Xiaomi Mi 9T/Redmi K20 review

A large and notch-free display

The key feature of the Mi 9T is definitely that notch-less 6.39" AMOLED screen and now it's the right time for it to shine. Xiaomi has chosen the same 6.39" size and 2,340 x 1,080 px resolution (403ppi) for the 9T display as on the Mi 9 but removed the notch. And looking at the past Xiaomi phones it seems this might be the same panel the Mi Mix 3 devices utilize.

Interestingly, Xiaomi usually mentions when its OLEDs are made by Samsung but that's not the case for the Mi 9T. Then again apps such as AIDA read the screen maker as Samsung, so if you were curious about this - now you know.

The display is protected by a Gorilla Glass 5 by Corning. Our (global) unit didn't come with a pre-applied screen protector, but we can't confirm this for other markets.

Finally, the screen is HDR10-compliant and fully covers the DCI-P3 color space.

The screen has an excellent brightness for an OLED panel of 450 nits - that's in line what Xiaomi promises. And it can go as high as 646 nits in bright light if you leave it on Auto, also matching and even exceeding Xiaomi's official promise for 620 nits.

Xiaomi offers three different Contrast settings, each one representing a specific color space. The Automatic contrast fully covers the DCI-P3 color space and we measured an average deltaE of 3.7. Only in this mode you can choose the color saturation (default, warm, cool) and the Delta E of 3.7 which we measured was taken at the default preset. Choosing warm will offer an even more accurate presentation with an average deltaE of 2.4.

The Standard Contrast corresponds to sRGB and we also recorded an average deltaE of 2.4 for the color accuracy, meaning it's a pretty great one.

Finally, the Increased Contrast makes the colors pop and they are no longer as accurate.

Battery life test

The Xiaomi Mi 9T is powered by a 4,000mAh Li-ion battery, about 20% larger than the 3,300 mAh cell inside the Mi 9. The Mi 9T supports Quick Charge and the supplied 18W charger fills 45% of a depleted battery in 30 mins. A full charge takes about 100 mins.

The Mi 9T posted a top-notch endurance rating of 100 hours and great scores across the board. The screen-on times are excellent - we measured 11 and a half hours runtime in our web browsing test and north of 17 hours in our video playback test.

The standby performance was better on the Mi 9T when compared to the Mi 9, probably meaning the Snapdragon 730 modem is more power efficient in standby than the S855's.

Our battery tests were automated thanks to SmartViser, using its viSerDevice app. The endurance rating above denotes how long a single battery charge will last you if you use the Xiaomi Mi 9T for an hour each of telephony, web browsing, and video playback daily. We've established this usage pattern so that our battery results are comparable across devices in the most common day-to-day tasks. The battery testing procedure is described in detail in case you're interested in the nitty-gritty. You can check out our complete battery test table, where you can see how all of the smartphones we've tested will compare under your own typical use.

Speaker test (old, new one below)

There's a single bottom-firing loudspeaker on the Mi 9T - it's decently loud and scored a Very Good mark on our test. The output is also very good - there is rich sound, but there are some high-pitched notes that come out wrong at maximum volume and this keeps us from giving it an excellent mark for quality of output.

Speaker test (new)

Use the Playback controls to listen to the phone sample recordings (best use headphones). We measure the average loudness of the speakers in LUFS. A lower absolute value means a louder sound. A look at the frequency response chart will tell you how far off the ideal "0db" flat line is the reproduction of the bass, treble, and mid frequencies. You can add more phones to compare how they differ. The scores and ratings are not comparable with our older loudspeaker test. Learn more about how we test here.

Audio quality

The Xiaomi Mi 9T delivered a very loud output when connected to an external amplifier and clarity was perfect too.

Our standard 32oHm headphones did cause a fair bit of damage though - volume dropped (although still remained high), and we got a significant amount of extra stereo crosstalk. We recorded some intermodulation distortion, too. All in all, we’d rate the performance here as good, mostly because of the loudness, but it’s far from impressive.

Xiaomi Mi 9T frequency response

You can learn more about the tested parameters and the whole testing process here.