there are boomy closed and clean ported designs, and vice versa, the principle alone imho does not determine the result a priori. The woofers are modelled and designed for the volume of Type 20 (plus appropriate equalizing) right from the beginning, and we wanted to have the cleaniness of closed designs enrichened by the add on dynamics and the lower - 3 dB point you can get from reflex ports. The proof like always is in the listening. Klaus from HEDD