If all you are worried about is protecting the outside of the speakers from scrapes and knocks ANY reasonably heavy duty plastic bags will do for cosmetic protection . I bought a 2nd hand Peavy sixteen channel mixer which had a 3/4 inch plywood box that is heavier than the mixer . I built a cardboard case(Tri-Wall actually) with Gaffa Tape and nylon cord which protects the sliders and knobs and is nice and light . In fact .card would probably do to protect the speakers too , though plastic would be waterproof as well .