John Curl's Blowtorch preamplifier part III

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#10,702
jneutron said:
Sheesh, I figured antimatter would be the want..I guess it's old hat now..

With the co-wound vc's, the coil being used as the sense, when subtracted from the first will give only the real component of the driven coil's voltage. If you connect the two coils at the hot side (and out), the low side of the sense coil will float off ground by the exact amount of the real part of the drive signal. The subtraction will remove all inductance, all energy storage, all velocity, and will present only the current times the resistive losses in the speaker. The losses are the coil resistance, eddy losses, acoustic energy transferred to the air. with DSP, you can derive the pure in phase component of the losses, the remainder should be the non linear stuff.

What I like about this is it is a real time instantaneous value for the non linearities. It's not a measure of the acoustic distortion, but the magnetic system.

jn
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Ok, but the measurement does not distinguish what part of the signal -is tied to what. The remainder thingie. Which part of the remainder is due to....? or the ..? That kind of problem.

For as the load changes on/in the system proper, the residual non linearity as a package, the components of it will alter in value, etc. The package of non linearity is built out of a system of dynamic non linearities. You get a sum to look at but not the ability to understand fully the meaning of the given sum in the given moment.

I'm sure you're aware of this, though.

Does that make sense?

You might be able to model it according to some good guesses and the delta of the given moment. Sounds messy at best, even as I write it..

Then it likely comes down to treating it as a lumped parameter - and sticking to low frequencies.

Oh. Servo woofers. Odd how that flew..... but never witnessed me a servo mid. System is too complex and too slow, it seems...
 
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#10,703
Mark Whitney said:
What about when you make modifications to a PCB like cutting a trace. Normally you would need to get permission from the author before doing so in other copyright works.
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Never saw this applied to any mass produced thing, aftermarket modding even for resale of electronics has been going on probably from day one. I would see a problem in the resale if you imply the original copyright or other IP is no longer valid.

There are plenty of stories of people at craft fairs getting in trouble with Disney (decoupage with cutout comics, etc. was very popular) some might even be true. Is this the same thing, I don't know and I never came across it myself.
 
#10,705
I always thought of doing a servo with a triple staggered strip written down the inside of the former, and then an optical sensor package tied to the top of the pole piece. the staggering and sensor are in triplicate, which might help in stability and quality of measurements. Three one and zero sets, staggered, for ultra fine detail in the measuring, and gauging the stop and start most accurately.

Perhaps something similar has been done already.
 
#10,706
The real losses in a speaker are:
1. IR drop of the copper in the coil.
2. Eddy drag losses
3. Acoustic energy.

I would go non conductive for material near the vc, eliminate any shorting ring. That way the only significant non linearity is the inductance variation of the coil vs position.

Because that inductance is mirrored in the second coil, feedback from the difference would essentially be the real part of the signal power.

The paper earlier linked by TNT, I have no idea if they even understood the significance of how their dual vc coil was designed. It might have been front/back, in which case the inductance slope would cause the two coils to see different things.

That is one of the issues I see with papers such as this, they may not have fully understood what they were doing with respect to the woofer design.

jn
 
#10,708
billshurv said:
AVM Ovation PA 8.2 modular preamplifier | Stereophile.com


Glad to see there are still modular preamps around (Burmester is the only other one I am aware of). But the price is scary. Even DIY has given up on the 19" rack card format.
Click to expand...

I made a modular amplifier (for myself and the second piece for a friend) in 1986. It was based on Eurocard 100 x 160 mm modules. Linear preamp, RIAA preamp, bass/treble control and 30W power amp modules. Power supply was fixed, in rear part of the case. Nice case from 4 mm Al, anodized. About 15 years ago I threw it to the thrash and it was a big mistake.
 
#10,709
But might not fine detail info in position, and thus being fine, relate to accurate measurement of delta, and then combine this with the second VC readings, would this give enough to gain insight into the nature of the complexity of the residual, and then build a correction/file fit? (DSP based correction file)


That via utilizing the two, this would enable the creation of a proper curve fit? AI subwoofer!
 
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#10,717
Yes, but I think your question is, what if you want to rehab the building and swap out the windows with a different design or change the roof line? Droit moral might make that difficult. The obvious answer is to plan ahead. When you hire the architect include a provision in the contract that says you can do anything you please. Random commercial architect probably will agree, Frank Gehry would tell you to take a hike.
 
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