Slightly off-topic, but you on the command line you could use ffmpeg to achieve this much easier:

ffmpeg -i input.wav -i "impulse_response.wav" -lavfi afir output.wav

impulse_response.wav would be your FIR.

See: https://unix.stackexchange.com/questions/612414/how-to-apply-reverb-effect-to-audio-files-using-commandline-tools-only