CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS

  • December 31, 2015, 09:37:09 AM
  • Welcome, Guest
Please login or register.

Login with username, password and session length
Advanced search  
Pages: 1 [2]

Author Topic: planars and output impedance/damping factor?  (Read 1156 times)

0 Members and 1 Guest are viewing this topic.

Solderdude

  • Grab the dScope Kowalski!
  • Able Bodied Sailor
  • Pirate
  • ***
  • Brownie Points: +206/-4
  • Offline Offline
  • Posts: 907
  • No can do skipper, the dScope was terminated
    • DIY-Audio-Heaven
Re: planars and output impedance/damping factor?
« Reply #10 on: September 11, 2015, 04:39:54 AM »
In a voice coil there is also inductance which is not negligible and is 'active' in the end of the audible range.
That makes the current frequency dependent as well.
It can also generate currents when it moves inside a magnetic field.

The PM1 driver traces are more like a real coil than most other ortho's which are mostly lines with corners near the egdes.

The impedance varies because the coil is not just a coil but it moves inside an electrical field and generates its own power when the movement is faster (due to resonance) than as dictated by the applied voltage. Less energy (current) is needed at the same voltage. less current at the same voltage = higher resistance.

Is that what you mean ?

Logged
Use your ears to enjoy music, not as an analyser.

Xen

  • Powder Monkey
  • *
  • Brownie Points: +13/-1
  • Offline Offline
  • Posts: 83
Re: planars and output impedance/damping factor?
« Reply #11 on: September 11, 2015, 10:19:34 AM »
Quote from: Armaegis on September 10, 2015, 06:57:33 PM
- electricity is not this instantaneous thing, electrons have to move, there is a mass and momentum there
... particle-wave/energy duality, let's treat it like particles
Those with EE backgrounds will know better, but I see electricity as a manifestation of the electric field, which is instantaneous at all reasonable sized loops (maybe instant for all sized loops?). In a model perfect DC resistance circuit, current either flows in accordance with V=IR or its zero. What adds time dependence is inductance and capacitance, which occurs in pretty much any circuit in real life to some extent.

Since voltage is like a "field" of work, it might also be considered instantaneous since it is based on the electric field.

Quote from: Armaegis on September 10, 2015, 06:57:33 PM
- everything has momentum, electrons have momentum, but momentum is this weird mathematical concept because it's not actually a real thing (unlike energy) but the mathematical construct manages to remain constant
Pretty sure the momentum (inertia) of the moving parts FAR FAR FAR outweigh, by orders of magnitude, any momentum of the electricity.

Back EMF is a bitch...
Logged

Solderdude

  • Grab the dScope Kowalski!
  • Able Bodied Sailor
  • Pirate
  • ***
  • Brownie Points: +206/-4
  • Offline Offline
  • Posts: 907
  • No can do skipper, the dScope was terminated
    • DIY-Audio-Heaven
Re: planars and output impedance/damping factor?
« Reply #12 on: September 11, 2015, 10:57:59 AM »
Quote from: Xen on September 11, 2015, 10:19:34 AM
Pretty sure the momentum (inertia) of the moving parts FAR FAR FAR outweigh, by orders of magnitude, any momentum of the electricity.

moving parts is up to 50kHz maximum where electricity can do >100GHz
DC to 50,000 Hz / > 100,000,000,000  no comparison.

Rather than viewing electrons to flow like liquids see them as marbles (that have no mass) in a large diameter pipe.
Push in 10 marbles at one end and to drop out at the other end.
Propagation is between 150,000km/sec and 300,000km/sec.

All components are far from perfect and have inductances, capacitances (opposite other wires/planes), resistances, non linear behaviour, efficiencies and pass though or fall over bandwidth limited components.
It's these practical limitations that are important, not so much the electrons or how they flow.
All electrical components are very 'complex' parts, even a piece of wire or a resistance.




Logged
Use your ears to enjoy music, not as an analyser.

Andre Y

  • Swabbie
  • Brownie Points: +1/-0
  • Offline Offline
  • Posts: 5
Re: planars and output impedance/damping factor?
« Reply #13 on: September 11, 2015, 07:08:22 PM »
Quote from: Xen on September 11, 2015, 10:19:34 AM
but I see electricity as a manifestation of the electric field, which is instantaneous at all reasonable sized loops (maybe instant for all sized loops?).

Another way to think about it is to consider the wavelengths of the electrical signals involved, and the length of the devices or wires those signals are moving over. As Solderdude points out, currents move so fast through conductors that its effect at the frequencies we're using (<100kHz) is basically instantaneous. Speed of light = 3e8 m/sec (and signals move well over 90% of that in wires), and our 20 kHz signal has a wavelength of 3e8/2e4 = 1.5e4 meters. 15 kilometers or 9 miles. A 3 foot interconnect or a 6-inch PCB trace is essentially point-like by comparison.

But this is not to say that there is no effect. Lots of lumped-parameter (as this model is known where we assume everything happens instantaneously) effects still abound and can mess things up. Back EMF, finite output impedance, change impedance with levels and heat, etc. Transducers are severely non-linear and their lumped-parameter models change if you look at them funny.
Logged

Xen

  • Powder Monkey
  • *
  • Brownie Points: +13/-1
  • Offline Offline
  • Posts: 83
Re: planars and output impedance/damping factor?
« Reply #14 on: September 12, 2015, 01:21:15 PM »
Quote from: Solderdude on September 11, 2015, 10:57:59 AM
Rather than viewing electrons to flow like liquids see them as marbles (that have no mass) in a large diameter pipe.
Push in 10 marbles at one end and to drop out at the other end.
Fluid flow is a pretty good analogy. I use it all the time in describing voltage (a "pressure" that can do work).

Drift velocity of electrons ... that throws a wrench into that analogy. Electrons drift about 1-10 milimeters/s (probably still off by a factor 10). The marble flow model is good to see why current starts to flow in all connected areas of a circuit, but doesn't quite get to the amount of current that will flow.

Quote from: Andre Y on September 11, 2015, 07:08:22 PM
Another way to think about it is to consider the wavelengths of the electrical signals involved, and the length of the devices or wires those signals are moving over. As Solderdude points out, currents move so fast through conductors that its effect at the frequencies.
Never thought about applying wave frequency to electricity  facepalm  seems so obvious now!

EDIT: Rephrased some of the above to make it sound like I intended - informative instead of corrective.
Logged

Solderdude

  • Grab the dScope Kowalski!
  • Able Bodied Sailor
  • Pirate
  • ***
  • Brownie Points: +206/-4
  • Offline Offline
  • Posts: 907
  • No can do skipper, the dScope was terminated
    • DIY-Audio-Heaven
Re: planars and output impedance/damping factor?
« Reply #15 on: September 12, 2015, 04:19:36 PM »
Fluid flow IS a good analogy for electrical current but NOT for describing what electrons do.
That's why I mentioned electrons and 'marbles' as a better analogy as that's how the electrons 'work'.

Logged
Use your ears to enjoy music, not as an analyser.
Pages: 1 [2]
« previous next »