You can achieve something similar with today's receivers by boosting the volume of the center channel, but that boosts everything in the center channel, not just the dialog. (techhive.com)
Playing with these can make a huge difference to the sound quality, and help boost the volume. (techradar.com)
This is usually in an effort to keep costs low while boosting volume and protein content, but also has other uses. (kittycatter.com)