Huawei FreeArc are here, boasting IP57 dust- and water-ingress protection It's Huawei's second open-ear option after FreeClip, but the firm's first 'shell' design They're affordable – and there's an extra saving if you buy now My main issue when considering open-ear earbuds? Actually, there are two things: something that will survive a particularly sweaty/rain-soaked attempt to improve my (abysmal) 5k personal best, and something that won't fall out of my ear during the aforementioned attempt. While the all-new Beats Powerbeats Pro 2 certainly claimed to have sorted the latter during their hotly-anticipated February 11 arrival announcement, their IPX4 rating won't…