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jigsISF
07-03-2013, 02:03 AM
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.

26543387

RangerDangerV2
07-03-2013, 02:04 AM
take vas/vb(liter)+1 sqroot x Fs

jigsISF
07-04-2013, 07:55 AM
take vas/vb(liter)+1 sqroot x Fs

what is Vb in this equation

RangerDangerV2
07-04-2013, 09:25 AM
what is Vb in this equation

volume

chefzane
07-04-2013, 10:37 AM
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
07-04-2013, 10:46 AM
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
07-04-2013, 10:50 AM
that equation is actually really accurate. It was about .5hz off from what it actually was when I tested it with my DATS

RangerDangerV2
07-04-2013, 10:53 AM
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
07-04-2013, 12:58 PM
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
07-04-2013, 01:00 PM
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
07-05-2013, 11:03 AM
Thanks, so since subsonic filter doesn't matter in my application, what would I set it to?

RangerDangerV2
07-05-2013, 11:35 AM
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.