ported or sealed based on T/S

[jacko 10+ year member]

What is the general rule for subs being in big, small, ported, or sealed boxes and creating an SPL or SQ box based on T/S parameters alone. I know that qts and vas and fs has a lot to do with it... other than that i'm a total noob? If anyone could explain or post a link THANKS!

-Tyler

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[squeak9798 5,000+ posts]

Sealed:

Qr = Qtc/Qts

Vr = Qr^2-1

Vb = Vas/Vr

Fb = Qr*Fs

F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

If Qtc>(1/2)^.5

then dBpeak = 20*log(Qtc^2/(Qtc^2-0.25)^0.5)

Else dBpeak = 0

where,

Vb = net box volume (litres)

Fb = box resonant frequency (Hz)

F3 = -3dB frequency (Hz)

dBpeak = maximum peak or dip in system response

Ported:

Vb = 20*Qts^3.3*Vas

Fb = (Vas/Vb)^0.31*Fs

F3 = (Vas/Vb)^0.44*Fs

dBpeak = 20*LOG(Qts*(Vas/Vb)^0.3/0.4)

where,

Vb = net box volume (litres)

Fb = box resonant frequency (Hz)

F3 = -3dB frequency (Hz)

dBpeak = maximum peak or dip in system response

Dv = internal diameter of port (cm)

 

[squeak9798 5,000+ posts]

General rule of thumb is Qts of .4 or above is best suited for sealed, below that best suited for ported.

Along with that, EBP (Qes/Fs) of closer to 50 is better suited for sealed, closer to 100 is better suited for ported, and in the middle can go either way.

 

[Chevyaudio 5,000+ posts]

Squeak, look at the Sealed spl box size recomendations on the Type R, why are they so small, and also those are all Gross box volumes, so after displacement, the 12 inch type R will be in about .35-.4 cubes....WTF?

 

[tRiGgEr 5,000+ posts]

That graph is .5ft^3 sealed. That is normal. And it needs to be .5ft^3 after displacment...

 

[Chevyaudio 5,000+ posts]

at the bottom of the first chart it says all volumes are Gross volumes.

 

[Chevyaudio 5,000+ posts]

.5 seems a little small to me.....

 

[Chevyaudio 5,000+ posts]

Jmac that is the Chart on Alpines Website. I was just looking around online and i found it.