Well, it took a while, but Apple has finally resolved whatever problem was causing wireless file transfers using its new 802.11ac MacBook Air and Time Capsule to be so slow. If you haven't already updated to OS X 10.8.5, do it now.
When I benchmarked the new router last June, I noticed that real-world file transfers were much slower than the WiFiPerf benchmark indicated they should. WiFiPerf was reporting TCP throughput of more than 450 megabits per second (mbps) at close range, but transferring large files and large groups of files (10GB in each scenario) happened at less than half that speed.
Once I updated the MacBook Air with the latest version of OS X (10.8.5, which includes a patch to AirPort Utility), and the Time Capsule with Apple's newest firmware (version 7.7.1), real-world wireless file-transfer speeds more than doubled.
With the old software, copying a 10GB collection of small files from the mechanical hard drive in an iMac hardwired to the router, to the SSD in a MacBook Air over the wireless network required more than 16 minutes to complete at 84.8 mbps.
With the new software and firmware, the same task required slightly less than nine minutes because the file transfer occurred at 164.3 mbps. The speed at which those files were read over the wireless network (that is, copied back to the iMac from the MacBook Air) also more than doubled, from 132.1 mbps to 309.1 mbps.
The speed at which I could copy a single 10GB file from the iMac to the MacBook Air jumped by an even bigger margin: from 134 mbps to 482.1 mbps. An operation that previously required more than 10 minutes could now be finished in less than five. Copying that file back to the iMac took place at 551.4 mbps, compared to 163.5 mbps before the updates.
As I reported in my earlier review of Apple's 802.11n AirPort Extreme, some non-Apple routers deliver better performance than Apple's products, but they lack the Apple-specific features that make Apple's routers so easy to use--at least with Macs. Since I compared the AirPort Extreme to an Asus RT-N66U 802.11n router in that story, I decided to compare the 802.11ac Time Capsule's performance to an Asus RT-AC66U 802.11ac router this time (neither Asus model has an internal hard drive).
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