The purpose of the tone ring is to make the sound louder and more crisp, as well as adding sustain. A more massive tone ring will give deeper and more crisp lower tones and more brilliant and projecting higher tones.

1/4" Steel rods are generally used, and seem to work as well as brass. Holes that range in size from 1/8" to 1/4" and in numbers of 20 to 45 are common. The Silver spun-over metal served the purpose of aesthetics and the practical purpose of keeping the rod aligned on its support. It may have also served the purpose of securely attaching the tone ring to the rim and thereby insuring a good transfer of sound vibrations.

Suspension of the rod was a common and an important feature among a number of tone rings. At first it seems like the purpose of suspension was to enable the rod to vibrate. However, it does not seem that there could be much actual vibration of the tone ring itself. The most suspended looking tone ring is the Whyte Laydie, but its tone rod is actually constricted by the roll-over metal sheath. The Tubaphone and the Vox had no suspension of the rod.

One would have to conclude that the areas under the rods are not for suspension and vibration purposes but for reverberation purposes. The sound is meant to vibrate off the rod, down to the facing metal surfaces and then back to the rod, and repeat again. The square tube of the Tubaphone created repeated echos before releasing the sound waves out the holes. The Whyte Laydie tone ring did not have a confined space for reverberation, but it did reflect the sound down on the supporting scalloped areas and then back again several times.

The excellent sound of the Electric as well as several other old time banjos suggests that the sound reverberations can immediately bounce against metal or wood to produce a good sound. In the Whyte Laydie, the sound vibrations reflect against the supporting metal. In the Tubaphone the sound vibrations have a prolonged contact with the metal before exiting through the holes. The Mastertone tone ring is one of the most powerful of all yet the entire bottom side of this reverberation chamber is wood.

Farland
The tone ring had about 20 1/8" holes drilled into a sheet-rolled brass (approx. height 3/8")

Eclipse
the tone ring is a steel hoop slightly raised (1/32") above
the top of the wooden pot and supported by about 20 small steel rods. It had a metal sheath extended half way down the outside of the pot.

Little Wonder
A tone ring with a 1/4" steel rod on top of the rim.
A spun-brass sleeve covers the rod and goes about half way down on the outside of the rim. It produces a mellow sound.

Fairbanks Electric
Electric tonerings are made from a one-piece metal ring and the notches are milled out at the bottom. Notice the bevelled upper edge. The second tone ring is of a thinner metal and has a strong bevel on top and at the bottom which would serve as good reverberation surfaces.

Whyte Laydie
a tone ring with a shorter scalloped ring than that of a
Special Electric tone ring. It consists of a round steel hoop, scalloped brass ring and spun-brass sleeve. It produces a clear, rich old-time sound.

Vega Vox
The Vox is the same as the Tubaphone, except that the top
of the tone ring is an integral part of it.

Bacon Professional FF
The Bacon tone ring is a curved shaped brass ring slightly
slanted inwards from the rim. The inside edge of the tone ring is not supported so it may vibrate. The sound waves reverberate off the 1/4" steel rod, then back and forth between the metal flange and the top of the wood rim. Notice that the wood is angled to be parallel with the metal flange. As well, it seems that sound waves would bounce back and forth between the top of the flange and the head. Of all the tone ring systems this one most likely involves the most vibration. Since the tone ring produces a very good sound, vibration of the tone ring likely is a good thing.