I don't have any direct experience with the Altec 414, but there are several here that have used this and other Altec midwoofers. Seems to me that they are usually used in a rather large bass-reflex cabinet, many of which include truncated (midrange) horns. I'm sure you're aware of that configuration - It's one of Altec's most popular, with the driver installed in a front-loaded small horn and with the back chamber being a large bass-reflex cabinet.I've also known many that used them in two-way speakers with a simple (non-horn loaded) bass-reflex design for the midwoofer and a large-format HF horn for the vocal overtone range up. Seems like PiAlign recommended something like 9 cubic feet tuned to 30Hz or so, but I may be thinking about Altec 416's.