About two months ago I finished building two Shiva sonosubs tuned to 16.5 hz in 170lt (6ft^3) cabinets. They are currenly powered by the internal amps from two Yamaha YST-sw300 subs 185w 4ohms. My room is quite small - 2.7m x 3m x 3.5m (1m = 3.3 feet I think) with no openings. I was running some SPL tests the other night using the TPM dvd and some sine waves, with no speakers connected, only the subs. I set the subs to approx 10db hot and played the THX intro repeatedly, increasing the volume each time. I stopped at full ref level on the amp (subs 10db over ref) because I thought I was going to damage the house. At this level the needle on the rat shak meter goes off the scale on the 120db range (126db+ the meter correction)on the exploding sphere at the listening position, I got down on the floor with a torch and watched the drivers at this level, the X-MAX is 32mm I think, they didnt appear to be going close to this. There is a large window 1.5m x 1.5m on the wall behind the subs, when doing the tests the window was vibrating so bad I was suprised it didn't break. There is also a crack the whole way around the outer edge of the ceiling along the cornices due to the subs. I want to push these things harder but I'm a bit worried about the window, is there anything I can do to strengthen it while I do the test again? I have read that some people measure peaks in the 130 - 145db range, what are they using to measure this? - the rat shak meter only goes up to 126db uncorrected. The amount of good clean bass I can get from these things is bullshit! I cant imagine what some of those 140db + subs would be like. Harry.