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Sealed box sub system to play from 50hz to 120hz
Sealed box sub system to play from 50hz to 120hz
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Old 11th June 2010, 06:24 AM   #1
ajhockett is offline ajhockett  United States
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Default Sealed box sub system to play from 50hz to 120hz

I have 4 21" subs in transmission line enclosures and I have line source main speakers. the transmission line speaker do not play very accurately above 50hz. I plan on adding 4 12in subs to cover the freq range from 50-60hz up to 100-120hz. There will be 2 boxes for the four speakers. I plan on building them out of 1.5in MDF fully cross braced and supported.
anyone with a box calc program and some experience please help me out.
here are the specs of the sub
Extreme-duty low frequency driver originally manufactured for a famous brand's THX Ultra2-certified 1,000 watt subwoofer system. Triple stacked magnet, dual spiders, two brass shorting rings, and 1" of linear excursion make this a tough sub to beat. Buyout, limited quantities. Specifications: *Power handling: 500 watts RMS/1,000 watts max *VCdia: 3" *Le: 1.23 mH *Impedance: 8 ohms *Re: 5.79 ohms *Frequency response: 20-1,000 Hz *Fs: 28 Hz *SPL: 86 dB 1W/1m *Vas: 1.89 cu. ft. *Qms: 3.31 *Qes: 0.42 *Qts: 0.37 *Xmax: 25 mm *Dimensions: Overall diameter 12-5/16", Cutout diameter 11", Depth 7".
  • Cast aluminum frame
  • 25 mm of linear excursion
  • 3" diameter voice coil with 2" winding length
  • Anodized aluminum former for high strength and optimized heat management
  • Double spider suspension provides positive mechanical control
  • Heavy rubber half roll surround w/integrated gasket
  • Triple-layer 240 oz. ceramic magnet with 7/16" top and bottom plates
  • Vented extended pole piece and two distortion-reducing brass shorting rings
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Last edited by ajhockett; 11th June 2010 at 06:27 AM.
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Old 11th June 2010, 04:15 PM   #2
GM is offline GM  United States
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A T/S max flat alignment is ~ 62.3 Hz F3-Fb, 11.283 L net/driver, so double this and add all the lost Vb due to the driver, bracing and make them bi-poles to ~cancel out box vibrations. This way you won't need the thick walls, just some bracing to both tie all six sides together and support/brace the driver motors. You can always Velcro on a massive granite, heavy potted plant or similar decorative top plate to mass load it.

Slick looking, no nonsense room/system BTW.

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

Last edited by GM; 11th June 2010 at 04:18 PM.
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Old 11th June 2010, 05:17 PM   #3
Rademakers is offline Rademakers  Netherlands
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Do you already have those 12" drivers? If not, efficiency wise they could be easily outrunned by 2 (or even a single) 12" Pro driver. Those drivers are made for excursion, 50-60 Hz and up doesn't require huge excursion capabilities. Personally I'd say like using a Ferrari in the city (for shopping).

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Old 11th June 2010, 09:04 PM   #4
chris661 is offline chris661  United Kingdom
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Based on efficiency, you'd need lots of those in series-parallel to get to the same efficiency as a pro driver (maybe 98dB@1w).

Alternatively, If you took one of the drivers mentioned, you'd need 16x the power to achieve the same SPL as the pro driver. Suddenly, that 500w power handling isn't looking so good.
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Old 11th June 2010, 09:58 PM   #5
richie00boy is offline richie00boy  United Kingdom
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Sealed box sub system to play from 50hz to 120hz
I think you would be better doing a different box for the 21 inch subs and having that reach up to your line arrays. Splitting the low frequencies between so many different driver/box systems isn't going to give the best results.
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
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Old 12th June 2010, 04:29 AM   #6
ajhockett is offline ajhockett  United States
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I had the 21s in huge sealed boxes before the TL setup. they still wouldnt make clean upper bass. I am guessing there is too much cone break up.
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Old 12th June 2010, 04:37 AM   #7
ajhockett is offline ajhockett  United States
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the 10's I plan on using have 87db efficiency. Not great i know, but they have dual 8ohm coils in series make 16ohm, so with a line of 8 woofers all in parallel I would get to 2ohms per side. Then I would wire them in series to make a 4ohm load for the amp which is a crown macro tech 5002vz. I think That would match the output of the TL subs. these woofers are 25.00 each.

1. What do you think the efficiency of the line of woofers would be(spl 1w 1m)

2. Do you think a line of woofers would sound better than 2 pro drivers per side?
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Old 12th June 2010, 05:00 AM   #8
ajhockett is offline ajhockett  United States
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after a quick search for pro drivers I found one that has a high power handling, most of the pro midbass drivers dont... I am thinking 2 of these per side, or maybe 4 per side. Anyone have an opinion on the quality and specs on these drivers?


Peavey's 12" BWX Neo subwoofer features a Kevlar® impregnated cellulose cone. The aluminum ribbon wire voice coil is wound on a polyimide-impregnated fiberglass former with Nomex® stiffener and solderless diffusion welded OFHC copper leads. Specifications: • Power handling: 650 watts continuous, 1,300 watts program, 2,600 watts peak • VCdia: 4" (100 mm) • Le: 0.36 mH • Impedance: 8 ohms • Re: 5.43 ohms • Usable frequency range: 50 Hz - 3.5 kHz • Fs: 56.1 Hz • SPL: 96.9 dB 1W/1m • Vas: 54.6 L • Qms: 9.51 • Qes: 0.45 • Qts: 0.43 • Xmax: 4.7 mm • Sd: 0.052 sq. m • BL: 15.13 T/M • Cms: 142.2 uM/N • Mms: 50.7 gm • No: 3.1% • Vd: 29.8 cu. in. (488 ml) • Disp: 109 cu. in. (1797 ml) • Weight: 11.6 lbs. (5.27 kg).

Last edited by ajhockett; 12th June 2010 at 05:07 AM.
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Old 12th June 2010, 05:05 AM   #9
jpruden is offline jpruden  United States
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Maybe you could replicate the original enclosure...

KW-120-THX Subwoofer - KW-120-THX - Overview
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Old 12th June 2010, 08:57 AM   #10
Rojoh is offline Rojoh  Norway
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Perhaps something like this would fit?
12" Sub - Speakerplans.com Forums - Page 1

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