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Servo controlled subwoofers - why arent they used more often
Servo controlled subwoofers - why arent they used more often
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Old 22nd May 2020, 10:26 PM   #51
bentoronto is offline bentoronto  Canada
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Servo controlled subwoofers - why arent they used more often
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Originally Posted by Sonce View Post
You don't have a clue how "Klippel Controlled Sound" is working. Please stop embarrassing yourself.
Is there a sensor and instantaneous feedback correction?

B.
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Old 22nd May 2020, 10:34 PM   #52
Sonce is offline Sonce  Macedonia
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Originally Posted by bentoronto View Post
Is there a sensor and instantaneous feedback correction?
B.
Yes, see Fig. 2 on the right side, next to the loudspeaker:
Klippel Controlled Sound (KCS) - Controlled Sound Technology for Nonlinear Compensation of Loudspeakers | audioXpress
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Old 22nd May 2020, 11:40 PM   #53
troystg is offline troystg  United States
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Meant to quote.
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Old 22nd May 2020, 11:41 PM   #54
troystg is offline troystg  United States
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Quote:
Originally Posted by Sonce View Post
Actually that is a very similar scheme as Mr. Erath used in his patent many moons ago.

Once I finish mine I will see if they would allow a comparison to see just how similar they are.
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Old 23rd May 2020, 01:58 AM   #55
bentoronto is offline bentoronto  Canada
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Servo controlled subwoofers - why arent they used more often
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Originally Posted by Sonce View Post
Kind of like the diagrams telephone systems engineers prepared, intended to clarify for you as little as possible and confuse you as much as possible. Except telephone engineers weren't motivated by making money in doing so (I think their purpose was to prevent amateurs from fooling with phone circuits in their houses).

Looks like the good old current sensing resistor in series with the driver. On the other hand, MFB systems to not have boxes called "Memory" or need transducer models. The feedback circuit is the model, not the imperfect driver.

So conceptually, the diagram could be almost anything from a fancy T/S Klippel model inverted into the signal path (my previous post) or plain old current sensing MFB based on driver back-EMF (and no independent sensor at all).... which most aficionados today find a pretty poor way to do MFB.

My best guess is that it is current feedback corrected by a model of the driver. Which is an inflated belief that Klippel really has a really perfect knowledge of the driver and uses this really perfect knowledge to "correct" the sensor feedback.

B.
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Old 23rd May 2020, 10:14 AM   #56
Sonce is offline Sonce  Macedonia
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Originally Posted by bentoronto View Post
Kind of like the diagrams telephone systems engineers prepared, intended to clarify for you as little as possible and confuse you as much as possible.
The diagram is self-explanatory, but only if one has enough engineering knowledge. Otherwise... well, someone will be confused. Don't blame engineers for that.
Quote:
Originally Posted by bentoronto View Post
Looks like the good old current sensing resistor in series with the driver.
Looks like you didn't notice the voltage sensing arm in the diagram, which together with the current sensing arm can track every change of woofer impedance - correcting, for example, the woofer resonant frequency change due to ageing, or voice coil temperature change.
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Originally Posted by bentoronto View Post
So conceptually, the diagram could be almost anything from a fancy T/S Klippel model inverted into the signal path (my previous post) or plain old current sensing MFB based on driver back-EMF (and no independent sensor at all).... which most aficionados today find a pretty poor way to do MFB.
My best guess is that it is current feedback corrected by a model of the driver. Which is an inflated belief that Klippel really has a really perfect knowledge of the driver and uses this really perfect knowledge to "correct" the sensor feedback.
The diagram is a simple explanation of the quite complex Klippel system. To grasp the whole picture, don't guess - read, watch and hear carefully everything here:
KLIPPEL CONTROLLED SOUND
There are many ways to skin the cat, some are more effective than those of most aficionados.
Hearing is believing, hear yourself what can Klippel Speaker Control do:
404 Not Found

Last edited by Sonce; 23rd May 2020 at 10:31 AM.
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Old 23rd May 2020, 02:28 PM   #57
ds23man is offline ds23man  Netherlands
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Please read chapter four:

https://rmsacoustics.nl/papers/whitepaperMFBtheory.pdf
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Old 23rd May 2020, 02:37 PM   #58
bentoronto is offline bentoronto  Canada
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Servo controlled subwoofers - why arent they used more often
Quote:
Originally Posted by Sonce View Post
The diagram is self-explanatory, but only if one has enough engineering knowledge. Otherwise... well, someone will be confused. Don't blame engineers for that.

Looks like you didn't notice the voltage sensing arm in the diagram, which together with the current sensing arm can track every change of woofer impedance - correcting, for example, the woofer resonant frequency change due to ageing, or voice coil temperature change.
I wish some new wise person would add their post here.

BTW, I think it really is the same old current sensing system that Erath, ACE bass, and almost everybody before cheap accelerometers started being used plus, and here I am guessing, some trick parametric correction from Klippel based on prior testing of the driver.

The voltage sensing circuit is the same as in every low output impedance audio amp in the entire known universe (as far as I can understand his inspirational picture). It is feedback that corrects the amp (and not incidentally, to render the amp a low output impedance source of power). It doesn't sense anything about the driver. In fact, as it is widely understood, its role is to nullify any fluctuations in the speaker such as back-EMF, inductance, hitting max excursion, or even noisy dirt in the voice coil.

Klippel's diagram - and other stuff of his I've read - is much distorted by commercial motivation and the need to fool the patent office into thinking you are innovative. But Klippel doesn't blush as much.

I think your personal insults are out of place here. Please stop it.

B.
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Last edited by bentoronto; 23rd May 2020 at 02:45 PM.
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Old 23rd May 2020, 03:04 PM   #59
bentoronto is offline bentoronto  Canada
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Servo controlled subwoofers - why arent they used more often
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Originally Posted by ds23man View Post
Thanks. Cap. 4 does explain everything (I've been re-reading that paper every once in a while for a long time and now understand 10% on a good day), including Klippel's mysterious interest in sensing temperature.

Yes, Klippel pre-distortion based on - I assume - prior measurement of the specific driver unit might be a good concept. But as Munnig Schmidt points out, if you need a sensor to sense instantaneous changes ("adaptive learning"), why not just use a sensor for MFB and be done. Why doesn't Klippel simply install an accelerometer? Can't patent it?

Feedback cycle "settling time" is a not an issue with subs unless you want to have DSP* in your loop.

B.
*I bought a spare Behringer DCX2496 to put in the loop to experiments but it seems to be too slow.
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Last edited by bentoronto; 23rd May 2020 at 03:08 PM.
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Old 23rd May 2020, 04:50 PM   #60
esl 63 is offline esl 63
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There is of course pros and cons with accelerometer feedback.
Fiddling and removing dustcap could be hard if you are not steady on your hand.
But when itīs properly and stiff installed, measuring the voice coil movement, and you decrease distortion with 15 dB and you can tune fs and Qts with a knob, thats amazing!

I canīt really find any reason for a DIY audio soul not to try.
There may be other ways to reduce distortion, but sensor feedback wins, if the sensor is good enough. ACH-01 works like a sharm...
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