Let's just chalk this one up to intellectual vacancy... I still feel that the best thing for your carpet is a powerful vacuum (good suction and airflow, enough to move the air and dirt properly) with good thorough agitation to loosen that embedded dirt into the stream of air. Also I've felt for years that letting the bottom plate breathe along the front will help cleaning, experience and observation tell me this. Then have a good shampooing done every so often to remove the dirt the vacuum doesn't.