[ardilla]

Well - the saying is that planarmagnetic (planars) AKA Orthodynamic (orthos) headphones need a lot of Watts to shine. But I have also read that they fancy nice Voltage swing capabilites. And I've read the opposite, they do not care about voltage at all. I know, however, that the voltage-capable but not so watty WA2 drives the LCD-2, 3 and the HE-500 very nicely.
 
Since the HE-6, HE-500, LCD-2 and LCD-3 are some of the hottest cans around, I ask: 
 
What's the truth?? Ampere and Watts? Voltage or What?

 

[obobskivich]

It's determined by Ohm's Law and sensitivity - they're insensitive and low impedance, they need a lot of power (watts) to reach the desired output level (this is the sensitivity part); which will require high-current (amperage) due to the low impedance (Ohm's Law). However, due to the insensitivity (especially of something like the HE-6) even "modest" voltage or current demands (all else relative on Earth) appear substantial compared to dynamics.  See here: http://www.sengpielaudio.com/calculator-ohm.htm
 
Measurement data:
http://www.innerfidelity.com/images/AudezeLCD2.pdf
http://www.innerfidelity.com/images/AudezeLCD3sn2312488.pdf
http://www.innerfidelity.com/images/HiFiMANHE5.pdf
http://www.innerfidelity.com/images/HiFiMANHE6.pdf
 
To pick on the HE-6 specifically:
 
90 dB SPL @ 19.7 mW, 53 ohms, and they want around 1Vrms. 
 
To pick a random non-ortho headphone to compare that to:
http://www.innerfidelity.com/images/UltrasonePRO2900.pdf
 
90 dB SPL @ .42 mW, 41 ohms, and they want around .13Vrms. 
 
So in context, the orthos want ten times the voltage and some 40 times the power for the same output level. That's big when you're an iPod. 
 
Even the HE-5 has more substantial demands, wanting something like 5mW and .4V. 
 
Now, in context of something like the WA2, which will deliver 300-400mW into the impedance range we're talking about (from Woo specs), there shouldn't be much of a problem. I actually fail to see why it would have a problem with the HE-6 even, 20mW is 10 dB down from half output. But again, if you're an iPod, or even some of the older headphone amp designs (like the OBH-11) then you might not like to think about your new friend the HE-6. 
 
 

 

[ardilla]

Great post!
 
So - why is the HE-6 and other orthos claimed to "grow" with the wattage - people are talking thousands of milliwatts for "optimal "performance (like the Lyr - up to 6 watts into 32 ohm... )
 
And yes, I haven't tried it but there are some posts about the WA2 doing fine with the HE-6, although OTL-design by many is regarded a no-go..
Quote:

 
Now, in context of something like the WA2, which will deliver 300-400mW into the impedance range we're talking about (from Woo specs), there shouldn't be much of a problem. I actually fail to see why it would have a problem with the HE-6 even, 20mW is 10 dB down from half output. 
 
 

 
 

 

[obobskivich]

I've got no good answers as to why many audio enthusiasts believe they need substantially more power than their speakers/headphones demand. It isn't just the HE-6 though; you can see the same thing in speaker discussions. There's a pervasive belief that having some massive amplifier to plug your speaker/headphone into will "improve the sound" when the reality is, if the load only needs 10W, it's only going to take 10W. It doesn't care (or know, or whatever) if the amplifier can deliver 15W or 15,000W. 
 
With headphone amplifiers, methinks it's a combination of two factors. First, TI (and a few others, but mostly TI) have put out some great amp-on-a-chip parts (like the TPA6120) that can do something like 1-2W into a 32-ohm load. And second, it's not really that expensive to have comparatively lots of power (a few watts) from an amplifier. So if you're in business to sell something and want to set yourself apart, you go out and design something that does 3 or 5 or 10W out. It won't hurt anything, and it really won't even be that bad from an environmental perspective. It also lets you stand apart from all of the amp-on-a-chip based devices (consider though, ten years ago an "entry level" headphone amplifier was something like the Creek OBH-11, or the Grado RA1 - today we have the Fiio E9 and others, it's absolutely another level). 
 
Finally, you've got the issue of "one-time trial" situations - where someone has a singular frame of reference, tries something else that improves the situation, and they attribute the change to whatever they tried (whether or not it helped or not, or without understanding why it helped). And that's how a lot of the myths about headphones and audio equipment in general perpetuate. It doesn't help when salesmen, advertisers, and "reviewers" (read: salesmen) feed into the whole situation simply to move more product. In order words, they give the people what they want. It sells magazines, cables, amplifiers, and so on, but that's about where it stops. 
 
Regarding the WA2 (and Woo amps in general) - SETs are inherently non-linear and OTL doesn't improve that situation any (especially if your load has a non-uniform impedance; a lot of headphones actually have pretty flat impedance (something that seems to go unnoticed by many), including the orthos, but it can foul things up with some devices). I understand, to a degree, the appeal, but on the other hand I'm perfectly content to leave such devices in the history books. Not condemning anything, but there's certainly a degree of "What" with an OTL Class A SET in 2012 - it's like driving a Dusenberg.
 
 
 
 

 

[ardilla]

 
 

.................... Not condemning anything, but there's certainly a degree of "What" with an OTL Class A SET in 2012 - it's like driving a Dusenberg.
 

 
 What -  I assume you mean What as in "Well, That's Fantastic"
 
 

 

[Skylab]

While obobskivich's post is excellent, it does not take into account the fact that the sensitivity ratings given to headphones are almost universally given only for how that headphone reacts at 1 kHz only. And in fact, many headphones have wildly different impedances depending on the specific frequency in question, and are often higher impedance in the bass range than they are at 1kHz. So the partnering amplifier may be required to deliver more current depending on the content of the music.

On the other hand, the vast majority of planar headphones on the market today are almost purely resistive and do not have their impedance fluctuate with frequency. So while it is true that many of these planars have generally low efficiency, and will require "more watts" as a result, they can often be a less challenging load to the partnering amplifier than a dynamic headphone whose impedance changes significantly over the audible spectrum.

 

[ardilla]

I'm still a bit confused - is this all about effeciency?
 
That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?
 
Or - as skylab implies - they might be easier on the amplifier due to the flat impedance curve (impendance/Hz)
 
Further - I've read that the output impedance of the amp itself is less relevant for orthos than dynamics due to the flat impedance curve. 

 

[iamthem]

Ohm's law states that I = V/R, or that current (measured in amperes/amps) equals to voltage (volts) divided by resistance (ohms). The point of getting a powerful amplifier is to provide as much current as needed whenever needed through the headphones without changing the signal at all. The volume knob changes the amount the voltage from the original signal is boosted.
 
Power = V*I or voltage times amperage. Amplifiers that can supply a lot of power can produce enough amperage to match the voltage and they can produce a large voltage boost to drive headphones with high impedance/ resistance.
 
The amount of electricity flowing through a coil (the current, measured in amps) determines the magnetic field it produces. Therefore more current = louder sound. Because the amount of current flowing is dependent on voltage and amperage, the volume knob and the impedence (resistance) of the headphones is what determines how loud it plays on a certain volume. In short, voltage change coming from your music allows more current to flow through the headphones changing magnetic flux and making the diaphragm move.
 
 
With what you said, "That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?" to drive a ortho you need more voltage to reach 1 milliwatt compared to the dynamic because it has a higher resistance, so the amount of power required is the same (same efficiency) but you need a lot more voltage, so you end up turning the volume knob up higher.
 
That's my understanding. I'm not an electrical engineer or anything, just an electronics enthusiast so yeah.. don't quote me on this.
 

 

[IEMCrazy]

 
Quote:

, they can often be a less challenging load to the partnering amplifier than a dynamic headphone whose impedance changes significantly over the audible spectrum.

 
AKG K/Q 70x is a lovely example of a dynamic with radical impedance changes that can require some crazy power at the edges.  A lack of this power is what produces the "plastic treble" sound some people cite.

 

[obobskivich]

No, more of a "whiskey, tango, foxtrot" kind of thing. I like the Dusenberg example - sure, you can have one and drive it around today, and sure, it'll get you where you want to go. That said, it's from another time. There's nothing wrong with it, it's just completely removed from what's happened since 1930. The WA2 is much the same way - much more efficient, compact, and affordable options exist that will get the same end result. But there is certainly something to be said for cachet, which the WA2 has in spades (just like a Dusenberg). 
 
Also, have pictures:

Quote:

 
 
 
 What -  I assume you mean What as in "Well, That's Fantastic"
 
 

 
 
It is and isn't about *just* sensitivity (efficiency is a somewhat different concept). You have to consider impedance and the amplifier's output abilities as well. So your statement about a 95 dB/mW ortho vs dynamic may or may not be true, depending on impedance (as Skylab alludes to). If that dynamic is highly variable, like say, the Beyer T70 (which is 250ohm and >95 dB/mW but whatever), it may present more of a challenge to an amplifier because it wants more voltage near the ~600ohm spike (which is in the LF, which uses a large portion of total power and I will fall as V rises). If that dynamic is not highly variable, like say, the Denon D7000 (which has an almost flat impedance but is also >95 dB/mW and only 25 ohm), then it will simply be a matter of Znom v Znom - the lower resistance unit will "give the illusion of higher sensitivity" (it resists less), but once that's factored out, yes - a 95 dB/mW ortho or dynamic or whatever else (MagicalSquattingGnomePower (TM)) will be just as "easy." 
 
If you want a better example of all of this, look at MartinLogan speakers vs something with similar sensitivity ratings. They'll both get to the same level on the same amplifier assuming it can handle both of them. 
 
Skylab does raise a very relevant point though, and that's that Znom doesn't tell us anything useful! 
 
Regarding Zout - that's true. I think the importance of Zout is overstated to begin with, but when you're talking about something with nearly flat impedance, all Zout is going to do is mean uniform attenuation and inefficiency on the amplifier's part (more power is going off into heat). This same principle applies to dynamics, but (to go back to the T70 example) when impedance has a huge range, that attenuation is non-uniform and you end up with an altered FR as a result. This isn't always for the worse though - in some cases higher Zout may sound better for the listener, or it may not even be noticed (if you aren't A/B'ing with something else, or don't have a little knob where you can change Zout in real time, you almost certainly won't notice it). 
 
So in summary, if whatever amplifier you have can deliver the rated POWER that your headphones' sensitivity dictates by a few times over, you're probably fine. The WA2 can do a few hundred mW from 32-600, and I really don't see any headphone that it should have serious trouble with. Something like the K1000 or HE-6 will probably require the volume knob to be turned up higher, but it's not like you even need 50 mW (I assume most people do not want to listen at 100 dB). 
Quote:

I'm still a bit confused - is this all about effeciency?
 
That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?
 
Or - as skylab implies - they might be easier on the amplifier due to the flat impedance curve (impendance/Hz)
 
Further - I've read that the output impedance of the amp itself is less relevant for orthos than dynamics due to the flat impedance curve. 

 
 

 

[obobskivich]

Really?
http://www.innerfidelity.com/images/AKGK701.pdf
 
It goes up over 10k, but their response (like most headphones and most people's hearing) goes over a cliff over 10k. Otherwise it looks pretty flat to me...
 
They don't need *that* much power overall, and they don't present that complicated of a load to an amplifier. Sure, the top-end will be impacted by Zout (http://en.goldenears.net/index.php?mid=KB_Columns&document_srl=1389) but remember that power demands go down as frequency goes up, and extreme HF content is relatively rare (with some codecs it simply doesn't exist). They'll just want somewhat higher V as you go over 10k, but it shouldn't be anything nuts for most competent amplifiers. I think the "plastic treble" probably has more to do with the 9k ridge, but I'm not entirely clear what is meant by "plastic treble":

 
Quote:

 
 
AKG K/Q 70x is a lovely example of a dynamic with radical impedance changes that can require some crazy power at the edges.  A lack of this power is what produces the "plastic treble" sound some people cite.

 
iamthem:
 
"
With what you said, "That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?" to drive a ortho you need more voltage to reach 1 milliwatt compared to the dynamic because it has a higher resistance, so the amount of power required is the same (same efficiency) but you need a lot more voltage, so you end up turning the volume knob up higher." 
 
Because what has a higher impedance relative to what? (confuzzled). There are dynamics that sit right around that 40-50ohm range, an example: http://www.innerfidelity.com/images/AudioTechnicaATHW5000.pdf
 
Lower Z means higher I and lower V, higher Z means lower I and higher V. That's why 'stats are "current-less" and orthos are "current hungry" (compared to conventional dynamics, and I think a lot of this is based on "if you were an iPod") - but you can't just arbitrarily have "lots" of I going into your load; that will increase power. I is determined by Z and V; Z is dictated by the load and V by the user. 
 
If we're talking about a dynamic with a very low Znom (and high sensitivity), like Beats Pro, then sure, the Ortho needs (relatively) more volts - so does the W5000 though. The Ortho just needs more power overall, because it's down there around 80 dB/mW while the W5000 is something like 100 dB/mW. 20 dB is huge. It's 100x (http://trace.wisc.edu/docs/2004-About-dB/). And because the Ortho needs more power to get to the same output level, we increase V which brings I up with it relative to Z. 
 
As far as reading this on specs, if the amp can deliver say, 200 mW into 40 ohms (let's just arbitrarily invent an amp with that spec), V and I are already dictated by Z. If your headphone requires 20 mW into 40 ohms (like the HE-6), that amplifier has enough V and I for them. If your headphone requires some fraction of a mW into the same (like the W5000), that amplifier has enough V and I. The HE-6 will require the volume knob turned up higher (how much higher depends on the thing's gain structure) due to the lower sensitivity. If the specs have been fudged on, that's the manufacturer's issue. 
 

 

 

[iamthem]

 
 
 
Quote:

I'm still a bit confused - is this all about effeciency?
 
That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?
 
Or - as skylab implies - they might be easier on the amplifier due to the flat impedance curve (impendance/Hz)
 
Further - I've read that the output impedance of the amp itself is less relevant for orthos than dynamics due to the flat impedance curve. 

Ardilla mentioned that in the hypothetical situation in which an ortho had same SPL @ 1mW as a dynamic, would it be just as easy to drive to which I responded you need more voltage in the ortho to offset the higher resistance of the ortho to reach 1mW of power compared to the dynamic, assuming that the dynamic has a lot less resistance as mentioned in the other posts from other members. In other words, technically the ortho consumes the same amount of energy as the dynamic so it is just as easy to drive, but it requires more voltage so you turn the volume up.Ofc, being a hypothetical situation most orthos would have a lower SPL @ 1mW compared to most dynamics so it would end up consuming more power to reach the same volume.
 

 
To pick on the HE-6 specifically:
 
90 dB SPL @ 19.7 mW, 53 ohms, and they want around 1Vrms. 
 
To pick a random non-ortho headphone to compare that to:
http://www.innerfidelity.com/images/UltrasonePRO2900.pdf
 
90 dB SPL @ .42 mW, 41 ohms, and they want around .13Vrms. 
 
So in context, the orthos want ten times the voltage and some 40 times the power for the same output level. That's big when you're an iPod. 
 
Even the HE-5 has more substantial demands, wanting something like 5mW and .4V. 
 
 

Like mentioned in the first post,  in a real life situation, even if an ortho had a similar resistance to a dynamic (such as the HE-6 compared to the pro2900), because its SPL/mW is lower the volume knob would have to be turned up if the same volume on both phones were desired as the HE-6 requires more power, and by increasing the voltage (turning up the knob) you allow more current to flow = more power. From the data up there, you can see that the ortho wants a lot more voltage which equates to more power.
 
Sorry if I stuffed up my explanation >_>.
 
Quote: "With what you said, "That implies that a 95 dB (SPL @ 1 milliwatt) ortho is as easy to drive well as a 95 dB dynamic?" to drive a ortho you need more voltage to reach 1 milliwatt compared to the dynamic because it has a higher resistance, so the amount of power required is the same (same efficiency) but you need a lot more voltage, so you end up turning the volume knob up higher." 
 
 

 

[obobskivich]

Volts != power.
V*I = power.
I = V/R.
R (or Z) is a known and constant value based on the load, V is variable relative to the amp's internal gain, sensitivity, the input signal, and attenuation. 
Acoustic output = dB SPL which is figured by sensitivity/power. 
 
Dynamics are not inherently "lower impedance" than orthos - 30-60 ohms is a pretty common range for most headphones methinks. That's where I'm hanging up on your post - there is no "offset the higher resistance" with the ortho; you're simply contending with lower sensitivity (SPL/mW) if you're holding Znom/Z constant/ignoring it for the purposes of this discussion. It's like a K1000 vs something else around 120ohms - the K1000 just needs more power overall to do it's thing. It's not about arbitrary voltage or current, it just wants power. 
 
 
 
 

 

[PurpleAngel]

Wow, all this info I can't understand.

 

[srkstan]

A question regarding the practical implications of this information:  What portable headphone amps work well with Orthodynamic headphones?  Here, I assume that the question is about which portable headphone amps have high voltage current more than it is about their wattage (as long as they give close to 500 mw per channel)?  
 
I recently got some Mad Dog headphones, and I found it interesting that they are driven better by the internal amp in my iBasso DX90 than by a Bottlehead Crack amp (showing again that OTL is not good for Orthos).  Still, they could use a boost from the DX90, hence the question about a good portable amp for orthos.