Help wanted building an optimal sealed box for a single 12" subwoofer. - diyAudio
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Old 4th January 2010, 12:02 AM   #1
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Default Help wanted building an optimal sealed box for a single 12" subwoofer.

I've just bought a new Pioneer TS-W308D2 dual 2 ohm VC subwoofer. This is the first sub I'm building an enclosure for so I wanted to keep it simple the first time around and stick with a sealed box to keep things easy and relatively foolproof. I may go ported in the future but that's another build for another time.

I have two different 2 channel amps (Kenwood KAC7204 ~500 RMS bridged 4 ohm for the subwoofer and an Earthquake T1000W/2 ~200 RMS x 2 channels 4 ohm for the 6.5" comps that I'm putting in the front doors (I'll keep the gains turned well down on the amp to the 6.5 comps).

I've looked at the Pioneer manual for the sub and it has the following stats for a sealed enclosure:
Minimum Sealed enclosure size: 0.85 cubic feet
Maximum Sealed enclosure size: 1.75 cubic feet
Recommended Sealed enclosure size: 1.25 cubic feet
These sizes include the speaker displacement.

Here are all the Thiele stats for the sub:

Nom. Dia.(In) 12
Qts 0.48
Qms 14.11
Qes 0.50
Fs [Hz] 33.7
Vas [l] 36.16
Vas [ft3] 1.28
Vd [l] 0.400
Vd [ft3] 0.01412
Sd [m2] 0.04597
Sd [ft2] 0.495
Revc [Ω] DUAL1.5
Levc [mH] (2000Hz) 2.18 (4Ω) 0.65 (1Ω)
Xmax [mm] 8.7
Xmax [in] 0.34
Zmax [Ω] 99.13 (4Ω) 24.81 (1Ω)
BI [Tm] 16.07 (4Ω) 8.04 (1Ω)
Rms[Ns/m] 2.773
Mms [g] 184.95
Cms [m/N] 0.00012
Mg.Wt.[g] 2350
Flux Density [Gauss] 6800
Hag [mm] 10
Hag [In] 0.39
Hvc [mm] 27.4
Hvc [In] 1.08
VC.Diameter [mm] 55
Eff [%] 0.27
S.P.L. [dB] 91.0
R.M.S.Power [W] 400
M.M.P. [W] 1400
Sp. Displacement [l] 2.16
Sp. Displacement [ft3] 0.076
Recom. Enclosure [l] 35.4
Recom. Enclosure [ft3] 1.25
F0 (in Cabinet) 47.9
Q0 (in Cabinet) 0.682

I also ran the numbers through WinISD and it calculated that the optimal sealed enclosure size for this sub is 1.093 cubic feet and gave the optimal box size as follows:
13.95" wide
21.46" high
8.93" deep

I'm using 18 mm thick MDF to build the box which is equivalent to 0.71 inches.

What I'm wondering as I'm new to this is which size within this range would be best for a sealed enclosure. Pioneer gives a large range of sizes to use from 0.85 to 1.75 cubic feet and their recommendation is basically right in the middle of that range @ 1.25 cubic feet whereas WinISD gives an optimal of 1.093 cubic feet.

What is the benefit of going as small as 0.85 cubic feet or as large as 1.75 cubic feet?

I'm basically looking for 50-50 SQ/SPL and I realize going sealed vs ported is giving up some SPL hopefully in favor of some SQ... and that's fine with me for this first build. What I'd like to know though is how the size of the enclosure within that range from .85 cubic feet to 1.75 cubic feet effects the SQ and SPL.

What size would you all recommend? What would sound the best and make optimal use of the sub for SQ/SPL in a sealed enclosure? Any advice is appreciated. Thanks in advance.
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Old 4th January 2010, 05:30 AM   #2
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You can't go wrong with the recommended size as Xmax is hit with the max power rating (usually).
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Old 4th January 2010, 05:43 AM   #3
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Just build it to a QTC of about .7? You'll be fine. If you like the response curve there, go for it.

Joe.
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Old 4th January 2010, 05:47 AM   #4
Volenti is offline Volenti  Australia
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"What is the benefit of going as small as 0.85 cubic feet or as large as 1.75 cubic feet?"

The smaller enclosure will have higher machanical powerhandling, less low end response and likely a peak around resonance, the larger one will have less mechanical powerhandling, a smoother response, and more bottom end.

I have experience using these in car tuned TL's and tapped horns if you have the space for the (much) larger enclosure. (for later)
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