Thanks Everyone,
Since adding the upper woofers, turning my MMTwo's into MMThree's, I wanted to add my 'subjective' impressions on the differences.
First, a little history. As I had mentioned in previous posts, I wasn't happy with the quality and amount of bass I was acheiving in my 16 x 22 x 10' room. Feeling that I had a room mode issue, I pushed the speakers and listening position around for months, in an effort to to get a smooth response across the spectrum, and to get a nice large soundstage, without spreading individual singing voices too wide (Scott refers to this as the 'Wizard of Oz, Big Head' effect). I eventually found a place that was simply magic in the mid-bass, through the high end. The sound stage was nice, and individual singing voices were spot on. But, no matter what I did, I just simply found the bass lacking. I could easily add in my Velodyne DD-18 into the mix, which as far as frequency goes, did add some of what I felt was missing. But the Velo made the low end sound disconjointed from the rest of the system, and killed the dynamics of the upper end. I finally decided that I really needed to add the upper woofers, and that is what I persued.
During all of the above, one thing that I had completely overlooked, was that the bass module on the MMTwo, have nearly a half dozen controls on the built-in amplifier (five to be exact). During break-in and positioning I delieberately left this at the factory settings, except for the volume control. After so much time, I literally had forgotten completely about them (it's tough to get old). It wasn't until after I had already ordered the upper woofer modules, that while listening to the system, I suddenly remembered that there were all of these other adjustments available on the bass amplifier. In the long run, I believe not playing with all of these controls turned out to be a good thing. It forced me to spend all of the necessary time and effort on getting everything else right first.
I quickly pulled out the manual for the MMTwo's, and brushed up on what the different controls all do, and what effect they have. To make I long story short, I mainly focused on just 3 of the 5 controls; Bass Filter, Bass Extension, and Bass Volume. The one control which brought in the majority of what I felt was missing, was the Bass Extension. This control added the deeper, feel-it-in-your-gut, bass. I enhanced these added lower frequencies with the additional volume. Although I liked the added lower extension, from this adjustment, the draw back was too much bass in the throats of the singers. Especially female vocalists. I was able to compenstate for this by lowering the crossover point of the Bass Filter control. The MMTwo's were now sounding more like I was expecting them to sound when I made the choice to purchase them. In fact, after 'rediscovering' all of these controls on the bass amplifier, I was so much happier with the sound, that if I hadn't already ordered the upper bass modules, I believe I may not have bought them... However, I now know what a huge mistake that would have been. After receiving and installing the upper bass modules, these speakers, were instantly catapulted into a much higher level of performance.
Bass is now smooth, robust, relaxed, and flows with ease. Which is what I expected. But I never expected how the overall sound of EVERYTHING would improve from just adding two 15" woofers, completely changing the overall personality and characteristics of these speakers. The soundstage is bigger. And not just a little bigger, but HUGE compared to what it was previously! The highs have smoothed out, with more detail and 'air' around the individual instruments and vocalists. The mid-range is organically palpable, and is simply sweet! (am I using enough subjectivist terms?
) These are not the same speakers I had been living with for the last year! Some of the more strident recordings I have, are now actually listenable. And stuff with bass, litterally now shakes the walls! Needless to say, I am very happy with this purchase. And I would suggest to any MMTwo owner, who is considering upgrading to the MMThree, that it is worth every penny.