02.10.2015 
Performance In Benchmarks
First, let's take a look at a diagram of how our test apartment is set up. It is a reasonably large apartment and, if you don't have very good router, the wireless coverage can get rather weak in rooms like the kitchen or the medium balcony which are far away from it. You can see that we have placed the router in the living room and the range extender in the hallway. The router that we used is ASUS RT-AC56U. We mounted the range extender on the hallway, to improve the wireless coverage in the rooms that are farther away from the router.
We compared ASUS RP-AC56 with two other range extenders: ASUS RP-AC52 (a device from the previous generation of ASUS range extenders, to see if there are any meaningful improvements when compared to past devices) and TP-LINK RE210 (a new range extender from ASUS's main competitor).
We started by measuring the wireless signal strength in all the rooms where we use our wireless devices. For this task we used a tool named inSSIDer. Since this is a dual-band range extender, we measured the signal strength for both 2.4GHz and 5GHz wireless networks.
As you can see below, the signal strength doesn't seem to be an improvement area for ASUS RP-AC56 when looking at the 2.4 GHz wireless network.
However, it does get better on the 5 GHz wireless network, at least when compared with a range extender from ASUS's previous generation of products.
Since the signal strength is not an indicator of how fast a range extender is, we moved on to the next set of measurements. We used SpeedTest to see how fast the Internet connection is when using the 2.4GHz wireless network.
As you can see below, ASUS RP-AC56 provides slightly slower downloads than its predecessor - ASUS RP-AC52, on the 2.4 GHz wireless frequency.
The same is true in terms of upload speed on the 2.4 GHz wireless network.
We moved on the the 5 GHz wireless network. Here we noticed meaningful improvements in all rooms. It looks like ASUS RP-AC56 focuses a lot more on modern 5GHz wireless networks than on older 2.4 GHz wireless networks.
We also noticed the same trend when measuring the upload speed on the Internet.
Then, we used LAN Speed Test Lite to measure the download and upload speeds when transferring a 350 MB file on the wireless network broadcasted by ASUS RP-AC56. Unfortunately, we did not perform this test in the past and we have comparison data only with the TP-LINK RE210 range extender.
In the graph below, we can easily notice that ASUS RP-AC56 delivers reasonably fast downloads across all rooms in our test apartment and it's definitely faster than the TP-LINK RE210.
The same is true when we looked at the upload speed over the network.
Lastly, we measured the download and upload speed when using the 5GHz wireless network. Again, ASUS RP-AC56 proved to be a very capable device.
Uploads though were not as fast as we expected them. In some rooms, the more affordable TP-LINK RE210 range extender was faster.
Our testing has shown that ASUS focused on delivering fast 5GHz wireless network connections. ASUS RP-AC56 is quite fast when extending networks using this frequency. However, older generation devices are faster than ASUS RP-AC56 when extending 2.4 GHz wireless networks.
Special Features
ASUS RP-AC56 offers as an extra-feature, a 3.5mm stereo audio port where you can plug in a speaker, a stereo system or an earphone. You can use that port to listen to online radio stations. This feature can be turned on from the device's configuration menus. You also have an app for this feature available for iPhone and Android, which you can download from their respective stores.
All we can say is that this feature works well but we don't think it will be an important selling point for most users.
Verdict
ASUS RP-AC56 is a capable range extender that's very good at extending modern wireless networks that use the 5GHz wireless frequency. When it comes to older networks using the 2.4 GHz frequency, previous generation devices from ASUS tend to be faster. However, its performance is not bad in this situation either. It's just not as stellar as it is when extending 5GHz wireless networks.
Overall, ASUS RP-AC56 is a solid device that will do well in large apartments and houses, when you need to extend fast wireless networks that use modern standards like 802.11ac. Since this is a top-tier range extender, it is more expensive than other devices of its kind, so do keep this aspect in mind.
