I use it for a decade. The 18 "is mounted transversely, if you ask the MTD horizontally, imagine that 18 inches is looking up. The wave goes through a maze to vent out through the moss-covered.
It is a bit soft compared to SB118 (which is 18-inch direct radiating like the SB218), but works well on small gauges. 4xMTD118 is perfect for 300/400 people.
It will run coupled with a MTD115MTD112 or provided as a sub for a head. Do not hesitate to cut certain frequencies to avoid an effect woo-woo, the best is to filter it through a Minidrive example, instead of the output sub processor brand as MTD115LLCa.
It should also if you want to bring back a little serious type diffusion MTD108a.