One angered attendee penned: "Absolutely shocking!! Sound awful should get a refund! Should of listened to their reviews from Ireland", while another simply wrote: "Very disappointed with the Spice Girls concert".
A third commented: "Left the Cardiff gig early. Really disappointed as couldn't hear a word. Was really looking forward to it but left feeling it was a a bit lame #spicegirls."
Picking up on the backlash, a cheeky social media user tweeted: "Surely the whole idea of a soundcheck is to check the sound?? #SpiceWorldCardiff #spicegirls #spicegirlsound #gladimnotthere #Spiceworld2019."
Another wrote: "The spice girls at their 2019 UK tour: so tell me what you want, what you really want... The fans: I wanna, I wanna, I wanna really really really wanna f****** refund."
"Are you joking??? I've had better sound out of an old flip flop! Terrible — girls were brilliant totally let down but sound!!!!", another expressed.
A dedicated fan pleaded with the group about the show's technical difficulties, as they revealed they're set to travel from Africa just to see the group hit the stage next month: "@spicegirls @MelanieCmusic @OfficialMelB @EmmaBunton @GeriHalliwell I hope these sound issues are sorted for wembley. Coming all the way from South Africa to see you guys!!."
Others took to the microblogging site to bemoan the venue's "soaking wet and cold" conditions, with a furious fan penning: "Why didn't you close the sodding roof!?!?!?"
"Having to leave the @spicegirls concert early at the @principalitysta because we were absolutely soaked, freezing cold and couldn't hear a word they were saying. What a waste of £77", another admitted.
A third wrote: "Hello @spicegirls @principalitysta do you know you have a retractable roof yes? Please use it next time it's pouring down. Kind regards, soaking wet, frizzy haired, freezing fan xoxo. PS. Girl power."
A series of pleased fans flooded Twitter to share their delight over watching the "magical" show: "Not gonna lie, I am totes emosh! I'm 10 years old, but instead of actual lighters & glowsticks it's smartphones & flashing wristbands & I understand life so much more. Shed a bit of a tear, for lots of reasons. @spicegirls je t'aime. Diolch yn fawr #SpiceWorldTour2019 #Caerdydd."
"Did this just really happen? Was I really just this close to my heroes? Best day of my entire life. Thank you a million times spicegirls — absolutely mind blowing show/stage/production/everything", another enthused.
A third gushed: "I absolutely loved the @spicegirls #concert #cardiff @principalitysta The girls all looked fabulous considering I first started listening to them in #1996 I've been happily married for 20 years to my husband but I can't help but have a #GirlCrush on @MelanieCmusic #SportySpice."
Following their first performance on Friday, which garnered both positive and negative reviews, Scary Spice Mel was the only member of the to address the backlash.
The mother-of-three uploaded a video to Instagram in which she admitted there were sound and vocal problems at the group's debut Dublin gig — and pledged to improve the sound quality for the next show.
After a fresh-faced Mel shared the candid video at 6am the day after the first gig on the reunion tour, her fellow bandmembers took to the photo-sharing site to gush over their performance and thank their "supportive" fans.
Speaking into the camera whilst lying in bed, she appeared irked as she said: "Hey guys thank you for attending our show tonight in Dublin. We will see you in Cardiff and hopefully the vocals and the sound will be much, much better."
Fans anticipation was rife ahead of the concert, as it was the first time the band had taken to the stage as a group in seven years. Posh Spice Victoria Beckham declined to take part in the string of performances, with the band continuing as a foursome.
Earlier this month, Ginger Spice blasted rumours of a rift between her fellow Spice Girl bandmates as they prepared for their impending tour.
Hot on the heels of bombshell lesbian claims by Mel B, as well as Scary Spice's recent health woes, Geri was quick to dismiss the supposed drama, telling critics: "You think, 'Oh f*** off!'"
Speaking to The Sun, she revealed that they were all "having a blast during rehearsals" and their relationship was "really good and positive."
She elaborated: "Our relationship is really good. We've all been really positive, so it's nice. It's natural. I'm really happy, everyone's happy."
When asked if they would be celebrating during rehearsals, Geri explained: "That's exactly what we'll be doing, with all of our imperfections, all our faults, but celebrate the good bits too. No one is perfect but it's all fine. We're having a blast. It's an absolute laugh."
Meanwhile, Mel B is said to have bounced back to health after being rushed to hospital following her complaint that she was "totally blind".
Giving an update on the singer's health woes, a source has told PEOPLE: "She's doing fine now, she's not blind. This has happened before. She has herpes in her eye, so this can happen."
It was also added by the source that despite the singer, 43, complaining to doctors that she couldn't see, her "eye is OK" and "they've given her some drops and she's good now. It was nothing major".
