Ports, advice?

[h5tuu]

Hi

I'm in the stages of designing a new sub using the B&C 15TBX100, Ideally I want to tune to 25hz, box size is restricted to 70 - 80l.

I'm hoping to use 2 - off 4" ports, but to hit my desired tuning frequency the ports are too long for the enclosure. Is it possible to use a 3" to 4" tube to lower the tuning frequency?

How would I work out the length required?

Do you think chuffing will be an issue?

Thanks in advance.

 

[GM]

Most definitely if you drive it to Xmax at 25 Hz with high power. This alignment needs to be designed as a TL, i.e. a simple pipe ~259 cm^2 x 308.3 cm long with the driver ~1/3 the way down from the closed end. Only add just enough stuffing to get rid of any 'hollow' sound.

GM