What is a B&W 801M?

Do they look similar to these?

http://www.soundsgoodtomehouston.com/bw801/801_pairopen.jpg

These are the early matrix cabinets.

I'm not a B&W historian by any means, but I had a friend back in my college days (mid '80s) who had a set. The "Matrix" moniker referred to the construction of the cabinets as there was an internal "Matrix" of bracing to reduce cabinet resonance.

Barry, those in the photo are NOT matrix cabinets. The first 801 with a matrix cabinet was a ported design.

These?

http://www.soundscapehifi.com/images/ttc16.jpg

and these?

http://assets.bowers-wilkins.com/med/Libraries/3/Matrix801S2_Archive_l2_w0_h0.pdf

Yah - these are ported - think they might be first generation Matrix 801s. I remember the matrix cabnet making a big difference in bass and midrange clarity on these.