Accessories for Guitar (electro-) acoustic hearing central round to improve the sound.
I use it for a year.
The effect corresponds to that described: improved sound projection, and the definition of notes.
In combination with a change to pine plastoc of ebony for example, a folk guitar can easily get a good perspective notch class of instrument.
That's what I did, and my Ibanez AEL20EVV now has a seriously magnified!
The implementation is very simple: just loosen the strings a bit, while keeping the head end by a capo. Remove pine trestle side, and positioning in hearing the O-port from which the plastic is soft. Replace the pins, remove the capo and retune.
There are two sizes depending on the size of hearing, and two colors: white or black.
The price is a bit expensive, having said that, but the effect is real. Therefore, the quality / price is not really bad, when considering the purchase in exchange of an instrument of a relatively higher.
It is therefore an attractive purchase. And when combined with other improvements, such as changing the quality of pines, for example, the degree of optimization can then correspond to a real change in class of instrument.