Cobbled together! It's probably better made than anything I could ever hope to build.
For the 6V6 competition, I 'cobbled together' a CD of various three minute tracks of different music genres, blues, classical etc which we played for each amp. David did the same last year for the Russian line stage.
We decided that this year, anybody who entered the competition could submit a track and it would be part of the test CD. So you can send me something in the 2-3 minute range. Wav or Flac would be fine.
I will try to include some test tones 60hz, 50hz, 40hz, 30hz, 20hz after the music tracks just to see how low our speakers can reach.