Moving Iron Speaker - Uses

Uses

Impedance

Early moving iron speakers were normally high impedance, being designed to be connected directly to the output triode with no transformer or dc blocking. Quality and output level can be significantly improved by removing most bass from the electrical input signal. This is simply achieved by using a capacitor in series with the speaker. Table-top horns can only reproduce the highest of bass frequencies, so no noticeable bass is lost by removing most of the bass input. This reduces diaphragm or reed excusrion, reducing harmonic and intermodulation distortion.

Polarity

Polarity matters when dc is present in the speaker. Wrong polarity weakens the magnetic field, and can sometimes demagnetise the permanent magnet, leaving the speaker non-functional. When powered with ac only, polarity is a non-issue. Nearly all modern amplifiers feed only ac to the speakers. However when using a moving iron speaker on an early radio, dc will be present, and either the polarity marked on the speaker should be observed, or means used to remove the dc component from the speaker. This was often done with a choke and capacitor.

Headphones

Use of balanced armature mechanisms is common in modern headphones. These use damping to achieve satisfactory sound.

Simple intercoms

Moving iron diaphragm transducers are highly microphonic, and connecting two together with no amplifier makes a usable intercom.