FDW is REW’s equivalent of SMAART’s FTW and SysTune’s TFC.
Whether or not to use it is completely up to you, and is based on your measurement environment and preferred workflow.
FDW, FTW and TFC are intended for situations where there might be strong mid and/or high frequency room reflections (which we’d like to remove from the TF with a window) and where shortening a traditional window (to remove these reflections) would cause loss of resolution in the LF. The frequency varying window provides for a longer window length at LF and shorter window length at HF. In a lab environment or anechoic chamber where reflections are minimal, FDW, FTW and TFC aren’t really necessary.
We have customers who use the SMAART FTW by default for measurements that they use in FIR Designer, and it gives them tuning results they are happy with.
See also…
https://www.rationalacoustics.com/download/Smaart-v8.3-Release-Overview.pdf See page 8.
https://www.prosoundtraining.com/2010/03/15/easera-systune/ See Figure 1.
Best regards,
EA Support