# FB z& F3 HZ ?



## seabreeze (Sep 1, 2010)

Whats the difference betwen fb & f3 hz


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## sqshoestring (Jun 19, 2007)

Car Audio: Thiele-Small Parameters

Fb is where the box is tuned, typically for vented or passive radiator boxes.

F3 is where the roll off is down -3dB, it would be where the bass is -3db less dB than it is at the peak (top of curve in a response plot).

Fs is resonance of the driver (sub) while above is response of the box and driver.

So say you port a box for 30Hz, it might peak at 40Hz and be -3dB at 26Hz....but that is just guessing it all depends on the sub and how you tune it. That one would have peak spl at 40Hz and -3dB at 26. You could assume it will not make much bass under F3 of 26Hz.


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