Allies and Morrison's plans to refurbish Leslie Martin and Robert Matthew's Grade I-listed Royal Festival Hall have come under fire from Britain's leading acoustic authority.
Arup Acoustics founder Derek Sugden and the Twentieth Century Society have warned that the scheme will both fail to achieve the acoustic improvements demanded in the brief and also destroy the integrity of the 1951 designs. They have told Lambeth council that the designs - drawn up in collaboration with American acousticians Kirkegaard - will fail to meet the standards demanded by the South Bank Centre (SBC).
The conservationists are determined to persuade the SBC to install a modern electric amplification system, leaving the building intact.
If the project wins the green light, Allies and Morrison admits it will 'substantially change' the auditorium. These alterations include modifications to the canopy, the organ space and the interior decoration.
Sugden told the AJ he was 'convinced' the project was 'not a worthwhile effort because the building is never going to be worldclass acoustically'. He added: 'Architecturally this is a real icon of the '50s and it should be left as it is.
'What will happen here is that they will spend millions of pounds on it and end up with something that is acoustically not that good.
What they should do is leave it alone and put in an excellent modern amplification system.'
Twentieth Century Society caseworker Claire Barrett has also written to Lambeth council objecting. 'Enjoying a concert is not solely about an audio experience, it is equally about enjoying a space visually, ' the letter says. 'The whole experience is important and it is problematic to divide them so starkly.
'The hall is and always has been used as a multiuse space for the presentation of many different kinds of music and art forms, ' it adds. 'Is it worth altering a space so radically just so it can fulfil one of its requirements?'
Allies and Morrison associate Diane Haigh defended the project but admitted the auditorium would 'never be in the global top 10 for acoustics'.
However, she dismissed the criticism, insisting that there was no electro-acoustic system that would work.
'We did a lot of soul-searching, as we all hugely admire the building, but we found there was no way to make the improvements without these radical solutions, ' she said. 'The fact is it has not remained untouched since 1951, there were also changes in the '60s.'