The importance of fit and seal

A little note on the fit of a custom in-ear monitor, I will cover our process on creating a good fit, the reasons why occasionally a good fit is not achieved and lastly the impact of having an incorrect fit.

The most crucial area for the fit is the ear canal and as result this is the area we focus on the most. During the impression detailing stage we take great care in not touching the thickness and shape of the ear canal, we take the length down and smooth off the tip only. The impression is dipped in immersion wax prior to the mould being made, this is to smooth the impression resulting in a smoother shell, we use our method of “double tip dip” when dipping in the wax, this means we dip the canal only in the wax first and then the whole shell a second time, this gives the canal area a double wax coating. When the shell is complete and is in the final finishing stage we take extra care not to over polish the canal as this removes material and reduces the size. A final measure is at the QA stage where we compare the canal on the shell to the canal on the impression.

Fit issues do happen and can happen for a number of reasons.

  1. The most common reason is the quality of the initial ear impression, this is why we are very strict when it comes to accepting impressions and will reject impressions we feel are not good enough quality, we copy and duplicate the impression for the final monitor, if the impression is wrong then so will the final monitor, it is impossible for us to guess an individuals ear.
  2. Seasonal and illness. An individuals ear size can change at different parts of the year (providing one lives in an area with seasonal changes) a colder climate and the ear size will be slightly larger as the muscle contracts, warmer and it is slightly smaller as the muscle expands due to the warmer temperature. If you wear a ring on your finger, the ring is much tighter the warmer the body as the finger is bigger, go to a cold climate, like Sweden in the winter :), and the ring will be less tight as the finger will be smaller. This seasonal/temperature change as well as location is something we also consider when creating a monitor. We have also experienced people taking ear impressions when they are ill, even just a cold, this is not advisable as we have seen ear shapes and sizes alter due to illness.
  3. People have different ideas on how a monitor should fit and this varies. For example, person A likes to have a tight snug fit that will ensure a great seal and sound. Person B likes to have a more relaxed fit to enable them to insert the monitor more easily. If Person B has a monitor made that is perfect for person A they would say the fit is wrong as it feels too tight and uncomfortable, on the flip side if Person A had a monitor made that is perfect for Person B then they would say the fit is poor and has a bad seal.
  4. Mistakes or over polishing can happen in the manufacturing stage but we have many measures in place to eliminate this as discussed above.

The bottom line in all this is that fit issues do occur due to one or more of the above, we take special care and attention to achieve a correct fit, however at the end of the day it will always be down to the individual, this is why we have a free re-fit warranty of all monitors as we want all customers to have the best fit possible.

The last think I want to discuss is the impact of the fit. A bad fit results in either the monitor being uncomfortable (example Person B with Person A fit) and/or poor seal. A poor seal impacts the low frequencies and the effect is actually quite astonishing. I carried out a little test and below is the resulting FR of the test.

  1. I measured a monitor using a good fit (this is in green line) and you can see healthy low frequencies.
  2. I then broke the seal with a 0.3mm hole, this is a very small hole but the impact can be seen on the red line. From 2Khz up there is no difference. The most astonishing result is the impact of the low frequencies from 300hz and down, this monitor would have very little bass impact.

This is why it is so important, whatever earphones, headphones, customs you are using, that the fit is good.