What Is A Balanced Armature? How Is That Different Than A Speaker?

In my travels I’ve learned a lot about IEMs and sound devices of all kinds. But I have to admit I was always a little confused about the pros and cons of Balanced Armature vs Dynamic Speakers, and I know I’m not alone.

In the world of IEMs there is a healthy debate and in the overall world of headphones the debate really rages. Lucky for us at UE University, we got a chance to ask some questions from the folks over at Knowles corporation. Knowles was started in 1946 by Hugh Knowles and by 1954 they developed first miniature microphone and receiver for hearing aids. Knowles Balanced Armatures also power many of the UE PRO monitors.

We sat down with Tim Wickstrom ( Global Applications Manager and with the company since 1988) and Andrew Bellavia (Director of Market Development) and tried to take some of the mystery out of BAs and point out some key differences between a BA and Dynamic Speakers.

Can you explain a little bit about the difference between Balanced Armature (BA) and Diaphragm sound reproduction?

In a balanced armature earphone, the metal armature moves driving a paddle. The coil is fixed. In a dynamic speaker the coil moves along with the diaphragm.

So BA is a bit like a reed where a diaphragm is a more like a drum head or a speaker?

The BA diaphragm is hinged at one end while the dynamic diaphragm moves axially.

Balanced Armatures were developed for hearing aids first and then applied to earphones, is that correct?

Correct, and they still are used essentially 100% in that application due to their small size, efficient drive, and tuning versatility to match different hearing impairments.

What are some of the advantages to Balanced Armatures versus small dynamic speakers?

In an ordinary earphone the primary advantage is that they are so small that multiple drivers can be fit in a single earphone. Just as with home tower speakers, more faithful sound is reproduced with separate speakers for lows, mids and highs. There is also wide tuning latitude which is good even with single driver earphones to achieve the sound the designer wishes. The diaphragm mass is light, giving more precise response.

So am I correct in thinking that BA has a higher or more efficient output than small dynamic speakers?

Correct. You see that in the output graph for same input power.