I just built a 4th order BP box for a Panasonic 10" woofer, and it sounds terrible. Not "bandpass" bad, just designed wrong. The frequency response is WAY off.

Here is what I have:

Panasonic 10" t/s

Vas: 42 L

Fs: 30.0 Hz

Qts: 0.37

I input that into the calculator on carstereo.com and came up with:

Volume front = .397 ft^3

Volume rear = .533 ft^3

Fb (front side) = 58.3 Hz

Frequency response ~ 35-90 Hz

Added sub displacement and port displacement to the front and rear volumes and built the box.

Due to the small area, I could only get a 3" port into the enclosure. Maybe that is too small? Calculated a 3" x 12" long port.

Anybody tell me what to do different?????

Thanks!

Brian

Found the problem. Amp I am using is made by Metra and says it has a LP filter. It does not, or if it does it is not very good..

Added a 80 Hz LP filter on the input to the amp and the sub came to life.

A little port noise, so I am going to try to find a 3.5" port tube tonight (that is the largest I can have in this design).

Thanks for the input!

Brian