So the linear distance then is the main key. In a very large room with little to no boundary reinforcement you would lose 6dB with every doubling of distance. In a smaller room with boundary reinforcement, it would be -3dB for every doubling of distance.
(Any corrections to that would be welcome!)
Not a correction, adding the math behind the SPL loss with distance. (ie you're right
)
SPL(Delta) = 20 * Log10(Distance 1 fom Speaker / Distance 2 from Speaker) in an open field (ie no boundary reinforcement)
eg)
A speaker with sensitivity of 90dB (ie measured at 1m from Speaker with 1w power input)
At 2m (ie 1m from reference(1m) doubling the distance) , there is a SPL drop of ~6dB:
20 * Log10(2m / 1m) =
6.02 [ ie SPL of 84 dB at 2m ]
At 3m , there is a drop of ~9dB : 20 * Log10(3m / 1m) = 9.54
At 4m , there is a drop of ~12dB : 20 * Log10(3m / 1m) = 12.04
so on..