Hi Im new here, I recently aquired a RCF 21" subwoofer and im looking for box ideas. I already have 4 old denon 12" subs in sealed cabnets, I dont have specs on them right now but if nesicary I can get them. This will be used for 100% home theater no music. The sub will be located in the connecting room with a vented door as there is not really anywhere else to put it. Here are the specs, there is some info around the net on it but not much. Here is the link with some specs from the manufacturer. http://www.rcf.it/web/rcf/products/precision-transducers/neodymium-low-frequency-transducers/lf21n451 4,5 - inch Inside/Outside copper voice coil -3000 Watt continuous program power handling -98.5dB Sensitivity -30Hz - 1kHz Frequency range -Dual-forced air ventilation for minimum power compression -Dual spider designed with silicon based damping control -BL of 33.5 T/m to provide a faster and accurate low frequency (Fs) : 30 Hz (Re) : 5,5 ohm (Qms) : 5,5 (Qes) : 0,25 (Qts) : 0.24 (BL) : 33,5 T.m (Mms) : 272 gr. (VAS) : 440 Litres (1220 cm² (Xmax) : 10,2 mm 1kHz (Le1K) : 2,9 mH (Eff) : 4,50 % Any help would be greatly appreciated.