Hey, I was just looking at a Retro web site where the publisher discussed the Wollensak. He also had great pictures of the speakers used along with them.
Check out this link: http://www.retrothing.com/2006/09/3m_wollensak_t1.html
Talk about nostalgia! Those massive speakers containing multiple speaker types to deliver their own portion of the frequency. I'll bet that had a lot to do with the warmth you were hearing.