Concept Questions: Driving Headphones and Transparent Amplification

[bLue_oNioN]

Hi,


I have two questions that I've been mulling over for quite some while.

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1. We know that if we have two headphones with equivalent sensativity and different resistivity, the one with the higher resistance requires less current than the one with the lower resistance. The headphone with the higher resistance will run longer than the one with the lower resistance on the same setup.

A headphone that is properly driven reaches its true potential.

What then, determines whether or not the headphone is being properly driven?

Can it be calculated?

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2. There are many posts that applaud the SR-71 in improving perceived sound quality (increased seperation, greater clarity, tighter bass, etc.)

If I remember correctly, Ray has stated himself that he designs his amps to be as transparent as possible, especially the SR-71.

I assume this means that the amp will aid in properly driving your headphones only. In other words, your setup should NOT benefit if you are using fairly efficient headphones.

Is this line of reasoning correct?

Thanks so much for your consideration!

 

[CRESCENDOPOWER]

Quote:

What then, determines whether or not the headphone is being properly driven?

Your ears.

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I assume this means that the amp will aid in properly driving your headphones only. In other words, your setup should NOT benefit if you are using fairly efficient headphones.

The only thing efficiency tells you is how loud a transducer can play with a given input, and distance; this has absolutely nothing to do with sound quality. A sensitive set of phones can, and will benefit from better quality amplification; they just might not need as much.

 

[bLue_oNioN]

Quote:

Originally Posted by CRESCENDOPOWER Your ears.

Surely there must be a better explanation..?

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Originally Posted by CRESCENDOPOWER The only thing efficiency tells you is how loud a transducer can play with a given input, and distance; this has absolutely nothing to do with sound quality. A sensitive set of phones can, and will benefit from better quality amplification; they just might not need as much.

So in other words, just because a headphone is efficient, doesn't mean we can assume that it can be easily driven?

 

[pbirkett]

I think some people use price as a guide. Only expensive headphone amps can drive headphones properly, according to some

 

[JaZZ]

Quote:

Originally Posted by bLue_oNioN Surely there must be a better explanation..?

No, Crescendopower is right with his answer: It's up to your ears to define if the headphones are properly driven. In fact dynamic headphones are easy to drive by dedicated headphone amps. Apart from the K 1000 and some tube amps designed exclusively for higher-impedance loads as well as some portable amps with limited power no amp has problems driving dynamic headphones. But the essential factor is the sonic synergy between a specific headphone and a specific amp.

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So in other words, just because a headphone is efficient, doesn't mean we can assume that it can be easily driven?

Not necessarily. But in the case of a (portable) amp with limited power the more efficient headphone is easier to drive. Apart from this scenario the «hard to drive» headphones are a myth. It's about synergy, not electrical compatibility. Nevertheless, most headphones sound best with amps with low output impedance. And tube amps usually have higher output impedances than solid-state amps, so they have a worse precondition for driving low-impedance headphones by nature. But that's just a rule of thumbs and not to be generalized (and depending on the headphone's impedance curve). The ears of the listener are the final instance.

I guess every headphone-amp developer has the goal to design a «transparent» amp, with as little transient corruption and coloration as possible. But in fact every amp -- tube or solid-state -- colors the sound in a characteristic way. A really «neutral» amp doesn't exist. That's why the headphone/amp pairing is so critical. That's not to say the source electronics are of minor importance...

 

[boodi]

Quote:

Originally Posted by JaZZ the essential factor is the sonic synergy between a specific headphone and a specific amp

I'd add also source in ( i have experienced that many sources on mid budget sound quite differently on different setup, anyhow the more you climb on the ladder - and many times this means the more you spend on - the more you'll find sources that sounds closer one to the other and similar .. this apply also to other gears )
If source has some evident colours it will be difficult to build an "as transparent as it can get" system, and what you'll do in the end will be try to compensate the source colour with other colours, a bad operation that will probably not last on you for much time

And interconnects for sure - they can change a lot the sound layering and the field of presentation and the wormness/coldness of a rig, if i think to the senn. replacement cables this is a further evidence

And ( take it as an imo if you want ) ears too, that is : your ears (your ears expectation ) have to be in synergy with what you are going to listen to , in the other case you'll find some "news" in the sound and you'll pass a first period of adaptation to the sound trying to understand if it please you for the particular colour you are experiencing
Everything is very relative to what you hear , to what please you , and so to your ears .


Everything take in parts in the mesh of the colors to compose the sound palette imo , and imo there isn't even a white or transparent listening to refer to and rely on .. When you climb up on ladder of gear' politeness and rightness, many time the little differences / distortions , the particolar mellowness or blackness or warmness of a source for ex. are perceived and/or misperceived too much more from ears (imo, again) as a part of the musicality then as a colour of the sound

Even an amp builder has his own ears ( other then his electronical/humans testers

) and i bet a good amp builder , other then having probably good ears , as this is a must for the kind of job he face - he build his amp also on what his ears listen and like.

 

[markl]

Quote:

I assume this means that the amp will aid in properly driving your headphones only. In other words, your setup should NOT benefit if you are using fairly efficient headphones.

It's not about *quantity* of power, but *quality*. Better components + better design = better sound. But there's no way for an amp to "improve" the signal per se, or add resolution; all it can do is amplify the signal it's being fed from the source.
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2. There are many posts that applaud the SR-71 in improving perceived sound quality (increased seperation, greater clarity, tighter bass, etc.)

Outside of the issue of providing enough of the right kind of power, I would look at the benefit of adding an aftermarket amp in terms of *removing the barriers* to sound quality being imposed by whatever cheap stock amplification you are using, rather than possessing some "magical" ability to *improve* the sound of the source signal. If you see your stock headphone jack as acting as a bottleneck on the sound of your source, you can see that a better quality amp will degrade the sound less. So, when people say, "wow, this amp really improved the sound", they're really just saying "wow, this amp is so much less crappy than what I was using before", and is harming the signal less.

 

[gsferrari]

After reading all the mushy responses here is a slightly more plausible explanation.


[size=small]
Headphone "Driving" :[/size]

A headphone is driven well when it reaches required driver displacement with minimum delay with respect to the source signal. The driver must follow the source as closely and as quickly as possible. This is not possible with low power amps and therefore amplifiers with more "overhead" do better in this area.

For example - a HD-650 out of a CMOY will not be as "FAST" as a HD-650 out of say...a Dynahi.

Ideally there is zero phase (time axis) difference between the source signal and the driver response. But this is not possible because of driver inertia etc. etc. More power (amp side) will allow the coil to overcome inertia etc. faster.


[size=small]Transparency :[/size]


No one knows how a source really sounds. All this talk about neutrality and transparency is BS. Everything colors the sound right from the headphone jack, attenuator, cables, interconnects, amp, headsets, power supply....EVERYTHING.

There is no component that is transparent. Not even the best "lab grade" measuring scopes

 

[saint.panda]

I think by using a direct path approach, one can come pretty close to the source's original sound signature. However, I'm not sure whether the frequency shift by using the direct path approach will influence the sound too much.

About driving a pair of headphones properly: I'm still having problems with thinking that you really need an amp as big as most power amps to drive a pair of headphones. Yet, I'll have to reserve my judgement until I can hear the Dynahi someday. Until then, this answer Quote:

Originally Posted by CRESCENDOPOWER Your ears.

has to be most accurate answer so far as it also takes the sound quality into account. My portable cd players can drive my HD 650 but it sounds crappy.

 

[JohnFerrier]

The ideal amplifier has been defined as a straight wire with gain. Personally, for headphone amplifiers, I think only current gain is necessary (in most cases). The advantage of low voltage gain is that this optimizes signal to noise.


JF

 

[JaZZ]

Quote:

Originally Posted by gsferrari A headphone is driven well when it reaches required driver displacement with minimum delay with respect to the source signal. The driver must follow the source as closely and as quickly as possible. This is not possible with low power amps and therefore amplifiers with more "overhead" do better in this area.

Of course you mean «membrane displacement», not «driver displacement»... I don't think we have to care about low-power amps in this context -- they are more or less restricted to the portable category. Among dedicated static headphone amps power isn't a quality characteristic, but only indicates how loud the amps can play. Within the limits of clean, low-distortion operation power sais nothing about sound quality and accuracy. A strong power supply can have an impact on bass quality and quantity though, and this is a feature more common in powerful amps.

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For example - a HD-650 out of a CMOY will not be as "FAST" as a HD-650 out of say...a Dynahi.

Fast transient response is a function of frequency response, not power. The CMOY will certainly sound less accurate, refined and powerful than a Dynahi because it uses much cheaper parts and a smaller power supply.

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Ideally there is zero phase (time axis) difference between the source signal and the driver response. But this is not possible because of driver inertia etc. etc. More power (amp side) will allow the coil to overcome inertia etc. faster.

I don't think so. More power makes the music louder, not faster.

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No one knows how a source really sounds. All this talk about neutrality and transparency is BS. Everything colors the sound right from the headphone jack, attenuator, cables, interconnects, amp, headsets, power supply....EVERYTHING. There is no component that is transparent. Not even the best "lab grade" measuring scopes.

Yes, but how does this affect the meaning of transparency and neutrality as the main goal of audio enthusiasts and developers? The more distorting and coloring a component, the less accurate. You can compensate for certain colorations with equipment matching, but you can't compensate all the losses from signal corruption.



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Originally Posted by saint.panda I think by using a direct path approach, one can come pretty close to the source's original sound signature.

Yes, that's my approach since quite some time. And I don't want an amp with serious colorations just because it sounds spectacular with one pair of headphones.

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About driving a pair of headphones properly: I'm still having problems with thinking that you really need an amp as big as most power amps to drive a pair of headphones.

Yes, that's exactly my point, too.

 

[saint.panda]

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Originally Posted by JaZZ Yes, that's my approach since quite some time.

Well, I got it from you afterall

 

[JohnFerrier]

One thing I like about headphone listening (which is really addictive--but everyone here knows that) is that local room acoustics are eliminated. Play time acoustics are an undesired layer over concert hall acoustics (captured during recording). Sure headphones will have some reverberation, but nothing like a room where unused sound is bouncing around everywhere... Having the transducers less than an inch from one's ears does a lot for accuracy and resolution...


JF

 

[gsferrari]

Quote:

Originally Posted by JaZZ Among dedicated static headphone amps power isn't a quality characteristic, but only indicates how loud the amps can play. Within the limits of clean, low-distortion operation power sais nothing about sound quality and accuracy

Think about it in terms of physics - the relation between power-on-tap and driver motion and then you may get the idea.

Fast transient response is a function of frequency response, not power. The CMOY will certainly sound less accurate, refined and powerful than a Dynahi because it uses much cheaper parts and a smaller power supply

Mostly because of the difference in the amount of power they have in reserve. Accuracy is all about power...brute force...singlepower knows this, gilmore knows this, emmeline knows this...power is everything.


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I don't think so. More power makes the music louder, not faster

Unfortunately you have mixed up attenuation and gain with power. They are not linked up quite as easily as you suggest. A more powerful amp with plenty of reserve will sound faster than a less powerful one. Speed of driver displacement in response to a signal change makes for a more accurate sound.

A CMOY sounds less refined for all the reasons you mentioned (except maybe cheap parts...you can make a maxxed out CMOY with top notch parts) but it mostly has to do with the amount of power it has on tap...which is not much...complex music will suffer through a CMOY relative to a more powerful amp.


Gain is what makes music louder. I can have high current gain without appreciable increase in output power because the voltage sags correspondingly.



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Yes, but how does this affect the meaning of transparency and neutrality as the main goal of audio enthusiasts and developers? The more distorting and coloring a component, the less accurate. You can compensate for certain colorations with equipment matching, but you can't compensate all the losses from signal corruption.

What I am saying is that the quest for "transparency" and "neutrality" is a fruitless one.

 

[JohnFerrier]

Once a person has capacitors out of the signal path, the attenuator is the weak passive component in a play back system (IMO). That is why the best ones are so expensive. I spent time to match resistors (0dB to -57dB) to <0.01 dB channel to channel... Not that anything <0.5 dB is audible, especially if the transducers are +/-1 dB...


JF