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Old 1st August 2009, 09:06 PM   #1
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Default First speaker build--questions!

So I've never built a speaker or done any other DIY audio, but after seeing an episode of Systm I thougt I'd build a sonotube subwoofer. Here are the details of my idea:


-12" driver
-Sealed
-Active
-Downfiring
-Nothing on the top so I can use it as a corner table.


Is there enough space to reasonably put a 12" driver and plate amp on the bottom of a sonotube design, or would the diameter of the tube have to be huge? I'm thinking of using this amp, which has no heatsink, looks relatively small, and is powerful.

Also, b/c of the controls on the plate amp, I'd have to have the sub quite a bit off the ground. Is this a problem?


Assuming I don't have to use a gigantic sonotube, this seems like a pretty freakin' easy project: just cut two circles of wood and essemble. Is this an easy first project?


THANKS
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Old 1st August 2009, 10:42 PM   #2
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Just some things to consider before going ahead.

Most Sonotubes are ported to avoid internal pressure differentials.

You have to use a woofer that can be mounted downfiring. Not all will put up with the sag.

It's sometimes tough to mount a flat plate amp to a rounded Sonotube. There is not enough room to mount it on the bottom beside the driver.
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Old 1st August 2009, 11:32 PM   #3
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Well, a 36" diameter tube ($$$) should be big enough and being short should be rigid enough with an 'X' frame brace or two, but there won't be enough cooling through the heatsink with the amp horizontally mounted, except at high SPL of course!

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Old 1st August 2009, 11:51 PM   #4
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So I did some math (hopefully I did it right) to find out what diameter sonotube I'd need. I determined that to fit that BASH plate amp and a 12" driver on one side I need a 20" diameter tube, minimum.

But then I looked at diysubwoofers.org and found that, for a sealed enclosure, I want about 17.5 cubic liters of space, which is WAY less than a 20" diameter sonotube of rought 2.5' height.

I was afraid of this.

Essentially...where can I put a plate amp on a sonotube build? I saw one design that built an add on box to put on the side, but I'd much rather put both amp and driver on bottom.

Is it possible to put a car style amp inside the body of the enclosure? Sounds stupid to me too but just wondering.
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Old 1st August 2009, 11:51 PM   #5
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Hmm ok. Probably just easier to build a conventional sealed design then: screw the sonotube! I'm just looking to do something rather easily that will be fun, and sound badass.


I'd prefer downward firing since it is more impressive looking and the driver is more protected, but I'm curious what the tradeoffs are. I'm looking to use this for music only, but a huge range of music that includes bass-heavy electronica.

THANKS
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Old 2nd August 2009, 12:22 AM   #6
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For an end table app you don't need real high SPLs, just a fairly wide, flat BW and this means either EQ and/or a relatively high Qts driver if sealed which can mean a large cab.

You have to cool the amp somehow, so this dictates where it goes/how it's enclosed. What's wrong with building a simple box to mount it to and put it with the rest of the electronics? There's normally enough scrap left over from the sub build to do it.

BTW, 'liter' is a cubic measurement, so it would be 17.5 Liters.

GM
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Old 2nd August 2009, 04:54 AM   #7
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Sorry GM, not sure what those abbreviations mean (Qts, BW)..

Also, do you mean make a box for the plate amp and then put that in the equipment rack, or make a box and mount it to the sonotube?


Again...just wondering what the easist solution would be since this is my first project.
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Old 2nd August 2009, 06:01 AM   #8
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Qts is a measured spec that defines the total quality factor for the motor with lower numbers (< 0.5/stronger motor) indicating an over-damped one, 0.5 being critically damped, ergo above this point they are under-damped (weaker motor). This is an over simplification, but the point I was trying to make is that all else equal, a higher Qts driver is a good choice in your app, though due to the physics of the situation, Qts has the most impact on box size, so it will be somewhat larger than a similar driver with a low Qts.

BW = band-width, i.e. 20-100 Hz or whatever.

A good site for learning the basics of speaker design: http://www.diysubwoofers.org/

Well, at least to set it on a shelf, but if you have an actual rack system with enough empty space you could make just a baffle to rack mount it.

For an end table, either convert a piece of furniture such as I did ages ago to make stereo speakers for my mom or do your own woodworking. If you're married, let her find something she likes and meets the needs of the app size wise if you don't want to deal with any more woodworking/finishing than absolutely necessary. Then again, some women enjoy doing staining/painting..........

GM
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