This subwoofer has a Hartley 24" driver, in a dual transmission line enclosure. It was custom designed by Noel Lee of Monster Cable, back in the early 70's. I got it through a mutual friend of ours, that had a high-end audio salon in San Francisco at the time. It is flat to 20 hertz and usable to lower. It produces sound that you can feel, as well as hear. It is BIG, at 4'high x4'wide x2' deep. I have no idea what it weighs, but it is heavy. I have it on castors to make it easier to move. I hate to sell it, but I moved from a 4400 square foot house to a 1370 square foot one, and I simply have no room for it. So I am giving it away for a fraction of what anything of equal ability would cost now. The cabinet is a little rough from all the years, there is no grill cloth. So it is probably is a 5 for that, but the sonics are a 10. Feel free to call me at 541-331-0294, if you have any further questions. I was using it with Soundlab electrostats and crossing it over at 40 hertz. It was awesome! Picking it up in the San Francisco, California, area would be best. But if you want to arrange for, and pay the freight I will gladly ship it. It is quite efficient for a true subwoofer in any living type room, but can handle a lot of power as well.