SPL calculations for a given speaker size and frequency.

[numberoneoppa]

I am curious, how can I calculate the amount of travel needed by a speaker cone/piston of a certain geometry to output a given SPL at a given frequency?

In other words, I have the geometry of a speaker cone (and distance to be measured from, 1m), I just want to figure out far it has to travel back and forth to give me a certain sound pressure level.

Need help as soon as possible, thanks a lot, guys.

[BOBinGA]

You can get that fromWinISD by simply modeling the speaker and increasing the input power until it reaches the SPL you want. Then look at the displacement page and see what it is. Vice versa, you can increase the input power until you reach the displacement you want and then look on the SPL page to see how loud it is at 1 meter.

-Bob

[numberoneoppa]

I will look into that, thanks.

Is there no mathematical equations, though? Not necessarily for a real driver, but for a hypothetical vibrating piston?

[Face]

May be possible with this: http://audio.claub.net/software/jbabgy/WBCD.html

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

[BOBinGA]

Josh,
The formula for SPL as a function of displacemment is something only a computer could love. It has about ten variables and is a log calculation if I remember correctly. It's also frequency dependent. If you lower the frequency by an octave with the same piston area, the displacement required is four times larger for the same SPL. That's why we use WinISD, Unibox, etc. Is there a particular reason you need the actual formula?

-Bob

[numberoneoppa]

Thanks.

Bob, It's for a materials selection project I'm doing at uni and I wanted some hypothetical numbers to work with and use to make device constraints.

Would you mind running some numbers for me? Looking for the excursion of a 10cm diameter cone (pick your favourite, this shouldn't matter much) at 15kHz, 5kHz, 1kHz, 200Hz, and 40Hz if the sound pressure at 1 meter is 100dB (is that too loud? whatever a loud-ish level would be, let me know, I'm looking for the maximum service excursion across a spectrum).

If you don't mind finding those values, I'd be super appreciative.