Final answer:
The Place theory best explains Phillipé's perception of the low pitch sounds from his speaker's subwoofer, as it suggests different parts of the basilar membrane respond to different frequencies, with the tip best responding to low frequencies.
Step-by-step explanation:
The theory of pitch perception that BEST explains why Phillipé might not be able to hear a sound if the pitch were any lower is the Frequency theory. The Frequency theory asserts that frequency is coded by the activity level of a sensory neuron, meaning that a hair cell would fire action potentials at a rate connected to the frequency of the sound wave. However, for sounds with a frequency too low for the hair cells to track directly through action potentials, because they can't fire fast enough, this falls short.
At that point, the Place theory takes precedence, which suggests that different parts of the basilar membrane in the cochlea respond to different frequencies of sound, with the tip best responding to the lower frequencies. Given Phillipé's description of a low rumble, it is actually Place theory that describes his experience with low-pitched sounds.