When you shop for headphones, it’s important to look at the specifications and the technology details that come with it. The driver type is something you will see specified in each pair, and a lot of times that will tell you a lot about the pair before you even listen to them. That begs a few questions: what is a headphone driver? Why is it important? What is the difference between them?

To put it simply, a driver is the mini speaker in each headphone that ‘drives’ the sound into your ear. It converts the electrical signal into sound waves, and allows us to hear all the sound we want it to output. There are a lot of different drivers that can be used, and they range from different sizes, materials, function, and so forth. All those things can affect the sound quality in a pair of headphones, so it's essential that companies take time and care into the driver they build. 

In this article, we talk about headphones with drivers of 40mm and 50mm. This seems like a small margin, and it is in the grand scheme. Drivers can be as small as 10mm in a pair of earbuds or as large as 90mm in over-ear headphones. As a basic comparison, there a few key differences between large and small drivers. For one, larger drivers have the capacity to move more air, so they can produce more depth in their sound and across a wider range. Headphones with large drivers have a tendency to have really rich bass tones, as well as be a little bulkier in design. Smaller drivers, on the other hand, provide better clarity in the upper ranges, as well as drive with less power. They are more efficiently run with more compact designs due to the smaller diameter. Again, I'm clarifying that all this is a general comparison, as the driver’s tuning and material composition can play a big factor in how it produces sound. 

40mm and 50mm isn’t a big difference in terms of size, but it can mean all the difference in a pair of headphones. Is there a noticeable enough difference between them? That depends on the listener and how sensitive their ears are. If you are an active listener, you might be able to pick up some slight differences between them and find you prefer one over the other. Let’s look at a list of some top picks that have 40mm and 50mm drivers, and you’ll see that they share a lot of the same qualities. 

Focal Bathys: 40mm – $699

The Focal Bathys were a favorite of mine when testing. The rich sound quality paired with an impressive bass response was an easy way to win my vote. This pair comes with a 40mm magnesium and aluminum driver, and it impressed me with its comfort and consistency while listening. This metal made the mid and high frequencies have a touch more brightness than I was expecting, and it made vocals and hi hats pop in every mix. As one of the headphones with the smaller driver, it was easy to pick up some sunny clarity in the higher end and a more narrow soundstage on the overall imaging. 

Bowers & Wilkins Px8, 40mm – $559

This is a brand that has yet to disappoint me. I was always a fan of the smooth sounds that Bowers & Wilkins provides, and this rings true with their Px8 headphone model. The dynamic 40mm driver is full-range and made of carbon, and it helps the headphones with easy listening. You can tell that these come with the smaller sized driver, as the bass is on the reserved side and the headphones themselves are more compact. An earlier model from this brand, the Px7 S2, is worth mentioning as an option that provides a lot of the same qualities at a lower price for people looking for a more budget-friendly option. 

PSB M4U 8 MK II, 40mm – $249

I was surprised to add the PSB headphones to this list. The 40mm dynamic driver in the M4U 8 allows for very natural listening, something they specialize in with their headphones. These strive to recreate space as if you were listening to a pair of speakers with room tone, and they achieve just that. There isn’t a lot of bass response, which can be expected, but it was easy to listen to these and enjoy my favorite tracks. 

Sivga SV021, 50mm – $149

The SV021 comes in at a lower price point than some of the other Sivga models, but the sound quality isn’t compromised. Stunningly, the 50mm dynamic driver delivers a punchy bass that drives the rest of the frequency response and a soundstage that is wide and inviting. Sivga’s other headphone models offer 50mm drivers, and a few others were a part of my testing process while looking at the larger driver range. Safe to say, Sivga holds a high place for standards in the 50mm driver game. 

Fostex TH808 Premium, 50mm – $1,299.99

These are on the top end of people’s budget most likely, coming in at over a thousand. For those who are looking for a premium headphone, this will likely check a lot of your boxes with the quality right in the name. Fostex TH808 Premiums have a 50mm Neodymium Magnet driver, which allows for the frequency range to have excellent sound reproduction. There is excellent clarity and richness in every area, which makes these definitely worth the purchase. 

Dali iO-12, 50mm – $1,300

Again, these land on the higher end of price scale. Their square ear design allows for easy noise-cancelation, and the technology included with the ANC feels like a precaution more than anything. Dali implements a 50mm dynamic driver that you can hear, with a wide soundstage across the board and a substantial low end. They were comfortable and easy to use, and I can definitely see why these are as popular as they are. The slightly larger driver here comes into play with its imaging accuracy, clear listening and bigger design.

Summary

After going through the list, it is clear to see that 40mm and 50mm have a lot of similarities, and both can make a great headphone. At the end of the day, determining what you like best in a headphone will help you make a decision on what kind of driver you like best. If you lean more towards a wide soundstage with a heavy bass, going on the larger end for drivers is a smart move. If you value efficient functionality and compact design, definitely look for headphones with smaller drivers. Testing these different types of headphones is a great way to tell what your ears like best!

You can demo and purchase the headphones mentioned in this article at Audio46.