In the Throughput test, where we test a router at its best settings with a wireless client that's only 15 feet away, the X-550N scored 50.2Mbps, among the top five of single-band routers. At this speed, the router can finish transmitting 500MB of data in about 80 seconds.
In the Range test, where the client is 100 feet away from the test router, the X-550N performed even better with the core of 48Mbps, topping the chart among 2.4Ghz routers by a significant margin. For comparison, the second fastest is the D-Link DIR-825 that scored only 40.4Mbps in the same test.
The Zyxel X-550N also did very well in the Mixed mode test, where the router was set to work with both Wireless-N and legacy wireless-G and B clients, with the score of 36.4Mbps.
Apart from these very good throughput scores, the X-550N performed well in our range test. It was able to hold a steady connection from a distance of 300 feet away. Most other wireless-N routers we've reviewed could only offer a range of up to 270 feet.
Though we were happy with the router's throughput and range performance, we were disappointed with signal stability after it failed our 24-hour stress test. In this test we transfer a large amount of data back and forth from different wireless clients to see if the test router can hold the connections continuously over an extended amount of time. The ZyxelX-550N's signal reset after about 7 hours, causing the data transferring to be interrupted. This might not translate into a bad Web-surfing experience, but it will likely kick you out of an online game or any kind of Internet-related tasks that require a steady connection.
We also noted that the signal stability varied depending on the clients. When tried with different laptops, some worked very well and others had a hard time keeping a stable connection to the router. The router also has no option to operate in just wireless-N, rather it always works in the mixed mode, supporting all clients, N and legacy G and B, all the time.
We tested the Zyxel X-550N with its latest firmware, version 360BFD3D0. We really hope that the router's wireless stability will improve with its next firmware. That would make it one of the best single-band wireless-N routers we've seen
(Longer bars indicate better performance)
Service and support
The Zyxel X-550N comes with a two-year warranty; most manufacturers only offer one year. The support page on Zyxel's site offers downloads for the firmware, manual, user guide, as well as other support recourses. The company's toll-free technical support is available Monday through Friday, from 8 p.m. till 5 p.m. PT.