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- Thread starter Disco-Pete
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The higher the impedance, the lower the current. i = v/R

Most ss amps are designed as a voltage source, so the output voltage

is independent of the load. Not so for the current. Reactive loads are

even more difficult, since current peaks can be several times higher

than would otherwise be expected with resistive load.

Most ss amps are designed as a voltage source, so the output voltage

is independent of the load. Not so for the current. Reactive loads are

even more difficult, since current peaks can be several times higher

than would otherwise be expected with resistive load.

Last edited:

So how does the speaker impede the current?To put it simply, a 2 ohm load comes closer to being a direct short than an 8 ohm load.

Just imagine how much your amp would struggle if asked to push current through its shorted speaker terminals!

So how does the speaker impede the current?

Most transducers impedance curve will be mounting situation dependant, current looks be the reverse of that executed impendance curve, in below free Xsim helped model curves.

I have to assume we are going back to basics here, so I hope the following may be of assistance.So how does the speaker impede the current?

A deeper explanation may be found here: Loudspeaker Impedance - Stetron

The opposition of a loudspeaker to alternating current is not simply due to

At certain frequencies a loudspeaker behaves like an inductor or a capacitor.

This introduces additional opposition, called

The total opposition to alternating current is called

Impedance (Z) is a complicated sum of resistance (R), inductive reactance (Xl) and capacitive reactance (Xc).

Although resistance does not vary with frequency reactance does, which results in the typical impedance versus frequency graph shown in the attachment.

You are right in the sense that the amp has to produce a higher output voltage to transfer power to a higher impedance speaker. Maybe we should be talking about speaker efficiency. The more efficient the less power the amp has to transfer for the same sound level. So a high efficiency speaker is literally an easier load for an amplifier for the same sound level.Okay so how/why is a high impedance speaker an easy load for a ss amp? The higher the impedance the lower the output. Seems counter intuitive.

Another aspect is the impact on the stability or other electrical behaviour of the amplifier circuit with different impedance loads. Using very low Z speakers, like less than 3 or 4 ohms, can cause problems with some designs even if the power transfer is low.

You are are definitely not making an *** of you and me hereI have to assume we are going back to basics here, so I hope the following may be of assistance.

A deeper explanation may be found here: Loudspeaker Impedance - Stetron

The opposition of a loudspeaker to alternating current is not simply due toresistance.

At certain frequencies a loudspeaker behaves like an inductor or a capacitor.

This introduces additional opposition, calledreactance.

The total opposition to alternating current is calledimpedanceand is measured in ohms.

Impedance (Z) is a complicated sum of resistance (R), inductive reactance (Xl) and capacitive reactance (Xc).

Although resistance does not vary with frequency reactance does, which results in the typical impedance versus frequency graph shown in the attachment.

Thanks for the explanation and link

Thanks for the feedback.Thanks for the explanation and link

I wasn't sure where to pitch it - there's such a lot of physics involved!

The higher the impedance the lower the output.

???

The higher the impedance the lower the mass / charge / current / weight.

The higher the impedance of an object (speaker), the smaller is the current in that object (speaker).

It takes less force to move a lighter object.

Currents do not flow.

Currents do not return.

Currents do not go anywhere.

Currents do not drive currents.

Currents do not drive voltages.

Currents do not drive anything.

Currents cannot be sensed.

Currents cannot be sourced.

Currents cannot be dumped.

Currents cannot be fed back.

Eternal loving Providence shines forth resplendent

Bringing deliverance to all.

Such a miraculous spectacle.

But they do undulate

Currents do not flow.

Currents do not return.

Currents do not go anywhere.

Currents do not drive currents.

Currents do not drive voltages.

Currents do not drive anything.

Currents cannot be sensed.

Currents cannot be sourced.

Currents cannot be dumped.

Currents cannot be fed back.

Eternal loving Providence shines forth resplendent

Bringing deliverance to all.

Such a miraculous spectacle.

The total opposition to alternating current is calledimpedanceand is measured in ohms.

Impedance (Z) is a complicated sum of resistance (R), inductive reactance (Xl) and capacitive reactance (Xc).

Square root of (R squared+(XL squared - XC squared))

.

Impedance lesson

Okay so how/why is a high impedance speaker an easy load for a ss amp? The higher the impedance the lower the output. Seems counter intuitive.

Quite the contrary.

1) ss amps in general are quite good (near to perfect) voltage sources

So much so that they will put out almost same voltage from rated impedance load to no load (infinite impedance) , go figure.

2) power out is V^2/impedance or V^2/Z

3) amp dissipation is a fraction of output power

so when, say, Z is doubled:

4) power is halved

5) dissipation is halved.

Which by definition is easier on the amplifier.

as a side note, components have maximum current limits, but no minimum current ones, so:

6) doubling Z halves current, putting devices used further away from a maximum limit.

What of the above you find counter-intuitive?

Please feel free to express yourself.

We do need a tight grip on Ohm's Law.

I have a power line to my house. Rated 240V, 100A max.

Say I know the "ohms" of all my appliances. (And say all my appliances are 240V.)

A 60W light-bulb is 240V 0.25A. (240V*0.25A is 60 Watts.) Its resistance is 960 Ohms. (Hot; nevermind the part-instant while it is cold.)

The toaster is say 240V 5A, 1,200 Watts, 48 Ohms.

The dryer is 240V 20A, 4,800 Watts, 12 Ohms.

The water-heater of my dreams is 240V 60A, 14,400 Watts, 4 Ohms. (mine is really 1/3rd this power.)

Which is the "easy" load for my power line? (And my power Bill!)

The light-bulb is easy, the power line has "no" heat", I can afford to leave the lamp on all month. (7 bucks.)

If I ran the monster water heater and two dryers, I'd hit 100 Amps. The wire is literally rated 95 Amps (in warmer states) and would run warm at that load. The electric bill for a month-straight of that would be $2,700 (gasp!).

So the 960 Ohm lamp is "easy", the 4 Ohm heater is "hard" (and heater+2dryers, 2.4 Ohms, is ridiculous).

The flip-side is that the 60 Watt 960 Ohm lamp will not warm the house enough to notice. Not getting a lot of work done. Whereas running 4 or 2.4 ohms of loads will cook the house very quickly! (It's twice the power of my whole-house gas burner.)

Citation needed.

However I met a passage in fiction which weaves electricity through Christian dogma.

Seven Day's Wonder, by Edward Wellen

The Magazine of Fantasy and Science Fiction, March 1963

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