The Philips 221SU is one of the simplest displays you can buy: It usually requires mains power, has no control buttons and hooks up to your PC or via a single USB cable.
If you're using a laptop with a small screen or simply want to boost your productivity with some extra desktop space, then a USB monitor can be a good plug-and-play solution. This is especially true when you don't have and traditional monitor connectors or mains power available. The Philips 221SU monitor appears externally rather unremarkable: Its build quality is perfectly sound, but it is a business monitor and styled as such in a rather unexciting plain black. It does however include an ergonomic tilt and swivel stand which also includes a 70mm height adjustment. See also: Group test: What's the best flat-panel display?
Its housing creates the illusion of slimness by being much thinner at the edges, with a square bulge in the middle, much like well-stuffed ravioli. While many LED-based monitors are much thinner throughout, this is often achieved by using an external power brick, which doesn't really make sense in a monitor powered via the USB. Unlike the vast majority of monitors, the Philips 221SU offers no controls or switches of any kind – there isn't even a power switch. Just plug it in and off you go. VisitGroup test: What's the best 19 to 24-inch LCD monitor?
This makes it very simple to use, but with the Philips 221SU you'll have no control over brightness, contrast or colour settings. Neither are there any traditional video inputs for connecting any other devices.
To display your desktop via USB, the Philips 221SU monitor uses DisplayLink technology which requires a driver to be installed on your PC before the monitor will work. However, our 64-bit Windows 7 system detected the display and installed the drivers automatically.
The way DisplayLink's software works makes the Philips 221SU unsuitable for use as the only monitor hooked up to your system – so, plugging it in via USB to a PC without an existing monitor won't work.
Connecting the display to a system which already had three monitors connected to its primary graphics card was less successful: While the automatic software installation started as normal, we were soon met by a Blue Screen of Death and upon restarting were left with only two monitors working and no Windows Aero effects. So, unlike a standard monitor, the Philips 221SU isn't a display you can just pick up and plug in on any system and be guaranteed to have it work.
The 221SU product manual states that Mac OS X is currently not supported as a host operating system, although Mac support appears to be currently under development going by the DisplayLink website.
Although it's possible in some cases to power the monitor from a single USB connector, this often won't work. The supplied USB cable therefore has two connectors which should be plugged into separate ports on your PC to double up on the available power. In some cases this won't be possible and you'll have to buy an external power supply available from Philips. In any case, the system won't work on versions of the USB prior to USB 2.0.
Philips 221SU: performance results
In general use, the 221SU performs competently and you're unlikely to notice the fact that it's working over the USB unless you hit it with something taxing like Full HD video. Of course this is just what we did, and we were pleasantly surprised to find that it had a pretty good stab at it. Although motion certainly wasn't as smooth as it would have been via a traditional video connection, it was no slide-show either. The level of performance varied depending on the video content used, sometimes feint colour banding was visible in moving video which would then disappear if the action was paused. The DisplayLink driver software provides an “optimise for video” option, but we found this didn't make any visible difference.
We certainly wouldn't recommend this monitor for use in any situation where video or fast motion performance is important. Text and other office applications were perfectly acceptable on this display. Viewing angles aren't great, but overall colour reproduction and contrast are better than we would have expected from a monitor which isn't aimed at sticklers for image quality. If you like your monitor turned up bright, perhaps to compete with a lot of sunlight coming through a window, then you may find the fixed brightness level of the 221SU a little low. However, in general it's more than adequate.
We usually measure power consumption by connecting the monitor's power cable directly to a power meter. This time we had to measure the power drawn by the whole PC, first with the monitor connected and then with it unplugged; the difference being the power consumption of the display. Using this method we measured the power 221SU's power consumption at just 10W.
Your selected brightness setting has a large impact on the power-consumption of your display, so we usually test at a standard 120 cd/m2 brightness. The 221SU can't be dimmed to this level so its power measurement has been taken at a higher brightness of 175 cd/m2.
Philips 221SU: lab results
Measured Black point luminance (calibrated): 0.25cd/ m2
Maximum measured brightness (calibrated): 175cd/ m2
Maximum checkerboard contrast: 700:1
Percentage of Adobe gamut: 74%
Percentage of sRGB gamut: 94%
Measured native white point: 6200K
Colour error (min/avg/max) 0.26/5.28/1.41 deltaE
Power consumption (at 175 cd/m2 brightness): 10W