DefTech speakers tend to inspire passionate opinions, both pro and con, as a result of their bipolar design. You either like the type of soundstage provided by bipolars or not. The conventional wisdom is that bipolars provide an expansive, deep soundstage, but without the ability to provide precise "localization" of the individual voices/instruments of the mix. Both are offshoots of the relatively higher percentage of sound energy that is coming from reflections, in the case of bipolars.
The other issue is that bipolars normally require placement in front of a wall, usually with a prescribed optimal distance between the speaker and the wall behind it. As such, they are best used in rooms where they can be in front of a flat wall, as opposed to being in a corner, or out in the middle of an open space. By the same token, given a reasonable room arrangement, bipolars tend to have a more forgiving "sweet spot" for the listener(s), so that you don't have the phenomenon where moving your head a foot to one side changes the sound completely, or causes the stereo image to collapse. (On the other, other hand, you won't get that magical feeling of having the sound image pop into place when your head is in just the right spot, either!)
I own DefTechs, and like the other poster above, they are ones without built-in subs. Despite the conventional wisdom, I think they do a pretty good job of localizing individual components of the stereo mix. Even though there is still a "sweet spot", the tonal balance stays pretty decent even when well off to the side of the sweet spot, so that everyone on the sofa gets pretty good sound, not just the person in the center
. When I bought them some years ago, I auditioned two other bipolar brands - Mirage and a line of bipolars that Paradigm had at that time. I preferred the DefTechs over the similarly-priced Mirages and bipolar Paradigms. But, there are a number of "monopolar" speakers that sound really good to me, including some Martin-Logan models, Vienna Acoustics, and some others.
Speaking of soundstages, I had a pair of the old Large Advents back in college (mid-70's), and put them outdoors once for a party. They were separated by about 20 feet, and toed-in a bit. When you stood equidistant between the speakers, and walked backward (staying equidistant, but getting farther away from the speakers) you would hit a sweet spot every 7-10 feet or so, where the soundstage all of a sudden expanded (even when you got 50 or more feet away from the speakers). I'm not sure why this wouldn't have been true all along the "equidistant" line, but it was a very distinct effect.
