As the market for In-Ear Monitors (IEMs) becomes more challenging—driven by professional musicians, audiophiles, and content creators—there’s a growing need for innovative designs that deliver superior sound quality, comfort, and performance. This post highlights Seltech’s capabilities in the electro-acoustic design of in-ear monitors that meet the demands of this market.
Our Customized Design Approach: The Power of Helmholtz Resonators
One of the most critical aspects in in-ear monitor designs is efficiently applying low-pass filtering to the different frequency bands. Using existing techniques, woofers can be filtered either electrically or acoustically. The simplest electrical filtering uses first-order passive filters (6 dB/octave) with an RC network, easily adjusted to a target frequency. However, achieving very low cutoff frequencies may demand high capacitance values, which can be impractical with standard SMT ceramic capacitors.
Alternatively, acoustic filtering often uses dampers placed within the tube; when these dampers have a high resistance, they effectively create a low-pass effect. Figure 1 below illustrates the typical low-pass effect created by a damper on a woofer-dedicated Balanced Armature (BA). From Figure 1, we see that if the BA is already relatively damped, the low-pass benefit created by a damper is not very significant.
Our approach is therefore to utilize the so-called “Helmholtz resonator” principle (illustrated in Figure 2) within the IEM’s tubing network.
As described in our post from September 2023 (here), the resonance frequency of such a cavity is given by:
As illustrated in Figure 3, this type of cavity allows us to more precisely control the low-pass frequency, thus reducing unwanted energy and resonances from the rest of the driver’s response.
Using this design approach provides us with the flexibility to develop IEM configurations like the three-way model illustrated in Figure 4.
By entrusting Seltech with your project, you benefit from a comprehensive approach to acoustic excellence. We offer precise acoustic tuning to define and optimize audio performance, ensuring an ideal listening experience. Our rigorous testing and validation phases assess audio quality, isolation, and comfort, with corrective measures applied as needed to achieve optimal results. This holistic approach brings true added value in terms of quality, making us a reliable partner in delivering outstanding acoustic performance.