Pics of the finished sinks for the HL10A's to fit in tuba spkrs. Started testing and discovered that my trusty old dvm isn't sensitive enough for this. Pretty much an electrician's meter. When I bumped the voltage (10v)enough for it to read I got no change with or without the sink in the parameters. I'm going to borrow a real meter tomorrow and try again Sunday. I have the HL10c sinks ready to test, but new ones from the bigger stock will be done by Tues. I scrapped the slot idea and just drilled 1/2 holes in the flats, polished a venturi and the interior. There's so much surface area to work with that slots were unnecessary. I have more exit volume than the original opening. You can feel the air pumping out at low frequencies.