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Impedance/sensitivity/efficiency/gain?

post #1 of 12
12/16/12 at 10:48pm
Thread Starter 

Hey guys, I was wondering about the difference between all of these terms.

 

I used to think that low impedance= easy to drive/high sensitivity/efficiency 

 

I've also seen gain settings on many amps/specs for phones w/ the greater gain having a wider frequency range.

 

Could someone care to explain in relatively straightforward way? An answer would be appreciated

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post #2 of 12
12/16/12 at 11:16pm

Take a look at this first, see what you can grasp: http://www.head-fi.org/t/607282/headphone-amp-impedance-matching-basics-you-need-to-know

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post #3 of 12
12/17/12 at 3:56pm
Thread Starter 

So the higher the ohm rating for phones, the more Vrms (power/voltage). So, impedance from how I understand is the resistance to the current, which the higher the resistance, the less current/power it's willing to take (made sense for batteries). But because of that, not enough power/current/voltage can get to the drivers and will not produce the sound needed. 

Lower impedance= accepts more voltage/current/power and can be run more easily since power is free to go to the drivers without much resistance. That'd presumably drain the battery faster? But this explains that if you plug a low impedance (say z1000 into a Dark Star amp, you'd mess up the diaphragm.

 

So the way amps work with higher rated phones, is that the force in more current? Not sure about nominal vs max still. SPL/ mW would translate into efficiency I think (amount of noise created from amount of power)?  

 

I'm still not sure how gain works exactly, and when I went to the links provided a lot of stuff just shot me. It was like omgwhatjusthappenedbbq^2. I could sort of understand the part where you calculated power needed (have yet to try that out since I'm still cramming for finals). 

 

But thanks a bunch man, you helped me learn/answer some questions!

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post #4 of 12
12/17/12 at 5:31pm
Quote:
Originally Posted by MrViolin View Post

I'm still not sure how gain works exactly.

 

 

The gain is just a multiplier figure, its a more technical term for 'amplification'. Gain tells you by what factor has the input been multiplied to be received at output.

 

Quote:
Originally Posted by MrViolin View Post

 

So the way amps work with higher rated phones, is that the force in more current? Not sure about nominal vs max still. 

 

Amps provide a potential (voltage), the current is decided by the headphone, based on its impedance. And nominal impedance is like 'mostly this impedance', while max. means 'maximum throughout the frequency spectrum'. I added a graph in the main article.

 

Quote:
Originally Posted by MrViolin View Post


Lower impedance= accepts more voltage/current/power and can be run more easily since power is free to go to the drivers without much resistance. That'd presumably drain the battery faster? But this explains that if you plug a low impedance (say z1000 into a Dark Star amp, you'd mess up the diaphragm.

 

Yes, a low impedance headphone will readily allow more current if you increase the voltage.

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post #5 of 12
12/17/12 at 5:39pm
Thread Starter 

And as for the gain multiplying the output, does it also affect the frequency range? I've seen a ton of specs with higher gain= more frequency response. Thanks a bunch for clearing up a lot of things proton! Have you heard a proton joke?:D 

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post #6 of 12
12/17/12 at 6:07pm
Quote:
Originally Posted by MrViolin View Post

 Thanks a bunch for clearing up a lot of things proton! Have you heard a proton joke?:D 

 

No problem. And I'm positive I heard the joke wink.gif

 

Quote:
Originally Posted by MrViolin View Post

And as for the gain multiplying the output, does it also affect the frequency range? I've seen a ton of specs with higher gain= more frequency response.

 

 

Increasing gain increases voltage, meaning its possible if some parts of the frequency were not getting enough power (due to high impedance etc), they'll do so. I think there's a link in the article, how impedance affects sound.

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post #7 of 12
12/17/12 at 6:20pm
Thread Starter 
Quote:
Originally Posted by proton007 View Post

 

Increasing gain increases voltage, meaning its possible if some parts of the frequency were not getting enough power (due to high impedance etc), they'll do so. I think there's a link in the article, how impedance affects sound.

Oh, it makes sense now. I'll read the links during this break. Thanks a bunch proton!

 

Edit: A question popped up in my mind, but I can't recall it right away, so is it ok if I ask you when it comes back?


Edited by MrViolin - 12/17/12 at 6:38pm
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post #8 of 12
12/17/12 at 6:59pm
Quote:
Originally Posted by MrViolin View Post

Oh, it makes sense now. I'll read the links during this break. Thanks a bunch proton!

 

Edit: A question popped up in my mind, but I can't recall it right away, so is it ok if I ask you when it comes back?


Just post it here, someone will respond.

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post #9 of 12
12/17/12 at 7:08pm
Thread Starter 

I don't think that this was the question that I intended to ask, but what is total harmonic distortion? Will a DAC/amp w/ less THD generally perform better?

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post #10 of 12
12/17/12 at 9:02pm

 

Quote:

Originally Posted by MrViolin View Post

I don't think that this was the question that I intended to ask, but what is total harmonic distortion? Will a DAC/amp w/ less THD generally perform better?

 

THD is ratio of power of total amount of harmonic distortion vs power of fundamental frequency.

I think you should read up on harmonic distortion first. Typically, the most common real world example is the guitar amplifier (and its also the most extreme). The distorted guitar sound comes from harmonic distortion.

This seems to work well for guitars as a single instrument, but you don't want something like this happening with your songs because firstly, there are a lot of instruments in a song which means all these distortions add up, and secondly, the purpose of (most of) the audio equipment is to reproduce the sound as accurately as possible.

 

So low(er) THD generally means true(r) to the source. Whether low THD in amps is desirable is debatable, some like the warm sound that tubes produce because of small amounts of harmonic distortion.

A common measurement used is THD+N, with an added Noise component. 


Edited by proton007 - 12/17/12 at 9:06pm
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post #11 of 12
12/18/12 at 3:44pm
Thread Starter 

Appreciate it proton! Embedded sound tech... that is secretly a physicist... 

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post #12 of 12
12/18/12 at 5:41pm
Quote:
Originally Posted by MrViolin View Post

Appreciate it proton! Embedded sound tech... that is secretly a physicist... 


I'm not really a sound tech, but thanks.

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