Patman's Sunosub III Construction Resource Page

The SunoSub III Construction page.

Sunosub I Sunosub II Sunosub III

This is a DIY (Do-It-Yourself) project. I hope to give you insight in the overall construction process of the SunoSub III that I built all by myself over the course of a few months from September 13, 2000 to December 1, 2000. The reason for the length of time was just waiting for the brand new 15" Tempest driver. Actual construction time shouldn't take over a couple of weeks if you know what you are doing. There are some places where I screwed up in doing this project, and it's all documented, but all I can ask from you is to learn from my mistakes!

After using up almost 9 feet of sonotube on Sunosub I and Sunosub II, all from a 12 foot section of sonotube, I still had a section that was 27" long left over, so what the heck, let's build one more sub!

This is a totally experimental subwoofer design with many trade-offs due to the volume constraint placed on using the leftover sonotube material on hand.


I'm using the Tempest 15" driver from Adire Audio (formerly Avatar Audio). Just to recap the design specs for this effort:

Why use a round cylinder of Sonotube? Sonotube is just one brand of cylinders made up of fiberboard for pouring concrete for the formation of round concrete poles and structures. It's very strong stuff. Here's a link for the Sonotube FAQ if you want to know why to use sonotube over conventional wood-making.


I was able to use the power tools from my previous Sunosub efforts, as well as non-power tools:

Tool costs: roughly $245 - but I had all of these tools from my previous construction efforts, so dividing among 3 sunosubs, my tool costs were about $90/subwoofer project (including tax).


As a bare minimum you'll need the following in raw materials:
Material costs - roughly $295 (these prices listed are estimates from my sieve-like memory)

Personal Protection

As a bare minimum you'll need the following in personal protection - wear them while using power tools:

Hint: For faster navigation, when you click on your first picture link, don't close that 2nd window, but resize this window and position it so you can see both windows concurrently. I've designed it so that you can leave that 2nd (photo) window open, and you can click to your heart's content in this first window, and the images will only show up in that 2nd other window. This should also speed up your visit here. If you want separate windows, then right click of the photo links and select the "open in new window" option.

Day 1: September 13, 2000

I took a leisurely pace on this project. Again, it'll feature some different construction challenges from the previous 2 Sunosubs. I think I'll go with a piano black table top cover, and perhaps use a black ribbon sock to cover the sonotube. The top cover will overhang the sonotube by 1"-1.5" all around.

I go shopping and come home with most of the raw materials from Home Depot:

The 23" length for the 4" wide port comes from modelling for the port length by using a handy little program called WinISD (ISD = Interactive Speaker Design). You can download the program at Linear Team.

The tune might be asking a little too much for a 6 ft^3 enclosure for the 15" Tempest driver, and I might pick up more port noise than optimal, but I'll get to see how adversely port noise will affect the overall sound quality of this subwoofer in normal operating conditions. The reason I choose 16Hz as the tuning frequency is to provide as much driver protection with such a low tune. This is because the driver is "unprotected" at frequencies underneath the tuned frequency of the box/enclosure, so by going with 16Hz, it's protected for most low end frequencies while sacrificing a bit of output near the 20-25Hz range. But for a subwoofer this small, I can live with a few less dBs of SPL (Sound Pressure Level) down in that low end region.

Day 2: September 16, 2000

It's a nice breezy Saturday, but I managed to get the tops of my feet sunburned because I was wearing flip-flops while working outdoors.

Since this design is a little different from the previous designs, I will only have a 3/4" layer of MDF on the inside of the top and and a 1" (3/4" MDF plus 1/4" plywood) bottom endcaps because I'm trying to conserve as much internal volume as I can.

This means I'll be cutting each layer's endcap individually because they will have different widths to them. The outer top endcap will be around 27" wide, the outer bottom endcap will be 24.5" wide (just flush enough to provide a ledge for the sonotube material) and both inner endcap will be roughly 23.75" wide.

Well, after some experimenting with the router on my previous Sunosubs, I figured out how to cut circles with the router guide. The main thing is to draw out the circles in pencil, and find the center of the circles, and drill a 1/8" hole all the way through the endcaps for the router guide to pivot around. Use the plunge router, make several circular cuts - starting with 1/2" depth, and then 1" depth since we are just cutting through 3/4" of MDF thickness. Do the largest circle first, and start on the smaller circles inward on the endcap. Make sure you route in the recommended direction for your router. I have to go in a counter-clockwise direction for my particular router, otherwise, you'll risk injury and bad router cuts.

Now I start on the bottom endcap and the holes needed: driver hole, terminal cup hole, and the port hole (which will have to be done when I receive the flared port since I don't know how wide of a hole to cut into the endcap).

That's all for today, I was getting tired, and the sun was giving me a redneck burn if I didn't get out of the sun soon.

Day 3: September 24, 2000

Today I paint the legs:

I prepare the top endcap:

Sonotube preparation and internal top endcap attachment:

That's it for today. I'll be working on the top endcap's piano back finish for the most part in the coming weeks.

Day 4-6: November 1, 2000

Well, it's finally November, and I'm still waiting for the Tempest drivers. But I hear that they are finally being shipped out from Adire, so I'm keeping my fingers crossed that I'll be able to work on the sub this weekend or next weekend.

Here's some photos of the final sanding for the bottom endcap from September 25, 2000:

What have I been doing for the past 3 weeks? Destroying my table top. My original plans was to go for a piano black finish on the table top for Sunosub III. Well, I'll document the horror story that I created all on my own through my ignorance.

Don't do what I show in the next section of photos. My fundamental mistake was using normal ENAMEL spray paint underneath LACQUER paint. You'll see what happens and what I tried to do to fix it...

So I decide to use the other side of the table top MDF. There's a lot of sanding by me to get as much of the ENAMEL paint off from the new side that I'm going to work on. Plus I also used some paint thinner to get the stuff off.

Well, you get the idea of wetsanding and painting: paint the surface, and then wetsand out all the imperfections. On the new side, I did this with only LACQUER spray paint (both clear and black), and for some reason, I still would screw stuff up with inadvertent gouges into the surface with my finger nails as I was wetsanding the surface, and had to do minor repair. I won't bore you with anymore horror photos.

Day 6-8: November 11-21, 2000

I applied about 6 coats of alternating clear LACQUER, wetsand with 400 grit and then 600 grit, black LACQUER, wetsand with 400 grit and 600 grit. Then I decided to try something that another HTFer, Julian Data, did to get a really nice finish. I renewed my efforts on the table top.

So since I wasn't too crazy about the scratches, I decided to punt and go back to wetsanding with the 1500 grit, got the surface as flat as I could, and then I applied 2 thick coats of clear lacquer. If I had a slow speed power orbital polisher, I would have been able to buff out all the scratches with the rubbing and polishing compound, but I didn't have the proper tool and it wasn't worth the cost for me to buy the polisher, so I opted for the best non-machined polished surface I could do. Here are the final results:

The top isn't anywhere perfect, but I can live with it. Using the 1500 grit did help in getting it a tad more smoother and shinier, so it wasn't wasted effort.

So here's what I learned: Never, ever, use ENAMEL paint underneath any LACQUER paint. It's a road paved with bad intentions. You must absolutely have good air flow when you spray LACQUER paint, that stuff will give you a headache if you inhale too much of it. Also, I'll be letting the table top's painted surface "harden" for 3 months before I wax it to get the final shine of the surface.

Also, I must confess: I've played the game of golf, but I've never cussed as much as I did when I saw what ENAMEL paint does when it interacts with LACQUER paint. I was cussing under my breath for quite a few days as I work to try and salvage the top. But I felt better once I moved to use the other side. It did go better once I figured out what I was doing.

Hopefully my Tempest drivers will show up soon so I can finish my Sunosubs!

Day 9: November 26, 2000

Okay, here's some updated photos of what I've been doing. Still no Tempest Drivers, most likely I'll get them on December 1st.

These are miscellaneous bits and pieces that needed to be done.

Now here are the photos for the bottom endcap preparation from routing out the port hole, drilling in needed screw holes, and painting the endcap. I decided to preserve as much MDF surface area, so the port hole will be just a bit larger than the width of the 4" unflared port section. I plan to assemble the port from the inside of the endcap.

Okay, now I'm at the point where I sit and wait for the Tempest driver once again. I need the driver so I can drill in the mounting screws. Once that happens, I can nail in and caulk the bottom endcap to the sonotube and really get Sunosub III completed.

Day 10: November 30, 2000

Oh happy day! My Tempest driver finally arrives.

Day 11: December 1, 2000

I let the glue dry a day before resuming work. This is the home stretch!

Okay, that's how to build a sonosub with the Tempest driver.

Day 12-14: December 2-5, 2000

Here's some of my comments in regards to how Sunosub III performs in my Home Theater setup:

My reaction: Holy Smokes! I'm really amazed at what this little beast can do! On my Sunosub I (2 Shiva's, tuned to 19Hz with 24" long 8" wide port, 12 ft^3 of internal volume), I would get some minor pops when I played the DVDs/LDs with really strong low frequency content, like TPM AC-3 LD, and dts Haunting DVD. Basically this means some form of bottoming out by the Shiva driver. It only happens on really stressfull LFE (Low Frequency Effects), so for most applications, my Sunosub I is still a nice sounding subwoofer.

I tested The Phantom Menace (TPM), and everywhere that I got pops/bottoming out (the Jedi ship getting blasted, Pod Race toward the end of the race, and some other spots) with Sunosub I, I got no such pops or bottoming out with Sunosub III with the single Tempest driver. That made me very happy.

I couldn't totally crank it up since it was around midnight when I was listening to stuff, but I will do so the next day just to see how hard I can push it. But at relatively low (normal DVD/LD listening levels) I was getting up to 106dB during the Pod race at my normal seating area about 11 feet from the speaker/sub. My dual Shiva would pop at this volume level in the past.

The next day, I tested the space dogfight fight at the beginning of the Lost In Space DVD, and it played through it without a hiccup.

It also survived the dts version of The Haunting DVD (for my purposes) with peaks hitting 109dB from my seating position (and even then I needed to be listening at insane volumes, probably measuring a reference level of 80dB at the same position) from 10-11 feet away, I normally wouldn't even listen to DVDs at this level, but I was curious to push the sub a little harder than normal.

Here's a graph I made from some measurements today of Sunosub III:

Click here.

The nearfield measurement shows a F3 around 22-23Hz (using 103-104dB as the average SPL level), you can see where the Fb (tuned enclosure frequency) of 16Hz show up in the dip near 17.5Hz on the 1m measurements. Remember, this particular enclosure isn't optimal, so I expected the low end F3 not to reach 20Hz, and I was right. If I tuned higher, I might have gotten it, but I would sacrifice driver protection, and I just would rather have driver protection (from bottoming out the driver) over a few dB's down really low.

I made the near field measurement by playing a 22Hz tone, placing the SPL meter right near the dustcap of the driver, and turning up the volume until it was near 93dB (totally arbitrary dB number, you can use any useful SPL, like 75dB if you wanted to, but I wanted some separation between the near field and the 1m measurement for the graph.

I got the 1m measurement by playing some pink noise and raising the volume to get 75dB on my SPL meter, and then left the volume setting alone, proceeded to play bass tones from my BassZone CD and recorded the values with the SPL meter 1 meter away from the sub.

My room absolutely pumps up the high end bass in the 56-89Hz range (hopefully a Behringer Feedback Destroyer will show up soon so I can do some peak taming).

As I stated at the beginning of this webpage, this design is a compromise brought upon by its limitation of enclosure space. I had this last piece of sonotube lying around, and I knew using the Tempest with this piece of sonotube would be a compromise. I would say that it would make a welcome addition for a HT setup but I wouldn't use it for a serious music setup (the rhythmic thumping might call attention to port noise and chuffing much sooner than any DVD would over the long haul). I have listened to music at loud volumes with this sub, and it actually surprises me as to the tight thumping bass it can put out. I didn't find much to complain about regarding the port noise (if any) because I didn't hear much of it.

Things I may change/add: I may add some bracing inside the enclosure, perhaps two 2"x2' poles glued snugly between the top and bottom internal endcap because I did feel some vibrations coming through the top endcap while it was being worked very hard by my tests.

Hope this helps people get off their duffs and build their own sonosub, with the right tools, they are easy to make and you'll be surprised at the quality of bass you can get with a lot less money. Also, the pride of building stuff you use in your HT is another plus.

Well, there you have it, how to build a Tempest sonosub in 151 photos. Take a bow if you been here with me the entire way! Thanks for words of wisdom and encouragement along the way from the following folks at: Home Theater Forum, Home Theater Talk, and Home Theater Guide:

I hope you've enjoyed looking at how I created my 3rd SunoSub! It was a time-consuming process, but I learn something from each one of these subs I build. And as always, I make mental notes on how I'd do something different/better the next time I do one of these subwoofer in the future.

So how many have visited this subsonic webpage since 12-6-2000?

Back to the Patcave

Sunosub I Sunosub II Sunosub III