Originally Posted by Nuance
Ha - same stuff, different day with you, DS-21. You provided one reference (a Wilson speaker), but that hardly proves all other speakers will have poor off-axis response.
You can tell by looking most of the time.
It's an inherent side effect of mating an acoustically large mid-range to an acoustically small tweeter. The 6-8" mid-bass, 3/4" - 1" tweeter, and ~3KHz cross-over used in most commercial 2/2.5-ways (and some 3-ways) fit that description. Exceptions using those driver diameters might have a shallow wave guide on the tweeter which looks significantly different, a cyclopean coaxial arrangement where the cone acts like a wave guide, or an extra beefy tweeter which tolerates a low cross-over point which is often identifiable, like the Seas Excel Millennium with its copper ring.
First over cross-over slopes force higher cross-over frequencies which exacerbate the problem. Given familiarity with the consumer speaker market you can often pick those out too (Vandersteen with the distinctive stepped baffles and grill configuration, Green Mountain Audio with their shaped baffles, etc.)
Oh, I don't disagree with any of that sir. He stated that a non-controlled directivity design flat out won't measure well or sound good, so that's where my argument lies.
It depends on how you define "controlled directivity". Acoustically small drivers and baffles do a fine job at controlling directivity for uniformity, although the directivity index will be lower than you'd get with acoustically large wave guides or acoustically small dipoles. Acoustically small dipoles also do the job producing a 4.8dB directivity index. Arrays which are acoustically small horizontally for uniformly broad directivity but increasing dimensions with decreasing frequency for narrow directivity work OK too.
It depends on how you define "good." My wife and I have a 1994 Honda Accord that's a "good" car - although it's approaching 200,000 miles it never breaks down or has problems keeping up with traffic. Of course our German sports sedan is measurably quicker around a race track and more likely to keep the interior at a comfortable constant temperature.
For my definition of "controlled directivity" and "good" (which matches Toole/Olive's for the speakers that rank highest in blind tests) you can't have "good" speakers without "controlled directivity"
He's simply wrong, and pushing his opinions as facts.
The Harman research group has come to the same conclusions. Sean Olive has actually produced formulas which predict loudspeaker preference based partially on the monotonicity of the polar curves that correlate very well with blind subjective comparisons.