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What are Ohms?

post #1 of 9
Thread Starter 

Title says it all, probably a newby question, but I have noticed there are different Ohm versions of headphones and such and I was wondering...

 

What are the differences of these headphones and what do higher/lower Ohms do for listening experience?

post #2 of 9

Ohms is the electrical resistance.

 

Usually (big over generalisation) headphones with more ohms have more coils in their voice coils.

Also they are usually (not always true) harder to drive than headphones with less resistance.

 

The reason they are not always harder to drive is that the simple fact that each driver is designed differently means that some have a higher sensitivity to electricity and are louder than others when fed the same signal. This means they are more efficient.

 

Usually high/low ohms will only change your listening experience if you do not have an amplifier strong enough to power a hungry/insensitive headphone.

post #3 of 9

There is no correlation between impedance and sound quality.

post #4 of 9
GREQ got it. Impedance is a factor, but how much electrical power gets turned into audio power is going to be a bigger factor.

To elaborate on Ohms, and why models have different impedance values, your driver turns electrical power into audible sound using magnetic forces. Current flows through a coil, which moves a magnet, which is connected to a diaphragm, which pushes air around (making sound).

Now you can get the desired magnetic field strength by either increasing the current or using more turns of wire. You can change how much current passes through the driver by increasing or decreasing the size of the wire. Larger diameter wire = lower resistance (fewer Ohms). Impedance won't directly translate to better or worse sound quality, but it is the result of the driver's design.

This explanation might not have been necessary, but there seem to be a lot of impedance and Ohm questions around here lately.
post #5 of 9
Quote:
Originally Posted by superjawes View Post

This explanation might not have been necessary, but there seem to be a lot of impedance and Ohm questions around here lately.

I enjoyed reading your extra info. The battle out of ones ignorance is all too often a courageous effort in a community which often labels it a sin. 

post #6 of 9

In DC circuits Ohms is a measurement of resistance.

In AC circuits (as we have in headphones and amps) Ohms is a measurement of impedance.

 

I see this mistake made a lot (and I am guilty of it too)... Inpedance is NOT the same as resistance.  More specifically, Impedance varies with frequency of the AC wave being produced.  So when you read a spec sheet that says the HD650 (for example) is a 300 ohm headphone, thats not entirely true.  At its lowest point in the FR it measures 300 Ohms, everywhere else its impedance curve it is ~2.5-3 times that.

 

This is partially why headphone + synergy is not black and white kind of thing.

post #7 of 9

Kind of an easy to mistake to make since to "resist" and "impede" have almost the same meaning.

post #8 of 9
I think one way to think of it is squares and rectangles:

A square is a rectangle, but a rectangle isn't necessarily a square.
Resistance is a form of impedance, but impedance isn't necessasrily resistive.

Resistance in the same value at all frequencies, so it always "impedes" the current in the same way. Capacitors look like open circuits in DC (infinite Ohms), but they have charging times, so as you increase frequency, impedance goes down. At "infinite" frequencies, capacitors look like short circuits. Inductors are like the opposite of capacitors. They look like short circuits in DC (since they're basically coils of copper wire), but impedance rises with frequency.

So impedance as a whole is partially resistive and partially reactive, so you can express impedance as Z = R + X * j, where "Z" is impedance, "R" is resistance, "X" is reactance, and "j" is sqrt(-1), indicating the imaginary component. (Side note: we use "j" instead of "i" because "i" and "I" are used for current...too many repeated letters!) If you know the resistance, inductance, and capacitance of a given circuit, you can take the magnitud of Z at a given frequency and get Ohms for impedance.
post #9 of 9

I wish my brain was bigger :D

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