Xiaomi Mi Mix 2 Sound-guided Speaker Design – Detailed Review

Experience Superb Sound quality through Sound hole

Recently, Xiaomi released a full-screen 2.0 mobile: Xiaomi Mi Mix 2. Compared to his predecessor, Xiaomi Mix 2 is quite a revolution,  packed with many noticeable improvements. One of such notable features is the return to conventional speakers. Although there is a subtle slit on the top of the frame, the use of “sound guided tube” offers a perfect solution to the full-screen mobile phone. How is it made possible? Let’s take a detailed look at the technology.

What is this “sound guided tube” speaker design?

To answer this, you have to understand that conventional mobile phone keep a larger “forehead” over the screen is to home earpiece(s), in addition to pile of sensors and front camera. Xiaomi Mix the predecessor of this phone, uses a cantilever piezoelectric ceramic acoustic technology.

Although this, cantilever piezoelectric ceramic acoustic technology enabled Xiaomi Mix to hold speakers without opening hole, it uses principle of resonance hence sound couldn’t be guided in a direction, thus delivering mediocre sound quality.  With Xiaomi Mix 2, the speaker uses “sound guided tube”, and with only a very small opening at the top of the body, it is able to achieve a very good sound quality.

How the design of Sound guided speaker is made possible?

If you open a Xiaomi Mix 2, you will find that the speaker (of 8*2.5mm in size) is at the back of the screen, and it even uses speaker component that is comparable to speaker of traditional phones, while there is only a subtle hole at the top of the body, over the screen. How did Xiaomi actually achieve this?

Xiaomi MIX 2 hasthe sound unit on the bottom of the screen, the position of the speaker was facing the back of the screen, and the sound of the speaker at the bottom is transmitted to the earpiece at the top of the screen through a tube. This design is very clever, identicalto the voice of the handset into the human ear. The picture below shows the structure of the “sound guide tube”, we lifted the cover plate to see this is a horn-shaped sound guide structure, which is location just below the high-power speakers.

How to solve the sound quality problem?

By resolving the structural issue, the design has introduced the quality issues associated with sound transmission. Since, Xiaomi Mix 2 is using horn shaped sound guide tube, which resembles Z shape, there are issues associated with the transmission of sound, as it needs to resonated twice before reaching the human ear. Though, Xiaomi Mix 2 uses radian design around the corner, compared to traditional earpiece which directly sends sound directly to the human ear, the sound transmission across the phone produces distortion, when the sound frequency is narrowed, it sounds more like talking to a walkie-talkie.

In order to resolve this distortion problem due to sound attenuation, Xiaomi Mix 2 uses 50mW speakers, compared to 20mW speakers in traditional handset. We compared Xiaomi Mix 2 with other traditional handsets available in market, and found that sound quality of Xiaomi Mix 2 is very impressive

In the end, here are the test results of frequency response of Xiaomi Mix 2 and receiver distortion of Xiaomi Mix 2 compared to another handset in the market. You will find that the sound quality of Xiaomi Mix is indeed very good.

  • Frequency response test (Xiaomi Mix 2 fits between upper limit and lower limit, providing better sound quality)

  • Distortion test (Xiaomi Mix 2 better than the threshold in red line )

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