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Headphones NEEDING Power

post #1 of 89
Thread Starter 

So I've been trying to balance the subjective side of audio with the objective. I see, quite often actually, that people claim X amp can provide enough power to get Y headphone to sound loud, but Z amp has more power and it makes Y headphone really "sing." So from that comparison, people often say Y headphone really NEEDS a lot of power to "sound good."

 

The LCD-2 with the O2/ODAC is an example I see often.

 

What in tarnation does this even mean?

 

 

 

Yes I know the basic power calculations and how to determine how much power an amp needs to provide at a specific impedance:

 

Power (W) = (VRMS^2) / (headphone impedance)

 

Power needed to reach 115 dB SPL (loud-volume, dynamic music situation) = [headphone power to reach 90 dB SPL, as provided by Innerfidelity.com for example] * 2^8.3333

8.3333 = (115 dB SPL - 90 dB SPL) / 3

Doubling the power increases the SPL by 3 dB

 

 

 

For an LCD-2.2:

Power needed to reach 90 dB SPL: 0.87 mW

Impedance at 1 kHz: 58 Ω

 

280.603 mW to reach 115 dB SPL at 58 Ω

 


The O2 provides more than enough power if I am interpreting these numbers correctly:

355 mW at 150 Ω

613 mW at 33 Ω

 

 

Sure maybe with an HE-500, the O2 might not provide enough power for an HE-500:

Power needed to reach 90 dB SPL: 2.04 mW

Impedance at 1 kHz: 47 Ω

 

657.980 mW to reach 115 dB SPL at 47 Ω

 

 

But by these calculations, the O2 is just fine with the LCD-2.2, no? I've tried an LCD-2 with my own O2 and it sounds just fine. I would subjectively say that it actually sounded better than any tube amp setup I've heard them on.

 

 

So then my question is: what does "sing" mean for a headphone?

According to the Merriam Webster dictionary, by definition, sing means:

Quote:
1
a : to produce musical tones by means of the voice
b : to utter words in musical tones and with musical inflections and modulations
c : to deliver songs as a trained or professional singer

2
: to make a shrill whining or whistling sound

3
a : to relate or celebrate something in verse
b : to compose poetry
c : to create in or through words a feeling or sense of song <prose that sings>

4
: to produce musical or harmonious sounds <birds singing>

 

So why do people suggest the LCD-2 needs more power than what the O2 can deliver? Are they suggesting that a 10 W amp is going to magically make the LCD-2 sound 500 times better than on the O2? People say Z amp sounds better with headphone Y than X amp, but do people ever consider that the amps are inherently different from the start and that their power output might not actually matter? Will an O2 with the exact same specifications but with 2 times the power output really make headphone Y "sing"?

 

 

I am utterly confused. Do so-called audiophiles even know what they are talking about when comparing amps with headphones?

 

Likewise for earphones actually. I've recently read a few inquiries about NEEDING an external amp with a PMP to provide power for earphones.

Even if the earphones were really inefficient and required 0.1 mW to reach 90 dB SPL at 16 Ω, you wouldn't need more than 15 mW to reach 111 dB SPL. A $40 USD Sansa Clip Zip provides more power than you really need for those purposes.


Edited by miceblue - 6/26/13 at 5:39pm
post #2 of 89

If it sounds good, it sounds good. Don't worry about people who use fancy flowery descriptions. They are describing what you already hear. Most headphones don't need amps.

post #3 of 89

Also keep in mind that everything varies in the frequency domain. Which is why, strictly speaking, most of those numbers are meaningless: 1 mW at what? 500 kHz? 1 kHz? 90 dB SPL what? A-weighted?

 

Low impedance and low sensitivity headphones, such as orthos, require lots of current. If the circuit cannot handle it, it will start distorting and even clip. High impedance headphones, on the other hand, don't need much current, only voltage which an amp can usually provide up to its limit with little distortion.


Edited by Wildstar - 6/27/13 at 3:13am
post #4 of 89

With regards to the LCD2 and amp recommendation, I observed that most if not all the reviews on amp pairing were purely subjective. I realized that in the LCD2 amp recommendation thread itself, the perceived sonic quality has a strong correlation with the price of the amps used in the reviews. In almost any amp recommendation thread on head fi, you'll find reviewers that claim only certain high end amps are able to "bring out the best" in the headphone. Whether or not those sonic differences are able to be discerned in a proper volume matched DBT/ blind test remains to be seen.

 

Moving forward, is there a particular specification of amps that affects sound stage?


Edited by Greenleaf7 - 6/27/13 at 5:26am
post #5 of 89
Sound stage is a function of speakers, not amps. However if an amp had phase problems or crosstalk it could affect soundstage. Not very likely though.
post #6 of 89
Quote:
Originally Posted by miceblue View Post

So I've been trying to balance the subjective side of audio with the objective. I see, quite often actually, that people claim X amp can provide enough power to get Y headphone to sound loud, but Z amp has more power and it makes Y headphone really "sing." So from that comparison, people often say Y headphone really NEEDS a lot of power to "sound good."

The LCD-2 with the O2/ODAC is an example I see often.

What in tarnation does this even mean?



Yes I know the basic power calculations and how to determine how much power an amp needs to provide at a specific impedance:

Power (W) = (VRMS^2) / (headphone impedance)

Power needed to reach 115 dB SPL (loud-volume, dynamic music situation) = [headphone power to reach 90 dB SPL, as provided by Innerfidelity.com for example] * 2^8.3333
8.3333 = (115 dB SPL - 90 dB SPL) / 3
Doubling the power increases the SPL by 3 dB



For an LCD-2.2:
Power needed to reach 90 dB SPL: 0.87 mW
Impedance at 1 kHz: 58 Ω

280.603 mW to reach 115 dB SPL at 58 Ω



The O2 provides more than enough power if I am interpreting these numbers correctly:
355 mW at 150 Ω
613 mW at 33 Ω


Sure maybe with an HE-500, the O2 might not provide enough power for an HE-500:
Power needed to reach 90 dB SPL: 2.04 mW
Impedance at 1 kHz: 47 Ω

657.980 mW to reach 115 dB SPL at 47 Ω


But by these calculations, the O2 is just fine with the LCD-2.2, no? I've tried an LCD-2 with my own O2 and it sounds just fine. I would subjectively say that it actually sounded better than any tube amp setup I've heard them on.


So then my question is: what does "sing" mean for a headphone?
According to the Merriam Webster dictionary, by definition, sing means:

So why do people suggest the LCD-2 needs more power than what the O2 can deliver? Are they suggesting that a 10 W amp is going to magically make the LCD-2 sound 500 times better than on the O2? People say Z amp sounds better with headphone Y than X amp, but do people ever consider that the amps are inherently different from the start and that their power output might not actually matter? Will an O2 with the exact same specifications but with 2 times the power output really make headphone Y "sing"?


I am utterly confused. Do so-called audiophiles even know what they are talking about when comparing amps with headphones?

Likewise for earphones actually. I've recently read a few inquiries about NEEDING an external amp with a PMP to provide power for earphones.
Even if the earphones were really inefficient and required 0.1 mW to reach 90 dB SPL at 16 Ω, you wouldn't need more than 15 mW to reach 111 dB SPL. A $40 USD Sansa Clip Zip provides more power than you really need for those purposes.

I love this post

Cheers
post #7 of 89

Most headphones are very sensitive and need very little power to reach dangerous levels.

 

Still haven't had time to double check all values, but take a look at my thread for headphone sensitivity, needed voltage, power, amplifier gain.


Edited by xnor - 6/28/13 at 1:00pm
post #8 of 89
Thread Starter 
Quote:
Originally Posted by xnor View Post

Most headphones are very sensitive and need very little power to reach dangerous levels.

 

Still haven't had time to double check all values, but take a look at my thread for headphone sensitivity, needed voltage, power, amplifier gain.

Whaat? The dead can talk? blink.gif

 

Wow, I'll take a more careful look at your thread. It looks quite informative. Thank you for pointing me to it! :)

post #9 of 89

I doubt you're interested in the technical details but content distribution networks cache files for a while at the risk of serving out-of-date files. tongue.gif That's what happened above.

 

 

I'm absolutely fine.


Edited by xnor - 6/28/13 at 3:51pm
post #10 of 89

Only mostly dead?

post #11 of 89
Quote:
Originally Posted by Greenleaf7 View Post

With regards to the LCD2 and amp recommendation, I observed that most if not all the reviews on amp pairing were purely subjective. I realized that in the LCD2 amp recommendation thread itself, the perceived sonic quality has a strong correlation with the price of the amps used in the reviews. In almost any amp recommendation thread on head fi, you'll find reviewers that claim only certain high end amps are able to "bring out the best" in the headphone. Whether or not those sonic differences are able to be discerned in a proper volume matched DBT/ blind test remains to be seen.

 

Moving forward, is there a particular specification of amps that affects sound stage?

 

With all the passive-aggressive comments you make towards other members on this forum about complex topics that you act like an authority-figure on, your questions seem rather elementary/embarrassing, being an audio-genius and all.

 

But I digress...

 

At the risk of being attacked, if an amp is just power, assuming two different amps with the same amount of noise are enough power for a certain pair of headphones, why would they sound any different, assuming everything is, besides the amps, exactly the same?  


Edited by Meremoth - 6/30/13 at 3:57am
post #12 of 89
Quote:
Originally Posted by Meremoth View Post

 

At the risk of being attacked, if an amp is just power, assuming two different amps with the same amount of noise are enough power for a certain pair of headphones, why would they sound any different, assuming everything is, besides the amps, exactly the same?  

Probably because the amps are not identical in some way.  Producing enough power is only one aspect of an amplifier, there are others, in particular source impedance which actually can make an audible difference given certain combinations of amps and headphones.  

 

So, say you have an amp with a 1 ohm output (source) impedance, and you use it to drive a pair of Shure E5c.  The impedance graph below (borrowed from another thread) shows they dip to about 11 ohms at 7KHz, but are way up at 123 ohms at 1KHz.  Since your amp has a very low source impedance, the actual voltage delivered to the drivers of he E5c will be fairly constant over all frequencies.  But if you have another amp with a source impedance of 50 ohms, that dip at 7KHz will significantly affect the voltage available to the driver at 7KHz, lowering it by 12dB or so compared to the available voltage at 1KHz.  That's a pretty big response wobble, and quite audible.  Both amps may be able to deliver enough power to achieve similar volume, but they will sound totally different.

 

 

post #13 of 89
Quote:
Originally Posted by jaddie View Post

Probably because the amps are not identical in some way.  Producing enough power is only one aspect of an amplifier, there are others, in particular source impedance which actually can make an audible difference given certain combinations of amps and headphones.  

 

So, say you have an amp with a 1 ohm output (source) impedance, and you use it to drive a pair of Shure E5c.  The impedance graph below (borrowed from another thread) shows they dip to about 11 ohms at 7KHz, but are way up at 123 ohms at 1KHz.  Since your amp has a very low source impedance, the actual voltage delivered to the drivers of he E5c will be fairly constant over all frequencies.  But if you have another amp with a source impedance of 50 ohms, that dip at 7KHz will significantly affect the voltage available to the driver at 7KHz, lowering it by 12dB or so compared to the available voltage at 1KHz.  That's a pretty big response wobble, and quite audible.  Both amps may be able to deliver enough power to achieve similar volume, but they will sound totally different.

 

 

 

Whoops, forgot to exclude impedance.


Well, let's assume the impedance is the same on both amps and include all the stipulations I mentioned above, then what would actually make the two amps sound different?  i.e.  When someone calls an amp "aggressive", or any other sonic quality, how does that relate to the amp as far as the construction is concerned?  I'm new to the audiophile world, but describing sonic qualities of headphones and DAC's makes much more sense to me than amps.  Where does the sonic quality people describe in amps come from?  


Edited by Meremoth - 6/30/13 at 3:40am
post #14 of 89
Thread Starter 

Ah the good 'ol audio glossaries...they kind of vary, but I've been trying to stick to these:

http://www.stereophile.com/reference/50/index.html

http://www.head-fi.org/t/220770/describing-sound-a-glossary

 

Also an amp's components can all add up to a different overall sound. i.e. a basic home-made CMoy amp with op-amp X isn't necessarily going to sound exactly the same as an Objective 2 with the same op-amp. And that's why I brought up in my original post how can someone say amp A with power 2X sounds better than amp B with power X and conclude that the headphone benefits from more power.

post #15 of 89

Haha, I guess I should have been more specific.  
 

I know what the words mean as far as their definitions are concerned, I just wanted to know what is specifically done (in the building process) to an amp to make it sound "aggressive", "bright", "laid-back" or whatever.  


Edited by Meremoth - 6/30/13 at 3:53am
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