Low freq. from small drivers? Is it possible

Small drivers, like 3/4 inch headphones, are perfectly capable of LF response, but not at any volume. Because a small driver cannot move enough air to achieve useful volume at low frequency they are designed for other characteristics like mid/high reproduction. A 6 inch subwoofer is technically possible, but would be almost useless for any real audio system.

Here is the Royd homepage if you are interested: http://www.roydaudio.com/main.htm

It is absolutely possible even without a port.
Karl E. Schuemann and the ultimate monitor have accomplished this very very well, at least in my system.
http://www.theultimatemonitor.com/default2.htm

Best Regards,
Michael Wolff

Yes, there are many speakers that can get to the 30hz range with those 6.5" drivers. VBT has a claimed frequency response of 18hz(-6db) with one of their subs using a 6.5" driver.

There are tradeoff though. A 6.5" driver generally can't play as loud as a 10" driver before breaking up. Second deep bass in small boxes generally means lower effeciency. So yep physics still applys.

The key is to move a large volumn of air. If long throw woofers are used then they don't need have as large diameter.