47st. Photo via Walmart offers the Opteka Portable Wireless Bluetooth Speaker with Built-In Speakerphone in Silver, model no. OPBTSS, for $12.95 with free shipping. That's the lowest total price we could find by $13. It's compatible with most Bluetooth-enabled devices and features a built-in lithium-ion battery, 3.5mm audio jack, and wireless range of 35 feet via Bluetooth 3.0.