FDN Sandbox: Real-Time Experimentation and Analysis of FDNs
This work presents sfFDN, a modular and real-time-capable C++ library for Feedback Delay Networks (FDNs), together with the companion FDN Sandbox application designed for interactive experimentation, analysis, and parameter optimization. The library implements the canonical FDN as well as several recent extensions, including filter feedback matrices, velvet-noise decorrelation filters, and two-stage graphic equalizers for attenuation and tone correction. The Sandbox application exposes these features through a graphical interface, providing a suite of real-time visualizations, as well as an optimization framework supporting nine algorithms from the ensmallen library, with built-in loss functions for both colorless reverberation and room impulse response matching. Both the library and the application are open-source.