Your burp freq. depends on your cars freq. My box is tuned to 33 hz, I peak at 40hz. You need to find the freq. of your car and build a box around 8Hz lower and that should give you the highest numbers. If I tried to burp at 60Hz I would be down 4 to 5 db's. Getting high numbers has nothing to with where you "think" you should burp at. Its all about where your car wants to burp at. Testing and more testing and then learning from the testing is the only way the get good numbers. Example of all this... I hit a 147.1 with a little over 1600 watts at a burp freq. of 40Hz.