How is wattage distributed?

[Bones]

for example: if i have a speaker that can handle 100 watts and a speaker that can handle 200 watts and i hook them up in parallell to and amplifier supplying 300 watts would the power be equally distributed, or would the speakers only take the necissary power?

[Gregory East]

The power goes by some fancy fractions I forgot. Google Faraday I think.

A lot easier if the speakers have the same resistance (ohms). Then they get the same power until the low power one starts to overheat, then the other one will get a bit more but the wee one will get killed.

If they aren't then the juice mainly goes to the low impedance driver as a result of the fancy fractions.

[Gregory East]

1/(system R)= 1/r1 +1/r2 etc
Then you can work out the power. So I'm starting to remember it's proportional to the inverse squares of the resistances. Gonna be late for work.

[Bill Fitzmaurice]

1/(system R)= 1/r1 +1/r2 etc
Then you can work out the power. So I'm starting to remember it's proportional to the inverse squares of the resistances. Gonna be late for work.

Impedance, not resistance,

[Gregory East]

Potato-potato? What's the difference?

At least it sounds like I remember the maths right.

[Bill Fitzmaurice]

Potato-potato? What's the difference?

The difference between resistance and impedance is huge, the only thing they have in common is that both are measured in ohms.

[Bones]

Potato-potato? What's the difference?

The difference between resistance and impedance is huge, the only thing they have in common is that both are measured in ohms.

i also thought it was the same thing...
so does anyone have a clear answer?

[SoundInMotionDJ]

For DC resistance and impedance are the same. The resistance is a way of relating the amplitude of current and voltage that is passing through the circuit.

For AC, both the amplitude and phase of the current and voltage are described by the impedance. The math involves complex numbers, and is not trivial. This is typically the stuff of a 2nd year electrical engineering course.

http://en.wikipedia.org/wiki/Electrical_impedance

[Gregory East]

Theile / Small parameters are an extension of all that maths that describes the way a speaker moves air converted into terms of electric current. All very clever and way over my head.

At least ohms are ohms and a/c or d/c they still work to figure power.

[Sydney]

Resistance is a scalar quantity, Impedance is a vector quantity. Like other calculations in physics it involves force and direction over time.
It can be calculated in several ways including Pythagorean Theorem.

See:
Physics for you By Keith Johnson ( page 96 )
Advanced Physics for You By Keith Johnson, Simmone Hewett, Sue Holt, John Miller
( page 10 )
Basic AC circuits By John Clayton Rawlins, Stanley R. Fulton ( page 240 )

Also sections on Physics and Electronics @:
http://101science.com/

[Gregory East]

Look who's off the bench!

I googled page 96 of that book and get a quiz on Boyle's Law. P proportional V.T, I remember that from highschool. Wrong edition methinks.

[Ron K]

I think more relevant to the discussion of Impedance as it applies to power distribution in loudspeaker design would be the basic effects frequency, and any additional load that designs force upon the driver, heat and other factors as well.

ie: in most transducers impedance rises at some point near the resonance frequency of the driver and also at any port frequency as well lowering the power dissipated by the driver at those points.

Effects from the air load; as the horn can also add impedance to the driver.

Effects from added heat over time

Those are probably why most prefer the term Impedance as opposed to Resistance when it comes to talking about loudspeakers although the two are commonly used in each others place.

[Gregory East]

Feel free to expand. I've been going through Sydney's links and not getting any wiser.

[Sydney]

Read this exchange:
http://www.newton.dep.anl.gov/askasci/p ... y00367.htm
and we will take it from there.
Think of the difference of force on a weight vs a spring.

[Ron K]

Probably the easiest way is to post a graph showing the effects of frequency on impedance right from the driver manufacturer.



Note the Grey line. That's the impedance curve.Note how it rises as the frequency goes lower towards the resonance frequency in this case that's 51 Hz. Also notice since its a base driver or low mid driver in a two way system as the frequency rises to the high frequency cutoff point of the voice coil the impedance rises yet again.

Now if you would add air load to the driver such as a horn load does then the impedance across the usable frequency range will rise yet again.

If you add a port into the design you would notice two impedance spike at the lower end 1 at resonance and one at the port.



Here the port is tuned to 150hz ( give or take a few Hz) to bring about a Fb or Box frequency of 95 Hz and the frequency response 3 db down @ 86 Hz. Notice the impedance spike at 150Hz!

In a broad sense power is distributed differently at different frequencies as impedance changes. The 4-8 ohm ratings are nominal ratings and used primarily for simple reference only.It's not truly indicative of whats really happening but far less complicated!

Add heat or change air density and things change yet again!