Now (correct me if I am wrong), but a backless guitar speaker is a small open baffle. The driver might be flattish down to 80 Hz but I doubt that the output from the guitar speaker is.
And in practice, if you put a monopole speaker near a back wall the bass in the listening position increases, because the omnidirectional output from the cone that goes round the cabinet and is reflected from the rear wall is near enough IN PHASE with the forward radiation from the cone ( at bass frequencies). If there was any phase reversal in the reflected sound the opposite would be the case.
Can someone else come in on this, I am not up to arguing the toss with vectors and expanding toroids. Tell me I am wrong. I am happy to be educated.
And in practice, if you put a monopole speaker near a back wall the bass in the listening position increases, because the omnidirectional output from the cone that goes round the cabinet and is reflected from the rear wall is near enough IN PHASE with the forward radiation from the cone ( at bass frequencies). If there was any phase reversal in the reflected sound the opposite would be the case.
Can someone else come in on this, I am not up to arguing the toss with vectors and expanding toroids. Tell me I am wrong. I am happy to be educated.