How can multiple woofers generate lower frequency?

They don't. Multiple woofers just move more air, thus sound more powerful with the illusion of deeper bass.

Assuming that the woofers are identical, they will have the same frequency response. However, when using two subs in the same room, it is possible to generate somewhat smoother low frequencies due to the effect of the room acoustics. A single subwoofer may excite resonant modes in the room which interfere with the acoustic output of the sub, thereby producing phase cancellation, or nulls, at certain frequencies. A pair of subs, however, will often acoustically load the room differently than a solo sub, so the effects of phase cancellation are reduced, thereby increasing the output.

There is another thread below, "Subwoofers and standing waves", that explores this topic as well.

Take the Soliloquy speakers as an example,

Model Woofer Number Low Frequency
6.2 one 6.5” woofer 28Hz
6.3 two 6.5” woofers 25Hz
6.5 three 6.5” woofers 22Hz

They all use the same woofers, how can it be explained?

Thanks for your inputs.

Otto

Is the cabinet the same size?

The exact cabinet sizes are unknown but the speakers are 42”, 44” and 53” respectively with the same base sizes (9” X 13”).

So again how can it be explained? Also what is the advantage to use this design over the single-large-size-woofer design?

Thanks for your inputs.

Otto