In addition to operating a 5GHz network based on the 802.11ac standard, the Time Capsule can also operate a 2.4GHz network to support older 802.11b-, -g, and -n clients, as well as a 5GHz network to support 802.11a and 802.11n clients. This is important, as the new MacBook Air is one of the few devices to support 802.11ac. Most computers, smartphones, media streamers, and other networkable devices rely on the older standards.
Using WiFiPerf once again, I measured TCP throughput with a mid-2011 13-inch MacBook Pro connected first to the older 802.11n Time Capsule (at 5GHz) and then to the new 802.11ac Time Capsule. TCP throughput was only a little higher at close range—301.7 mbps with the 802.11ac Time Capsule versus 285.3 mbps with the 802.11n model—but the new router was dramatically faster at longer distance: 67.7 mbps compared to just 32.3 mbps with the client separated from the router by 65 feet and three insulated interior walls.
Apple's 802.11ac Time Capsule delivers great performance with an 802.11n MacBook Pro client, especially at range. (Click to enlarge chart.)
Once Apple fixes the file-transfer problem, upgrading to the 802.11ac Time Capsule should also deliver better network performance with older Macs outfitted with 802.11n adapters.
I typically cover a product's feature set at the beginning of the review, but in this case I thought it more important to discuss Apple's file-transfer issues first. As I've already mentioned, the 802.11ac Time Capsule is a dual-band model, capable of operating networks on both the 2.4GHz and the 5GHz frequency bands. It's equipped with six antennas: three transmit, three receive for its 2.4GHz radio, and three transmit, three receive for its 5GHz radio. The antennas are mounted near the top of the 6.6-inch-tall columnar device, which likely helps it achieve longer range. It supports three 433.3 mbps spatial streams for a maximum physical link rate of 1.3 Gbps. (The 802.11ac adapter in the new MacBook Air supports two spatial streams for a maximum physical link rate of 867 mbps when connecting to an 802.11ac router.)
The new Time Capsule also supports an optional feature of the 802.11ac standard known as beam forming. With this technology, the router and each of its clients exchange information as to their physical locations. They use this information to concentrate their radio energy to achieve the highest possible throughput.
The Time Capsule is currently available with either a 2TB hard drive or a 3TB drive. Both models are equipped with an accelerometer that will park the drive's read/write heads if the router is dropped or tipped over (older Time Capsules do not have this feature). Unlike some other hard-drive-equipped routers, the Time Capsule uses a SATA interface to the hard drive, versus a USB-to-SATA bridge. Apple, however, declined to disclose the rotational speed of the drive's platters and if the drive has a SATA 6 Gbps interface or a slower SATA 3 Gbps interface.
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