If you are an audio enthusiast or a professional musician and still haven’t heard about IEMs, then you are missing a lot. In-ear monitors/IEMs are very similar to earphones but offer way better sound thanks to their more complex architecture. They can offer high-fidelity and lifelike audio in a very compact package.
If you want to upgrade your listening experience, then we highly urge you to grab a pair. However, you will quickly realize that choosing the right pair for you isn’t a simple task.
In the past, all you needed to do was grab a pair from reputable brands such as Sennheiser, Shure, and Westone, and you’re good to go. But things have changed. There have been so many advancements in IEM technology, and you now have so many options from both reputable brands and more obscure brands that you have likely never heard of.
If you are very confused with how complex in-ear monitors are, then you have come to the right place. We present you with everything you need to know about IEMs all in one place.
We will be talking about various topics such as IEM shell materials, IEM driver types, sound signature, and many more. And hopefully, by the end of this article, you will have a more informed purchase decision.
This guide covers a lot of IEM related topics, so feel free to jump into any section that you need. And without further ado, we present you with the complete guide to IEMs.
Disclaimer: The models that we feature or recommend are the ones that we have personally tested or reviewed. We are not directly affiliated with any brands mentioned in this article.
IEMs vs. Earbuds
Before we dwell deeper into IEMs, let us first differentiate them from earbuds. In-ear monitors or IEMs are sometimes referred to as earbuds by general consumers and even non-audiophile manufacturers (Samsung calls their TWS earphones Galaxy Buds despite not being traditional earbuds). However, they should not be confused with unsealed earbuds that are commonly bundled with smartphones.
IEMs have a different physical structure and often have more complex driver designs. The most obvious difference is that IEMs have ear tips and are inserted directly into your ear canal. Earbuds, on the other hand, sit on your outer ear.
The deeper insertion gives lots of advantages to IEMs. Since they form a seal, they offer better isolation, meaning you do not have to turn up the volume as loud as you would with earbuds. This can be crucial and can potentially save you from hearing damage.
Additionally, the innovations in IEMs, such as the more complex driver structure seen on high-end models, have made them sound close to high-end over-the-ear headphones. This isn’t to say that there are no well-built or great-sounding earbuds. However, the fact is that most brands have generally spent their time and resources developing IEMs.
Of course, IEMs are not for everyone. Some may not enjoy the pressure sensation that you get while wearing IEMs. Some users may also have oddly shaped ears that simply do not play well with IEMs. In those cases, earbuds may be a better fit.
The first thing that you have to decide is what you will be using your IEMs for. This will help determine what kind of sound signature and build quality your IEMs should have to fit your desired application.
IEMs are generally designed for music listening or professional applications. Of course, you can use any IEM for both use cases, but IEMs that are designed for a specific task will generally perform the best.
For professionals, we highly recommend prioritizing build quality, comfort, and sound quality. Build quality and comfort are prioritized since these will mostly be used in live or studio scenarios and will be continuously worn for several hours.
As for enthusiasts, sound quality is the most important aspect to consider. Of course, you still need great build quality and comfort. However, these do not need to be taken to the extreme since these IEMs are not meant to be abused.
One of the most important things to consider when buying IEMs is their build quality. Even if you have the best sounding IEMs, they will be useless if they fall apart in just a matter of months. So in order to prevent buying poorly made IEMs, we’ll learn what materials make a durable IEM.
Different manufacturers use different kinds of materials for the shell of their IEMs. The materials used to affect not only the durability but also the acoustics of the IEM.
Additionally, shell materials aren’t the only thing that we need to go through. We also have to take note of the overall construction of the IEM. That is why it is also very important to do a background check on the brand or model that you are interested in. Brands that have poor quality control are generally well documented online.
Also, despite most brands having better QC tolerances, there is still a chance that you may end up with a defective unit. So always make sure that the brand you are dealing with has a good warranty or exchange policy.
Here are some common IEM shell types.
Acrylic shells have been gaining popularity with a lot of newer universal IEMs. This is because they look great, they are durable, and are comfortable. Most manufacturers use medical-grade acrylic to make sure that they do not cause any issues with your skin.
Another perk of this shell material is that IEMs can come in a clear finish. This allows the brands to show off the internals and design of their IEMs.
Acrylic shells are most common with Custom IEMs (CIEMs) or custom-molded IEMs. But as we mentioned earlier, universal IEM manufacturers are also adapting this material. We will be talking more about CIEMs in their separate section below.
The main disadvantage of this shell is that they are prone to cracks. They are durable enough for daily use. However, major drops or accidents can crack and potentially ruin the shells. Luckily, IEMs with acrylic shells can be easily reshelled by the manufacturer or via third-party services.
Another popular choice for universal IEMs is aluminum. This material is very sturdy and can look very good when utilized correctly. Aluminum is mostly used with universal IEM shells but is not used with CIEMs since they cannot be easily molded.
Some brands such as Campfire Audio utilize the acoustics of the aluminum shell to achieve their desired sound signature. This is the concept behind their TAEC technology found on their highly acclaimed Campfire Audio Andromeda IEM that is capable of producing a spacious sound.
Just like acrylic shells, aluminum shells have their own downsides. Most aluminum shells are prone to scratches and paint peeling. They are also quite heavy, which can lead to discomfort during long listening sessions. And lastly, they can feel cold when initially wearing them.
Plastic shells are commonly used in budget IEMs due to their lower cost. They do the job, but it is generally not the best choice. Compared to every option on this list, plastic shells are the least durable. And if the overall build isn’t good, to begin with, don’t expect your IEMs to last.
They do have some upsides, such as their lightweight design. They also hold up well enough if properly taken care of. But overall, the other shell materials on this list are simply better.
Other Shell Materials (Silicone, Titanium, etc.)
There are, of course, other materials that are used for IEMs. However, these aren’t commonly seen on most production models.
Silicone, for example, is a material that was previously used for CIEMs. However, most manufacturers have chosen acrylic as the default choice since it is more comfortable and durable.
Another material that is rarely used for CIEMs is titanium. At the time of writing this article, the Fitear Titan UIEM/CIEM and Fitear EST Titan UIEM/CIEM are the only IEMs that utilize this material.
The use of titanium makes the IEM feel very durable and premium. However, the complexity of the process and the long production give these IEMs a very high price tag. And that is possibly not something that other IEM brands can offer.
UIEM Nozzle Material and Size
Aside from the shell materials, you should also pay attention to the size and material used for the IEM’s nozzle. This part is very important for universal IEMs since it determines the type of ear tips that can be used. It also determines the durability of the nozzles.
Some nozzles are shallower or wider than others. This can cause issues when using third-party ear tips. Most IEMs that we have reviewed didn’t have any issues. However, we had a few that didn’t play well with our Azla Xelastec ear tips.
Common nozzle materials include plastic, aluminum, or resin (directly part of the shell). We have reviewed several IEMs and have encountered these three materials. All of them held up pretty well.
However, we imagine that poorly implemented plastic nozzles can eventually snap. This can cause major damage to IEMs or major issues if they happen to snap while wearing them.
Fit, Comfort, and Isolation
Aside from the build quality, other aspects that should be considered are fit, comfort, and isolation. If an IEM does not fit well, it will not be comfortable for long listening sessions, and it will not create a good seal. And if it doesn’t create a good seal, the sound quality will be impacted.
To know if your IEM fits well, try wearing them for at least an hour. Your ears should not feel sore, and there should be no pressure points. Also, a good seal should be formed, which can be determined by listening to the low frequencies.
A good IEM seal should enable you to hear full-bodied bass. If the bass seems off or tinny, and if you can clearly hear external noise, this usually means that you are not getting a good seal.
We highly recommend changing ear tips to get a good seal. Most IEMs include at least three pairs of silicone ear tips, and some even include foam ear tips. If you are having comfort issues or are still struggling to get a good seal, we highly recommend trying third-party ear tips, which have a dedicated section in this guide.
But one thing you must consider is that some IEMs may not play well with your ears. This is normal since not all ears are the same. Universal IEMs are made for most ears, but they will surely still not be compatible with unique ear shapes.
Again, we highly recommend trying out IEMs at stores or purchasing from stores with a good refund policy to avoid such issues. You can also get CIEMs to get a perfect fit. We’ll talk more about them in their dedicated section.
Third-Party Ear Tips
As mentioned earlier, you can purchase third-party ear tips to improve fit, comfort, and isolation. These ear tips come in all sorts of flavors.
There are silicone ear tips that are very soft and comfortable. There are also foam ear tips that mold to the shape of your ears. And, there are hybrid ear tips that combine the properties of silicone and foam.
There are even TPE (Thermoplastic elastomers) ear tips that can be deformed to mold to the inside of your ear through body heat. And while they still won’t replace CIEM solutions, they will get you close and help you achieve a great listening experience.
However, these aren’t the only things that ear tips can provide. Ear tips can actually alter the sound of your IEMs. These aren’t drastic differences. However, these are measurable and can affect how you enjoy your IEMs.
Some ear tips can alter the bass response, while others can slightly increase vocal presence and soundstage. We have listed our favorite models below, and we urge you to try them to get the most out of your IEMs.
Final E Type
JVC Spiral Dots
Removable Cable and Cable Type
One of the best breakthroughs in IEMs is the inclusion of removable cables. Cables are the first thing that breaks with regular earbuds. But since the cable is now removable with IEMs, their lifespan is significantly extended.
The only issue is that there is no standard cable interface. Each company uses a different cable type which can be a pain when shopping for aftermarket cables. We will be going through the common cable interfaces along with their pros and cons.
MMCX (Micro-miniature coaxial) is often seen in older generation IEM models such as the Shure SE 215. They used to be considered the standard, but most brands have moved on to different connection types. There are still brands such as Campfire Audio that use MMCX on their high-end IEMs, such as the Andromeda, Ara, and Solaris.
The MMCX interface offers good stability due to its locking mechanism. This means that your IEMs won’t be going anywhere as long as they are connected to the cables. Other options, specifically the 2-pin interface, aren’t as secure and can often lead to the IEMs accidentally detaching from the cable.
There are, of course, some known issues with MMCX. IEM shells tend to spin, which can be annoying when trying to wear them. The lock also proves to be a double-edged sword since detaching the cables can be very hard.
The worst issue that can be encountered is that MMCX sockets can wear out over time. And when this happens, the connection won’t be stable, making the audio cut out. Nevertheless, MMCX connectors aren’t bad, and many brands still trust this cable interface.
The most common cable interface for modern IEMs is the 2-pin connector. Unlike MMCX, 2-pin cables are easier to attach and detach. They also do not spin around, making wearing IEMs a lot easier.
The 2-pin connection system is, however, still not perfect. They can still become loose over time, especially if the cables are always being detached from the IEMs. The 2-pin sockets in entry-level IEMs wear out faster and can lead to the IEMs accidentally detaching from the cable.
Despite their downsides, newer manufacturers and CIEM brands prefer them over MMCX due to their stability. Overall, the better cable interface will depend on your personal preference.
It is worth noting that there are different variations of the 2-pin design. The standard size used in most IEMs is 2-Pin 0.78mm. Always make sure to check if your IEMs have a different size 2-pin connector.
Proprietary (Sennheiser, JH Audio, Fitear, Ultimate Ears, QDC Reversed 2-Pin, etc.)
Some manufacturers such as the ones stated above also use their own proprietary cable system. They aim to fix some of the common issues found with 2-pin cables and MMCX cables and to overall improve the stability and durability of the removable cable of their IEMs.
We have tried Ultimate Ears’ IPX SuperBax system and the Fitear 2 Pin system (same as Sennheiser 2-pin for the Drop HD6XX series). Both were very good systems since they had a locking mechanism. However, unlike MMCX, they were easier to remove, and we did not encounter issues despite several years of use.
Driver Type and Driver Count
The most important aspect of any audio device is, of course, the sound quality. It is, after all, the reason why you are buying IEMs. Before we get to the main section, let us quickly talk about drivers and driver setup. Just like full-sized headphones, IEMs are also powered by drivers.
Most IEMs either utilize dynamic drivers or balanced armature drivers. You can read our guide for an in-depth discourse on this topic. But basically, most dynamic drivers produce better bass while most BA drivers produce better mids and highs.
But with the advancements in technology, manufacturers are able to utilize multiple drivers in IEMs. Manufacturers can even combine balanced armature and dynamic drivers to utilize their strengths and circumvent their weaknesses. This produces a unique sound that is normally not possible with a single driver configuration.
However, we want to stress that driver count shouldn’t be the only basis for IEM purchases. An IEM can have as many as ten drivers per ear but still not sound good if they are not implemented properly.
High-end IEMs such as the Fitear Titan only contain two drivers. Other IEMs such as the Sony Z1R only utilize one dynamic driver. So the takeaway here is that the tuning and the implementation of the drivers are the keys to making a great-sounding IEM.
Sound quality is subjective. What sounds good with one person may not sound good to the other. But to objectively understand what makes an IEM sound good, we need to understand the concept of tuning and technical performance.
There are different tunings available. Common tunings include V-shaped where the lows and highs are more pronounced, and the mids are a bit recessed; flat tuning/neutral tuning where no specific frequency is highlighted; mid-focused, where the mids are highlighted; dark tuning where the highs are recessed, and the lower frequencies are more emphasized, etc.
The thing that you should take note of is that there is no best tuning. Tuning is pretty much subjective and will depend on your use case or your preferences. Some users may like bass, while others may like a more accurate representation of their music.
Of course, professional users will need a neutral or flat-tuned IEM that can easily adapt to their mixes. Musicians may also want an IEM that best reproduces the key frequencies of their instruments.
For those who are interested, you can further understand sound signatures by reading their graphs. You can learn more in our dedicated article about headphone frequency.
Another thing to consider is the technical performance of the IEM. Two IEMs may have similar tunings. However, their technical performance may differ.
For example, two IEMs can be bassy. However, one of those may be technically superior and can produce deeper, more textured, and more detailed bass over the other. This can be due to better and more capable drivers, but there are lots of factors that can determine this.
Overall, when auditioning or purchasing an IEM, make sure that you like the sound signature or that the sound signature fits your intended application. Also, to get the most enjoyable experience, make sure to get technically capable IEMs. These can usually be found with mid-fi and high-end IEMs.
CIEM vs Universal IEM
For those looking for the perfect fitting IEM, you can achieve that by purchasing a Custom IEM. CIEMs are molded to fit your ear, which gives you a perfect seal and superior bass response to any universal IEM. Also, CIEMs will be superior to any universal IEM in terms of comfort.
Additionally, there are also lots of IEMs that are only available in the CIEM form factor. These include Ultimate Ears CIEMs, Fitear CIEMs, etc. This is because their IEMs are specifically made to be experienced with the CIEM form factor.
And if you are a musician, upgrading to a CIEM is highly recommended. They block off more sound compared to UIEMs. This is crucial in helping protect your ears and hear your mixes better during live performances.
And the best part about CIEMs is that you can customize the aesthetics to better suit your personality. Depending on the manufacturer, you can potentially customize the faceplate and the shell colors.
There are, however, several things to consider when purchasing your CIEM. The whole process of ear molding and CIEM production will take at least one month. Most CIEM makers do offer a rush service, but often with an added fee.
And depending on how good the audiologist is, the CIEM may not perfectly fit your ears. Of course, companies offer refit services if this ever happens.
And the last downside is their resale value. Since they cannot fit others (unless they pay for a reshell service), they are generally not sought after. This is why you must be 100% sure that you like the sound of the CIEMs before purchasing them.
But overall, we believe that the benefits of CIEMs outweigh the downsides. If you can afford them, we highly recommend purchasing a custom pair.
The most important thing to consider when buying IEMs is your budget. Make sure to identify how much you are willing to spend and the goal of your investment to get the best bang for your buck.
Spending less does not mean you will be getting a bad pair. And conversely, spending more does not guarantee that you will get the best sounding IEM. This is why it is important to try out the IEM in person to see if it is a good match for you.
We highly recommend spending at least $200 since we consider that to be the sweet spot. IEMs in this price range often have a great build and sound quality. And if you have a more flexible budget, we advise checking out IEMs in the $300-400 price range.
Stephen is a musician, cinematographer, and headphone enthusiast who is passionate about reviewing audio equipment. He has been playing guitar for at least a decade, which introduced him to professional recording equipment such as headphones and in-ear monitors. With the help of reviews and online content, he was able to learn the ins and outs of the hobby. His goal is to give back to the community by providing quality content to help others enjoy the beautiful (and expensive) world of audio.
Favorite Headphones: Sennheiser HD660s