cabin gain,, and octaves

[jadenlinkletter]

ok,, winisd predicts that 2 kicker comp vr 18 inchers will produce a max spl of 120 db at 30 hertz,,,

what would the cabin gain be,, considering your in a honda element. which is a relugar sized suv

i've been reading about cabin gain,,,, one question

whats an octave? and if its 12 db per octave gain below 40 hertz, when does it reach its first 12 db of gain,, 30 hertz??

[ocool_15]

one octave is a doubling or a half of frequency ie
20 40center 80Hz. 2 octaves im not sure but i think it goes like this: 40center 80 160 320 640 1280Hz

[mwmkravchenko]

Here's how it works

16-32hz
32-64hz
64-128hz
128-256hz
256-512hz
512-1024hz
1024-2048hz
2048-4096hz
4096-8192hz
80192-16384hz

These are rough numbers

Different instruments and such tune slightly higher or lower and the octaves shown are therefore not exact. But the concept is pretty damn close.

A pipe organ and a synth are about the only things that plumb the lowest octave.

Kick drum is around 100 hz

The highest note on a violin is in the 4000 hz range.

Heres a freaky one. THe harmonics of cymbals are up and above 40,000 hz dog and bat zone.

Cabin gain works like this. Say it starts off at 60 hz. Down one octave or down to 30hz you will get a natural boost of 12db or a little more than twice as loud. The next lowest octave will get another 12 db on top of what you allready have. THis again is theoretical. In a car the interior dimensions are short. SOme lower frequencies will naturally collapse because of the produce air pressure wave being swamped out by its own reflection. These are calling standing waves.

MArk

[Bose(o)]

To get an idea of the loudness your subs will create (theoretical MAX) while pushing drivers to maximum linear excursion you can use this equation:
=(197+20*LOG(Sd*(Xmax/10)/1000000))-20*LOG(Vroom)

Sd (cm^2), Xmax (mm), Vroom (m^3)

Lucky for you I've got a spreadsheet that spits out information quickly.

Should hit a max of about 138dB.

[Bose(o)]

Oh yeah, Canada represent...eh!