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Headphone & Amp Impedance Questions? Find the answers here!

Discussion in 'Sound Science' started by proton007, Apr 25, 2012.
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  1. obobskivich

    They aren't inefficient though, unless your point of reference is a Beats Pro or A.00 or something equally insane (you know, 120-130 dB/V - like a boss). Seriously, by pre-iPood standards they really don't stand that exotically apart, and if the original reviewers back in 2006 had tried them from home hi-fi equipment or similar (which we all "know" is evil and not designed properly for use with headphones (Because if it was, companies like Corda and Woo couldn't hawk multi-thousand dollar components to us!)) instead of their mobile devices, the entire mythos about their "hard to drive" qualities would've never started up.

    Of course, the converse problem is now that the HE-6 is out, and just as bad as the K1000 from years gone by, the 70x gets grouped in the same schema of "hard to drive" with it. So now you've got people convinced that you need a 6W headphone amplifier (which you don't need for anything), for 70x.
  2. Chris J
    I hear ya, I hear ya!
    Maybe someone else is listening, too!
  3. proton007
    No!! the 70x needs more juice to get the best out of it! [​IMG]
  4. proton007
    I also have this question. Does it make sense to use impedance cables/adapters? 
    I mean if your headphone is already so low impedance that you have to use such a cable/adapter, you don't really need to use an amp either. To me it just feels like holding your ear from around your head rather than just directly.
  5. maverickronin
    Do you mean just a straight series resistor?  That's usually just silly.  You'll either ruin the damping factor on a dynamic or screw up the FR on BA IEM.
    BA IEMs can benefit from an impedance matching resistor network when used with a high Z out source or just as attenuation if the source is too noisy.
  6. obobskivich

    I have one very specific example that makes the above make sense (aside from the Etyomotic P/S adapters) - the Sony MDR-F1 and MDR-MA900. They are 12 ohms nominal, and include a Zobel to smooth out their impedance (which should make them completely amplifier agnostic in terms of FR changes) - some headphone amplifiers are not stable into 12 ohms, and series resistors could bring those cans up to a higher Z and allow them to work. It will waste power through the resistor, but due to the Zobel it shouldn't cause too drastic a change in the FR.

    With other cans, especially very reactive ones (like HD 600s) you should expect more dramatic changes to the FR. And that's where I agree with Maverick - it's just silly. The Sony example is pretty extreme, and the only other full-size can with such low Z that I'm aware of is the Beyer DT48A.00 - you'd have to wade through the megathread to see what the consensus is on adding Z to that can (it's 5 ohms nominal from the factory). Given that the F1 is out of production, and the A.00 is fairly obscure, that really only leaves the MA900 - and as you said, you probably don't need an amp, so it's unlikely people are buying OTL amplifiers to drive their MA900 and having issues. From an iPod or something it's no problem.

  7. Chris J
    I suppose you could argue that using an adaptor allows you to use the low Z can with a variety of high quality amps. Of course this only makes sense if the combo of low Z can and resistor network sounds better than what you were using before.  So the answer is "it depends".
    As O'Bob was saying, OTLs are off the table. You really only want to do this with a headphone amp with a reasonably low output Z.
  8. YoengJyh
  9. Chawanwit
    This is the most complex article I have encounter in headfi and I do not understand a thing.55555:p
  10. proton007
    Why? Too much maths? I've tried to keep it minimal. I don't know how to make it simpler without removing actual information.
  11. Chawanwit

    Yep I never get math. Anyways really nice useful post about headphone and amp. When I have time I will definitely come back to reread this post so maybe I can gain some new knowledge.:)
  12. JohnSantana
    ok, supposed we're using headphone amp already, can I still use graphical EQ ?
  13. xnor
    Do you mean a software or hardware EQ? Both can be used with a headphone amp.
  14. JohnSantana
    both ?
    in this case:
    Soft: DENON music apps in iPhone
    Hard: EQ preset button in Fiio E11
  15. xnor
    I'm not sure if I understand the question. But yes, you can use both, even at the same time.
    JohnSantana likes this.
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