Acoustics

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Appendix B: Enclosure Parameter Formulas

Figure 7: Important dimensions of bass-reflex enclosure.

Based on these dimensions [1],

$C_{AB} = \frac{V_{AB}}{\rho_0c^2_0}$	$M_{AB} = \frac{B\rho_{eff}}{\pi a}$
$B = \frac{d}{3}\left(\frac{S_D}{S_B}\right)^2\sqrt{\frac{\pi}{S_D}} + \frac{8}{3\pi}\left[1 - \frac{S_D}{S_B}\right]$	$\rho_0 \leq \rho_{eff} \leq \rho_0\left(1 - \frac{V_{fill}}{V_B}\right) + \rho_{fill}\frac{V_{fill}}{V_B}$
$V_{AB} = V_B\left[1-\frac{V_{fill}}{V_B}\right]\left[1 + \frac{\gamma - 1}{1 + \gamma\left(\frac{V_B}{V_{fill}} - 1\right)\frac{\rho_0c_{air}}{\rho_{fill}c_{fill}}}\right]$
$V B = h w d$ (inside enclosure volume)	$S B = w h$ (inside area of the side the speaker is mounted on)
$c a i r =$ specific heat of air at constant volume	$c f i l l =$ specific heat of filling at constant volume ( $V f i l l i n g$ )
$? 0 =$ mean density of air (about 1.3 kg/ $m 3$ )	$? f i l l =$ density of filling
$? =$ ratio of specific heats for air (1.4)	$c 0 =$ speed of sound in air (about 344 m/s)
$? e f f$ = effective density of enclosure. If little or no filling (acceptable assumption in a bass-reflex system but not for sealed enclosures), $\rho_{eff} \approx \rho_0$

? Sealed Box Subwoofer Design ��Acoustics�� Polymer-Film Acoustic Filters ?

Acoustics polymer film acoustic filters.JPG