equations for FR charts

[Dave Jones]

The various loudspeaker books I have show frequency response charts for Qts's of .5, .707, .8, 1.0, 1.1, etc... Can anyone tell me what the formulas are for those charts?

[Ron E]

Go to www.diysubwoofers.org
...everything you need for writing software is there.

[kelticwizard]

Well, the response at resonance can be given by the formula:
20 Log Qts.

So a woofer with a Qts, (or Qtc) of 0.5 is -6 dB at resonance.

I also have a copy of Richard Small's article Loudspeakers in Closed Boxes from the Journal of the Audio Engineering Society on my hard drive. I think the formulas are there.

I can Email it to you if you want.

[Dave Jones]

Originally posted by kelticwizard
Well, the response at resonance can be given by the formula:
20 Log Qts.

So a woofer with a Qts, (or Qtc) of 0.5 is -6 dB at resonance.

I also have a copy of Richard Small's article Loudspeakers in Closed Boxes from the Journal of the Audio Engineering Society on my hard drive. I think the formulas are there.

I can Email it to you if you want.

I'd love to have a copy. I'm djones at innovativerobotics dot com.

Thanks.

[Ron E]

Pasted from www.diysubwoofers.org

-------------------------------------------------------------------------
To calculate the frequency response of a sealed enclosure system, you will need to know the following:
Fb = resonance frequency of the system
Qtc = Final Q of the system at resonance


then,

Fr = (F/Fb)^2
dBmag = 10*LOG(Fr^2/((Fr-1)^2+Fr/Qtc^2))

where,

F = frequency (Hz)
dBmag = SPL 1W/1M at frequency F
------------------------------------------------------------

Now you plot dB vs. Frequency and you have your chart.