BillFitzmaurice.info

Calculator that generates SPL output with sensitivity, power, number of cabs, surface loading, and listening distance as inputs. Perhaps not 100% accurate but should be helpful in doing "the math" on what to build:

Edit: Read the rest of the thread before clicking.

http://myhometheater.homestead.com/splcalculator.html

It's wrong. It only gives 3dB boost per boundary instead of 6dB, and it totally misidentifies 'room gain', which is not the same as boundary loading and is not accounted for in the calcs.

Ok, peace offering for not checking the math . Here it is, fixed for 6db per surface (and stripped of all the unneccessary crap):

http://splcalculator.110mb.com/

If the math isn't right, I'll do my best to edit.

There is a estimation for dispersion, that needs explanation or correction.

Dispersion as per Olson:
"Acoustic dispersion is the separation of a complex sound wave into its various frequency components, due to variation with frequency, or its equivalent, of the wave velocity of the medium."
Dispersion is separation not attenuation and varies with frequency and the medium involved.
Attenuation of sound over distance also has to take into consideration the frequency and the qualities of the medium.

Sydney wrote:There is a estimation for dispersion, that needs explanation or correction.

+1. Dispersion would impact off-axis SPL, not axial. The calc shown is axial response corrected for distance.

Bill Fitzmaurice wrote:

Sydney wrote:There is a estimation for dispersion, that needs explanation or correction.

+1. Dispersion would impact off-axis SPL, not axial. The calc shown is axial response corrected for distance.

Poor wording, I agree. I'll update to use the above language. Anything else I can do to make it more correct?

Edit: changed a few of the descriptions for accuracy.

BrentEvans wrote:Anything else I can do to make it more correct?

Note that it's only 100% accurate outdoors. Indoors the permutations created by multiple boundaries change everything. Also, boundary loading is reduced by 6dB above the baffle step frequency, so to be safe you only consider boundaries below 500 Hz.

FYI: See Set2 on this .xls spreadsheet
http://www.dni-inc.com/things-here/misc ... _v1.12.xls

As Mr. Fitzmaurice just stated succinctly, a calculator has to have it's variables included and qualified.
Even outdoors has factors that cause deviations from pure theoretical assumptions.

Most calculated responses are only good at small signal levels. Hence, 1w/1m.
Above this, all bets are off. Too many variables, i.e. power compession.

Indoors, a measurement rig is mandatory. Anything else is a SWAG.