Normal
Plus one to everything Art said of course.Remember also that a shelf vent can behave as if it's larger than the physical shelf, due to 3 out of the 4 walls continuing on beyond that.So if you were comparing the predicted vent length from a modelling program like WinISD etc, you'd need to adjust that expected length downwards.Using the alternate End Correction factors in the first post here, a rough estimate of something like the 3TX (30l net internal tuned to 73Hz) the actual shelf length required might be as low as 3cm; ie only a double thickness of the timber. Even if the net internal volume of the cab is smaller, or the tuning lower, the required length is still short - 25l to 70Hz would need 15cm of shelf, compared to the 39.2 predicted by WinISD.HTH,David.
Plus one to everything Art said of course.
Remember also that a shelf vent can behave as if it's larger than the physical shelf, due to 3 out of the 4 walls continuing on beyond that.
So if you were comparing the predicted vent length from a modelling program like WinISD etc, you'd need to adjust that expected length downwards.
Using the alternate End Correction factors in the first post here, a rough estimate of something like the 3TX (30l net internal tuned to 73Hz) the actual shelf length required might be as low as 3cm; ie only a double thickness of the timber. Even if the net internal volume of the cab is smaller, or the tuning lower, the required length is still short - 25l to 70Hz would need 15cm of shelf, compared to the 39.2 predicted by WinISD.
HTH,
David.
