TAS had a chart in past issues going through the instruments in the orchestra and their frequency ranges. Other than an organ with 32 foot stops, and synthesizers, I don't think any instrument goes below 20 hz in its fundamental pitch (double bass and contrabassoon go only as far as 27 hz, as I recall, and a tuba doesn't go that low). However, there is a great deal of ambient information in recordings that may extend below 20hz, even in recordings that might otherwise not have musical content in that range (some you might not want to hear, like air conditioning systems and subways); in that regard, a full range speaker that can reproduce those sounds is more likely to give you a better sense of an acoustic space. As far as recordings with deep bass go, I recall that the Michigan Woofer and Tweeter Society had a listing of recordings with deep bass below 25 hz, any members out there remember? I may have the list at home, I'll try to dig it up if no one else can find or recall it. One recording I do remember with content below 20 hz was an old M&K direct to disc record, The Power and the Majesty, a recording of a Los Angeles church organ reputed to have an 8 hz content if your phono replay system was up to it. I tried to play it to hear it, but the vibrations made me sick and caused my house to collapse, so I had to stop the record, and my system only goes to 20 hz! There may also be a sub 20 hz note at the very end of the first cut on Pomp and Pipes (the Karg-Ellert piece, not necessarily the other tracks on that disc), and the second (quiet, not the finale) movement of the Philips recording of the Saint Saens Organ Symphony with Gillou and the San Francisco Symphony has some true 16 hz pedal notes. I recall that I was surprised that there were not that many recordings with true sub-20 hz content. Just remember not to do your listening on a full stomach, as some of those notes can really make you sick at high volumes.
