Why use horn loaded speakers?

[Bill Fitzmaurice]

It's because a horn is an impedance transformer. Moving coil loudspeaker drivers have an inherent flaw, in that they're high impedance devices operating into a low impedance load, that load being air. 2 ohms doesn't sound like it's a high impedance, but it's huge compared to the impedance of air. When a high impedance device operates into a low impedance load the power conversion efficiency is low. Direct radiator speaker efficiency is very low, around 2% on average. A horn provides a driver with a higher impedance load, so the speaker works with far greater efficiency. The Tuba 60 runs with an average efficiency of 30%. That efficiency is at the heart of why horns are better.

Look at it this way. You're in a rowboat using a pair of pool cues for oars. You'll get where you're going eventually, but those pool cues can't grab enough water to do the job effectively, no matter how fast you row. That's a direct radiator. Switch to a good pair of oars and you go a lot faster, while doing less work, because they grab the water so much better. That's a horn.