What are CIEMs?

In-ear monitors (IEMs) are devices used by musicians, audio engineers and audiophiles to listen to music or to hear a custom crafted mix of vocals and stage instrumentation for live performance or recording studio mixing. They are often custom fitted for an individual's ears to provide comfort and a high level of noise reduction from ambient surroundings.

The in-ear monitors themselves are the last stage of the signal path in the system. The IEMs are often custom molded, hence called CIEMs (custom in-ear monitors) and therefore are more comfortable to wear and allow the sound to be sent directly into the user’s ear canal. They also provide a better seal, though it is only able to isolate ambient noise, thus resulting in a lower level of ambient noise heard. Depending on the quality of the fit and length of the canal portion of the earpiece, a custom fit in-ear monitor will generally provide somewhere between 25 and 34 Decibels of noise reduction. Custom in-ear monitors come in a variety of colors but usually are clear or a color that closely matches the skin color of the performer. Some manufacturers can also place custom artwork directly on to the custom in-ear monitors. The IEM cable plugs into the receiver pack via a 3.5 mm stereo jack clipped onto the belt, guitar strap, clothing of the performer, or placed in a pocket. Non-custom IEMs are also available and include a variety of universal foam and silicone tips that will fit into most people's ears.

Generally speaking, custom molded IEM are very good in quality, but with a high price tag. If you are not those who have an unlimited budget, budget custom like Rooth Pro Audio or Cosmic Ears are among some of the best budget custom IEM makers out there, providing quality products with the advantage of custom yet cost much less than products from big name companies like Westone, UE, JHAudio and Unique Melody.

A few things you might want to know before investing into Customs:

  1. A good impression is essential for a good fit. DIY impression kit is very simple to use, but often the impression isn't as good as those from professional. Trying to save cost and time by using DIY kit sometime will cost more time and money as you will need to redo the impression again and again to get a good fit.
  2. Unlike universal IEMs, the product life cycle (how long you are expected to use the product) of custom is quite short, often estimated to be less than 5 yrs. The reason is, your ears will keep growing till you kick the dust, therefore your ears will change in a couple of years thus render your custom useless as it isn't custom to your ear anymore.You should expect to get a new custom (or at least a remold of your old custom IEM) every few years in order to prolong its shell life. Note, many IEM companies do not re-shell / remold old IEM, thus you should ask the corresponding company about detail of remolding service before ordering. There are companies in the market that do provide reshelling service for custom IEM from another company, or even turning universal IEM into custom.

    Of course, there are exception that people are able to use their custom for more than 5 yrs. The experience very from person to person on different age group thus there is no definite answer to how long your custom will fit your ears.


Monitoring System

A monitoring system is any system that provides a mix of audio sources to a performer on stage. Traditionally, monitors were loudspeakers placed on stage directed toward the performer (often called floor monitors or wedges). Depending on the sophistication of the audio system, they may be more distracting than helpful to their singing. Since performers wear an IEM in each ear, they can also hear a stereo mix if a particular monitor system allows it. This can allow additional definition of the audio by panning different elements to each ear. Recent advances in this technology also allow the user to incorporate an ambient feature, allowing them to adjust the amount of ambient noise filtered by the IEM.

One additional consideration for mixing IEMs is that while getting rid of floor wedges can improve the overall clarity of the mix for the performers and decrease the overall volume on-stage, one important piece that is often lost is crowd noise. It is not uncommon for a microphone to be placed near each side of the stage, facing out to the audience, to provide a way to get some of the crowd noise back into the performers' IEM mixes. Larger live shows could have several microphones for this purpose spread across the front of the stage, which could also be sent to a multitrack recording device used in an outside broadcast production truck, or other destinations.


Shell materials

  • Acrylic: Acrylic is a hard material that is smooth to the touch.  Acrylic shells are usually said to be more durable due to their hard properties, and easier to insert/remove than silicone.  However, they are usually a shell and not a full fill (EM3 Pro is not a shell, but solid acrylic), so they can break.
  • Silicone: Silicone is a softer, more pliable material that is generally regarded as more difficult to work with for custom IEMs.  There are many different types of silicone, so the specific properties cannot be summarized.  Silicone can discolour (white or clear) over time, and some say is more prone to shrink.  However, silicone does give better isolation than acrylic and is more comfortable.  Also, since it is pliable, it is said to be better for singers as they won't lose the seal when there are mouth movements. Some silicone can shrink, while some manufacturers use a harder silicone material compared with others.  Softer material can provide more isolation than harder material, however there are other factors such as canal length that play into isolation.
  • Vinyl tips: Some manufacturers such as Westone uses vinyl tips. The comfort levels are said to be closer to silicone than acrylic.
  • Filled acrylic: Some manufacturers such as Earsonics and Starkey Norway fill their shells, which provides more isolation and a change in sound properties.



Customization of an earphone allows for the opportunity to also customize the artwork for many manufacturers.  There are levels of customization ranging from just shell colour to complete customization of the canal colour, shell colour, backplate colour and artwork.  Silicone shells usually have the least options, however Minerva can do some artwork.  Some companies that provide great artwork include Unique Melody, Earsonics, Hidition, 1964 Ears, JHA, and a special mention should be made of Heir Audio as they have created some spectacular artworks.


Proper fit and refits

It is important to have a proper fit with your custom, just like it is important to use the best tips for your universal. With an improper fit, the sound will not be ideal.


Ear Impressions

Impressions are critical to avoiding refits. It is important that the audiologist follows the manufacturers directions and the impressions are deep. If you are sending impressions overseas, it may be worth it to you to get 2 sets of impressions done either by different audiologist or by the same audiologist (if they will give you a discount). This will allow you to pick the best and see if there are differences between the two. Typically, acrylic shelled custom IEMs require an open mouth impression while silicone requires a closed mouth, but double check with the company that is making your custom IEMs.

The audiologist you choose should be familiar with taking impressions for customs, not just hearing aids. Many companies recommend opened mouth with a bite block, but regardless, you should be relaxed and not talk when your mold is being made. However, it seems that some audiologists have recommended people open and close their mouth during the impression process. It appears there is no right or wrong way to do it, but I would get an impression the way the custom manufacturer recommends.

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