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RE: You local dudes have completely run out of ammo. So sad. Maybe take up macrame.

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In Reply to: RE: You local dudes have completely run out of ammo. So sad. Maybe take up macrame. posted by Geoffkait on May 11, 2025 at 04:32:47

Music could be the signal or noise or what ever but what the signal is supposed to be or starts as is a Voltage / time representation of the acoustic pressure from a microphone.
From there and through every stage of electronics, it is a Voltage signal and that's a key thing, it is NOT a power signal and is why an ideal amplifier puts out x in = X Voltage out independent of an open circuit load or low impedance.

The simple case woofer, the cone only moves and produces sound if there is a force applied. While the audio or test signal is Voltage referenced, the motor produces force proportional to the current in the wire and the direction according to polarity.
If this was an electrostatic speaker, the force is electrostatic and so is proportional to Voltage itself and a step-up transformer is usually used to supply the higher drive V they need.

Follow Ups:

RE: You local dudes have completely run out of ammo. So sad. Maybe take up macrame. - Geoffkait 10:49:43 05/11/25 (2)
Voltage is a characteristic of the signal, but it's not the signal - it's the power or strength of the signal. And the same for current, voltage and current are both calculated quantities. Have you looked at the magnetic b or electric e fields?
- RE: You local dudes have completely run out of ammo. So sad. Maybe take up macrame. - tomservo 11:39:19 05/11/25 (1)
  I would disagree, starting at the microphone, it proportionally turns pressure into a Voltage representation of that pressure. While sound power is the sum of pressure and velocity, it is pressure our ears detect.
  
  Every stage of the electronic chain, amplifies or modifies the Voltage signal and the gain is in dB Voltage ref. The final stage, the audio power amplifier is also normally a Voltage amplifier with X dB of Voltage gain and has an output impedance (damping factor) that is a small fraction of the load impedance so that the Voltage does not depend on or change with different output impedances.
  
  The sealed box woofer i described is meant to be Voltage driven however, if one examines the load impedance, one sees that although the response to the input Voltage may also be flat (ideally), the power delivered due to the impedance changes a GREAT DEAL from the impedance peak at the low corner to the hf roll off to Rmin. The output is ideally flat compared to the input Voltage, the power delivered to do this changes a lot.
  
  Yes, B is a key element, the BL in a driver spec is the force per amp i mentioned it can also be stated the Magnetic field strength in Tesla (B) in the gap and the (L) length of wire in that gap in meters.
  
  Here is a way to picture what happens inside a woofer, examine a DC motor.
  So you have a simple pm dc motor, it has a DC resistance of say 1 Ohm and has no load on it.
  
  You have a battery and a switch connected and can monitor current and motor speed.
  The instant you close the switch, the motor is not moving and so, has no back emf. As a load it looks like 1 Ohm and so with say a 12V battery, 12 amps of current will flow through the winding.
  
  That current produces a force that starts the motor moving. As soon as the motor moves and accelerates, it produces a Voltage and this Voltage cancels out some of the input voltage so the current flowing is less and the rate of acceleration slows. This continues until the motor stops accelerating and is at "top speed" for that Voltage. Now the motor back emf is nearly equal to 12V and the only current flowing is the small amount needed to overcome the rotating static friction and windage friction inside the motor.
  
  When you put a load on the motor, it slows but then the back emf V falls which then increases the current flowing and the force the motor is producing fighting the reduction in speed.
  - RE: You local dudes have completely run out of ammo. So sad. Maybe take up macrame. - Geoffkait 15:17:25 05/11/25 (0)
    As I stated I'm only interested in the "audio signal" in the playback system, excluding acoustic waves in the room. As I also commented current and voltage are both characteristics of the signal but not the signal. Therefore, the signal the audio signal must be something else. Hint, it's all about the electrons.

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