Marshall's Stockwell III portable speaker offers more than 40 hours of use per charge

It resembles a guitar amp and is available right now for $250.

Marshall just announced the Stockwell III portable Bluetooth speaker , which offers some real improvements over the Stockwell II . First of all, the battery life has doubled, up from 20 hours per charge to over 40 hours per charge. That's five whole workdays of pumping tunes to annoy coworkers.

The Stockwell III features the company's proprietary True Stereophonic technology, which delivers 360-degree audio no matter where the speaker is placed. It also includes a dynamic loudness algorithm that keeps "the bass, mids and treble balanced at any volume." At lower volumes, bass and treble are heightened.

This is a Marshall Bluetooth speaker, so it sort of looks like a guitar amp . This is assisted by a PU leather carry strap and velvet lining. There's a brass control panel that lets users skip tracks, jump to presets and make audio adjustments.

It's dust and water resistant, with an IP55 rating. Many of the components are also modular and user-replaceable, including the strap, battery, front and back grille and silicone sleeve.

Finally, this is an incredibly light speaker. It weighs under three pounds. The Marshall Stockwell III is available in two colorways right now directly from Marshall and will head to big box retailers on August 4.