Even before you start looking at sound quality, there are several more things about headphones that you need to know about. In the first instalment of this series of posts, you heard about the different types of headphones available. Continuing from there, this post will look at some technical aspects of headphones.
Do technical specifications matter? What are drivers? Do the number of drivers matter? How about the N-way (number-of-ways) crossovers? What about frequency range? Well, let’s find out more about them!
But before we go on, let me remind you about this. Technical specifications and characteristics are nice to know. They are nice for comparing with. Some of them may even be relevant. Nothing, however, beats listening with your own ears. So, please do not get carried away by the things you’re going to read here.
Different Types of Drivers
Drivers are speakers. These are the things that actually produce the sound. They’re just like the desktop computer speakers, or your home theatre speakers. Except that, of course, in a headphone, these drivers are much smaller. Far much smaller.
The drivers play an important part in the sound quality of the music produced in headphones. There are other important factors too, but certainly, sweet music has to start with the drivers. You’re not going to get good sound if the drivers can’t produce them in the first place.
In the world of headphones, drivers can be categorized into two primary types: dynamic drivers and balanced armature drivers.
Dynamic drivers are more conventional in design. They are also known as moving coil drivers, and you could have learnt about them during physics class in school. Generally, dynamic drivers produce warmer, richer sounds with deep bass, and they work pretty well across the entire musical frequency range. They are often cheaper to produce. However, it is difficult to miniaturize dynamic drivers down to the tiniest sizes without making some compromises.
Balanced armature drivers are characterized by their tiny, diminutive size. They are popular in hearing aids as well as more expensive in-ear headphones. I won’t bore you with the science, but if you’re interested in how they work, you can look up Google to find an explanation. Balanced armature drivers usually produce comparatively more precise and accurate sounds. However, compared with dynamic drivers, they only work well across a smaller frequency range.
You’ll sometimes come across what sounds like new types of drivers. However, if you dig deeper, you’ll often find that they are ultimately either a dynamic driver or a balanced armature driver.
One type is not better than the other. They each have their strengths. It is more common to find dynamic drivers in full-sized headphones, and balanced armature drivers in in-ear headphones. The AKG K518LE, Q460 and Q350 all use dynamic drivers. The flagship K3003 in-ear headphones are relatively unique: they use both dynamic drivers and balanced armature drivers.
N-way and Number of Drivers
If you have any sort of room speaker system, you’re probably familiar with the concept of subwoofers and the main speakers. These would be referred to as two-way speakers.
There is a difference between the number-of-ways and the number of drivers. The latter is simpler explain. It’s just the count of the number of drivers, or speakers, in the headphones. The former, however, needs a little more explanation.
Some drivers, particularly the balanced armature types, have more limited frequency range. To compensate for that, the headphones are designed with multiple drivers. Each driver is tuned to perform at different frequency ranges, like at the lows, mids, or highs. Balanced armature drivers generally lend themselves to more flexible tuning. Then, you need a crossover to send the correct range of frequencies to the drivers that were designed to perform them. The number-of-ways, thus, refer to the number of frequency ranges that the crossover splits into. A two-way headphone has a crossover that splits the incoming audio signal into two ranges, typically a bass and treble, which are then fed into two separate drivers, one tuned to handle bass while the other tuned for trebles.
The number-of-ways and the number of drivers can differ when there are more drivers than the number-of-ways the crossover splits the frequency ranges. For example, some in-ear headphones are designed with three drivers, but only two-ways, using two drivers for bass and one driver for trebles. The AKG K3003 is a true three-way three-driver design. As already mentioned, it is a hybrid driver design that uses both dynamic drivers and balanced armature drivers: one dynamic driver for the lows, and one balanced armature driver each for the mids and highs. This seems like a good mix, because, dynamic drivers deliver more convincing, deeper bass, while the balanced armature drivers will produce clearer, more accurate details in the mids and highs.
Currently, there are in-ear headphones that can go up to 4-ways and 8 drivers. More ways and more drivers may seem superior, at least on paper, but don’t forget that the ultimate test is listening with your own ears.
Should you believe the frequency range listed in the technical specifications? Is 10Hz – 20KHz better than 20 Hz – 18 kHz?
Truth be told, the frequency range doesn’t tell you anything about how well the drivers actually perform within that range. First of all, they may roll off toward the extreme ends of its stated frequency range. Then, do you expect that you would go from full-sound to no-sound when you cross over to the next Hz outside its stated frequency range? I.e. for a headphones with 20 Hz – 18 kHz, do you get appreciable sound at 20Hz but nothing, or even a sharp drop-off, at 19 Hz?
In fact, it’s not just the extreme ends of the frequency range that present problems. It’s quite possible for a driver to be stronger or weaker at different parts of the stated frequency range, or even distort sounds at parts of it. This is one reason why headphones can sound different from each other, even in the mid frequencies that are well within the comfort of their stated frequency range.
The human ear is capable of hearing sounds from 20 Hz to 20 kHz. Most people, however, only hear up to 16 kHz. At that high frequency, you might not even perceive much details, other than that they are just “high pitched” sounds.
If you read the technical specifications, you’ll come across a few things like impedance and sensitivity. Put simplistically, the impedance (i.e. resistance) is about how hard it is to drive the headphones. Most earbuds and in-ear headphones can be easily driven by any mobile phone, music player or other mobile gadget. Some full-sized headphones, however, have high-enough impedance that require a headphone amplifier to sound their best. The sales people at the audio shop should be able to advise you.
The AKG range of headphones (Q350, Q460, K518LE and K3003) all have relatively low impedance and don’t require any headphone amplifiers. If you want to listen to your music on-the-go, this may be an important consideration, because you may find it a hassle to carry one more piece of gadget, the headphone amplifier, even though there are relatively portable ones available. Remember that portable headphone amplifiers will have to run on batteries, which means you’ll have yet another gadget to charge.
Sensitivity refers to the “loudness” of the headphone, given a known standard input. High sensitivity sounds like a good thing. However, a very highly sensitive headphone paired with a high powered headphone output could result in noticeable noise at low output volume levels. This is usually not a problem with sound sources from mobile gadgets, but it’s usually good to be selective about where you play your music from anyway.
In-Ear Headphones Focus in Next Instalment!
You’ve learnt several things about the technical aspects of headphones. Just like owning and driving a car, you don’t have to be a car expert or a mechanic, but it’s good to know what’s under the hood. Similarly, it’s good to know what’s in your headphones.
In the next instalment of this series, I’ll zoom in on in-ear headphones. It’s my favourite type of headphones. You’ll find out more about them, so stay tuned!
This post was originally written as part of my participation in Omy.sg’s K3003 / The Sound of Luxury blog. I’m now reposting some of those posts, with some minor edits, on my own blog.