## 3 Results
### Alignment of the Model Based on Principal Component Analysis  
Prior to the comparison of the predictive performance of the two models, the formulations should be aligned in order to facilitate the contrast. Thus, the principal component analysis-based formula is transformed to the standard form in order to support the performance evaluation. The principal component analysis-based method adopted the four components and z-scores of the sound quality indicators as inputs and outputs, respectively. The z-scores of the sound quality indicators and their numerical values in seven levels can be connected by the standard derivation of mean values. Thus, the z-scores and scores in seven levels can be linked with the following formula. \[\left[ \begin{array}{c}\text{Z}-\text{score of THD}\\ \text{Z}-\text{score of Power of Output}\\ \text{Z}-\text{score of Range of Frequency Response}\\ \text{Z}-\text{score of SNR}\\ \text{Z}-\text{score of Impedance of the Speaker}\\ \text{Z}-\text{score of Headroom}\end{array} \right]\] \[=\left[ \begin{array}{cccccc}1/2.227&0&0&0&0&0\\ 0&1/2.213&0&0&0&0\\ 0&0&1/2.200&0&0\\ 0&0&0&1/2.112&0&0\\ 0&0&0&0&1/2.205&0\\ 0&0&0&0&0&1/2.197\end{array} \right]\] \[\times\left( \begin{array}{c}\text{THD}\\ \text{Power of Output}\\ \text{Range of Frequency Response}\\ \text{SNR}\\ \text{The Impedance of the Speaker}\\ \text{Headroom}\end{array} \right]-\left[ \begin{array}{c}3.92\\ 3.87\\ 3.99\\ 4.01\\ 4.03\end{array} \right]\]  
Hence, with respect to the inverse of the functions, the conversion from z-scores to the seven-level values can be accomplished, which is expressed as follows. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Design Parameter** & & & & & & & & \\ \hline Type of the Primary Driver & 0.338 ** & 0.392 ** & 0.514 ** & 0.480 ** & 0.439 ** & 0.266 ** \\ Magnet of the Primary Driver & 0.448 ** & 0.464 ** & 0.229 ** & 0.203 ** & 0.192* & 0.349 ** \\ Voice Coils of the Primary Driver & 0.179 * & 0.155 * & 0.148 & 0.300 ** & 0.145 & 0.120 \\ The Diaphrag of the Primary Driver & 0.452 ** & 0.398 ** & 0.599 ** & 0.215 ** & 0.206 ** & 0.491 ** \\ Type of the Secondary Driver & 0.475 ** & 0.488 ** & 0.324 ** & 0.579 ** & 0.495 ** & 0.522 ** \\ Magnet of the Secondary Driver & 0.352 ** & 0.424 ** & 0.266 ** & 0.498 ** & 0.493 ** & 0.495 ** & 0.495 ** \\ Voice Coils of the Secondary Driver & 0.625 ** & 0.631 ** & 0.592 ** & 0.692 ** & 0.714 ** & 0.597 ** \\ Diaphrag of the Secondary Driver & 0.619 ** & 0.608 ** & 0.238 ** & 0.582 ** & 0.761 ** & 0.700 ** \\ \hline \hline \end{tabular}
*: Correlation is significant at the 0.0 level (2-tailed).  
\end{table} 
Table 8: Pearson correlation values of the testing data between the eight design parameters and the six sound quality performances. \[\left[ \begin{array}{ccccc}\text{THD}\\ \text{Power of Output}\\ \text{Range of Frequency Response}\\ \text{SNR}\\ \text{TheImpe dance of the Speaker}\\ \text{Headroom}\\ \end{array} \right]\\ =\left[ \begin{array}{ccccc}2.227&0&0&0&0&0\\ 0&2.213&0&0&0&0\\ 0&0&2.200&0&0&0\\ 0&0&0&2.112&0&0\\ 0&0&0&2.205&0\\ 0&0&0&0&2.197\\ \end{array} \right]\times\left[ \begin{array}{ccccc}\text{Z}-\text{score of THD}\\ \text{Z}-\text{score of Power of Output}\\ \text{Z}-\text{score of Range of Frequency Response}\\ \text{Z}-\text{score of SNR}\\ \text{Z}-\text{score of Impedance of the Speaker}\\ \text{Z}-\text{score of Headroom}\\ \end{array} \right]+\left[ \begin{array}{ccccc}3.92\\ 3.87\\ 3.99\\ 4.01\\ 4.03\\ \end{array} \right]\]  
On the other hand, the connection between the design parameters and the four components can be expressed by:  
\[\left[ \begin{array}{ccccc}\text{Component 1}\\ \text{Component 2}\\ \text{Component 3}\\ \text{Component 4}\\ \text{X}\end{array} \right]=\left[ \begin{array}{ccccc}0.306971&0.297114&0. 296176&0.33795&0.387704&0.400377&0.395214&0.385826\\ 0.445829&0.441501&0.381985&0.288923&-0.33654&-0.26187&-0.28892&-0.3343 7\\ -0.07285&-0.64326&0.759317&0.04571&0.028397&-0.02469&-0.03704&-0.02593\\ -0.82963&0.368576&0.215333&0.335549&-0.03038&0.071337&-0.09644&-0.02774\\ \end{array}