London (CNN) Fans of the Spice Girls are demanding refunds after the girl group's long-anticipated reunion tour was plagued by sound problems for the second consecutive night.

Several attendees complained they struggled to hear the British band during their performance at the Principality Stadium in Cardiff, Wales, on Monday night, with some saying the problems ruined the experience.

"Amazing show from @spicegirls but the sound was terrible! Can barely hear vocals!" a concert-goer wrote on Twitter on Monday evening.

"Those in charge of sound need to improve. You couldn't hear a word when they were talking," another added, while a third said the sound at the gig was "bloody awful."

The tour marks the first performances by the 90s act for nine years, and both venues the group have played have been packed with fans.

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