Cylinder subwoofers, redux

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Project by ferstler posted 08-20-2012 12:43 PM 5821 views 16 times favorited 14 comments Add to Favorites Watch

Some time back, I wrote a construction piece on two “cylinder-style” subwoofers that are now installed in my main music room. The article can be found at:

These units work very well, but even after I finished them I swapped out the Dayton Titanic drivers for Dayton Reference drivers. The Titanics were not quite right when it came to handling very low bass (pipe organ) and the Reference versions, although less potent in terms of maximum output, were cleaner down in the 20-25 Hz range. That room is strictly for music, with no home-theater abilities.

The question now was: what would I do with the two Titanic drivers? Solution, make two more subs for use in my home-theater in another part of the house. The Titanics are better at head-banging action-movie sound than much of the competition, and there is no need in there to go below 25 Hz. The result can be seen here, with each unit located in a room corner, flanking three bookcases I built recently out of a mix of redwood and mdf. A piece about the building of the bookcases can be found at:

The redwood was obtained from a friend of mine who had been using it for shelving purchased way back in 1980. He sold me 260 feet, at a buck a foot, and he still has another 600 feet that I may buy into down the line.

Note that the spacing between the two taller bookcases is more than wide enough to handle that 56-inch TV monitor, because down the line I hope to replace it with a 70 incher. The wife will have to agree with this first, of course.

Anyway, the new subs are 57 inches tall (the earlier ones in the music room were 68 inches), with the main functioning body made of a Sonotube concrete post mold 14 inches in diameter and 48 inches long. This adds up to about 4 cubic feet and the 4-inch diameter port tube at the bottom is sized to give the subs tuning at 22-23 Hz. (The bigger subs in the main room, with an interior displacement of 5 cubic feet, tune at about 18 Hz.) While the sizes are different, the main difference is that I used that recycled redwood for the top and bottom sections instead of mdf.

This required more work, because the redwood boards were only 5.5 inches wide, and so I had to join them edge to edge to give me the diameters (16 inches) needed for the visible sections. For the joining work I used Kreg pocket screws, obviously located so that they would not interfere with the need to cut holes in the tops for the woofers and in the bottoms for the long port tubes and electrical binding post clips. The end of each Sonotube contains an mdf “plug” inserted into the opening with the top and bottom redwood caps glued (Elmer’s carpenter glue) and screwed to them. The plugs are secured in place at the tops and bottoms by screws and PL constructive adlhesive. The bottom plates attached to the Sonotubes are held away from the bottom plates by three 2-inch dowel sections with drilled out centers and screwed in place by bolts threaded into t-nuts fitted between the stacked redwood bottom plates. There has to be spacing down there for the downward-aimed port tube to “breathe.”

On top, a thin redwood, driver-protecting plate is held off from the top Sonotube plate by three 2.75-inch dowels also drilled out, with machine screws tapped into t-nuts and with brass cap nuts on the very top. The upward-facing Titanic driver does not have interaction problems with that protective plate, because the spacing is not close enough to matter.

The cylinder interior is covered with .75-inch fiberglass batting (furnace-wrap) held in place with Scotch photo-mount spray-on glue.

Redwood has a natural red look, but to goose that a bit I stained the surfaces with Minwax red-oak stain (applied and removed quickly to keep things from getting too dark), and then the plates were given five coats of Minwax spray lacquer. The first three were high gloss, with the last two satin. Actually, I may go back and give the protective top plate a sixth coat, again with high gloss, which in this case may be better than satin. The plate is easy to remove and reinstall.

Each tube was painted flat black, and each is wrapped in conventional speaker grill cloth material. To cover up the ragged edges of the cloth at the top and bottom, a heavy felt band was wrapped around and secured in back with Gorilla tape. The backs of these subwoofers are not meant to be seen.

Sonotube is actually dense cardboard, 3/8-inch thick, and one would think that it was not particularly strong enough to make a subwoofer enclosure. However, remember that box-shaped subwoofers have walls that are trying to flex into a circular shape when strong bass notes happen. Sonotube is already circular and because it is obviously strong enough to hold a mass of wet concrete it is obviously not going to stretch when put under stress. The bottom plate, with the double redwood and mdf interior plug is 2 inches thick and the top plate is mostly filled up with a woofer driver, and so there is not much flexing going on with them. The result is an enclosure that is surprisingly inert. Companies like Hsu Research and SVS have used Sonotube material successfully in their subwoofer designs for years.

These two units are powered by the same stereo amp that I use to power the subwoofers in the main system: a 350-watt-per-channel Crown XLS1000 that I got from Parts Express for 300 bucks. A Hsu “Optimizer” equalizer adds some electronic bass boost below 35 Hz (subs like this begin to gradually roll off below that frequency), and the sub-EQ section of a Rane THX-44 equalizer is used to flatten some room modes between 90 and 30 Hz. The result is very good acoustic performance.

Howard Ferstler

14 comments so far

View Lanaug's profile


188 posts in 3550 days

#1 posted 08-20-2012 12:57 PM

wow, I bet that room sounds nice. Very nice setup and looks great. Do the sonotubes have to be that tall to sound right or could they be shorter?

View Bertha's profile


13624 posts in 4034 days

#2 posted 08-20-2012 01:20 PM

That’s really fine work. I bet the top baffle in front of the driver really makes a difference with the bass. It’s like a giant bazooka. I used to be really into music, still am, I guess. I need the low frequency stuff too and my theater/music room is the same room. I’ve got a velodyne 18 and a Mirage bipolar. The velodyne will literally take your breath away. It’s an unpleasant feeling if you get near it when it’s really moving.
I really love your sub.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View ferstler's profile


342 posts in 4862 days

#3 posted 08-20-2012 01:25 PM

Hey, Lanaug, thanks for the thumbs up.

No, they do not need to be all that tall. You could use a larger diameter tube and just make it shorter. Hsu Research did that years ago with one of its early models.

The idea is to have the right internal space, in combination with the proper tube diameter and length. I prefer a 4-inch diameter, with flared ends, to keep wind turbulance under control. The earlier ones I built were 5 cubic feet and these newer ones are 4 cubic feet. The Hsu Research TN1220 sub was about 3 cubic feet, and the SVS 16-46 model was 5 cubic feet.

There are some helpful internet sites out there that will make it easy to calculate the parameters for cylinder subwoofers.

First, you need to calculate the area of a circle that will be the internal diameter of the Sonotube you intend to use. To do that you can go to:

Note that Sonotube diameter measurements are for the interior diameter. Many good lumberyards carry the things, and usually they are only available in 12-foot sections. I got my 12 footer for 60 buckis at a local yard and cut it into three four-foot sections. I therefore have one four footer left over and I have a Destijl driver in storage that I might combine with the tube to make a sub that I could sell cheap to a friend. An outboard sub amp would be needed, of course, and they would have to buy that item on their own.

Anyway, with that area size calculated in square inches, you multiply it times the height of the Sonotube. This will give you the internal displacement in cubic inches, and all you then have to do is divide by 1728 (the number of cubic inches in a cubic foot) to get the displacement in cubic feet. It can be a decimal number like 4.6 or 3.2 and does not have to be exactly 3, 4, or 5 cubic feet for the next calculations.

Those next calculations involve finding the right port-tube size. To do that you can go to:

Using this, you can determine how big a port tube to buy (I recommend using tubes with flares at both ends) and what tuning frequency you want. Remember, below that tuning frequency some woofer drivers will begin to distort considerably, so you have to be sure just how low you want to go. Obviously, the lower you go the bigger the enclosure needed and the bigger the tube, too. Fortunately, the Dayton Titanic drivers used in the recent project do not have any problems below the 22-23 Hz tuning frequency of my enclosures, a nice characteristic. For home theater I recommend the Titanics; for music I recommend the Dayton Reference series units, although the latter are actually more than adequate for all but the most wham-bang program sources..

I got my drivers from Parts Express, and also got the port tubes from them, too. I also got the binding clips and grill-cloth material from them, as well as both of the Crown XLS1000 amps used for both subwoofer projects. I order by phone out of their catalog, but they also have a web site at:

This is a fine company and I have used them for years.


View ferstler's profile


342 posts in 4862 days

#4 posted 08-20-2012 01:33 PM

Hi, Bertha,

I had a Velodyne F1800 series II for years and sold it to a buddy. I also had a Hsu VTF-3 (MK4) in the room that now holds the two new cylinder subs. Both the Velodyne and the Hsu were terrific, but if you look at the photo of the room you can see that they would just not integrate with the decor along that wall.

I used to be an audio product reviewer (I also published two books on audio and home theater, two more dealing with record reviews, and also did writing and editing work for the second edition of “The Encyclopedia of Recorded Sound”) and wrote reviews of those Velodyne and Hsu units (and also the later HGS 15 and HGS 12 Velodynes), as well as units by SVS, Triad, Polk, Paradigm, and others, and I will say that the Velodyne servo units are champs when it comes to low distortion. (The big Servo 15 that Paradigm had a while back was also excellent.) With most sources (including pipe organ) super-low distortion is almost overkill, but like car horsepower you cannot have too much of a good thing, and low distortion is a good thing.

These new units I built are mainly for home theater, but I gave them a spin with some pipe-organ music yesterday and they are almost equal to the bigger units in the main music room. Good subwoofers are a good thing to have.


View ChrisK's profile


2061 posts in 4423 days

#5 posted 08-20-2012 01:44 PM


Impressive work. How do you like the Dayton speakers. I am in the design process for the Dual 8” woofers for the L and R speakers for a surround system and I was planning on using st210-8 in parallel. My only experience with Dayton was two subs with there 8” Quattros (I think) both died in less than two years.

-- Chris K

View bunkie's profile


417 posts in 4488 days

#6 posted 08-20-2012 02:00 PM

Chris K,

I entered the speaker competition at this years Midwest Audio Fest and a there were a number of very nice sounding systems using the Dayton Reference drivers. I’m looking very seriously at the 8” woofers for a transmission-line application as they have an incredibly low Fs which should translate to flat response down to 20hz! They also seem to do well in the upper midrange and that leads me to believe that with a good tweeter with an Fs around 1500hz, I should be able to produce a very decent two-way system.

I have to say that PartsExpress has really done a great job with their offerings.


Very nice job with the subwoofers! I’ve wanted to use Sonotubes in a speaker application for quite some time. I had a thought of using two tubes, one inside the other and filling the space with sand (Wharfdale did this back in the day).

In any case, it’s great to see more speaker projects here on LJ. we’ll never achieve the same numbers as the cutting-board contingent, but I’m glad there are at least a few of us trying our hand at it.

-- Altruism is, ultimately, self-serving

View ferstler's profile


342 posts in 4862 days

#7 posted 08-20-2012 02:11 PM

Hi, ChrisK,

The 12-inch Titanics I first used in the bigger systems were quite good down to 25 Hz at even hgih levels. However, at those same high levels at 20 Hz the drivers emitted some “ticking” noises. No big deal most of the time, but that is a music system and purity is important. I deal with a chat group on Parts Express and I querried some of them about the Titanic drivers vs the Reference Series drivers, and the consensus was that the Reference units were cleaner, although with a greater xmax (14 mm vs 18 mm) the the Titanics should theoretically be able to play louder and resist damage better at head-banging levels. (Incidentally, the Titanics are made in USA and are cosmetically excellent; the Reference units are made in Taiwan, and are cosmetically no better.) So, I ordered some 12-inch Reference units and swapped out the Titanics. I had planned on building some additional subs, anyway, and now I automatically had my second pair of drivers.

The result was about the same, except down at 20 Hz, where the Reference units were indeed less noisy; very clean, actually. That left the Titanics, and so we have them now in the new systems. Those are mainly for home theater and they should do just fine. Interestingly, the Titanics cost about $170 each and the Reference units cost about $150, and yet the latter are heavier (25 pounds vs 20 pounds). Usually, the more expensive speakers a company sells (and the Titanics are Dayton’s top-advertised models at Parts Express) are at the very least heavier than the cheaper models. Well, in any case, the combinations I have now work very well in both rooms.

Obviously, any driver will die if pushed hard enough. I have drivers here (mostly Allison models in my various Allison speaker systems) that are 35 years old and still work fine. Usually, the surrounds (if they are urethane foam, at least) will rot out, but I have replaced many of those. Spiders can often become a tad brittle, too. Driver voice-coil wire should last indefinitely, unless the speakers are played continuously so loud that the insulation melts and they coils short out. If the wire itself melts, or the coil jumps out of the gap and perhaps the cone itself warps, well we thn have us a customer who likes his program sources playing very loud, indeed.

I think that car audio speakers take a much greater beating than home-audio versions, mostly due to the weather extremes. In that case, all bets are off with any types one obtains.


View Bertha's profile


13624 posts in 4034 days

#8 posted 08-20-2012 02:16 PM

Thanks, Howard. I built a few pairs of speakers many years ago, before the high end separates were available (if they were, I couldn’t find them). I have some Paradigms and a bunch of Mirage right now. My ears never needed much more (between Slayer concerts and powertools). I’m curious about your amplification. I always had a thing for amplifiers. I’m a Krell guy but I’ve always wanted a McIntosh.
And yeah, the Velodyne isn’t the easiest thing to tuck into your decor, lol:) At least it’s not a Vega;)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

View ferstler's profile


342 posts in 4862 days

#9 posted 08-20-2012 02:18 PM

Hi, bunkie,

I have read about the double-Sonotube approach, but I do not think it is necessary. I have pushed some loud and low bass into both of my pairs, and have felt the outside of the cylinder walls while this is happening, and they are not vibrating any more (and probably less) than what I can feel when touching the outsides panels of the various Hsu, Velodyne servo, and Paradigm models I have had on hand here in the past. I have also reviewed (and owned) several different Hsu and SVS cylinder subs, and those outfits did not see a need for a douoble-wall approach. The models from those companies got consistantly good published reviews, including reviews from me.

I figure that a 3/8 inch Sonotube is designed to hold a LOT of concrete weight when being used as a post mold, and it is not about to stretch or flex much when facing some wimpy woofer waves.

I keep a Parts Express catalog in my bathroom, ready to read for entertainment and enlightenment when nature calls.


View ferstler's profile


342 posts in 4862 days

#10 posted 08-20-2012 02:34 PM

Hi, Bertha,

I got each of the Crown XLS1000 amps from Parts Express for $299, plus about $5 shipping. They got here in two days and both have worked perfectly. They are very flexible units to use (check the internet sites out there for more tech info) and they are digital class D designs that run cool, and I mean cool. They have fans, but the fans are nearly silent (you have to put your ear against the front panel to hear them at all), and the XLS1000 only weighs in at about 8 pounds!! They might heat up a bit with full-bandwidth work, but with a subwoofer hookup they just are not working all that hard. The XLS1000 version can pump juice into 8- and 4-ohm loads, but can also driver 2-ohm loads, something unheard of with many other designs. The XLS1000 is rated at 350 wpc into the 4-ohm impedances of any of my drivers. They also have XLS1500, 2000, and 2500 versions that are VERY powerful.

They can be found in the Parts Express “pro” section, and what sets them apart from most of the other pro brands is that in addition to balanced and jack inputs they also have RCA inputs, and five-way binding post outputs in addition to speakeron outputs. This makes them workable for both hobby types and pros.

Class D amps have a tad more distortion than other types, but from what I gather they still are as subjectively clean as anything else out there. The important thing is that “subjective” term. Other amps may measure a bit better, but the proof is in the listening.

Years ago, Tom Nousaine loaned me his QSC double-blind Comparator to do some A/B testing with various amplifiers. I compared all sorts of brands, from budget receivers (input via the aux inputs) to more upscale stuff made by guys like James Bongiorno and Bob Carver) and I never could hear a difference. (Neither could several guests I had over, and Nousaine has never found anybody who could hear differences, either, at least up to the clipping points of the weaker amps in the comparisons.) The trick is to get the levels PRECISELY matched on each channel before doing the comparing. Without precise matching any kind of amplifier A/B comparison is a waste of time. Also, doing comparing sighted, without a blind protocol, allows even the most level-headed participant to let preconceptions color their perceptions.

Anyway, for subwoofer use the Crowns are plenty good enough, since distortion down below 100 Hz is not as big a deal ast it is at higher frequencies.


View lumberjoe's profile


2902 posts in 3590 days

#11 posted 08-20-2012 10:31 PM

My two favorite passions in one! Sound and woodworking. This is awesome. I am going to apologize in advance if you mentioned it, but I am in awe of the pics and had to ask a few questions.
1 – I take it your are an audiophile. I am looking to move my velodyne optimum 12 from the music room to the home theatre. It is too “boomy” and over powering for music enjoyment. I see you reviewed home audio equipment in the past, so you likely speak my language :). In the Home theatre I have a Denon AVR5800 fed by a Tag McLaren AV 32RDPEX. Both of which I got used at a substantial discount. I am not that big of a high roller. I have a set of PSB Image 10 series towers and PSB book shelf rears, as well as infinity beta series centers (front and rear). Not the best stuff, but good enough for movies and TV. I think the optimum 12 would fit in well there.

Now to the Music room. I need something that will compliment my Mac tube amp (also a discount but not as substantial) fed Bowers and Wilkins CM9’s. This room is set up exclusively for stereo music enjoyment. No multi stage arrangement. 2 speakers, 1 chair. I find they do need a sub to reproduce deeper bass at lower listening volume. I’d love to build something as you did. What driver would you recommend?



View dust4tears's profile


397 posts in 3490 days

#12 posted 08-21-2012 12:21 AM

@Lumberjoe, I have a Denon, with Boston acoustics~~it is a bad a$$..

This is a question for everyone. This is a project idea I have had for a lil’ bit~~~can you tell me if it is feasible for a reasonable cost? So that I do not take away from Ferstler’s post….I want to ask the question and if y’all say it is a possibility I will start my own forum topic….and prolly ask Ferstler, Lumberjoe, and everyone else a ton-o-questions~~~
I want to buy an ‘iHome’ device for my iPhone…..for my garage. I was hoping I can build a tube like you did~~to amplify the sound of the iHome, so that I can rock my garage out…over the sound of tools. I know I can buy loud systems, but I am trying to keep it simple. My garage is an accident waiting to happen and I do not want to put expensive audio equipment in my greased, saw-dust filled 1 car garage. I want my design to keep dust out, and airflow for the electronics in~~~
I have a BASIC~intermediate~ish understanding of electronics and electrical work…and basic knowledge of acoustics~~from my Navy days.
I havent bought the iHome yet, my wife is going to go to local pawnshops tomorrow to try and find one someone will trade for an AMP that was given to me.~~~~So, I do not know any specifics yet.

Like I said, I am NOT looking to ‘hijack’ your post~~~I am just asking~~~because this has been a thought in my brain, but didnt know where to start~~~~~~and then your post…...I was like, ‘Eureka!!!!!!!~~~~~and just had to ask…..

If you folks are kind enuff’ to answer, please keep it to yes, it is worth looking into, or no it isnt.

I do not want to ‘take away’ from Ferstler bad ass speakers.

(Meeee meeeanzzzz no disrespect askin’ on your post.)

-- Ride hard or go home~

View ferstler's profile


342 posts in 4862 days

#13 posted 08-21-2012 12:47 AM

Hi, lumberjoe,

My experiences with raw drivers is limited (product reviewers usually review finished systems made by commercial outfits), but for serious musical work I would recommend the Dayton Reference Series driver from Parts Express in whatever size you need. That line actually sells for a bit less than their Titanic Series models in the same sizes, but the Reference versions are definitely cleaner down below 25 Hz. I had the 12-inch Titanics in my main-room system enclosures for a while, and even though they worked OK, they were a bit “ticky” sounding down really low and really loud. You would not notice this with home-theater action movies, but it would show up with powerful organ works, many of which I have.

I replaced the Titanics with 12-inch Reference models and they were cleaner down there. Interestingly, even though they cost less than the Titanics the Reference units are more massive units (25 pounds vs 20 pounds). The Titanics have a greater xmax (18 mm vs 14 mm), but while that can impact ultimate loudness abilities, it does not necessarily impact the distortion levels at least up to the limits of the shorter-throw driver.

Both are OK, but if I had to choose one for all types of program sources I would opt for the Reference line. Now, there probably are better drivers from outfits like TC Sounds (I have auditioned one of their AudioMobile models) and Peerless and Scanspeak, but those are going to be considerably more expensive than the Dayton lineup.

For the record, the tall speakers in front of the bookcases shown in the above photos were built by me from scratch, using Allison tweeters (Roy Allison is a good friend of mine), Tang Band mids, and Allison woofers, with me doing all the crossover voicing, and they perform very well. (I measure with an AudioControl SA-3051 RTA to get a good room curve by means of the unit’s time-averaging function, which I consider more important than typical, close-up or gated direct-field measurements.) Unfortunately, Allison is no longer in business, so getting his drivers is out. He never made subwoofer drivers, anyway.

My main system has large Allison IC-20 models for the mains (completely refurbished by me a while back), and home built (with Allison drivers) center channel. My two processors are a Yamaha receiver and integrated amp, which I like for their reliability and surround-synthesis qualities. The main system has four Allison Model Four surround speakers (also refurbished by me), and I use the Yamaha surround-synthesis feature for all of my musical listening.

The big Allison speakers are pictured in that first article I referenced above dealing with my first subwoofer construction project.


View ferstler's profile


342 posts in 4862 days

#14 posted 08-21-2012 12:54 AM


Read my response to joe, above for info on drivers. I think that the Dayton Titanics and Reference units are suitable for automobile use, which means they should work in a garage environment, too. The magnet areas of those woofers are vented, by ther way, so if you use them or use any kind of woofer drivers with vented magnets I suggest you use a sealed enclosure to keep garage and any woodworking dust out of the works. Ported enclosures are a no no in such a situation. Parts Express also has kits that use those drivers, so you can give them a lookover if you check out their site. A Sonotube is probably not the best material for building a sealed subwoofer enclosure, with a conventional box design a better idea.

PS: Boston Acoustics makes some fine speaker systems.


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