What happens when you play 10hz? You wont hear anything so what effect can it produce?
I have no budget because this is just a hypothetical question out of interest. Loud at 10hz means it should be able to cause vibrations which can be felt from a large distance.
I'm just going off measurements taken in my room, my statement was an example, I don't really care about output down to 10hz, as you say, all it does is shake things a good deal.
Is there any subwoofer on the market which can go loud at 10-20hz?
I answered your question - but it really all depends on the quality of a subwoofer and that Subs interaction with the room. If you have a small to medium sized room adn the right placements you may experience a good amount of room gain netting you good performance in the subsonic region....
Even with my stupid subs I built - being placed in a stadium that doesn't give me much room gain at all, I don't see alot performance below 20hz.... the measurements are showing them rolling off @ 17-18hz. In a smaller - medium sized room, it is a very good bet that I would be hitting the single digits with ease. Do I care - heck no - the sonic region output is wicked. It is because of the room interaction, long tall walls, wood floors over long joists, large windows - all of those things are basically absorbing the deep bass waves (subsonic freqs) - flexing and in turn counteracting - which produces cancellation in those freq regions....
Again my point was - one needs to define the room size & layout to get a better understanding of how those subsonics will react, every room is different. Square, rectangle, obtuse, oval , open to other areas, concrete floor - joist floor, windows, totally closed.... way to many variables not accounted for in the question to say whether x sub is going to do subsonics....