In the latest issue of The Abso!ute Sound, Robert E. Greene singles out Jim Goulding's "Diffractionbegone" thick felt anti-diffraction pads for a Golden Ear award. Quoting REG: "If your speakers suffer from tweeter diffraction-effects, these elegant and inexpensive felt devices will make an improvement all out of proportion to their low price."
Okay let me give you my take on diffraction, drawing from conversations with Dr. Earl Geddes. Diffraction can degrade not only imaging but also clarity, because while the ear is very good as masking (ignoring) a coloration that arrives at the same time as the original signal, it is very poor at masking when the coloration arrives at a different time. A look at diffraction's effects on a frequency response curve does not begin to reveal how the ear responds to it. The most important region for diffraction control is around 4 kHz, as this is where the ear is most sensitive. It is also the region where a tweeter's radiation pattern is very wide, so there's more energy to diffract off the cabinet edges in that region than elsewhere in the spectrum - a rather unfortunate situation (which now can be effectively addressed at a very reasonable price). Also, diffraction is more audible at high sound pressure levels than at low levels. The edginess that characterizes most prosound systems at high volume levels is largely the result of diffraction and diffraction-like artifacts (and not driver non-linearity).
Note that Jim custom makes his devices for your specific speakers. So for less than the price of a tank of gas, you can make a significant improvement in your sound system. Significant enough to be honored with a Golden Ear - and this is THE LEAST EXPENSIVE product to be so honored.
Congratulations, Jim!
Duke
