I am using the 816 for over 30 years I worked in biamp frquence cutoff 800htz long grills are the HP I replaced them with OEM hp ev a small wonder the boxes also work very s well with the proline hp ev type above 800htz j utilisedepuis bit of a 3-way speaker comunity al epoque j've seen this system run on a rotated fr3 but equipped for Section multimdia by Altec team in 2 ways not found on the walk