Has anyone built the Raver Cinema Sub-Woofer? This uses the Monacor SPH-450TC 18" dual coil sub.If you have I'd like to ask a couple of questions. In the documentation it states "Insert the bass-reflex tubes and screw them in, so that all inner ends face each other." I take this as meaning all the ports (4, one in each corner) point in to the back of the speaker on a 45 deg. angle. However in the parts list is states "4x MBR-85 (maximum length)" for the bass-reflex tubes. The tubes face inwards from the front also on a 45 deg. angle and have a sliding extension to the tube. This can't be extended to the "(maximum length)" without hitting the magnet on the speaker. Does this mean to extend it to the maximum length without hitting the speaker or have I got this wrong and they don't point to the back of the speaker?