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DIY outdoor subwoofer build x2, Marine Subwoofers, Fiberglass Enclosure

post #1 of 11
Thread Starter 
Hello everyone, this is my first post on this forum and my first subwoofer build though I am a proficient carpenter. Here is what I would like to do... please be brutally honest if this won't work.

I have 2x Powerglass fiberglass enclosures that normally cover electrical equipment at power substations. They were used as equipment shelters for water monitoring stations and then donated to our local Habitat for Humanity where I bought them... so if this doesn't work at least I made a donation to a worthy cause. I want to build a subwoofer enclosure to fit inside each of these enclosures. Conservative internal dimensions are 38"x38" at the base and 34"x34" at the top with a height of 50" (max height 54"). The enclosures have large lift off door on each side and are vented. There is a 4" lip on each side under the door that may be an issue. Build cost excluding amp (under $750 best, $1000 max).

1) First and introductory question, am I going to find a marine subwoofer 2x12" or 15" that I can use in a Tuba, Titan, or other suitable design that fits in the fiberglass enclosures and will fill a backyard with base (remember I am building 2 so 4x12" or 2x15") I don't think they make a 18" marine and from what I read on here you don't use 18" in horns unless they are way bigger than my dimensions.

2) What enclosure design is best for outdoor music/theater. Yes, I want something that can play everything. I like the idea of using horns so that I don't need a massive amp. I plan on pairing these with commercially available water resistant outdoor speakers still to be purchased.

3) Is anyone interested in helping me select a woofer for the final design. I know this takes some optimization and knowledge which I don't currently have. I don't have a problem using an off the shelf design if I can find a marine subwoofer that doesn't rob most of the enclosure's performance. Even using an existing design selecting the correct woofer will be something that I will need guidance/help.

4) tell me what I forgot.

Thanks In Advance!

I included photos below.



post #2 of 11
So these have to be left outside? There is not an option to store them indoors when not in use?
post #3 of 11
Thread Starter 
I can bring them in for the winter but yeah the idea would be to leave them outside for the whole summer but something year around would be better. I live in Illinois so winters may be too much as you suggested and I would move them to the garage. I do want something that is relatively water and critter proof.

Yeah and I said 'base' in the original post... ummm I meant bass
post #4 of 11
I wouldn't consider a horn "critter proof". All of the folds would be an inviting place for spiders, wasps and dirt-dobbers to build their homes.
post #5 of 11
Quote:
Originally Posted by rlj5242 View Post

I wouldn't consider a horn "critter proof". All of the folds would be an inviting place for spiders, wasps and dirt-dobbers to build their homes.

sure but you can put a screen or chicken wire over the mouth to keep them out.
post #6 of 11
Thread Starter 
Yes, a screen will be sufficient. I will just have to use my subs periodically to keep them free from insects.

Any ideas on using marine subwoofers in these enclosures. Do any marine subwoofers have compatible specs? Recommendations for enclosure design?
post #7 of 11
I'm seeing an open-bottom cover with access panels front and rear... I'll suggest using this as a cover for a conventional box-style subwoofer. 33"x33"x50" yields 24.5 cu ft, so you have room for a folded horn or a large ported box. I see no issues with dual 15's or 18's in an LLT alignment for lots of low bass. In an outdoor space, you may want to consider passive radiators, so there are no access paths to the inside. That's the straightforward option...

A horn design may not keep out the critters as easily, but it's far more efficient with far less distortion if used properly. Here's a link to 20 cu ft., 20Hz design that's the wrong form factor for you, but form factor is adjustable... horns can be folded different ways. Maybe there's one that fits; there will be no option with higher output and lower distortion, if you can fit it to your space.
http://www.avsforum.com/t/1329971/lilmikes-cinema-f-20/0_100

BTW, horns encapsulate the driver, so you can use conventional drivers, as long as the box is water tight (marine plywood). To eliminate critters, I'd add a flap door on the horn mouth. You're opening these enclosures anyway; a simple flap is trivial, and improves your weather seal as well.

HAve fun,
Frank
post #8 of 11
Thread Starter 
Frank, thank you for your reply. So you think that a horn which is sealed around the subwoofer is sufficient to not worry about humidity and corrosion? I think the direct contact with water problem is fixed by the fiberglass housings but I still thought I would go marine for corrosion concerns. Maybe I don't have to... that would be great!

Anyone know of a good horn/sub combo that matches my dimensions? Frank, at this time I don't know enough to reconfigure a horn.
post #9 of 11
Thread Starter 
Yes, you are correct. The bottom of the fiberglass enclosures are open so you could use them as just covers. There are boards inside which span the base (about 3" above the bottom) but they are removable. Originally they were placed on concrete pads, but I will likely put them on patio pavers or gravel.
post #10 of 11
Quote:
Originally Posted by crazyish1 View Post

Anyone know of a good horn/sub combo that matches my dimensions? Frank, at this time I don't know enough to reconfigure a horn.

Seems like Bill's T30s would fit inside there just fine.
post #11 of 11
+1 The largest Tube 30 would be a drop-in and BFM designs are well respected because they work. Seems worth $15 to see the detailed plans before deciding. Once you see the plans, you'll see how protected the driver will be. Being a "pro" design, I suspect it's quite well protected, and I think you can figure out how to seal the mouth.

Other designs would require some folding changes, and I was hoping someone might volunteer... but with options like this, what's to gain?

HAve fun,
Frank
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