Intro - What is "DDR"?
DDR stands for Downwards Dynamic Range, coined by David Dlugos of Planet10 HiFi. The concept behind it is that some speakers are better than others at transmitting the quiet details in music.
The good speakers, then, would still let you hear the swish of a conductor's baton while the orchestra is in full force. Lesser speakers would allow the sound of the baton to fall into the background "mush", never to be heard again.
This sounds plausible. I can imagine that cheap speakers with bendy plastic cones might well add a certain amount of "grunge" to a signal which might mask low-level details. Similarly, speakers with high-tech motors and rigid cones are probably very clean in comparison.
However, just thinking about this stuff isn't going to get us anywhere. What really needs to happen is some measurements, preferably with a nice easy-to-understand number at the end which would correlate with how much detail is retained (or lost) when higher-level signals are present.
How do we measure this?
It's a difficult question to answer. While the concept of DDR has been around for a while, attempts to measure it, so far, have been largely unsuccessful. However, I think I've found a way to do it which involves embedding a test signal, at a low level, in a section of pink noise.