Hi Thomas,
The ADAU1452 is quite new -- so just as you found out, SigmaStudio 3.9 doesn't support it (the ADAU145x.dll notwithstanding). Please install Version 3.10.3 Beta from
http://www.analog.com/en/dsp-software/ss_sigst_02/sw.html
Even this version has fewer blocks for the -1452 than for some other SigmaDSPs -- this will only improve with time.
Best regards,
Bob