Scientifically Understanding Good Headphones

It’s a daily drivel! I’m sick and weak and barely able to eat so this is about all I can do to pass the time. In addition to writing, and philosophy, I’m also an audio geek. This is more than someone spending $200 on a pair of Beats. I was the chief sound engineer of a music venue and in time a part owner of it. When I say amp, I don’t mean a guitar amp, I mean a black rectangular block of wire and power, pure awesome power. In my living room I have a PA system. That’s how much of a geek I am. I also own five headphones stretching through the various times of my life leading me to audio fidelity heaven.

I started off not knowing much at all about headphones, or audio, or music. My first pair of headphones were the Grado SR60 (now SR60i – which makes me feel ancient since Grado never changes anything). Great pair of headphones for under a hundred, their bigger brother, the SR80, is a better upgrade for not a lot more. There’s an even better headphone than both though, that’ll be below, it’s the Sony MDR-7506. From their I bought a bad pair not knowing what I was doing. And then AKG 70x series headphone, with amp, and digital-analog converter. Then something fun, that’ll be at the end.

I thank the Beats for making people think about spending more than $5 on a pair of earbuds. That’s all I thank them for. They are terrible headphones. The idea that they resemble studio equipment is an affront to me. It’s that bad. Most people making this claim might be brushed off as simply contrarian to popularity. For a lot of people this might be true. But the claim can be measured objectively. The claim that most headphones are good can be met objectively. Most headphones are bad. The only reason why you don’t hear about it is because not a lot of people have listened to studio grade equipment. Once you do, then you look back and go “oh”. I did that. The only way is to actually hear the difference.

But there are objective measures and knowing them will help you find ones to test and listen to.

This isn’t bashing like most sites (I’m thinking of the pretentious snobs at Head-Fi at this moment). I’ll use Beats as an example so you know what the claim is to begin with. For starters I’ll accept that you know what a frequency is when dealing with sound. What is meant by studio grade? Well, one of the reasons why they are not studio grade is because they do not have what is known as flatness. This is the simple concept that for every frequency, from 20hz to 20khz, they do not play one frequency more loudly than another when given the same voltage. Flatness is chased after with insane fervor in the world of audio because a flat speaker, a flat amp (which powers the speaker), and a flat DAC (converts digital signals to analog voltages), means that the sound is perfectly reproduced. There’s more to it, specifically square wave tests. This is where a square wave at a certain frequency is fed through the speaker, locking it all the way in one direction, then instantaneously snapping it all the way to the other direction.SquareWave_700 In and out instantaneously and holding it. These are very hard things for a speaker to do and they flutter and fail to hold resulting in a saw tooth wave (one that slopes down from the initial peak). Having that knowledge of frequency response and square wave tests lets one look at a chart and know for all intents and purposes how that pair of headphones will sound. In a square wave test, if they hold the shape, perfect (the one below is pretty good). If the initial movement upwards is high, then it’s an overshoot and can be sharp to the ears and mildly painful at higher volumes, too slow and it lacks detail, if it shoots up really high and then drops below the zero horizontal line, then it has phase issues and will be garbled. But this is what a real one looks like:graphCompare (1)

Flatness can be had for just about $100. It’s the standard pair of headphones found in every studio and on every movie set. They’re so ubiquitous that it’s absurd and they last forever. They’re the Sony MDR-7506. Here’s what I mean by flat:

graphCompare

As you can see, it’s not perfect, but ignore the ends that aren’t flat, those can barely be heard by the human ear and if you’re listening to Spotify they won’t be there at all in the music stream. It’s good, but nothing under $10,000 is in fact flat. So for $100 bucks it’s ridiculous. That’s studio grade. What sets it apart from the Beats is that the area from 100hz up to 300hz (the graph is logarithmic so it’s two lines to the right of 100) it isn’t flat. There’s a hump. A big hump. That’s the area that is usually called warm by engineers. It’s also where it’s called muddy. A little hill and it feels cozy and classical music has more heft, but too much and it doesn’t work anymore. 3 decibels is considered acceptable and still an accurate reproduction of music. With more than 3db (which is also the threshold for an average human to hear a difference in volume) the music is overwhelmed with bass and our brains naturally equalize to it so the other frequencies sound distant. And it’s called muddy because it’s too thick, that heft is too much, and the music just slogs on.

Earbuds are at the other end of the spectrum. Their tiny diaphragms can’t produce low frequencies at all. So everything below 250hz is basically non-existent. They also over emphasize the high end, from 1khz on up. It creates the acoustic effect called tinny. Think of it like tinnitus (though I have no clue if they’re related). There are good earbuds out there, Shure makes some spectacular ones, but it’ll cost you. The advantage of those is that they seal the ear so environmental sound can’t get in, perfect for planes.

Then there’s infrasound, or sub-bass. This is the kick in the chest that subwoofers produce and it’s imperative that there is good square wave reproduction to really get a solid punch. Beats favor this sound on a frequency response graph so you would think that they would be good bass headphones, but like most headphones struggle they to reproduce it. No clean square wave. This is where the square wave test is important – quality. Below, the blue is what is wanted. Something close to what a square would look like. The beats are an example of what most cheap headphones do. They dip below the line after an initial spike (the impulse) rather than following the blue line and remaining in position. That dip is the speaker moving past the neutral midpoint and beyond. That means, in short, that it’s creating a second sound wave outside of the first one. It’s called phase because it’s producing the opposite of what it’s supposed to do. There isn’t a nice push of air out and then a nice pull back in tune with what impulse is applied (remember, it’s dipping back while the signal should have it locked in a single position), it wobbles and introduces noise in a sense.

 

graphCompare (2)

What about fun? I love fun headphones, my gravatar is of my fun headphones. It’s that kick that we all love and is 100hz and below, centering around 60hz (the graph above is 50hz). That’s the frequency that a kick drum is centered on. It’s also the sound that makes our brains go nuts and we can’t get enough of it in electronica or metal or even classical music. It doesn’t matter whether someone is a music snob or someone who just likes listening to music for fun, a little more kick can make music a lot more fun. And as much as engineers chase flatness, sometimes hitting that sweet spot of a touch more punch is what is wanted.

Beyerdynamic Custom Pro One. They’re what I use for the graphs. Pretty damn good. $200 bucks best spent on headphones in my life. You can control how much kick is involved, from flat to booming, with a little switch on the back. And they rumble. God do they rumble. Listening to Radiohead’s Incredible Sounds of Orgy makes my jaw shiver every time the deep rumble seeps into the foreground. It’s flat too. And it kicks. It’s perfect. It still sounds like a closed headphone. It’s hard to describe, it just sounds claustrophobic (another audio term that can only really be described by having someone hear it). But they sound wonderful. In short, it’s the marriage of engineering and fun by hitting the sweet spot in sub-bass while leaving midranges and highs to sparkle.

I hope that helps you see what goes into good headphones and bad ones. I have good ones that are affordable as examples of what you should be looking for. At Headphone.com you can find these charts all over the place for each headphone. InnerFidelity also has them for their reviews. There’s a science behind all of audio, good and bad can be measured objectively when it comes to hardware. Most headphones are bad. Many have phase issues, many have bad frequency responses, it’s why studio gear like I have costs $700. The manufacture and design of good headphones is incredibly difficult and requires advanced engineering techniques. So it pays to shop around, and most importantly, try the headphones before you buy. But with this you can at least narrow down what you want to try.

 

http://www.headphone.com/headphones/beyerdynamic-custom-one-pro.php#tabs

http://www.headphone.com/headphones/sony-mdr-7506.php#tabs

http://mathworld.wolfram.com/SquareWave.html

 

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