I have already built some “bass-barrels” from 10 and 20 l barrels. now it should be abe pure 50l barrel. it is made of alu and I have reinforced it from the inside with 2 stainless steel rings and 2 crosses. now to the first question. how must the barrel be obtained from the inside??? had before the other end of the barrel, where no one should be supposed to use a reflex tube. goes that way, or should you still love an open tube. in the autumn I then have 2 audiobahn DUB 2 woofer left, of which then one should in there. had thought of some part of ebay… as I said, nothing great, do I have to pay attention to something?? thanks to you already ma