If you take a first glance at the new Apple EarPods, you’ll notice quite a few unique characteristics about them. Their shape is probably going to be the first one. However, the multiple holes in the stem, front face, as well as the back of the earbud aren’t aesthetics.
A port on the back of the earbud, and even at times hidden on the front, are common practice for many IEM manufacturers. Generally, a port allows better bass reproduction through the majority of the spectrum, each providing a different use to boost the bass levels. One such IEM that uses dual porting is the Brainwavz M5 with one visible port in the back and one hidden right underneath the silicone (or foam) eartip.
However, Apple’s odd 3-port system is used by no one in this industry. In Apple’s system, there are some curveballs. Some of the ports boost the bass, some reduce. They each focus on a different part of the bass as well. Even further, one of the ports also controls the upper highs.
So let’s take a quick look at the first port, the front port. This port is actually here to control the bass, rather than boost it. This, essentially keeps the bass in check by reducing the low-to-sub bass regions. When you cover this port, the bass will increase dramatically. It is not favorable to completely cover this port.
The next port we’ll look at is the port in the rear of the housing. This is the port that has been used on a lot of Apple’s headphones. I haven’t tested it on the others, but on the EarPods, this port gives a small mid-bass boost to tighten up the bass a bit, but also controls the upper highs producing less air. Covering up this port results in an unnatural amount of airy space and thins out the bass a bit. It’s not recommended that it be covered.
The last port that is used is the port visible on the stem of the EarPods. Other manufacturers that have a port in this region usually have a bit of space between the strain relief and cable that allows airflow (at times, this is called the boot). Apple has created a physical port. These serve to boost the sub-bass. Additional airflow in and out of this port allows the sub-bass regions to be boosted allowing for better texturing. If any of the ports could be covered, this would be the one. It would control the bass just enough to balance out the headphones a little better.
Apple engineers used these 3 ports to fine-tune the headphones to the sound that they wanted. The result is a boomy, v-shaped sound signature that has become popular in the consumer market. Modding these areas with filters and other things may prove worth-while to tune a great earbud. It may also be a bit of work though.