The Two Vents — Physical Principles

by Jürgen Kraus

Typically (but not always), an iem has two vents, one in the front and one in the back. Here the Tinaudio T2 as an example:

two vents

Head-Fier James444 explains the functionality of the vents:

Front Vent: making it smaller increases bass. Explanation: the front-mod adds a tiny amount of front leakage which avoids over-pressurization in the ear canal and reduces bass quantity. Attenuation is a bit stronger in deep bass than in mid/upper bass, resulting in a bass-lighter, but slightly more mid-bassy signature. Because of the leakage, isolation is slightly reduced.

Back vent: adding air increases bass; decreasing back vent diameter makes bass roll off. Reducing the air flow through the rear vent by taping it reduces bass (cover up and poke). Explanation: the back-mod restricts airflow through the back vent, resulting mainly in mid/upper bass attenuation. Deep bass remains unchanged and strong. Due to partial blocking of the back vent, isolation is slightly increased.

Both vents: the combination of front and back-mod yields the largest amount of bass attenuation and results in a significantly more balanced signature than stock.

You find James444’s original article including a modding example here!
FB Group
Click To Join Our FB Group!


  • The Two Vents -- Physical Principles 1

    Head-Fier since 2016. He has been known as “Otto Motor” to Head-Fiers, as “Dr. Schweinsgruber” to users and Youtubers, and as “Brause” to Super Best Audio Friends and the Headphone Community. - For the purpose of confusion, he decided to pose under his real name Jürgen Kraus (“JK”) from now on. - This is a hobby. In “real” life, Jürgen is a professional geologist operating his own petroleum-exploration consulting company Franconia Geoscience Ltd. (see ad in the footer) based in Calgary, Canada. He holds German and Canadian passports. Jürgen had a classical music education from childhood through high school in Germany and he has been following popular music developments since the late 1970s. His understanding of arts and crafts was influenced by Bauhaus pragmatism: “less is more” and “form follows function”.