I am only intervening because you involve Pavel in this and try to show that Pavel agrees with you on this.
Pavel was addressing you when he showed those measurements and he insisted to make clear that his opinion on those measurements is:
Any nonlinearity signs in the current waveform is due to the nonlinearity of the load and it has nothing to do with the amplifier, voltage or current source.
It is a slippery road …
George
But will it expose the same impulse response? And I don't mean a calculated response from a steady state FR measurement but observing the actual envelope for a couple of ms?
PMA, care to make some measurement?
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Mark, I very well remember Centauri. My favorite rocket of theirs back then (the 70's) was named the 'SST', which was an Concord looking booster that carried a small piggybacked glider plane. At apogee, the glider would release and fly down, while the booster came down via parachute. Back in middle school, before we all discovered girls, my friends and I used to carry both Centauri and Estes catalogs around in our book bags. Much wasteful classroom day dreaming took place.
Balsa wood, sanding sealer, Testors paint, parachute wadding, rocket motors, launch control electrical - a nerd's paradise. And when those old style igniters failed to fire the motor, which they frequently seemed to, the suspense filled slow sneaking up on the unlaunched rocket like it was an live grenade. The blissful innocence of that time.
Ahh. I can tell you a story about this. Back in '70 or '71 I was also a 'rocket nerd' and a bit of a classroom joke to be honest as a 13 or 14 year old.
I took naphthalene (mothballs) and melted it in a tin jar (on an open flame mind you) into which I added crushed permanganate of potash (the oxegenator) and mixed it together (4 parts permanganate to 1 part naphthalene if you must know). This concoction was then rammed into an aluminium tube to make a solid fuel rocket. They never flew too well because I never figured out a way to line the tube but have the fuel hollow in the centre to increase the surface area.
Anyway, it all came a sticky end when during one session the naphthalene caught fire up in my bedroom and filled the room with fumes and small black 'twirlies' that stuck to the ceiling. My parents were less than impressed . . . grounded for weeks as I recall and banned from going anywhere near matches, flames, mothballs or permanganate. After that I started to get interested in electronics but still did some really stupid things.
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I learned that:
1. Make sure that the nose cone of your 3 foot tall Saturn 5 (Estes) model is sufficiently loose that when the ejection charge initiates, the nose cone actually comes off. Accordians cannot be launched a second time..
2. When assembling your Zenith 2 Payloader (centauri IIRC), FOLLOW the instructions to tape the second stage motor to the first. That way, it hangs around long enough to be ignited. Oddly enough, the rocket is still stable with the second motor unlit. The first stage C lofted it sufficiently high that when it nose dived into a muddy patch, the tail fins were below ground level.
3. Elmers glue may look to have held a broken fin sufficiently 30 minutes before launch, but alas, not quite. Amazing how fast a D engine with a nose cone and 66% of it's fins attached can spin, gyrate, and do an incredibly fast 3-d drunkards walk 100 feet above a large crowd of spectators. Luckily, nobody was hurt.
4. When using a car battery as the launch power source, do NOT wire the battery to a 1/4 inch PLUG. As in, when you try to plug it in, sigh....I love the smell of burning pvc in the morning..
John
Yes, it *is* exactly the same signal output whatever stimulus you choose and how you look at. This possible because we are dealing with so-called weakly non-linear systems. When you have the same complex-valued transfer function you have the same output, in all regards.
That means, once you have the IR obtained from a reasonable measurement, neither plagued with noise nor significant (>1%) distortion from overdriving the speaker, you can use an arbitrary stimulus, including real music signal and compare the real time-domain response seen at the mic with that calculated by convolution of the test signal with the IR. If you subtract them you should get a good null signal, you get the error, the noise and distortion alone, isolated. This includes a linear term from the IR when it was taken at an operation point far off of that used for the real signal (too loud, notably).
This subtraction is actually a sanity check system designers should do from time to time to check the validity of the IR, especially when working with CAE tools where that IR is used as the raw response worked on to make an xover, for example.
What is different though, and I try to emphasize on that, is the reaction to externally-induced cone motion. If you tap the cone there will the difference according to the electrical damping applied (and this is true regardless of any EQ). The current-driven cone will ring quite a while, with its mechanical Q factor dominating. The shorted driver (shorted by the amp output impedance) will react with much better damping. Seen from that point, we should look for aperiodic damping here if it does not violate other constraints. Then, finally EQ the reponse to target and you have speaker with the desired response, and a quick and clean recovery from any error signal, be it external or internal. Might not be the best operating point for distortion at the same time, though, it's all a compromise.
John, that has been the least professional thing written so far in this whole back and forth. Well, notwithstanding Joe using your silver wire/directionality silliness to make the claim, "I may be batty, but at least I don't propose something that ridiculous".
So I find it quite hilarious that you're defending Joe.
Anyways, there was a Nova episode about all the recent advances in rocketry last night. I lapped it up enthusiastically. And the SLS is still a giant boondoggle.
Okey - thanks! "One" wold have thought that in current drive, the cone was sort of set off forward with no control and you would see an overshot... but alas not...
So if current and voltage drive results in the same "steering" of the cone, one would tend to lean towards current drive given the reduced distorsion?
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So if current and voltage drive results in the same "steering" of the cone, one would tend to lean towards current drive given the reduced distorsion?
//
As long as we are talking rockets...a friend and I though the Estes Saturn V was too expensive and wimpy, so we built our own with a 5-D engine 1st stage, 3-D engine second and 1-D engine 3rd. Understand we were 12 year olds and not engineers so power to weight may have been off a bit. Upon completion it looked really great, but apparently we had not solved the synchronization of engine ignition because...a few of the 1st stage engines lit with insufficient thrust to lift it off the launch rod, but when the others came alive it slowly lifted, cleared the rod...then began to fall over, all the while accelerating. Everyone yelled "Hit the deck" and fell to the ground as this monstrosity roared over us, whizzed across the street and ended up in the Country Club pool 1/4 mile away. We never got it back.
Great fun!
Howie
I'm sure others have thought of it before, but it took someone to actually make it and provide the "duh, so obvious, now..." moment for everyone else.
And that's how innovation can sometimes become the norm, almost overnight. the rest of the monkey clan needs time to get it.
Sometimes they need centuries of time.
Fluid intelligence, speed of cognition, IQ bell curves, and all that.
Howie: I believe Mr Marsh was Mr Monster so should have the info.
I did wonder how long someone would take to point out that this is linear catching up with SMPS. Nevertheless better late than never.
Speaking of catching up I hope in the next 24 hours to finally move my phono stage onto a silent switcher and start my plan to battery power everything low level. Lets see how many more years it takes.
@Daniel: The planned test being a week ago I can only hope the shutdown delayed it and nothing bad has happened.
I did wonder how long someone would take to point out that this is linear catching up with SMPS
. Nevertheless better late than never. Speaking of catching up I hope in the next 24 hours to finally move my phono stage onto a silent switcher and start my plan to battery power everything low level. Lets see how many more years it takes.
@Daniel: The planned test being a week ago I can only hope the shutdown delayed it and nothing bad has happened.
I enjoyed KTSR's post and don't see why you're going on about other than to be a little obtuse, with a small spatter of technical stuff.
I too dreamed of model rockets when I was a youth as well, but alas it was not to be.
I lived less than 1 mile from the end of the main runway for McClellan AFB, at the time home of AWACs and the supply and repair depot for the Pacific Theater.
Any (and all) vertical activity was rapidly and swiftly pursued. Even balloons and paper bags with tin foil candle holders for thermal lift.
Cheers
Alan
I lived less than 1 mile from the end of the main runway for McClellan AFB, at the time home of AWACs and the supply and repair depot for the Pacific Theater.
Any (and all) vertical activity was rapidly and swiftly pursued. Even balloons and paper bags with tin foil candle holders for thermal lift.
Cheers
Alan
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