I am looking for some info on some possible issues I'm having with design of a 4th order bandpass box and a tempest 15" driver. Note: I have built tons of boxes in the past but nothing within the last 8 years, so it is an understatement that I'm rusty with design let alone with the math. After say that here goes. I want to use a 1 tempest driver in a 4th order bandpass design and then move to 2 in a isobaric design depending on the output I can achieve from a single driver. I have been using the equations that I found off the “DIY subwoofer page: by Brain Steele” and I have some concerns/questions about the results obtained. With the use of the white paper for the tempest driver I calculated the box volumes for both the ported and seal side of the design. I received the following values: Vented chamber 94.503 liters Sealed chamber 79.847 liters This was with a lower 3dB cutoff frequency of 28 Hz and a gain of 3.4. When I calculate for gain of zero I get the following values at the same lower cutoff frequency: Vented chamber 94.503 liters Sealed chamber 134.641 liters Neither of these volumes seems to be appropriate for a driver of this nature. A sealed chamber for a high power 15” with the T/S numbers of such I would suspect would run a lot more efficient in a much larger enclosure. I triple checked my math and the techniques to obtain these values and all seem to be correct. I would like to know if anyone has tried this. What type of volumes are you guys getting with sealed boxed with a similar cutoff frequency?