The lever can theoretically go to any ratio, but beyong 2:1 we found that the parasitics were eating up the advantages. The mechanical parameters on the radiating side are mutiplied by the ratio squared. So acoustic mass load soon gets to be a problem, etc. Beyond 2:1 and we could not get the lever to survive very long. They get beat pretty hard. You don't have to use just one lever there can be more than one - if thats what you mean. We used two levers one driver.

You understand the lever function well enough. It can be used wherever a passive radiator is used.