"There's something wrong when the crowd at a Spice Girls concert are all sitting down because no one has a clue what song is on because the sound really is that bad." said one concert-goer.
However not everyone went home disappointed last night, with many calling the concert "amazing from start to finish", and a "magical night".
The Spice Girls - minus Posh Spice, now Victoria Beckham - kicked off the first of 13 concerts on Friday with their hit single Spice Up Your Life and a fireworks display, the Press Association reported.
Melanie "Mel B" Brown, aka Scary Spice, addressed complaints from multiple concertgoers that the sound at the Croke Park venue wasn't up to par, making the pop stars hard to hear.
Fans attending the show at Croke Park blasted engineers via Twitter during the gig for ruining their experience, and many concertgoers walked out because the sound was so bad.
Another viewer wrote: 'I'm actually surprised at how lovely Mel B is, she's amusing & seems very down to earth.
Although they have since made up, Geri was believed to be upset over the claim, with sources saying Mel B had "done damage" to their friendship.
Mel B told fans in an early-morning Instagram video that she hopes the vocals and sound quality will be "much, much better" for their next show in Cardiff on Monday night.
Spice Girls are set to perform 12 more shows in the United Kingdom wrapping up the tour on June 15th at Wembley Stadium.
"Another tweeted: "@spicegirls now sitting in croke park, was absolutely buzzing to see you lot but its very disappointing cos the sound is really bad!
"What can I say yous didn't disappoint!" Like a king or a queen, we celebrate you.
Victoria Beckham has publicly wished her former Spice Girls bandmates good luck ahead of the first date of their reunion tour.
They split in 2000, reuniting for a tour of Europe and the United States in 2008 and last performing together at the closing ceremony of the London 2012 Olympics.
In a clip posted online from the Dublin show, during the performance of Wannabe, when Horner rapped: "Easy V doesn't come for free, she's a real lady", Mel B added a loud, sarcastic laugh.