Some horns particularly those which are W folded have a relatively short horn length for mouth area. They are often large meaning that low cutoff frequency can be achieved often with only 2 boxes rather than 4 or 6.

These days people will use more cabinets to get more volume as this is what is demanded. Therefore it makes sense to make smaller cabinets which on their own have limited extension but when used in the proper quantity end up being both lower and louder than old designs like w bins because the mouth area is larger and the horn length is longer.

Stu