ModRob wrote:s...I don't have tech stuff like scopes and such (hmmm...wish I did though), other than a DMM, and again, at my age, my learning of ohms and impedances is troubling.
- Any modern DMM has high enough impedance and bandwidth to accurately measure audio amplitude. Just read the audio level with your DMM in AC low scale if you have no oscilloscope. Apply a sinewave 1KHz or play a standard CD with the tone, or record your own CD with several minutes of standard tones.
Audio readings will be in Volts RMS as should, instead of f%#$@&* decibels. An oscilloscope would show peak and peak-to-peak amplitudes in Volts as should, instead of f%#$@&* decibels.
- About impedance matching :
Form a cotton ball; throw it as far as you can; it will land about 4 feet away.
Make a paper ball; throw it as far as you can; it will land about 25 feet away.
Throw a tennis ball as far as you can; it will land about 100 feet away.
Throw a golf ball as far as you can; it will land about 150 feet away.
Throw a baseball as far as you can; it will land about 200 feet away.
Throw a football as far as you can; it will land about 120 feet away
Throw a basketball as far as you can; it will land about 80 feet away.
Throw a bowlingball as far as you can, it will land about 15 feet away.
Throw a lead demolition ball as far as you can, watch your feet.
Now, have the same test done with a seven year old kid:
Distances reached will diminish accordingly to the strenght of the kid.-
What is going on ?
It is not the lightest nor the heaviest the one that got the farthest away.
It is not the lightest nor the heaviest the one that used up the full strenght
CAPABILITY of the arm muscles.
It is the one that MATCHES the arm strenght. There is one object
that flew the farthest for each person... you ; the kid.
When an audio amplifier drives a speaker or a
subsequent load, there will be an optimum FORCE -TO- LOAD ratio
=(ARM -TO- BALL) that will deliver the most POWER.
That load will not be a tiny nor a huge one.
A rated output is the capability of a certain device AT a given
impedance load.
Unmatched driver-to-driven does NOT mean that there will be no action.
Your 400 watt stereo will burn yours ears off at full volume knob through
headphones but will be delivering only a couple of watts power, not
the 400 rated watts... because your headphones impedance is 600 ohms
instead of the at-rated 4 ohms... it is like the grown up throwing the paper ball.
As mismatch extremes, it is possible to push a ship by swimming,
or use a bulldozer to tow a bicycle.
Miguel