Planar magnetic headphones require "at least one watt" of power to drive properly.

[White Lotus]

This is the common phrase around online audio world.
 
One prime example is on the Audeze website - when looking at the specifications of the LCD 2 headphone:
 
"Optimal Power Requirement: 1-4 watts".
 
So - 
 
Is there truth to this? 
 
It seems very widely accepted by the online audiophile community, and I myself am not sure what to believe. 
 
To get the "most" out of a planar magnetic headphone, do we require 1-4 watts of power? 

 

[castleofargh]

it's a line they should have removed from their website a long time ago, because it doesn't make them look very serious.
look at the sensitivity of a headphone @1mw, check out how loud that would become into 4 watt, have a good laugh.
 
and if you want even more fun, you just have to go read the same exact "1 - 4 W" on the LCD-X where 1W should be like 133db loud...

oh I got it, it's the optimal power to use it as speaker ^_^

 

[gikigill]

Powered and powered properly are two different things. By that logic, an IPhone should be more than enough.

I say that as an owner of Audeze, Hifiman and Maddogs Pro.

 

[White Lotus]

Powered and powered properly are two different things.

What's the difference?

 

[gikigill]

Headphone amps almost always apply gain in the voltage, but also have a maximum current output. When you're aiming for a high SPL, you get a lot of voltage, but if you don't have the current to compensate they distort and most planars need more current than voltage.

 

[Joe Bloggs]

Power = current x voltage. :rolleyes:

Anyway these days your run-of-the-mill solid state headphone amp is more likely to run out of voltage into high-Z phones than current into low-Z planars.

 

[gikigill]

How about a high current custom amplifier for planars? Anyone willing to give it a go or do some brainstorming?

 

[Joe Bloggs]

Like I said current run-of-the-mill headphone amps already are tilted towards humongous power output into low impedances with possibly inadequate output into high impedance cans (thankfully these tend to be very efficient). Unless you like blowing up all your 8-ohm IEMs, powering planars is about the only legitimate use case for such high power outputs at low impedances.

 

[castleofargh]

Headphone amps almost always apply gain in the voltage, but also have a maximum current output. When you're aiming for a high SPL, you get a lot of voltage, but if you don't have the current to compensate they distort and most planars need more current than voltage.

when you read the amp specs at a given impedance for 1%THD, you're getting exactly the information you're talking about. if current under the given conditions wasn't enough, the amp would not stay under 1%THD.
 
the only problem I see with the example of an iphone is that we usually lack those very power specs into several loads at 1%THD(and I've been complaining a lot about DAPs not giving them, because there is no reason why it's a given for amps and not for amps inside a DAP). else yes, an iphone can have enough power for a few high sensitivity planars. it doesn't mean the sound will be amazing as there is more to fidelity than power, but the opposite is just as true. you don't usually go for your speaker amp to drive your headphones and IEMs. thinking we need some headroom for a few reasons, I can agree with that, but more power=better is a lie. magnitudes do matter in both directions.

 

[jcx]

do the sensitivity/efficiency numbers, understand real music dynamic headroom - some recordings do have over 20 dB dynamic peak SPL over average level
 
a point to use could be THX Home Theater SPL calibrated levels:
 

  http://www.acousticfrontiers.com/2013314thx-reference-level/ reference level explained - Acoustic Frontiers
 
individual mains speakers are calibrated for digital full scale = 105 dB SPL at the listening position
85 dB SPL is the "0 dB" volume control setting, you can dial it up, dynamic peaks are expected to be above
the LFE channel is supposed to have an additional +10 dB max capability
the LFE 115 dB SPL certainly dominates, 5x 105 db mains does add to 112 dB if linearly summed, adding less than 2 dB to the 115 dB of the LFE

 

[/quote]

 
LCD's low 90's SPL re 1 mW requires ~10x less power, few 100 mW,  than HiFiMan's lower 83 dB SPL re 1 mW Ortho which needs over a watt to reach THX levels

 

[gregorio]

Originally Posted by jcx /img/forum/go_quote.gif
 
a point to use could be THX Home Theater SPL calibrated levels ...

 
To be honest, I wouldn't aim for those levels.
 
1. The article to which you linked is incorrect in a few significant areas.
 
2. Theatrical levels are NOT applicable to home theatre levels and even less applicable to music playback levels.
 
G

 

[castleofargh]

well aiming for 110 or 115db as max possible level ever, seems reasonable to me. not that I'll ever go there

. but with replay gain and some EQ, I may need some of the extra headroom.
and because most people tend to listen way louder than I do, I usually make power requirements based on 115db when people ask me in PM.

 

[gregorio]

  well aiming for 110 or 115db as max possible level ever, seems reasonable to me. not that I'll ever go there

. but with replay gain and some EQ, I may need some of the extra headroom.
and because most people tend to listen way louder than I do, I usually make power requirements based on 115db when people ask me in PM.

 
I'm not saying that you should not aim for a max peak output level of 110 or 115dBSPL or recommending to others that they do. It's entirely up to you what peak output level you specify for your sound system, I'm just pointing out that it's fallacious to do so on the basis of it being some sort of reference to theatrical SPL calibration levels. There are a few of reasons why:
 
1. In a theatrical system, each of the main speakers have a peak output of 105dB measured at the listening position (datum point), which is generally about 2/3 to the back of the auditorium. The datum point is therefore generally at least 10m from the speakers and often considerably more. This distance makes a substantial difference to the perception of loudness, although I believe the reason for this is not currently fully understood. Theatrical mixes are made in theatrical dub stages which are effectively cinema sized mix rooms. Sound design and other audio post tasks are normally carried out in much smaller rooms, not dissimilar to the sorts of sizes of consumer living rooms. To get in the same loudness ball park as cinemas (and dub stages) these smaller rooms have to be calibrated much lower than theatrical levels. Typically, anywhere from around  -20dBFS = 68dBSPL to 78dBSPL in order to match the loudness of a cinema/dub stage calibrated to -20dBFS = 85dBSPL. Peak output would therefore be 88-98dBSPL.
 
2. Theatrical mixes virtually never employ limiting, and compression, if used at all, is very slight. Getting very close to peak levels is a relative rarity in theatrical mixes. This is very much in contrast to music mixes/masters, which are brickwall limited extremely close to peak and usually spend a very considerable amount of time at these near peak levels. As a very rough generalisation, RMS levels on music mixes are commonly around 20dB higher than those of theatrical mixes.
 
3. The +10dB gain on the LFE channel does not work out quite the same as it does for the main speakers, it's band limited to 120Hz. Peak level of the LFE channel is therefore not 115dBSPL (105dB + 10dB) it's actually closer to 111dBSPL. And of course, it doesn't sound so incredibly loud because it's very low frequency, where our hearing is least sensitive. Music mixes do not contain nearly as much energy down to around 25Hz as say a theatrical action mix.
 
G

 

[White Lotus]

I've heard it said that not supplying sufficient power to a planar can cause roll-off in frequencies on each end of the spectrum.
 
Any truth to this?
 
If a planar is loud enough, does that mean it's receiving sufficient power? 

 

[jcx]

our ears are less sensitive to the far ends of the audio frequency range so more power is needed there to give the same sensation of loudness as at our more sensitive regions of hearing