Whenever DCM is mentioned I think of the media frenzy over the DCM Time Windows back in the (70-80s?)
Never had the chance to actually hear a pair
More than 20 years ago, I bought a mint pair of Timewindow 1as to play with, as I too had witnessed the hype back in the day (early 80s) and was curious as to how good (or not) they were. Also grabbed a few pairs of Timewindow 1s in poor cabinet condition to compare (in case I needed "parts" etc)
The 1s used two types of Philips woofers and a very cheap Philips polycarbonate tweeter. The 1as used a different Philips woofer and the Vifa D19 tweeter. They were so cheaply and poorly put together, made of cardboard tube and particle board, both on the first two series and the 1as. The best part was the American Oak tops on the 1as, except the method for securing the top to the bottom was flawed and most of them fell to pieces. (a big threaded rod top to bottom)
My 1as were perfect condition wise and I initially thought they were a very special speaker. That quickly wore off. Mine clearly had a midrange balance issue (shifting image with freq) and it was only when I peered through the brown grille fabric with a torch, I noticed one woofer was different to the others. They were all original, had the DCM chalk marks for matching, same nasty black sealing original glue on them all (they'd never been apart) and yet one appeared to have a smaller dustcap and cone colour. Ran an impedance sweep and found one speaker was different to the other. (S/Nos were matching) Dismantled them only to find one woofer was a 5 ohm and the others were 7 ohm.
They used to describe them as "hybrid transmission line". Not true at all, unless a "transmission line" is just a whole lot of wadding and a couple of ports at the bottom offset on each face.
Wrote to Mitek (they had DCM at that point) and they confirmed that a) they had no woofers left and b) DCM had mixed up towards the end of a woofer type run putting 5 ohm on the inside faces to change the overall balance. They sent me a nice letter and a brochure. Mine were a pair, and yet they left the factory all those years before, not matching. Poor in my opinion.
Anyway, I gutted (smashed up) the Timewindow 1s and sold off the crossovers and tweeters. The woofers are all in a bucket in the storeroom if anyone ever needs Timewindow 1 woofers to rebuild (rubber rolls surrounds have perished last time I looked)