I'm stumped. I have a 4th gen. AirPort Time Capsule (ATC) that is connected directly to my DSL modem (it's a PPPoE connection at 25 Mbps) that provides Wi-Fi for my apartment. My iMac connects to the ATC via a cat 6 cable and it gets 25 Mbps via speedtest.net. However, devices (iPhones, MacBook Pro, etc) connected by Wi-Fi only get 3-8 Mbps down, but connect to the ATC at 145-300 Mbps. The same issue happens on 2.4 GHz and 5 GHz, even when I'm just a few feet from the ATC. Wireless diagnostics warns me there's some crowding, channel-wise, but even if I use an non-crowded channel, it's the same thing. I had an AirPort Express (802.11n 1st gen.) extending the 2.4 GHz network, and tried disabling the extension (and just joining the network) but also nothing changed. Most of the settings on the ATC are default, except a DHCP reservation for my Xbox One and some ports forwarded to it for Xbox Live (53, 88, 3074, 3544) and it's set to use a different name for the 5 GHz network (obviously). DNS wise, I'm using the DNS servers provided by the ISP, and if I change a client's DNS to, say, Google DNS the improvement is negligible. Also, I haven't experienced any issues with speed doing file transfers and whatnot over Wi-Fi. Both Macs run OS X 10.11.5, the iPhones (6s and 5c) run iOS 9.3.2. ATC and AirPort Express firmware are 7.6.7. Any ideas on how to increase the internet throughput over Wi-Fi? (Also, enjoy the Arrested Development themed network name).