There was a problem earlier when I was trying to set up audio capture in Kdenlive so that I could do some voice overs. No matter what settings I chose, Kdenlive would return the error, "Capture crashed, please check your parameters" whenever I tried to capture audio.

I found out that the simple fix in my situation was to install additional codecs with the following command run in a terminal:

sudo apt install libavcodec-extra

That was all it took for me. After installing those codecs, I went back to Kdenlive and found that audio recording worked. 

This worked for Kdenlive version 17.12.0 and Kubuntu 16.04.

I hope this little fix solves the problem for you.