Guys, I was going to start a similar thread, but it looks like this one is getting some traction, so I'll chime in.
My mom is 83 and still has decent hearing but she lives in a condo with an upstairs neighbor (can be a noise issue) and a common wall downstairs neighbor (not much of a problem). She is impossibly polite and doesn't want to turn up the speakers in the 40" Samsung LCD TV, but it's hard for her to discern some of the rapid dialog in today's TV shows. I believe that it is more than just a volume problem, but more of an EQ issue. I'm a professional live sound engineer, and when I'm working corporate events I always high pass the microphones at 150 -160hz to improve intelligibility, so I'm looking for speakers that naturally roll off in the bottom 3 octaves. She's not going to be watching Saving Private Ryan at 100db, so big bass is not a priority for her, and without a separate sub, she's not likely to play them loud enough to produce any real low end anyways. The TV has a primitive 5 band graphic EQ, that helps, but let's face it, the speakers in just about any flat panel are shite.
The Zvox units look promising as they have analog and digital inputs, as well as volume leveling and basic bass and treble controls. They claim vocal intelligibility "ZVOX's Dialog Emphasis feature uses hearing aid technology to make voices unbelievably clear. It's amazing.", do any of you guys have any direct experience with these products?