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Old 11th January 2013, 02:57 PM   #1
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Default $500 DIY Subwoofer Challenge!

Here is a challenge for the "best" subwoofer you can build for $500, total, including driver(s), amp, crossover/electronics, wood, cables and hardware needed to get it completely operational with a normal stereo/home theater system. Assume the builder has all normal tools needed for speaker building. If your design requires PEQ or time correction to the mains (such as with a horn), the electronics for that is part of the $500 budget. Prices should include shipping, local taxes, and be your actual local costs for goods. If your cost are much higher locally, note that or adjust accordingly.

Clearly there is no best design because everybody's needs are different, but the baseline design goals here should be a music/ht sub with good extension (below 30hz) and output for a moderately sized room.

Since this a practical challenge, the winner will be the best all around design - considering performance, practicality, and form. There are no specific perfomance criteria except it must provide impressive, accurate bass for ht and music in a normal sized living room. This should be a project that a novice DIY'er should be able to build with a high degree of confidence that it will work well and look good.

See here for more guidance: $500 DIY Subwoofer Challenge!

- Sine wave output capablity of 106 db @ 1m 4pi @ 45hz
- Reference size of 14"H x 19"W x 7.5"D @ 18.8 lbs
- For each doubling of size, increase output 3db or improve low extension by 1/2 octave

Thus, if you were to double size twice to build a sub 75lb & 14"x19"x30", it should be capable of 109 db 1m 4pi @ 34 hz or 112 db 1m 4pi @ 45 hz or 106 db 1m 4pi @ 22 hz.


I'll start:

15" Dayton Reference HO RSS390HO-4, $150 on sale PE
Behringer NU1000DSP $258
3/4" birch 5-ply sheet $45
Drywall screws $6
Wood glue $6
Paint $5
Roofing mastic $10
Speakon connectors qty 2 $10
10 ft speaker cable $8
RCA to TS adapter $2

Total $500

Model response in WinISD or Hornresp to find prefered tuning. Should be roughly 3.5 to 4.5 cubes tuned to ~20hz. Use one slot port with less than 6:1 aspect ratio and flared ends, area at least 30 sq inches, 45's with any bends. Build with birch ply, brace as desired. Internally coat with roofing mastic. Setup with nu1000dsp amp in bridged mode (~700 wrms @ 4 ohm), set HP filter to avoid over excursion, low pass, EQ, time delay as desired.

Should be quite powerful in most living rooms and sound excellent, this will beat pretty much any pre-built sub under $1000 in output and SQ. Enjoy!

Last edited by turbodawg; 16th January 2013 at 10:02 PM.
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Old 11th January 2013, 03:14 PM   #2
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Just wondering if material costs should be local or standardized somehow, birch ply can be silly expensive here. Material cost will be a big variation pending on where in the world you are.
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Old 11th January 2013, 03:56 PM   #3
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Quote:
Originally Posted by KaffiMann View Post
Just wondering if material costs should be local or standardized somehow, birch ply can be silly expensive here. Material cost will be a big variation pending on where in the world you are.
Feel free to go by your own local material, component and shipping costs, or adjust accordingly!

Keep in mind I'm spec'ing cheap 5-ply birch from home depot, not baltic birch. I prefer the 5-ply because it's cheaper, a hair lighter, and stiffer, IMHO, at the expense of a few voids and not being as nice to work with. MUCH lighter and stiffer than MDF.

Last edited by turbodawg; 11th January 2013 at 04:00 PM.
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Old 11th January 2013, 04:03 PM   #4
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Location: Colorado, USA
How are you getting that price on the Dayton? I'm getting $172.69.
http://www.parts-express.com/pe/show...number=295-469
Yours will be tough to beat. I can't see this finishing without some sort of awards ceremony.
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Old 11th January 2013, 04:08 PM   #5
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Quote:
Originally Posted by audiomagnate View Post
How are you getting that price on the Dayton? I'm getting $172.69.
Dayton Audio RSS390HO-4 15" Reference HO Subwoofer 4 Ohm 295-469
Yours will be tough to beat. I can't see this finishing without some sort of awards ceremony.
They were on sale last month for that price, and probably will be again. So, I'm already cheating. LOL.
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Old 11th January 2013, 05:10 PM   #6
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Location: Colorado, USA
Since cheating is OK, stealing must be too: Mine is also in a 4 cu ft box:


Infinity 1260 12" woofer $59
Acoustic Elegance PR-15 700 $60
Behringer NU1000DSP $258
3/4" birch 5-ply sheet $45
Drywall screws $6
Wood glue $6
Paint $5
Roofing mastic $10
Speakon connectors qty 2 $10
10 ft speaker cable $8
RCA to TS adapter $2
--------------------------------
$469!
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Old 11th January 2013, 06:11 PM   #7
nirvana is offline nirvana  Canada
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Location: Amos , Québec
Critical Q-sub : Bash 500 amplifier and Peerless 12" XLS.
Critical Q Sub-Woofer
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Old 11th January 2013, 06:23 PM   #8
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Quote:
Originally Posted by turbodawg View Post
Here is a challenge for the "best" subwoofer you can build for $500, total, including driver(s), amp, crossover/electronics, wood, cables and hardware needed to get it completely operational with a normal stereo/home theater system. Assume the builder has all normal tools needed for speaker building. If your design requires PEQ or time correction to the mains (such as with a horn), the electronics for that is part of the $500 budget. Prices should include shipping, local taxes, and be your actual local costs for goods. If your cost are much higher locally, note that or adjust accordingly.

Clearly there is no best design because everybody's needs are different, but the baseline design goals here should be a music/ht sub with good extension (below 30hz) and output for a moderately sized room.

Should be quite powerful in most living rooms and sound excellent, this will beat pretty much any pre-built sub under $1000 in output and SQ. Enjoy!
Lacking an actual specification to achieve, ie "X dB +/- 3 dB from 30 to 100 Hz" there is no way to judge the winner of your challenge.
Horns can be quite impressive even without time correction, though integration can be better with.

I built a very cheap, decent sounding, reasonably loud, very efficient sub for a lot less than $500. The efficiency opens up many low power (cheap) amplifier options.
The "Tub Sub" was designed to fit in the space that was available between a hot tub and the building wall. Two layers of grill cloth and Duratex paint make it weather proof. The shape would also lend itself to fitting behind a couch or under a bed.

$10 Two 10" speakers, on sale from Parts Express, PE # 299-284 (sold out)
$100 Sub output from used Technics SA EX600 receiver
$90 Two sheets 3/4" Aruco 5-ply sheet
$10 Drywall screws
$10 Wood glue
$20 Paint
$15 Grille cloth
$10 1/4" female connector and plate
$10 Ten foot 1/4" speaker cord
$5 On off switch and plate
$280 total, or $180 considering the Technics sub output was already there when the project was started.

The tapped horn Tub Sub uses two $5 buyout Sammi 10" speakers.
It's sensitivity is 99 dB one watt one meter in half space at 60 Hz (open field) but located against the wall behind the hot tub, 24 Hz is only 3 dB down from 60 Hz, with a "loudness contour" peak at 40 Hz.

The cheapo 30 watt 8 ohm Sammi's are wired in series, 12 volts (about 10 watts into 16 ohms) will hit their 4mm Xmax, doing about 114 dB in half space at that level.
They are wired in series so that the receiver's sub output can also drive the home theater and kitchen sub at the same time without overheating.
The good thing about the speakers is when pushed hard (that would be around 60 watts for the pair), they do not have enough magnetic fource to make them clack or flap.

Although I would prefer to time align the subs, as you can see by the Tub Sub with left and right 2x8T speaker's FR charts, other than a dip around 130 Hz the integration is not terrible. A lot of the peaks and dips are due to the mic placement at ear level instead of ground plane.
IIRC, the top speakers built for the deck integrate a little better, but I lost the files.

If this sub used "real" speakers, it could do some serious damage.
As it is, with about 10 watts driving them I can clearly hear bass lines at my southern neighbor's property line about 800 feet distant from the deck location.
Not bad for $10 in drivers ;^).

Art
Attached Images
File Type: png TS in Place.png (607.4 KB, 1330 views)
File Type: png Tub Sub.png (801.7 KB, 1289 views)
File Type: png Tub Sub Guts.png (966.9 KB, 1263 views)
File Type: png TubSub &2x8T.png (117.7 KB, 1209 views)
File Type: png TubSub1watt.png (74.7 KB, 1181 views)
File Type: png TubSubLayout.png (527.3 KB, 212 views)
File Type: png TubSubResponse.png (146.0 KB, 226 views)
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Old 11th January 2013, 07:04 PM   #9
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Art, that's totally awesome, but tough to say it's the best for all around use....!
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Old 11th January 2013, 07:30 PM   #10
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Quote:
Originally Posted by turbodawg View Post
Art, that's totally awesome, but tough to say it's the best for all around use....!
In your opinion, what makes a sub "best" for "all around use" ?

You wrote in the OP:
"The baseline design goals here should be a music/ht sub with good extension (below 30hz) and output for a moderately sized room."

The Tub Sub certainly meets those goals, though "a moderately sized room" is as ambiguous as "good extension".
There are many that would consider 700 square feet to be a moderately sized room.

I have a 700 square foot (total) house with 6 rooms, the only room the tub sub would not fit in easily has a tub and a toilet .

Art
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