Hi Just made a sub woofer based on following design :- 85L Vented enclosure from 25mm & 50mm MDF Fully braced sealed and 80mm tuned vent. Driver Peerless 850140CSC 10" 150W 8 ohms FS=25.6, Xmax=6mm, QMS=3.39, QES=0.39,QTS=0.35, VAS=136L I Designed it using WinISD giving me an 85L box for Tuning Freq=29.5Hz. Box lightly lagged and quite square in dimensions (on castors) However on powering it up im not happy in fact my mates stereo Boss 10" speakers gives more tighter power output. I will attempt to explain what it does and doesn't do :- At low levels seems nice and low in frequency and good quality with tight bass and no distortion. When I crank the amp right up the bass goes sort of boomy because the driver cone seems to be going wildly in and out (vibrating). It seems the driver cant handle the high volume low bass. The box is built like a brick **** house, vibrations of the enclosure is very minimal even at high outputs. I was expecting this thing to make my guts rumble and my ornaments dance but no way. others on the newsgroups tell of such things with subs no bigger than mine. Whats wrong ?? Please help. I spent 4 months reading up and designing this thing and im not happy. Normal listening levels is fine low and tightish, but at high volume its not awesome its disappointing. Things im gonna try 1. Running it in longer at its only had about 3 hrs under its belt 2. I have about 15mm of insulation on all but the front inner face, I will fill 50% with loft insulation. 3. If all else fails buying a 12" Shiva driver and Vent from Adire and putting that in my box based on their 85L design. Any suggestions welcome.