What Affects Custom IEM Impressions?

What Affects Custom IEM Impressions?

What Could Go Wrong with Custom IEM Impressions? Lots.

Custom in-ear monitors (IEMs) are often seen as the ultimate solution for personalized audio. However, several factors can impact the accuracy of custom IEM impressions, leading to ill-fitting and uncomfortable monitors undermining the exact reason you ventured down this path to begin with. Understanding these potential pitfalls can save you from a painful and frustrating experience. Here’s what you need to know about what can go wrong with custom IEM impressions.

Anatomical Narrowing of the Ear Canal

One significant issue with custom IEMs is the anatomical narrowing of the ear canal. This natural constriction can make the molding process quite painful. During the impression process, the mold material can get stuck behind this narrowing, making the process of removing the mold extremely painful once it's in place. To address this, it’s crucial to work with a skilled audiologist who can adjust the molds to account for these anatomical variations, ensuring a more comfortable and precise fit.

Weight Gain or Loss

Significant changes in your body weight can also affect the fit of custom IEMs. Weight gain or loss can change the shape of your ear canal, leading to a poor fit. If the custom IEMs were molded when you were at a different weight, they might not fit properly after your weight changes. This underscores the importance of getting new impressions if you experience major weight fluctuations or holding off to begin with if you anticipate changes.


Being sick can impact the shape and size of your ear canal. Conditions like colds, sinus infections, and allergies can cause swelling and fluid buildup in the ears. This can lead to inaccurate impressions and, subsequently, ill-fitting custom IEMs. It’s best to schedule your ear impressions when you are in good health to ensure accuracy.

Recent Flying

Flying can cause changes in ear pressure, which can affect the size and shape of your ear canal temporarily. This can lead to inaccurate ear impressions if taken too soon after a flight. We recommend waiting a few days after flying before getting your ear impressions done to allow your ear pressure to normalize.

Ibuprofen & Other Medications

Medications like ibuprofen can reduce inflammation and affect the size of your ear canal. If you take these medications before getting ear impressions, you might end up with IEMs that don’t fit correctly once the effects of the medication wear off. Avoiding such medications prior to your appointment can help ensure a more accurate fit.

Use of Bite Blocks

There is some debate over the use of bite blocks during ear impressions. While some professionals recommend using a bite block to create a loose jaw and an accurate impression, others advise against it. In our 15+ years of experience making custom IEMs, we recommended not using a bite block. Although intended to keep the jaw relaxed, clients often end up biting down on the block, which alters the ear shape and can lead to inaccurate impressions. Opting out of using a bite block can help maintain a more natural ear shape during the impression process as long as you keep your jaw nice and relaxed.

Other Factors to Consider:

Ear Wax Build-Up

Excessive earwax can alter the shape of your ear canal, leading to poor impressions. Ensure your ears are clean before getting impressions.


Seasonal allergies can cause swelling and changes in your ear canal. Plan your impressions during a time when your allergies are under control.


As you age, the cartilage in your ears changes, which can affect the fit of custom IEMs over time. Regularly check the fit and consider getting new impressions periodically.
Custom IEMs can offer increased comfort, but only if they fit correctly. Understanding the factors that can affect the accuracy of ear impressions is crucial for getting the perfect fit. Whether it’s changes in your ear canal due to health, weight, medications, or recent activities, being mindful of these issues can help you avoid the discomfort and frustration of ill-fitting custom IEMs. Always consult with a professional audiologist who can guide you through the process and help ensure that your custom IEMs are a perfect fit, providing you with the best possible audio experience.

If you want to avoid these headaches and the expensive process of custom IEMs, shop our Unity IEMs. Our universals fit like customs, thanks to our patent-pending design, offering you the best of both worlds without the hassle.

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