I did a recording experiment recently.
Use your best headphones!
0:16 Close microphone recording. Last weak note is 32 hz.
0:40 Microphone recording 8 feet from amp. Last note is a much stronger 32 hz.
1:02 Direct recording. No amp or mic limitation. Now that is LOW.
http://www.youtube.com/watch?v=OR2-eq7ruzk