Does the material of the audio shell determine the sound quality 100%?

Not 100%, but the speaker shell material is part of the reason for affecting the sound quality.

Generally speaking, it usual has three different materials to do audio shell, plastic material, metal materials and wood materials.

Compared with other materials, plastic speakers are light in texture and low in density, and the thin outer wall cannot effectively restrain resonance. Therefore, many people think that the sound quality of plastic speakers is dry, not round and delicate enough, and not as full as wood and metal materials.

In regards of metal materials, due to the higher density of metal materials than plastic and wood, the probability of resonance is lower, and the audio reproduction rate is more accurate. However, this is more expensive than two others.

For the wood materials, it is more elegant together with high sound quality. But it is not waterproof and not available for outside enviornment.

In total, the sound quality of a speaker is not only determined by the material of the speaker shell, but also limited by many factors such as the speaker amplifier, structural design and power, etc.