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Old 2nd December 2008, 10:04 AM   #1
diyAudio Member
Join Date: Dec 2008
Default SUB woofer enclosure size

I would like to build a simple "sealed" or "ported" enclosure for this SUB & powersupply!

Tang Band W5-1138SM 5-1/4":::
Specifications: Power Handling: 40 watts RMS/80 watts max
*VCdia: 1-1/4" *Impedance: 4 ohms *Re: 3.6 ohms *Frequency
range: 45-1,500 Hz *Fs: 45 Hz *SPL: 82 dB 2.83V/1m *Vas: .24
cu.ft. *Qms: 2.68 *Qes: .61 *Qts: .49 *Xmax 9.25mm
*Dimensions: A: 6-1/8", B: 4-3/4", C: 3-1/8"
Dayton SA70 70W Subwoofer Amplifier::::
Specifications: Measured power output: 45 watts RMS into 8 ohms @ 0.1% THD, 70 watts RMS into 4 ohms @ 0.2% THD. Signal to noise ratio: 90 dB (A-weighted). Dimensions: 7-1/2 W x 8-11/16 H x 3-1/2 D. Enclosure cutout: 6-5/8 W x 7-3/4 H.

Can some one tell me in plain old english "inches and feet how to build an enclosure for this. Just give me the dimentions for the best sound and any interior mod's ,i can do the rest. Thanks for your help in advance!
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Old 2nd December 2008, 01:23 PM   #2
HK26147 is offline HK26147  United States
diyAudio Member
Join Date: Jan 2008
Bass Box Pro 6 * from PE catalog
Sealed .12 cu. ft. F3 77Hz
Ported .39 cu. ft. F3 39Hz ( 2 2" ports 8.5" L )

These are rough interior volumes, add for the volume of the driver and port(s) if making a Bass Reflex.

I think I would size up for approx .5 cu. ft. It's a small box so a bracing is not a huge concern.

A far as dimensions: if the smallest dimension = x, then the other 2 dimensions are not even multiples ( not a cube )

6.13" x 9.2" x 15.325" is one possibility * Internal Dimensions - Add 2x the wall thickness of the material you choose - 1" for .5" wood, 1.5" for .75" wood.

I believe that others ( on this forum ) have threads about this driver?
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Old 3rd December 2008, 10:27 AM   #3
diyAudio Member
Join Date: Dec 2008
Default samll sub

I would like to thank you for the post and also point out that the dimensions for the power panel
Dimensions: 7-1/2 W x 8-11/16 H x 3-1/2 D. Enclosure cutout: 6-5/8 W x 7-3/4 H.
so the back/front would need to be at least 8-1/2"W X 9-11/16H
so what would the depth be? and how would that affect the sound ?

I tried to run a free sealed box caculator
and this is what it came up with but I don't know if it's right or not?
VB (in3) 398.456
addl. V (in3) 0
Total V (in3)
Length (in) 7.35857
Width (in) 11.9209
Depth (in) 4.54233
no constraints used
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Old 4th December 2008, 04:32 PM   #4
HK26147 is offline HK26147  United States
diyAudio Member
Join Date: Jan 2008
You are welcome.
One of the areas of obsession is the ratios of LxWxH in a speaker cab.
I haven't really seen an analysis of different ratio boxes using the same driver.
I don't think that you could perceive the differences on a well built box of that volume, if you choose another ratio:

Using a spreadsheet I set up the equation as follows:
Vb = LxWxH so If I wanted to set the relationship 2:3:5 ( prime number ) it becomes Vb = 2n * 3n * 5n or Vb = 30 (n)3. If Vb = 864 then n = 3.0652", 2n = 6.13", 3n = 9.1956", 5n = 15.326".
That's how I derived the dims. I gave you. Again this is not a magic ratio, just one of several irrational ratios
You could set the ratio as 3:5:7 or sqrt{2)/sqrt{3/sqrt{5).
set the spreadsheet up to do the division, so that no dimension is an even multiple of another.
Spreadsheets with goal seeking functions make this easy.

I don't know if it's right or not?
In general there is a range of possibilities for putting a driver in a cab.
For simplicity sake, programs like BassBox will generate an "optimum" alignment - but this is based upon a middle of the range of possibilities:
A sealed box can be set to a Qtc from .5 to 1.5, with of course a big difference in box volume and performance.
Likewise with vented designs, they can be set to accepted alignments ( BB4, QB3, etc ) or "jammed" to ranges in between.
From my Q & D calcs. that free sealed box calc gave you a middle of the road Qtc of .707 Second Order Butterworth ( B2 ) Max Flat Amplitude Response; a popular alignment - but not the only one.
Hope this helps.
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