vivo X23 Review: Audio


X is the main series of vivo. Although it is not a flagship, it is very important. It is a series that claims to be brand value. This series of models follows the balanced design concept of the bucket theory, there will be no extreme design, and there will be no obvious short board. The X23 is the latest in the X series.

The X23 uses the Qualcomm Snapdragon 670 AIE and still has an audio I/O controller integrated. These years, Qualcomm Snapdragon processors perform exceptionally well in audio I/O, providing the most basic sound quality. The X23 still retains the "metamorphic design", which uses a separate DAC, AK4377A, supplied by AKM. The previous X21 was the AK4376, and the AK4377A was a simple revision. For example, the output power from 16 ohms was increased from 45 mW to 60 mW, but it was still 25 mW at 32 ohms. Compared to the Cirrus Logic CS43199 used by the NEX S, it is definitely worse, but the AK4377A is excellent compared to the CODECs.

The music player finally updated, still inheriting two major sections of local and online playback, but the UI design is refreshing. Local playback supports various common formats, and the operation is stable, no flashback. However, the lyric and album cover online matching function is getting weaker and weaker, with more than 70 tracks, only 11 matched correctly, while more than half of them would be matched correctly before. HIFI is still managed as a system authority, and third-party players such as Netease Cloud Music require authorization to support HIFI output. X21 began to build the "deep space sound effect" independently developed by vivo, which will increase experience in some use, but it will not help the sound quality significantly.

We start to add USB audio device compatibility test and Bluetooth decode supported test as the popularity of smartphone external device. We choose Musiland MD30 Plus as our audio device, using SuperDSP platform that is compatible with UAC2.0. Another one is Matrix Mini-i Pro 2S, adopting XMOS program. The reason why we choose these two is that they can display the current sampling rate on screen. We will add more devices in the future.

Testing Smartphone iPhone X iPhone 8 Plus Samsung Galaxy Note 8 Samsung Galaxy Note 9 Samsung Galaxy S8+ Samsung Galaxy S9 Huawei Mate 10 Huawei P20 Pro vivo X20 Plus OnePlus 5T vivo X21 vivo X23 One Plus 6
UAC 2.0 Device Auto Switch Sampling Rate Auto Switch Sampling Rate Locked to 48kHz or 192kHz Locked to 192kHz Cannot Work Properly Locked to 48kHz or 192kHz Locked to 96kHz Locked to 96kHz/16bit Locked to 48kHz Locked to 48kHz Locked to 48kHz Locked to 48kHz Locked to 48kHz

The test results show that the X23 external USB audio device is not so friendly. When the USB device outputs, the sampling rate will be locked at 48kHz, which means that SRC will be generated. The solution is to use some third-party software, but the most common cloud music player can't set the output sampling rate, which means that SRC may be generated when using these online music players, no good for sound quality. We have feedback this many times, but we have not received the attention of vivo. In fact, we only need to modify a few code segments. Unfriendly is also reflected in the fact that the external device is not supported by default and needs to be enabled in the settings. The X23 has a criticized design that uses the Micro USB port, and most mobile USB DACs are designed for mobile phones have been replaced with Type C ports.

Testing Item aptX 44.1kHz aptX 48kHz
Noise Level, dB -95.1 -96.2
Dynamic Range, dB 94.5 96.1
Total Harmonic Distortion(THD), % 0.0017 0.0014
Intermodulation Distortion, % 0.0040 0.0037
Stereo Crosstalk, dB -96.2 -96.9

X23 supports mainstream Bluetooth codec solutions such as SBC, aptX, aptX HD, and theoretically supports LDAC, but in fact we have not used LDAC successfully, so the result we recorded here is the best solution X23 supports, aptX HD. If you only say sound quality, LDAC is significantly better than aptX HD. During the X23's use of aptX HD, the performance was stable, and there was no such phenomenon as broken chain, popping, or jamming. From the test results, if you want to equip the X23 with a Bluetooth headset, you can choose the model that supports aptX HD. You can also choose the model that supports LDAC. Maybe one day vivo will suddenly fix the LDAC problem.

The X23 provides a 3.5mm headphone jack.By convention, we use professional sound cards to record sounds, combining with common analysis, to provide quantitative results. The maximum of vivo X23 in Hi-Fi mode output level is -9dB, while -12.5dB in normal mode.

Testing Item 44.1kHz [Normal] 44.1kHz [Hi-Fi] 48kHz [Normal] 48kHz [Normal] 96kHz [Hi-Fi] X23 44.1kHz [Hi-Fi]
Noise Level, dB -96.1 -96.3 -96.3 -96.7 -109.3 -96.0
Dynamic Range, dB 96.1 96.3 96.3 96.7 109.5 96.7
Total Harmonic Distortion(THD), % 0.0006 0.0005 0.0005 0.0005 0.0004 0.0013
Intermodulation Distortion, % 0.0044 0.0043 0.0042 0.0041 0.0012 0.0044
Stereo Crosstalk, dB -74.9 -75.1 -75.1 -75.0 -74.8 -75.1

The test went smoothly, and no SRC occurred in both HIFI and normal mode. Hi-Res sampling specifications are not supported in normal mode. The recorded indicators were good, but the resolution was not ideal in both modes. Even for the 24-bit test project, the resolution did not improve. This problem occurred almost on all AK437X-based models.

In the real hearing part, the new AK4377 did not bring an audible improvement, and the performance was consistent with the X21. Compared with the mobile phones without separated DAC, the X23 does not have an advantage in terms of output power, sound stage, transient and dynamic. It is no advantage in powering the headphones. However, the resolution, level, and stereo image of the X23's sound will be significantly better, the overall sense of hearing is more delicate, the shape is clearer, and the taste is more audiophile-trending. Compared to the NEX S, which represents the best level, the X23 is completely defeated. Although both have separated DAC, it is basically the best and the middle-to-lower contrast.

Compared to mobile phones without DAC, the X23 still has an advantage in terms of sound quality. Not the best, but stronger than competing products, the sound quality target of the X series has always been this positioning, and the sound quality is still the bonus item of the X series. To make this advantage better, Soomal suggested that X23 users can match a good wired headset, with High-sensitivity and low-resistance, would be more suitable. For example, Aurvana air, the bounding earphone cannot play the X23 level.

In terms of external USB devices, the X23 is not the best device to play, because of some problems in both hardware and software. These problems are not fatal, but they are enough to reduce the enthusiasm for use. Bluetooth can also be better, according to the X23 support LDAC, but the test did not succeed. Engineers of the vivo please find where the problem is, and fix them as soon as possible.

In the trend of removing the earphone port, Samsung seems to be extra conservative. In fact, this approach takes care of the habits of consumers. Those who like the wired earphones, the performance will not be too bad, and for those preferring the Bluetooth headset, it can provide very good support. This gentle transformation and guidance are actually worthy of appreciation.

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