SAN FRANCISCO - Jawbone on Monday began rolling out an even louder version of its portable wireless speakers, which have caught fire among smartphone and tablet users.

The Big Jambox speakers could be pre-ordered online at jawbone.com for US$299 (S$375) ahead of their release in stores on May 15. They will roll out in other countries in the coming months.

Jambox has been catching on in Australia, Brazil, Europe, Japan, and elsewhere, with smartphone and tablet adoption evidently driving sales of the easy-to-carry wireless speakers engineered for rich sound.

"Jambox was the first wireless speaker to bring stunning audio quality to the music, movies and games normally trapped between earbuds on mobile devices," said Jawbone chief executive Hosain Rahman.

"With Big Jambox we utilized state-of-the-art audio technology to fill a much larger space with amazing sound without sacrificing portability."

The original Jambox is credited with starting a wireless speaker trend with a sleek, pocket-sized sound system that synchs to gadgets using Bluetooth capabilities.