Are on machines with 2.4GHz WiFi. I've seen that and usually we try drivers first then move to testing with the newer dual channel USB WiFI sticks.
I have tried 1 windows desktop, 3 windows laptops, and 1 IPAD on our new business internet setup. The IPAD and two laptops have no problem getting speeds up to 300 mbps. One laptop and the desktop only reach 11 mbps. I’ve tested the desktop and the one laptop on my home system and they work fine there (home is capable of 100 mbps). Interestingly the two computers that can’t get more than 11mbps on the office internet have AMD chipsets. They do have an ac adapter. Any ideas?