In Figure 15 (a, b, c,) it is possible to compare the simulation of the response of a fiber-filled TL (without coupling chamber and offset equal to 0) with that of a bass-reflex box (with a quality factor of 5) and an ideal closed box (without losses). All systems have a volume of 4.5 litres; the bass-reflex and TL are tuned to the 87 Hz driver fs. All simulations have been implemented in LTspice. We can immediately note that the roll-off of the TL has a slope between 12 dB/octave typical of the closed cabinet and 24 dB/octave of the bass-reflex. Actually an over-damped TL would have a roll-off very similar to that of a closed box as well as a TL without damping material would have a roll-off very similar to that of a bass-reflex box. On a practical level it is with the latter system that the greatest similarities can be noted and, in fact, both are damped resonant enclosures. In my opinion the main advantage of the TL is that the resonance at the tuning frequency (λ/4) is much more damped than that of a bass-reflex and the contribution of the opening extends over a wider spectrum of frequencies around the resonance.