The SVS PB-17 Ultra advertises a range of 12-220Hz at -3dB. I imagine it could play a pure 7Hz tone if you turn it up.
And most speakers can play infrasound for many non-sinusoidal waveforms [0]. They'll drop the fundamental and some lower-end harmonics but can still give a sense of what it sounds like
And most speakers can play infrasound for many non-sinusoidal waveforms [0]. They'll drop the fundamental and some lower-end harmonics but can still give a sense of what it sounds like
[0] https://szynalski.com/tone#7,saw,v0.5