How To Build A Subwoofer
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How to build decent home theatre sealed active Subwoofer for around $300AUD.
This is a guide to building a 100 litre enclosure for an active (powered) Subwoofer than can be used on ANY home amplifier, computer sound card, or basically anything with a line out plug or speaker wire outlets. The finished box will be ready to hook up and use, the actual finish of the box, whether painted, carpeted, veneered, or whatever will be up to you. It is designed for a 12" woofer but I'm finding a 10" one works just fine.
Tools you'll need:
- Tape measure.
- Straight edge.
- Drill, any variety.
- Phillips head screwdriver.
- Jigsaw (can be used for all cuts but specifically for the speaker cut).
- Pliers/wire strippers.
- Cordless drill/screwdriver.
- Mitre Saw.
- Soldering iron.
Hardware you will need to do the job:
- Paper/Polycone Woofer.
- Subwoofer amplifier.
- MDF (Medium Density Fibreboard).
- 50mm Chipboard screws.
- PVA glue.
- Screws to suit your speaker (woofer).
- Rubber feet/stands.
Parts I used for this project:
- Jaycar 80w Sub amplifier - CAT:AA-0503 - $209
- Jaycar 10" Paper Cone Woofer - CAT:CW-2119 - $35.95
- 3 sheets of 18mm MDF. 450mm wide x 1200mm long. These sheets can be bought straight 'off the rack' from any *Bunnings store. $14.13 per sheet.
- 4x 55mm Rubber furniture feet. Available at Bunnings for $1.10 each.
- Bag of 50, 50mm chipboard screws. Bunnings - approx $10.
- PVA glue - We all have this lying around.
- Dampening batts - I had some lying about and don't know what this costs.
Here's the amp module and Woofer I used.
These bits and pieces you can get cheaper if some are on sale and if you know how to haggle well, or if you have a trade discount at these stores.
Now, onto the work!
Here's the sizes of the pieces of MDF we're going to cut.
First up we need to cut our sheets of MDF. You need to cut 4 pieces of part "A" and 2 pieces of part "B". Parts "A" are the sides of the box and parts "B" are the top and bottom.
You'll get 2 of these pieces from each of the sheets of MDF you bought from Bunnings.
You don't need to cut the width (450mm), only cut the lengths. We save a lot of cutting time by using these pre-cut sheets and that's why I've listed them. You only need to make 6 cuts for your 6 pieces of MDF we're going to use for this unit.
I used a mitre saw for this. You can also use a circular saw, jigsaw or panel(hand)saw to do it. Just keep those cuts nice and straight and you'll have no problems whatsoever putting the box together.
Now that we've got all our pieces cut we're going to drill some evenly spaced pilot holes along the LONG (500mm) edges of 2 pieces of part "A" and all around (all edges) of both part "B" pieces. The centre of these holes should be 9mm in from the edge of the sheet. I've also countersunk the holes so no screwheads stick up later on.
Along with this we also cut out the hole for the Sub Amplifier module in one of the pieces we just drilled pilot holes in. The Sub Amp module will have an instruction sheet that came with it telling you exactly how large the hole is that you need to cut. If you only have the bare minimum of tools then the way to accomplish this is to drill a 10mm hole in each corner of your marked hole and use your jigsaw to neatly cut along your lines.
If you want your woofer speaker in the front of the box rather than the bottom as I did then follow the next instructions making your cut in the other part "A" piece that you drilled pilot holes in.
I want the Woofer pointing down so to do that grab one of our part "B" pieces. Find the centre of that piece and mark out your hole using your compass. Cut your hole using the same method you cut out the hole for the subwoofer amp. Again, the speaker will come with a size for your hole. If all else fails, use your tape measure!
Now all the cuts are done we just have to glue and screw it together. Using glue is advisable as you don't want any little gaps for air to be pushed out making for some annoying little noises now and then when you turn the bass right up!
Before you screw it all together you will find you have a few little offcuts of MDF lying around. You can use this for internal bracing if you like (I didn't and it seems fine without it).
Screw all the sides (parts "A") together first using the 50mm chipboard screws, lining your edges up with the faces of the pieces with the pilot holes. Use plenty of glue! If you're measurements and cuts are good then it'll slot together in no time.
Remember, it's just a box. It aint too hard at all, even for a complete novice.
After the sides are screwed together screw both the top and bottom on. One side is longer than the other on these pieces so it's easy to see which way these pieces go.
Again, use heaps of glue!
At this point I advise sanding the whole thing back if you want a neat finish. This is the completed box ready for hardware. You can paint it or whatever you like at this stage too.
Now I'm going to put my rubber feet on it and take it inside to do the rest.
Now I'm inside I'll stuff it full of deadening batts. You can staple or whatever this to the walls if you like. I just put a few screws on the inside of the case, pulled the batts over it and then bent the screws (how slack eh!)
Now all we have to do is put the Woofer in (do this first), put the screws in, hook the speaker wire up to it and then put the Sub amp module in and screw that in.
Again, if your cuts are on the money then all this is a breeze. We're now ready to hook it up and test it.
Here's the finished Subwoofer standing next to my crappy Pro Logic system. The TV is a 72 cm job to give you an idea of size.
Now just tweak around the back of the Sub amp to get the bass feel you like.
This has been a very worthwhile project to undertake as I went down to JB HiFi and tested out a lot of their Subs. This thing is easily comparable to anything they had around the $1200 mark and that's only with the little 10" cheap woofer in it. If I blow it up (I doubt I will, I've had it at full volume for prolonged periods) I'll probably try a 12" or 15" woofer in it. What you choose it up to you.
I'd also like to thank McNugget for his advise along the way when I was researching how to do this.