From: Roy Allison Refer# 494
To: Steve Brunkow
Subj. Misc. speaker questions Conf: (1) SoundAdvic
------------------------------------------------------------------------------------------------------------
Hello Steve
Sorry for the delay in responding. Your questions are short, but they require answers
that aren't!
The F-1 is very similar to the Allison CD-8 except in the middle range; the CD-8 has a
separate midrange driver and the F-1 does not. One other difference: price! The retail
price of the CD-8 was $950/pair, while the F-1 price is $549/pair.
The standing-wave formula is fnx, ny, nz = 565[(nx/x)2 + (ny/y)2 + (nz/z)2]1/2, where x,
y, and z are the room dimensions (in feet) and n is any whole number.
If you set two of the n values to zero (nx and ny, for example) the formula reduces to f =
565n/z. Plugging in whole numbers for n beginning with 1 gives you the series of
resonance frequencies for room dimension z. Single-dimension resonances are called
axial modes, and there is a set for each room dimension.
Setting only one n value to zero yields three sets of two-dimension resonances, called
tangential modes. And if you assign non-zero whole numbers to all three n values, you
are rewarded with a set of oblique modes.
Software is available for such calculations. Sitting Duck sells one version. However, they
and some others appear to believe that only the axial modes need be considered
significant. That certainly simplifies matters, but I find no basis for the claim.
As for calculation of speaker power-handling capacity, I dunno. The experimental
approach is what I've used: You apply X power at Y frequency for increasing time
periods (allowing for cooling time in between), and when failure occurs you've got one
point on a complex time/frequency grid. Unfortunately it isn't a practical thing for home
speaker-builders!
Roy