Nuu Mobile X4 Review: What Do You Get for Less Than $200? Not Quite Enough

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The challenge with bargain phones is balancing their alluring price tag with the reality of compromised features. Take the Nuu Mobile X4, a 5-inch unlocked Android device that comes in a fancier frame than you'd expect from something with a $170 price tag. Reality sets in when you consider the phone's dull photos, lackluster sound and tendency to warm up when in use. Still, bargain hunters will appreciate the X4's uncluttered version of Android Lollipop, superbright display and solid performance for a low-cost phone.

One stylish hothead

The Nuu X4 features a sleek look that you wouldn't normally expect from a budget device. Its attractive zinc-magnesium-alloy frame reminds me of more expensive phones such as the HTC One M7, though its plastic back panel is unmistakably cheap. I reviewed the X4 with the white back, but I wish I could have tried out the black version, which looks better on the Nuu website, even though it would likely show more fingerprints.

Credit: Jeremy Lips/Tom's Guide

(Image credit: Jeremy Lips/Tom's Guide)

It's not unusual for phones to get a little warm when you're using them, but the X4 really heats up. As I installed a few apps onto the X4, its frame got so hot that a colleague joked that it could become a safety liability.

Credit: Jeremy Lips/Tom's Guide

(Image credit: Jeremy Lips/Tom's Guide)

At 5.55 ounces, the 5-inch X4 is a bit heavier than other 5-inch unlocked phones, such as the KPhone K5 (4.7 ounces) and the OnePlus X (4.86 ounces). Its weight is closer to the 5.5-inch Huawei Honor 5X, which tips the scales at 5.57 ounces.

When you pop off the phone's back, you'll find the Nuu X4's removable 2,250-mAh battery, dual SIM trays (it's compatible with GSM and WCDMA networks) and microSD memory slot that allows you to add another 32GB of storage on top of the 16GB of onboard capacity.

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Carrier: Unlocked
Phone Display Size:
5 inches
Display Resolution:
1280 x 720
Android 5.1
1.3GHz MediaTek quad-core processor
Memory Expansion Type:
microSD card (up to 32GB)
Battery Life:
8 hours and 11 minutes
Bluetooth Type:
Bluetooth 4.0
802.11 b/g/n
5.6 x 2.8 x 0.31 inches
5.36 ounces

Bright display, muddy music

Nuu gave the X4 a bright and colorful screen. When I watched a Suicide Squad trailer on the phone's 5-inch display, I was impressed by the vivid orange of El Diablo's flaming hands, the inky blacks of silhouettes, and the strong blues and reds in Harley Quinn's outfit and hair. But although the cracks of Killer Croc's scales came through clearly, I spotted digital artifacts in the smoke surrounding a crashed helicopter. That visual noise may be due to the phone's 720p resolution, which is lower than what you'll find on other phones, such as the Honor 5X (1920 x 1080).

Registering 618 nits (a measure of brightness) on our light meter, the Nuu X4's display outshines rival budget phones (which range from 295 to 529 nits), as well as the average brightness for smartphones (437 nits).

Credit: Jeremy Lips/Tom's Guide

(Image credit: Jeremy Lips/Tom's Guide)

The Nuu X4's panel reproduced 100.5 percent of the sRGB spectrum, which is good but still less colorful than the Honor 5X (120.5 percent), the OnePlus X (186.2 percent) and the average for smartphones (137 percent).

Earning a Delta-E error rating of 1.79, the Nuu X4 produces more accurate hues than the Honor 5X (3.52), the OnePlus X (2.95) and the smartphone average (4.42). (Numbers closer to 0 are better.)

Credit: Jeremy Lips/Tom's Guide

(Image credit: Jeremy Lips/Tom's Guide)

As nice as the display is, the X4's speaker just isn't good enough. The small bottom-mounted speaker produced lackluster sound that barely filled a small conference room. It turned DJ Shadow's "Nobody Speak" into a muddied mess, robbing the song of its bass, taking the kick out of El-P and Killer Mike's vocals and turning guitar riffs into shrill noise, as if it needed a retuning.

A thankfully minimal interface

The Nuu X4 runs on Android 5.1 Lollipop, which is becoming an aging version of the OS now that Android Nougat's summer release is looming. At least it's a clean installation of Android 5.1, free of bloatware, with a couple of useful features found only in newer Android devices.

SmartWake allows users to tap and slide a finger on the X4's screen to wake the display, unlock the device or open the camera. You can draw a C, E, O or W on the screen to open apps such as the dialer, Chrome and YouTube.

Enabling Air Gestures allows you to navigate the Gallery app and adjust the tuner in the FM radio by flicking a finger left or right in front of the top-right sensor.

Budget-size performance

Armed with a 1.3-GHz dual-core MediaTek CPU and 2GB of RAM, the Nuu X4 provides enough performance for multitasking. I was able to play a round of Jetpack Joyride and listen to a podcast in Pocket Cast while 14 apps ran in the background, but the device sometimes paused before loading apps from the switcher. 

The X4 tallied a score of 1,842 on the Geekbench 3 general performance test, which is far below the 3,176 smartphone average. But when you look at that result in the context of comparably priced budget models, the X4's performance falls squarely in the middle of the pack. Nuu's phone outpaced the KPhone K5 (1,496) and last year's Moto G (1,591), but it trailed the Honor 5X (2,990) and the OnePlus X (2,402), both of which feature more capable CPUs than what you'll find in the X4. 

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The X4 took 10 minutes and 22 seconds to convert a 204MB video from 1080p to 480p. The Honor 5X (7:41) and KPhone K5 (9:45) completed the task more quickly, and the average for smartphones (7:57) was also a quicker time, suggesting that the X4 isn't the phone to turn to if you plan on performing a lot of processor-intensive tasks. 

Even though I played the casual Jetpack Joyride on the X4, its 4,808 score on the 3DMark Ice Storm Unlimited test shows that it isn't a gamer's daily driver.The Honor 5X (7,792) and the OnePlus X (16,705) earned higher scores, while the KPhone K5 (4,428) finished just below the X4.

The 13-megapixel rear camera takes crisp photos but suffers from color and autofocus issues.

Cameras are off the mark

Credit: Jeremy Lips/Tom's Guide

(Image credit: Jeremy Lips/Tom's Guide)

The Nuu X4's 13-megapixel rear camera takes crisp photos, but it suffers from color and autofocus issues. When I snapped images of a pink elephant in front of a kitschy antiques store, I noticed that while the X4's camera could capture the wrinkles on the fake beast's trunk, the body appeared as a washed-out purple.

Credit: Henry T. Casey/Tom's Guide

(Image credit: Henry T. Casey/Tom's Guide)

Portraits taken with the rear camera looked great, as the X4 captured accurate skin tones, from my whiter chin and jaw to the pinks in my sun-drenched cheeks and brow. The 13-MP camera also captured fine details, including pores and stubble.

Credit: Henry T. Casey/Tom's Guide

(Image credit: Henry T. Casey/Tom's Guide)


Nuu claims that the X4 handles nighttime and photography well, thanks to its low-light sensor. But the camera's performance in the dark was disappointing. When I pressed the shutter button to take a photo of the Lincoln Center steps at night, the X4 paused for a count of 4 seconds before it captured the shot. As long as you have the patience to wait, the camera produced well-balanced photos with auto-flash enabled; turning off auto-flash improved the speed of the shutter but produced darker, unbalanced results.

Even when I used auto-flash, on several occasions, the X4's camera would produce shots with a yellow hue, as it did in a photo of some street art taken at night.

Credit: Henry T. Casey/Tom's Guide

(Image credit: Henry T. Casey/Tom's Guide)

Selfies taken with the X4's 5-MP front camera turned out a tad better. The camera accurately captured the green grass behind me but muted the purple of my shirt.

Credit: Henry T. Casey/Tom's Guide

(Image credit: Henry T. Casey/Tom's Guide)

The Nuu X4's front camera offers a Face Beauty Mode that can remove wrinkles, smooth out skin and shape features. Even at the lowest setting, I found the beauty mode features went too far, magnifying my eyes to a nightmarishly bizarre size and removing most details from my skin tone. Thankfully, the feature is disabled by default.

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The X4 can record 1080p video, but the footage I shot of Midtown Manhattan streets during the day looked choppy. However, it didn't suffer from the same dull-colors issue I saw in the photos shot with the same camera. An orange truck hood and yellow taxi rendered vivid and accurately.

OK battery life

A 2,250-mAh battery powers the Nuu X4, giving it enough juice to last through a workday, though just barely. In our battery test (which involved web surfing over AT&T's 4G LTE network at 150 nits of brightness), the X4 clocked in at 8 hours and 11 minutes.

That's not bad, but it's not great, either. The average smartphone lasts 8:38 on our test. More to the point, a growing number of budget phones have impressive battery life. The Honor 5X lasts for 9:22, while the K5 can go 11 hours in between charges. Still, the X4 outlasted the OnePlus X (7:21).

I appreciate that the X4 held most of its charge when idle. Its battery life only dropped from 99 percent to 80 percent as it sat in my bag for 17 hours.

Bottom line

You'll get a decent-looking phone with the Nuu Mobile X4, with a design that doesn't give away its sub-$200 price tag. We also like the bright and colorful display. Unfortunately, the phone's performance and battery life don't exactly sparkle, and the back camera is lackluster, especially in low light.

Overall, other budget phones are more capable and don't cost much more than the X4. The $199 Honor 5X from Huawei offers better performance and photos in a device that lasts much longer on a charge. Still, if you want an uncluttered Android experience in a good-looking phone that won't break the bank, the Nuu X4 may fit that bill.

Henry T. Casey
Managing Editor (Entertainment, Streaming)

Henry is a managing editor at Tom’s Guide covering streaming media, laptops and all things Apple, reviewing devices and services for the past seven years. Prior to joining Tom's Guide, he reviewed software and hardware for TechRadar Pro, and interviewed artists for Patek Philippe International Magazine. He's also covered the wild world of professional wrestling for Cageside Seats, interviewing athletes and other industry veterans.