Thank You for your response. It is not a standard tweeter-woofer configuration. The 8" driver is full range with a stated frequency response of 36Hz-17,000Hz. The piezo will be "crossed over" at 15,000Hz (1.33 uF) only to enhance high frequencies above that. I can also experiment with different capacitors up and down from there. I have recalculated a similar box and vent based on the replacement 8" driver parameters for an FS of 33Hz. The box is larger, with different port dimensions. What kind of clamps are appropriate or are in your arsenal for making speaker boxes?
http://www.d-s-t.com.au/data/Misc/CTS/QuasiMoDo.htm
Are you aware of the fun of full range drivers enhanced with a piezo?
http://fullrangedriver.com/forum/ http://www.zillaspeak.com/