Sealed Box frequency??

[jigsISF]

Are sealed boxes tuned to a certain frequency or is that just for ported enclosures?

The reason I ask is I have a sealed box and was wondering when I get my system hooked up, what I should set the subsonic filter to. I heard usually a few hertz below the "tuned" hertz. Here are the specs of my box and speakers:

2 Fi Q 12" :

Fs: 34.2 Hz

Re: 0.7 Ohms/coil

Qms: 7.63

Qes: .39

Qts: .37

Mms: 249g

Cms: 0.87mm/N

Sd: 481cm^2

Vas: 28.3 l

Spl: 86.5dB 1W/1m

Bl: 13.9 N/A

Xmax: 28mm

Rms: 1500W

Sealed box: .8-1.5 High QTScuft

Ported box: 1.8-2.5 cuft @ 28-33Hz

Sub OD: 12.500”

Cut ID: 11.125”

Mounting depth: 7.000”

Displacement: 0.16cuft

and the box specs (sealed):

- 3/4" and 1/2" MDF Construction

- Black automotive carpet

- Holds 2 round 12" subwoofers (10" subs may be substituted upon request)

- 1.15 cubic feet per chamber (volume can be reduced upon request)

- 9.5" mounting depth

- Round spring loaded speaker terminals

- Sealed air tight w/liquid nails caulk

- Roughly 25 lbs.

View attachment 26543387

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[RangerDangerV2 5,000+ posts]

take vas/vb(liter)+1 sqroot x Fs

 

[jigsISF]

take vas/vb(liter)+1 sqroot x Fs

what is Vb in this equation

 

[RangerDangerV2 5,000+ posts]

what is Vb in this equation

volume

 

[chefzane]

So vas x box volume in liters + 1, find the square root of that then x the resonant frequency, in that order or do you follow basic order of operations

 

[RangerDangerV2 5,000+ posts]

So vas x box volume in liters + 1, find the square root of that then x the resonant frequency, in that order or do you follow basic order of operations

no. Vas/Vb (ltrs) then add 1, then sq rt that, then multiply that by the fs of the woofer.

 

[RangerDangerV2 5,000+ posts]

that equation is actually really accurate. It was about .5hz off from what it actually was when I tested it with my DATS

 

[RangerDangerV2 5,000+ posts]

in regards to the OP, the Fc is where you are going to start rolling off. I have found that you are good for about one octave under the Fc playing wise. Granted it will have a gradual roll off, it is more pronounced the lower and lower you go.

 

[trumpet 5,000+ posts]

You don't need a subsonic filter with a sealed enclosure. The woofer suspension will always have the extra resistance from the pressure in the box, so it can't unload like a ported box woofer.

 

[RangerDangerV2 5,000+ posts]

You don't need a subsonic filter with a sealed enclosure. The woofer suspension will always have the extra resistance from the pressure in the box, so it can't unload like a ported box woofer.

unless you go incredibly large, but that would be pointless. So yes, good point!

 

[jigsISF]

Thanks, so since subsonic filter doesn't matter in my application, what would I set it to?

 

[RangerDangerV2 5,000+ posts]

Thanks, so since subsonic filter doesn't matter in my application, what would I set it to?

as low as it will go, or as low as you feel safe with, play around with it a little.