[RJMiranda]

The labyrinth concept is OK and very interesting for a radio of that era. It should have been a "selling point".
But cardboard and any easily-vibrating material is bad for anything acoustic. It colours the sound by absorbing some frequencies and reinforcing others, and thus the frequency response has peaks at the fundamentals and harmonics of every piece of vibrating surface in the speaker enclosure.
That said, I wolud not be very surprised if the set had a very pleasant sound. Acoustics is a very subjective subject. And the theories on the physics books work much better in the books than in the real life.
Good luck with your new-old radio!!