[sarathcpt]

Power transfer theorem and impedance matching is valid for any electrical circuit which is terminated in a load. The load could be anything which draws power from the source even another amplifier. Agreed reflection losses are not significant here..but there could be thermal power dissipation in the source.

Here is a more detailed account :

Maximum power theorem - Wikipedia, the free encyclopedia


Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif Dude, we're talking about headphones here, not transmission lines. The most efficient transfer of power over a transmission line occurs when the source and load impedances are matched because then you're not losing power due to reflection losses. Reflection losses are only an issue when the length of the line is on the order of the electrical wavelengths of the signal you're sending down the line. But again, we're talking about headphones here. The shortest electrical wavelengths at audio frequencies are MILES long! Transmission line theory just doesn't apply in this situation and invoking it only serves to cause more confusion and erroneous assumptions. se

 

[prone2phone]

is it a real problem of impedance matching? if there is too litle power transfering you just crank the volume up, my grandma said

 

[Steve Eddy]

Quote:

Originally Posted by sarathcpt /img/forum/go_quote.gif Power transfer theorem and impedance matching is valid for any electrical circuit which is terminated in a load.

Yes, for a given source of a given output impedance, you'll be able extract maximum power from it when the load impedance is equal to the source's output impedance.

I assumed, perhaps erroneously in hindsight, that he was referring to the efficiency of power transfer which led me to believe he was referring to impedance matching in the context of transmission line theory.

se

 

[Steve Eddy]

Quote:

Originally Posted by prone2phone /img/forum/go_quote.gif is it a real problem of impedance matching? if there is too litle power transfering you just crank the volume up, my grandma said

Yeah, but what if your amps don't go to "11"?

se

 

[JaZZ]

Koyaan is right: 0 ohm output impedance is the best «impedance match» for all dynamic headphones, as far as power transfer goes. And 95% of the dynamic headphones sound best at low output impedances.
.

 

[MomijiTMO]

Good reading so far. I ran out of counter arguments due to a lack of knowledge and experience in the dt880 thread. Interested in the entire dt880 600ohm thread debating their findings.

 

[aimlink]

Quote:

Originally Posted by Koyaan I. Sqatsi /img/forum/go_quote.gif But now the output impedance of the source is burning up as much power as is being delivered to the headphone. And in order to deliver the same power to the headphone as from the zero impedance source, the "matched" source has to produce twice the power. se

Hence the use of low impedance output amps with high impedance cans in the pro setting where multiple cans are plugged into the same source?

 

[eneloquent]

I've read through this thread, and I think I'm more confused than when I started. I even read through this to try and clear things up;
Understanding Impedance
And while I think I grasp the theory, the application still escapes me.

Here's my example;
I'm using the new FOTM: Nuforce.com | Icon uDAC
The output is listed as;
Power output: 80mW x 2 @ 16-Ohm

Now, I'm considering getting a pair of DT770s to see how they compare to my HD580s (300ohms.) I've looked at the 80ohm and 250ohm models.

Given the amp I'm using, which would be the better choice? The lower or higher impedance version?

 

[aimlink]

Perhaps what we need to understand is that impedance issue isn't really all that important when using headphones in our homes? This is my take on it, especially since there's a lot of backing and forthing about it. The only time I see where it does matter is when you're using multiple cans in parallel from the same source. But again, I may be wrong.

 

[Helmore]

Quote:

Originally Posted by eneloquent /img/forum/go_quote.gif I've read through this thread, and I think I'm more confused than when I started. I even read through this to try and clear things up; Understanding Impedance And while I think I grasp the theory, the application still escapes me. Here's my example; I'm using the new FOTM: Nuforce.com | Icon uDAC The output is listed as; Power output: 80mW x 2 @ 16-Ohm Now, I'm considering getting a pair of DT770s to see how they compare to my HD580s (300ohms.) I've looked at the 80ohm and 250ohm models. Given the amp I'm using, which would be the better choice? The lower or higher impedance version?

I think you should decide that based on their sound signatures. From what I gathered they sound quite different. I'm not talking from experience though.

 

[userlander]

In for the debate, as I debate upgrading to 600ohm.

 

[eneloquent]

Quote:

Originally Posted by Helmore /img/forum/go_quote.gif I think you should decide that based on their sound signatures. From what I gathered they sound quite different. I'm not talking from experience though.

I can't get both at the same time. So, I'm looking to get my objective parameters straight first, which will help me decide where to start considering subjective parameters.

 

[Helmore]

Quote:

Originally Posted by eneloquent /img/forum/go_quote.gif I can't get both at the same time. So, I'm looking to get my objective parameters straight first, which will help me decide where to start considering subjective parameters.

Yes you need to get the objective parameters right, but in the end you're doing it for a subjective experience. What I was trying to say is that there seems to be quite a big different in the different DT770 versions. Most will say they have bloated bass, but if you look in this review here: http://www.head-fi.org/forums/f4/rev...-990-a-424130/ (not directly related to the DT770) You'll see Skylab actually say the DT770 600 Ohm are kind of lean on the bass and he has a lot of other headphones to compare them with. That's just to give you an idea of how big the difference between the DT770s can be. In other words, pick the one that best matches your sound preference.

 

[JaZZ]

Quote:

Originally Posted by eneloquent /img/forum/go_quote.gif I'm using the new FOTM: Nuforce.com | Icon uDAC The output is listed as: Power output: 80mW x 2 @ 16-Ohm

The 16 ohm aren't a recommended load impedance. They're just used as reference for the output power. E.g. at a 32 ohm load the output power would be about 40 mW – and so on.
.

 

[Helmore]

Quote:

Originally Posted by JaZZ /img/forum/go_quote.gif The 16 ohm aren't a recommended load impedance. They're just used as reference for the output power. E.g. at a 32 ohm load the output power would be about 40 mW – and so on. .

The amount of power it can output is not always the a function of the reciprocal of the headphone's impedance. You may very well be right in this case, but twice the impedance does not always mean half the amount of output power. It also depends on the maximum amount of current it can provide. Just look at these specifications for example: н¨ÍøÒ³ 1