Trying to understand impedance

[bigguyca]

It is exactly proportional. 300 to 16 is a current increase of 300/16 = 18.75 times greater. 8 to 4 is 2 times greater.

Ohm's Law is Z (impedance) = V (voltage)/I (current). The math is pretty simple.

This of course is nonsense. Ohm's Law in this form is R = V / I, where "R" is resistance.

Impedance includes both resistance and reactance and varies with frequency.

As a "Technical Expert" with tens of thousands of posts, you really should understand these very basic concepts and use them correctly in your posts. Others who lack a basic technical background may read your posts and internalize incorrect information and concepts. Two people already "liked" your post which is sad.

 

[JustAnAudioLover]

This of course is nonsense. Ohm's Law in this form is R = V / I, where "R" is resistance.

Impedance includes both resistance and reactance and varies with frequency.

As a "Technical Expert" with tens of thousands of posts, you really should understand these very basic concepts and use them correctly in your posts. Others who lack a basic technical background may read your posts and internalize incorrect information and concepts. Two people already "liked" your post which is sad.

I don't think it's that important, given that "Z" seems to appear in some other forms of Ohm's laws, like V = Z * I

(from Wikipedia: We can now write

where V and I are the complex scalars in the voltage and current respectively and Z is the complex impedance.)

Also letters don't matter that much, it's better to use standards but the formula is still correct especially given the explanation of all letters was given in the comment

 

[Cbdb2]

Well technically shouldn't speaker amplifiers be able to drive any headphone? Just put the amplifier's master volume at super low levels and it'll work fine! Right?

Or a dozen of any HPs. This is what many recording studios use to use to drive large numbers of HPs.

 

[SIY]

This of course is nonsense.

I'm sorry you're confused by generalizing Ohm's Law to AC. Nonetheless, it still holds.

I'm afraid to mention the most general version, J=σE, with bolding indicating vector quantities. Nonetheless, if you're interested in improving your understanding but aren't ready to be tortured by Jackson, I highly recommend David Griffiths's "Introduction to Electrodynamics."

 

[Cbdb2]

This of course is nonsense. Ohm's Law in this form is R = V / I, where "R" is resistance.

Impedance includes both resistance and reactance and varies with frequency.

As a "Technical Expert" with tens of thousands of posts, you really should understand these very basic concepts and use them correctly in your posts. Others who lack a basic technical background may read your posts and internalize incorrect information and concepts. Two people already "liked" your post which is sad.

Pretty clear here. Seen it written that simply in many EE texts. V and I can be complex or not, he did not actually have to write V=Acos(wt+Phase), which might confuse newbees more than clarify.

 

[antcollinet]

Ok so my first impression was right, but then does that mean most headphone amplifiers can just accommodate a 18x current increase going from 300 to 16 Ohms? And if so, why can't speaker amplifiers do the same?
Sorry if these seem like dumb questions but I have a hard time wrapping my head aroudn it...

I suspect:

Headphone amps might be voltage limited. You can put more power into a low impedance with the same voltage

P = V^2/R
P is also = I^2 * R

So with a 300ohm headphone you need 4.33 times more volts to get the same power compared to 16 ohm.

Speaker amps on the other hand are normally current limited - especially at 4ohm load. You need 1.41 times as much current into 4ohm for the same power.