Pilar of power

SonoSub subwoofer project

This subwoofer (made about 2002) is from my archived web pages . The Adire Audio 15" subwoofer was a great sub, but Adire audio is no longer in business (now they are back again!). If you are interested in a sealed sub, be sure to use a speaker that has a long throw (Xmax) and give it plenty of power. I still use this sub in my home theater. It does a great job

The pillar of power is one of the many "Sono-tube" subs on the web. There are many great how-to web pages (linked below) so I will just show general info and a few specific things that I found helpful when making a sonosub.

The specs: I chose to put an Adire Audio Tempest 15" subwoofer in a sealed enclosure. The enclosure is approximately 4.6 cubic feet (130L). The long sides of the enclosure are made out of 20" diameter sonotube. The top and bottom of the sonotube is capped with 1.5" MDF (two 3/4" pieces glued together). Two 24" "beauty caps" add a little style and match my Audio/Video center. The woofer down fires the air in/out of the 4" gap between the bottom of the cylinder and the bottom beauty cap.

Bottom cap

This is the bottom cap that the Tempest bolts to. It started off as 3/4" + 3/4" MDF glued together. I used a router to gradually dig through the 1.5" MDF to form the round circumference and the inner hole. The four legs are 1.25" diameter avocado dowels (how appropriate for a California sub). They go into the countersunk holes on the bottom beauty cap( more on that later). I drilled the four holes for the binding posts (I brought both coils to the outside world in case I decide to do something different later). I have one binding post in to check for fit. The posts are from Parts Express (# 091-1245). They become wider near the top of the post and have a ribbed pattern to help grip into the wood to keep them from spinning while tightening down the speaker wire. I drilled the holes just slightly smaller than the rib and used a rubber mallet to pound them in once I painted the bottom cap.

Beauty caps

Here are the two beauty caps. I got the idea of using the lower beauty cap and legs from the company SV subwoofers. Half way through the build I decided to put an identical beauty cap on the top also. Sonosubs aren't the prettiest things plain, but some wood make them presentable. The bottom piece is the one with the four countersunk holes in it. This is where the four legs will slide into. The 24" circles were bought from Home Depot already cut with the edges rounded. All I had to do was stain them. The staining process started with a pre-stain treatment that is suppose to help the stain go on evenly. Next was one coat of stain. Finally, two coats of polyurethane. I bought the semi-gloss polyurethane to give it a shine, but not so much of a shine that it made every imperfection stand out.

Ready for speaker

The bottom is now painted black and has the speaker binding posts mounted. The bottom sits lightly in the sonotube. This made it convenient to mount the speaker to it before it was glued in. I added some Acousta-Stuf insulation (Parts Express # 260-317). It is the white insulation. I left the previous fiberglass in there. Speaker sealing caulk (Parts Express # 269-300) can be seen on the circumference of the speaker hole


I forget how truly monstrous a 15" woofer is. It was a little unwieldy pulling that thing in and out of the box. Next to it sets a 6.5" woofer used in the Dayton III speaker. Will was building a pair while I was working on the Tempest. He has fancy router bits and it sure is nice to be able to leave all that MDF dust behind.

Ready to roll

It is ready for travel back home now that I smeared Liquid Nails inside the bottom of the sonotube and pounded in the bottom cap (using a rubber mallet). It is only missing the top and bottom beauty rings to be complete. When I got home I took out the eight bolts holding the speaker down and pulled the speaker out a few inches to let the Liquid Nails dry. I am glad I did because there were some nasty fumes coming out of there for several hours. You can see one of the advantages of using a sealed enclosure.... the woofer can almost be the same size of the Sonotube diameter. For ported designs, you have to use a much larger diameter of tube or put the port on the opposite end.

Beauty caps on

Back home now for the finishing touches. I bolted on the bottom beauty cap and I am trying to center the top beauty cap so I can mark it before I apply the Liquid Nails. I rotated the top cap after I put on The Liquid Nails to line the grain of the wood in the top and bottom caps. After applying the "nails", I put three boxes of leftover kitchen tiles on top to keep pressure on until the glue dried. I was sure to not put too much Liquid Nails near the outer edge so it wouldn't ooze out and get on the painted Sonotube or the bottom side of the beauty cap. It would be hard to retouch either since they are soon to be inseparable.

This project was all made possible by Sonosub tubing. You just can't beat the strength of a cylinder shape for equal pressure (darn close) applications. The woofer can be breathing deeply, but the Sonosub walls don't flex. It sure does make the woodworking part of the project much easier. This picture was taken off the Hub web page (a concrete accessory store). You can see the intended application for Sonotube. Aren't speakers a much better use?