Guessing here...

Had my woofers re-foamed. Pretty good for more than 15 years - Magnat built some nice drivers. Anyway, I now have a huge dropoff at around 100-110hz - almost 10dB. Rolls back pretty quick. If it was lower, I would be thinking this is just drivers that need to be exercised. Nope, no problem down to port freq and room gain. Not sure if this is house or what since the room they are in is not a simple box shape. First time I have had these speakers running in this house. Thoughts? What length am I looking for here?