pure sine oscillating mechanical structure (a spring supported mass) and measure the linearity from the sensor.
It would be interesting to put the sensor on a pure sine oscillating mechanical structure (a spring supported mass) and measure the linearity from the sensor.
How linear are the sensors out of the box? Could they be used without fancy vibration calibration setups? Or is there any way you could calibrate the sensor other way?
Interested in this thread.
A couple of things.
(1) Here in Australia in 1987 (think) a diy MFB design was publish in a local mag' (that's now out of print). (It was a reprint from ELEKTOR in Europe.) It involved modification of an existing sealed box sub. It used the piezo diaphragm from the common plastic horn tweeter as a sensing element under the sub' dust cap and a few readily available op-amps and passive components. It did look good and an ideal project for members of this sort of forum.
It was going to be one of my "retirement" projects.
Question has anyone tried it? Impressions?
(2) Secondly, I've skimmed this thread but not read in depth so this may have been mentioned. But another reason MFB's may not have become more popular is the development of bandpass enclosures. The sort of results I was looking for from a diy MFB sub' seems to be also achieved by using a bandpass box....with more woodwork but less problems with the electronic side of things......
Any thoughts?
Cheers Jonathan
A couple of things.
(1) Here in Australia in 1987 (think) a diy MFB design was publish in a local mag' (that's now out of print). (It was a reprint from ELEKTOR in Europe.) It involved modification of an existing sealed box sub. It used the piezo diaphragm from the common plastic horn tweeter as a sensing element under the sub' dust cap and a few readily available op-amps and passive components. It did look good and an ideal project for members of this sort of forum.
It was going to be one of my "retirement" projects.
Question has anyone tried it? Impressions?
(2) Secondly, I've skimmed this thread but not read in depth so this may have been mentioned. But another reason MFB's may not have become more popular is the development of bandpass enclosures. The sort of results I was looking for from a diy MFB sub' seems to be also achieved by using a bandpass box....with more woodwork but less problems with the electronic side of things......
Any thoughts?
Cheers Jonathan
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I also built MFB subs in early 90s but todays sensors i better, and knowledge i greater (skim the different threads here on diy audio) and in combination with current feedback you get higher phase margin and also distortion reduction from te current feedback loop itself. 1+1=3
With piezo tweeter, a distortion reduction from 5% to 2% can be achieved. With a sensor like ASH-01 you go from 5% to less than 1%.
In this measurement the 3d harmonic went from 9dB below fundamental to 35dB below fundamental.. Thats impressive!!
https://rmsacoustics.nl/papers/whitepaperMFBdesign.pdf
With piezo tweeter, a distortion reduction from 5% to 2% can be achieved. With a sensor like ASH-01 you go from 5% to less than 1%.
In this measurement the 3d harmonic went from 9dB below fundamental to 35dB below fundamental.. Thats impressive!!
https://rmsacoustics.nl/papers/whitepaperMFBdesign.pdf
That link is the clearest presentation he's made. Thanks.
I think we need to get a lot more clarity about the sensor touted here. In feedback theory, the behaviour of the feedback loop becomes the behaviour of the system.
Philips, bless their hearts, took a cheap driver and used a cheap sensor and got pretty good results.
Finally, the ACM sensor is a very fine device with specs layed out for all to read. If you can't find a used ACM-01 on eBay, the price seems high for one very little component for us DIY folks (and quite high for a manufacturer). But in reality, it is just a small part of the total effort and cost of building a MFB system and hardly compares to the big dollars spent on amps, etc.
So just saying the sensor here was "validated" (whatever that means) by comparison to some B&K test device, tells us nothing at all about the accuracy and THD of the sensor being touted here. It matters a lot and folks are entitled to know a lot more about this new accelerometer.
B.
What impresses most is the harmonic reduction of 5th 7th and 9th. That is a proof of concept that MFB does not introduce any side effects at higher orders in this case at least...
Remember that the ears sensitivity is increasing all the way up to 1-2 kHz and that odd harmonics is the bad guys. While the even harmonics is already present in the instruments itself.
The measurment graph on the last page of the PDF i linked to tells you a lot!
Some of us has understood.
And i hope we will get lots of rain here soon so that i can continue with some adjustments, then I will present some pictures and measurements.
Remember that the ears sensitivity is increasing all the way up to 1-2 kHz and that odd harmonics is the bad guys. While the even harmonics is already present in the instruments itself.
The measurment graph on the last page of the PDF i linked to tells you a lot!
Some of us has understood.
And i hope we will get lots of rain here soon so that i can continue with some adjustments, then I will present some pictures and measurements.
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The MFB concept works great because it provides much better control over the loudspeaker driver. It doesn't provide ANY control over a bass reflex port or passive radiator or other forms of helmholtz resonators.
Those helmholtz resonators also tend to have very high Q, which is often undesired (q of 0.5 of 0.7 is generally the desired value). This can 't be tuned with MFB, because there's no control over the port. The result is that you have to put lots of effort in a good MFB system and then proceed to ruin it's dynamic behaviour with a port.
You could of course make the bandpass electronically, but MFB is only really viable in the low frequency area. This is due to the bode equality integral. It's also very difficult to control high frequency signals due to the phase shift caused by sampling.
A whole lot of clarification is needed to that post.
First of all, there is NO linearizing control external to the driver you take out of the shipping box except by using MFB, "acoustic suspension" being the only exception I know of.
The MFB we're talking about tries to make the cone move matching or proportional to the input signal. For a sealed box and an infinite baffle, that's a good goal.
For BR, TH, TL, OB and the like, it is not exactly a good goal since the total output of the speaker includes the port and related misgyrations of the cone. However, many people have done so, theory be damned, and you can have better sound with a BR with MFB, or so I have been told. MFB cleans up the cone motion in a variety of wonderful ways and, I suppose, you can always fix the final room FR using DSP later.
B.
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