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Deciphering Headphone Stats

post #1 of 6
Thread Starter 

(the first paragraph can be skipped as it is simply a short introduction of myself)

 

Hello there. I am fairly new to personal/consumer audio, especially at  the hi-fi and audiophile levels. I do know a thing or two about audio, but much of what is considered the basics escape me. I am a freshmen in college studying audio fro the purpose production and in the end a more prestigious life as a composer and film scorer. I have for a few years now been flying blind in the world of audiophilia. Until recently I made my personal audio decisions based on popularity and looks. After some education I found out how serious my love of sound and music was and now I am here.

 

Now for the question. I searched for quite some time and honestly found no thread with this question being answered( at least not out right like I need it) and I am shocked. What do the statistics on headphones translate to? I am not numb to the ways of the internet so I can search what the individual stats stand for. However, I need layman's terms and to be held by the hand on this because I am slow on the uptake.

 

Ohms, impendence, total harmonic distortion, contact pressure, nominal impedence, magnet type, driver diameter, voice coil, maximum input power, input impedance, so on and so forth. What part of the sound do things like this affect? I have seen cord type, max input power and a few others too. At this point you can't convince me that a few of these are different names for the same stat. At one point I wasn't totally in the dark. I know what frequency response is. I have seen phones with two separate frequency response measurements though, so now I am lost on that. SPL is still clear to me though...  I hope.

 

I need clarification here please. A few measurements and stats aren't so common and I know this. I just want a breakdown of the usual suspects so to speak.

post #2 of 6

The frequency range doesn't matter. Contact pressure.. can't use that for much either. Driver diameter.. Neither.

 

Input impedance = impedance = ohms I suppose.

 

Impedance is like resistance. I suppose you know about that?

 

Can't use total harmonic distortion (THD) for much really when just looking at the specs..

 

SPL is measured in either dB/V or dB/W. Will continue to help you later, this post will be long. This, along with impedance are really the only truly useful specs.

post #3 of 6
Quote:
Originally Posted by 5thAngel View Post

 

Ohms, impedence, total harmonic distortion, contact pressure, nominal impedence, magnet type, driver diameter, voice coil, maximum input power, input impedance, so on and so forth.

 

You can find most of them here.

 

Quote:
Originally Posted by 5thAngel View Post

 

Ohms, impedence, total harmonic distortion, contact pressure, nominal impedence, magnet type, driver diameter, voice coil, maximum input power, input impedance, so on and so forth. What part of the sound do things like this affect? I have seen cord type, max input power and a few others too.

...

I need clarification here please. A few measurements and stats aren't so common and I know this. I just want a breakdown of the usual suspects so to speak.

 

Quick answer: most of those don't affect the sound directly and/or by themselves. Here's a slightly more detailed discussion but don't skip on reading the glossary becasue I'm not going to put in definitions for all the terms I'm using here aside from a brief explanation of the specs you mentioned:

Impedance (measured in ohms) : impedance of the headphone drivers have more effect on what's driving the headphone than the headphone itself; high or low both have advantages or disadvantages. Generally, in most speaker and some headphone amps, lower impedance means more power is squeezed out of the amplifier, however, there are at least two things that need to be noted about amps. With most speaker amp an some headphone amp designs, lower impedance can mean more continuous power, but there's no more "headroom" or peak power to draw from for dynamic passages. For example a typical speaker amp is rated at 8ohms, then maybe 50% more or even double the power at 4ohms. Just because it has a 4ohm rating however does not mean it can drive 4ohm speakers well; it may provide more power for that speaker but as much as it may go louder it may lose dynamic range relative to an easier 8ohm load.

 

The other thing to note is that many headphone amps aren't designed this way. Some can make more pwoer at lower impedance, some can make more power at higher impedance. Speaker amps can be made that way but it's unnecessary because they don't have the same varied impedance range as headphones. Typically, a high impedance headphone needs an amp that has a lot more voltage, while a low impedance headphone will need more current. A low efficiency headphone will require both, more of one over the other depending on the impedance.

 

Nominal impedence : in layman's terms it's an average impedance. There is no transducer, headphone or speaker, that has a perfectly flat impedance throughout its entire frequency range; if there were and its response was flat then it's the absolute best headphone or speaker design and any amplifier that can get it loud enough would definitely all sound absolutely the same on it. Basically, in some headphones, soem frequencies can drop  the impedance, and if the amp can't handle that drop with enough headroom, you lose some dynamic range.

 

Total harmonic distortion : This is an amplifier spec. It basically refers to the deviation from the input signal at a given output level. Note that there are many types of distortion, such as euphonic distortion (as with vacuum tubes or even solid state designs) and then there's also clipping, which is what happens when you're pushing an amp too far, including but not limited to an impedance too low for it and at too high volume levels.

 

Contact pressure : Where did you even see this? I've never seen this on a headphone because as much as it's a reality measuring it is irrelevant given headphones have adjustments in the headband, plus some people deliberately bend the metal headbands out or inwards to decrease or increase contact pressure. Basically, you'd need a tight enough fit so the earpads are slightly compressed against your head, but too much will be uncomfortable on top of the drivers getting too close to one's ear, which affects the sound on many headphones. Some portable on-ears may need more pressure than circumaurals particularly if you're walking around wearing them.

 

Magnet type : Does not really affect the sound, just the packaging. A magnet is necessary for moving the transducers, but using a different type comes down to being able to use smaller and lighter magnets. You might notice that smaller speakers or car speakers, and also headphones, might have a higher tendency to use "neodymium" or "rare earth" magnet and cost more; that's also because you might want the same capability from a smaller magnet on a small high-quality multimedia speaker, tweeters that have to be mounted in a car's A-pillar or midwoofer's that need to be mounted in a car's door that has only about 3" of clearance (compared to a speaker cabinet you can build to any shape), or a headphone you need to hang on your head.

 

Driver diameter : Generally speaking, a larger dynamic driver can reproduce more bass, whether it's a fullrange driver (as on headphones and some speaker designs) or a specialized driver like a subwoofer. On a speaker system for example the subwoofer is always the largest, followed by the midbass+midrange/midwoofer, then the tweeter. However frequency response is measured at a given distance, so in theory, you can use any size driver and make it reproduce any range of frequency, provided you don't have to be sitting too far away from it, hence fullrange, hi-fi headphones (as opposed to fullrane speakers which are either very expensive or extremely cheap with no regard for fidelity, like on some stock car systems). With in-ear monitors, particularly because many were made by hearing aid manufacturers, balanced armature designs aren't the same as dynamic drivers especially when it comes to bass, so it's not unusual to see multiple-BA's being used with any number of them on any given frequency range, same way some floorstanding speakers are. Search for "dynamic vs balanced armature" here for more on this.

 

Voice coil : It's a part of a dynamic driver that, along with the magnet and suspension, helps it move air. Search for how a dynamic driver works to see how each part relates to each other in detail, but basically this is what is connected to the amplifier (or passive crossover on speakers) receiving the electronic signal, and with the other parts, they move the dynamic driver to pump in and out, moving air and making sound you can hear from the vibrations. You can think of this as a muscle, if you think of how doctors toyed around with electricity and went around sending a current through corpses and the muscles would move - like Frankenstein's monster without actually reviving a dead brain.

 

Maximum input power : just the maximum power, in watts or fraction thereof, that can be taken by a transducer before it can overheat the driver or push it beyond its movement capacity. Just because an amp makes more than that does not mean it's actually pushing enough into the transducer to damage it; it all depends on how loud you're listening. Low power amps being pushed too hard can distort, clip and damage transducers too.

 

Input impedance : Again, this isn't a headphone spec. Amps and preamps have analog inputs that are several thousand or hundred ohms; beyond that I have no technical know-how on why that is. This is not the same as output impedance on an amplifier driving a headphone or speaker, which typically needs to be much lower than what it's driving otherwise it may distort, but isn't the only determining factor.

 

 

 

post #4 of 6

Frequency Graphs give you an idea of the sound signature of a headphone.

post #5 of 6
Thread Starter 

Alright. Thank you guys for the help. If you have anymore I am open to hear. I hated looking at all of this not knowing what anything meant or how could apply it to building a system.

post #6 of 6
Just ask if there's anything..
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