Helmholtz resonator equation help? Anyone?

I think the book might have a typo on that line. I get 300Hz based on their numbers.

The reason I'm thinking it's a typo is because they have a table of values a couple pages later. It has a list of depths, hole diameters, and panel thicknesses. I made a spreadsheet and it matched the table when I typed in the values.

Yeah, none of the scearios on the table of values on the next couple of pages add up for me! When I work the equation, with the values they provide, I get a different answer than what they give!!! I'm SOOOOOOOOOO frustrated!
I just want a consistent way to figure for this stuff, and it's driving me batty!
I mean, I don't think my math skills are off or anything. Or then again, maybe they are. But I don't think so. Something ain't right, that's all I know. I would like to hear from maybe Rivesaudio or someone on this one personally.

I had another acoustical consulting company GRACIOUSLY send me a "plug in formula" for an Excel spread sheet. Not knowing how Excel spread sheets function, it's a little greek to me. Here's what they sent me.

C4 (the internal depth inside box between back plate and front skin, inches)=(((78.5)*(POWER((B4/E4),2))/(D4+(0.8*B4)))*(POWER((200/A4),2)))

Where:

B4 = diameter of the hole you drill (inches)
E4 = center-to-center hole spacing pattern (inches)
A4 = target frequency in Hz
D4 = thickness of the front plywood skin (essentially the throat length of the drilled hole) (inches)

I'm told that the following traslation applies for the "POWER" thingy!...lol:

POWER(x,2) = x squared

POWER((x/y),3) = (x/y) cubed, etc, etc

K,here's the deal...when I plug either of these formula configurations in with the variables, and compare the charts in the MASTER HANDBOOK OF ACOUSTICS no less, I get completely wrong answers from what they have!!!!...double, doh!!! This has been nothing short of down right pissin' me off! (lol)
For instance, using the chart in F.Alton's Master Acoustics book, some of their chart examples bellow give:

Air Depth Hole Diam. Panel Diam Perf% Hole spacing Freq rez.
3.625" 1/8" 1/8" 1.25% .991" 248

3.625" 1/8" 1/4" 1.25% .991" 199

3.625" 1/4" 1/4" 1.25% 1.98" 199

If I plug in the variables in these equations, I DON'T GET THEIR ANSWERS! And this is supposed to be the MASTER HANDBOOK! Or maybe I'm just a mathematical numbskull!? Lol
Again, plese post to audiogon for all to see, if anyone has answers here.

I made up a nice spreadsheet and stuck it on my website.

http://www.dyacoustics.com/Links.html

I'm not sure what math you are using :), but I get the same answers as the book for the table.

It's the 420Hz in the text that I think is a typo. The same spreadsheet that matches all the values in the table comes up with 300 Hz, not 420.

Take a look, let me know what you think or if you have problems with the file. You need to have Excel to run it.

Careful with the formula they sent you. It is correct of course, but has been rearranged to solve for the air space depth instead of the frequency.

Let me know if you get my spreadsheet to work.

Here's a sample calculation (first line in the table).
hole size = 1/8" (0.125), spacing = 2.22, thickness = 1/8", depth = 3 5/8" (3.625)

using the square configuration:
perf % = 78.5*(0.125/2.22)^2 = 0.25%

t (effective hole length) = 0.125 + 0.8*0.125 = 0.225

f = 200*(0.25/(0.225*3.625))^0.5 = 110 Hz