or ACU, empowers user to control the sound of the dynamic driver via interchangeable filters. The ACU controls the amount of air in the rear chamber of the Dynamic driver.
Dynamic driver in a hybrid IEM design works in the same way as it's working in a HIFI speaker. The internal structure of the HIF speaker is part of the acoustic design as the total volume of air in the speaker chamber affects the sound of the dynamic driver greatly. In an IEM enjoyment, the shell size vary depends on each individual users' ear geometry therefore the total volume of the air in the shell changes from one and another. If we just dump the dynamic driver in the shell, like what other brands are doing, we will not be able to make sure that each and every custom IEMs will sound the same. The universal demo shell is always much smaller than the actual custom, so there will always be a great difference between the demo and the actual custom IEM.
To completely eliminate this problem once for all, we calculated, simulated and came out with an optimized, fixed volume for the rear chamber of the dynamic driver that we know and sure that will always sound the same for each and every pair of the hybrid IEMs*. With the ACU, what you hear from the universal will be what you hear from your custom*.
By introducing the ACU interchangeable filters, from unable to predict how the IEM will sound (without ACU module) to have absolute certainty of very pair will sound the same, we will also have the power to CONTOL the sound. By controlling the amount of air flowing into the optimized rear chamber of the dynamic driver so that we can control the sound signature. We came out with 4 different filters (Balanced, Musical, Energetic and Impact. Balanced has the least amount of bass and Impact is highest) that will give 4 different level of bass response from mildly v shaped to +15dB of bass.
No two audiophiles will ever agree on the amount of bass they want. With the ACU system, users will have the capability to choose how they hear their music. Just like what we did with the Flamenco, we allow user to customize their IEM by themselves.
Balanced armature driver is highly inductive. Traditional passive electronics filters in the multi-driver crossover system introduces phase shift at crossover point by 90 degrees to 180 degrees. As the analogy signal coming from the DAC to the IEM is an AC signal, out of phase electronic signals will produce out of face soundwaves from the drivers. Converting the out-of-phase issue from electronic (electronic signal) domain into analog (soundwaves) domain. It results multiple drivers cancelling each other at crossover point and cause a big dip on the frequency response together with a dirty Fast-Fourier Transform analysis.
CSU utilizes both electronics filtering design and acoustic path design to create crossover system including passive electronic low pass filter, band pass filter and high pass filters. And the acoustic filters help to eliminate unwanted frequency from the driver and smooth the frequency response. By adjusting the placement of each driver, soundwave phase cancellation at crossover point can be eliminated and all drivers will produce synchronized soundwaves at the same time. Resulting the drivers to produce wider frequency range improve sound pressure level at super high frequency range. And for the users’ experience, they will be able to hear more detail, full-bodied and engaging sound with a nature sound stage.
* Hearing difference caused by individual ear canal geometry, hearing loss, different types of ear tips, run-in time is not discussed in this case.