I can't even begin to talk about building my subwoofer without first thanking Thomas W! Without his help I'd still have my old Infinity BU-120 and not be given the chance to know what it's like to own a piece of NICE home theater gear! Thomas invited me down to his house, as he had ALL of the tools needed to build any speaker, and walked me through the whole process, as well as did most of the work. We spent about 12 hours building the subwoofer. We are on two different levels of knowledge...me being the newbie to HT, and Thomas having a very advanced knowledge of the hobby. He took his time to explain each step in terms that I would understand, and never once lost his patience. I wouldn't know where to begin to try to thank him, as his kindness allowed me to gain a new appreciation of the work that goes into building speakers, as well as the savings you can enjoy when you choose to build one yourself. I spent a total of about $175(US) on the subwoofer, but it sounds as though I paid a good $2,000 for it! Because of his help, as well as Andrew Pratt's, I named the subwoofer the MW AP-12 SonoSub...when broken up it stands for M(first letter of my last name)W(the first letter in Thomas' last name) AP(Andrew Pratt, inventor of the name "SonoSub")-12(we used a 12" Shiva) SonoSub(self explanatory). The following instructions are for a single driver sealed SonoSub.

Building the SonoSub

• All of the raw materials.
• Laminating the MDF together.
• Highly advanced press system.
• First we laminated up 2 ¾ layers of MDF for the top cap. And then laminated up 2 ¾ layers of MDF, plus a single 15/32 layer of OSB for the speaker baffle. The OSB is for added strength and to give the T-nuts used for mounting the woofer something to grab into.
• Routing the end caps.
• Another shot of the routing.
• The routed baffle with markings for the driver.
• After that step was complete, we routed each of these to size using a plunge router with a ¼ up cut, spiral twist, solid carbide router bit, The Jasper Audio Model #300 router jig was used for these cuts.
• Rounding off the edge of the endcap.
• Then we used a ½ radius round-over bit to ease the inside edge of each cap. This allowed the caps to glide easily into the tube, and created a convenient grove between the cap edge and sidewall of the tube for sealing with caulk.
• Cutting to make the recess.
• The completed recess.
• A ½ recess was cut in the baffle board to inset the woofer. This helps provide a better air seal. The woofer recess and cutout were done using a Jasper Audio #200 router jig.
• Cutting the panel slot.
• A cutout was made for the dual input panel. This was done with a saber saw.
• Applying the caulk.
• Hammering in the baffle with a rubber hammer.
• The baffle hammered in.
• The baffle board was installed first. A coat of siliconized acrylic caulk was applied to the perimeter of the board. This was to a) seal any potential leaks between the wood and the tube and b) act as a lubricant when placing the board into the tube.
• The acrylic caulk.
• After the baffle was put in place, it was tacked using 1 ½ wire brads with an air nailer. These brads functioned as clamps while we worked on the cabinet. Then a thick bead of the siliconized acrylic caulk was applied around the interior perimeter between the baffle and the side of the tube.
• The internal alignment mark.
• Making the alignment mark on the outside of the sub.
• An interior measurement was taken from the inside of the baffle, to the inside of the top cap, this dimension was 25.5. The thickness of the top cap was added to this measurement. Utilizing a combination square, a line was scribed to both inside and outside surfaces of the tube. This provided a reference for proper alignment of the top cap.
• Ready to take the top cap out of the press.
• Applying the caulk.
• The top cap pushed through to the alignment mark.
• The top cap was then caulked like the baffle, and installed. It too, was tacked in place with an air nailer. Caulking was run around the baffle to interior sidewall edge as well.
• The internal cross bracing.
• Oak 1X2 cross bracing was glued and tacked in place to stiffen the top cap.
• Making a flush cut.
• Using the router to flush out the extra tubing.
• The tube was then cut to length using a bearing under flush cut router bit, tracking the MDF cap. The router was maintained perpendicular to the cap. This makes for a very smooth and accurate cut.
• Rolling the batting (damping material).
• Connecting the driver.
• The enclosure was damped with Bonded Polyester batting. We used 5lbs of polyfill for stuffing. The purpose of the stuffing is to tighten up the bass.
• Connecting the cables to the driver.
• Neoprene foam, single sided tape, was used as the gasket, to create an air seal for both input terminal and Shiva.
• Clamped in place.
• The mounting technique for the Shiva we used is as follows. 4-½ EMT conduit clamps had the tips ground down to a point. The points grab the mounting hole slots in the Shiva frame. Use of these clamps allows significantly greater space between the woofer cutout, and the holes for the mounting screws. They also generate considerable clamping pressure, while allowing quick removal of the driver as necessary. Cosmetically they are lacking, but for a down firing woofer this isn't an issue. The driver was secured with 10-24 Phillips head machine screws, 10-24 T-nuts, the 4-customized conduit clamps, and bonded sealing washers. These washers are a convex metal washer with a rubber gasket bonded to it. The convex shape preloads the machine screws and prevents them from loosening. The rubber decreases metal to metal contact.

Finishing the SonoSub

• Painting the tube on the patio the night before I went to Tom's house. I removed the driver for this step.
• Tube after painting the outside. This is done so the cardboard doesn't show through when the sock is attached. The bottom of the SonoSub is shown here, face up. This is not painted completely, as this side will never show.
• Tube upside down after the paint finally dried.
• Back down at Thomas' house. Using the largest Jasper Audio router jig to cut the endcaps. Pete's "supervising", Evan is encouraging Thomas to work faster.
• "Rounding over" the inside edge of the ends caps with a ½ inch radius bit. This make's it a lot easier to get the endcaps into the tube. Now Pete's helping stabilize the piece!
• Spraying the granite finish on his top end cap. Evan is now trying to encourage me to work faster :)
• Pic of the finished endcap drying in the garage.
• Raw materials for "finishing" the tube. Shown is this picture is the sock and four black painted legs with leg mounting brackets.
• "Dualing" drills! For high speed production work, it's very handy to have one drill with the bit mounted, and another with a screwdriver tip. In this pic we're getting ready to attach the mounting brackets for the leg brackets.
• Leg mounting brackets attached complete with legs screwed in place.
• SonoSub with a sock on.
• Trimming the sock to length.
• The sock was attached to both the top and bottom of the sub using an electric staple gun. It was stretched snug, not too tight.
• Bottom shot of the completed sub. It's in Thomas' HT with the woofer is pulled while we optimize the amount of damping material inside.
• And here is a close up of the completed product!
• This was the same sub being used in my second home theater setup.