(all article in this website under AV University)
Books:
Introduction to Loudspeaker design
Speaker Building 201 Book - Ray Alden
Bullock on Boxes
Advanced design and technology (second edition)’ by Norman, Cubitt, Urry, Whittaker (Longman press)
The Loudspeaker Design Cookbook by Vance Dickason (Audio amateur press)
‘An introduction to loudspeakers and enclosure design’ by V. Capel (Bernard Babani press)
‘High power loudspeaker enclosure design and construction’ compiled by Eminence (parts manufacturer) (Adam Hall publishers)
Papers:
http://www.klippel.de/pubs/papers.asp
Other websites with good data:
http://www.linkwitzlab.com/
http://www.hometheaterhifi.com/volume_5_2/cmilleressayporting.html
http://www.humblehomemadehifi.com/
and of course, all paper from Theile/Small that developed or refined the 'book' on sound reproduction.
That should keep you busy.
PS. From what I remember from my senior design project, make sure you clearly establish the scope of the project. For a senior project, keep it simple. You aren't getting a doctorate. I would recommend that you find a specific problem (whether it be, 'flat frequency response', room modes, box volume, port noise,etc.) and show how you applied sound theory to fix the problem (with measureable results).