As of 2015, the Shark Spk6800-spks, the BOSS Audio MC420B and the BOSS Audio MC470B are the three best motorcycle speakers, according to ConsumerTop.com. All of these models attach to the motorcycle's handlebars.
Of these three models, the Shark Spk6800-spks is the cheapest. These 300-watt speakers are waterproof and measure only 4 by 3 inches. The 600-watt BOSS Audio MC420B is similar in size, but it is not waterproof. The four-speaker setup of the BOSS Audio MC470B is meant for bigger bikes, as these speakers are water resistant and measure 4.5 by 4 inches. The system also comes with Bluetooth pairing support.