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Old 13th March 2006, 07:13 PM   #1
eag is offline eag  United States
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Hey, I just spent a week building a nice sub box that turned out to sound quite pathetic. I'm quite disappointed in myself because it "kicked" about as much as my subwoofer that was included with a $30 set of computer speakers. I'll set up the situation and if you can please help me pinpoint what went wrong.

materials:
TB 8" sub (aka PE special 2 weeks ago)(used speaker sealing caulk)
70w dayton plate amp
ported enclosure of .75ft^3 (21L)
-> I put in some cheap foam I had lying around

Problem: Sub is not loud at all, even with amp gain at 100%. I messed with the LPF and gain and neither produced a "kick". The box also produced a "whizzing" type noise (I have no insight about this). I don't know if this help you diagnose the problem but it barely felt like there was any air moving through the port. Could the foam I used be useless and perhaps part of the problem?

Solution: ?. I would very much like to keep this box as I spent so long sanding smooth and putting PE laminate over. It looks quite good, just sounds pathetic. I don't believe I have an air leak. Do I need a more powerful amp?

THe video from realmofexcursion had a 100w kenwood amp with the tb and as you can see it kicks 1000x more than mine:
http://realmofexcursion.com/videos/T...d/w8740c.2.wmv
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Old 13th March 2006, 07:16 PM   #2
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Sounds like you put enough foam in there to kill all the air movement.
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Old 13th March 2006, 08:08 PM   #3
eag is offline eag  United States
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It was just a 1" sheet of foam along the walls. It didn't displace the entire volume.
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Old 13th March 2006, 08:13 PM   #4
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What are your port dimensions?
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Old 13th March 2006, 08:13 PM   #5
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You said :

"ported enclosure of .75ft^3 (21L)"

Can you give us more information, what is the port diameter? What is the length of teh port? What was your intended tuning frequency...

--Chris
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Old 13th March 2006, 08:15 PM   #6
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Quote:
Originally posted by leadbelly
What are your port dimensions?
Dang, you Ninja'd me...

--Chris
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Old 13th March 2006, 08:17 PM   #7
eag is offline eag  United States
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1.5" dia/ 7" length
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Old 13th March 2006, 08:31 PM   #8
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This guy?

8 Tang Band W8-740C 264-854

Specifications: Power Handling: 150 watts RMS/300 watts max *VCdia: 2" *Impedance: 4 ohms *Re: 3.2 ohms *Frequency range: 28-1,000 Hz *Fs: 28 Hz *SPL: 84 dB 2.83V/1m *Vas: .81 cu. ft. *Qms: 10.53 *Qes: .30 *Qts: .30 *Xmax: 12mm *Dimensions: A: 8-1/4", B: 7-1/4", C: 4-3/4"

See attached.

Recommemed box size is .26ft3 for ported.

Attached Images
File Type: jpg tb sw.jpg (12.7 KB, 805 views)
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Old 13th March 2006, 08:37 PM   #9
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link to recommendations;

http://www.partsexpress.com/resource.../sb_guide.html

Put a few bricks in a sock and put them at the bottom of the box and see if the sound changes. If you can remove any of the panels, partion the box to reduce the volume.
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Old 13th March 2006, 09:06 PM   #10
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9"x9"x10"=810 inches cube

Divide that by 1728 (linear foot)= .47ft3

Allow for: plate amp and rear cone and magnet and you are closer to the recommended size.

You can be off by 10% either too big or too small, without noticable difference.

Hope this helps. Someone check my math please!
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