I keep telling myself I gotta try out a sonotube type enclosure one of these days. The benefit that gets me going about it is because of it's cylindrical shape there is not the flexing (and therefore need of bracing) that you get with a conventional wooden box-shaped enclosure. No panel vibration = clean sound, more predictable frequency response & higher power handling.
Most people seem to make one of these things from a large diameter cardboard tube normally used by the construction industry for pouring concrete into to make supporting pillars for buildings etc. Anyway, I got to thinking about stuff and it seems to me that you could make a workable unit from an old propane cylinder. You still have the same advantages from the cylindrical shape of course, and the sealed end is already sealed (well, duh!) and it is a dome shape so it's rigidity is enormous! All you have to do once you have cut off the valve end at (maybe) the full diameter of the cylinder is weld on a circular flange to mount the driver. A certain amount of damping material to line the inside surfaces too.
The setup I want to try in particular is a 2-chamber, 2-port bandpass unit made from a large and small cylinder face-to-face with the driver at the junction of the two but I haven't decided whether to have the ports come out the side just near the driver, or at the extreme ends of the cylinders.
Depending on the frequency range pumped into the system, it might be useful to have a layer of carpet or similar wrapped around the outside to absorb any tendency ring, depending also on the thickness of the metal. Hmmm.....
Most people seem to make one of these things from a large diameter cardboard tube normally used by the construction industry for pouring concrete into to make supporting pillars for buildings etc. Anyway, I got to thinking about stuff and it seems to me that you could make a workable unit from an old propane cylinder. You still have the same advantages from the cylindrical shape of course, and the sealed end is already sealed (well, duh!) and it is a dome shape so it's rigidity is enormous! All you have to do once you have cut off the valve end at (maybe) the full diameter of the cylinder is weld on a circular flange to mount the driver. A certain amount of damping material to line the inside surfaces too.
The setup I want to try in particular is a 2-chamber, 2-port bandpass unit made from a large and small cylinder face-to-face with the driver at the junction of the two but I haven't decided whether to have the ports come out the side just near the driver, or at the extreme ends of the cylinders.
Depending on the frequency range pumped into the system, it might be useful to have a layer of carpet or similar wrapped around the outside to absorb any tendency ring, depending also on the thickness of the metal. Hmmm.....
The safety aspects involved with cutting and welding a propane cylinder make that a very bad idea! A great way to loose a hand. Even an empty cylinder still conatins some propane, just not under pressure. When you cut that cylinder, the sparks you create have a very high chance of igniting that propane, and causing an explosion.
A used but empty propane cylinder can be safely cut with a torch or electric welded if completely filled with water, but being a machinist myself I think it is not the way to go. Besides being a lot more work there is one reason here that still applies that causes people almost exclusively to never make HiFi speaker cabinets out of steel. If you don't know, rap the cylinder with your knuckles to find out. 
They don't make church bells out of sonotube for the same reason. One of these materialsd rings like a bell and the other doesn't, ...at least that's my story and I'm sticking to it!
They don't make church bells out of sonotube for the same reason. One of these materialsd rings like a bell and the other doesn't, ...at least that's my story and I'm sticking to it!
Propane is heavier than air. Even though the propane tank seems to be empty there can be residual propane laying in the bottom of the tank. The only way to empty the tank of propane completely is to displace the propane with some other medium. The easiest would be water. Beware, as you fill the tank with water you are forcing the residual propane gas out of the tank. Do not do this anywhere near an ignition source. Once the tank has been completely filled with water, it can be emptied and cut.
You ever bang to tanks together by accident? What did it sound like? Get used to it as the speaker will have the same sort of ring to it. The reason sonotube is used instead of metal is that it is selfdamped, i.e. no ringing. Besides that, being a circle the sonotube is very rigid when it comes to pressure changes. Thats why it is used for a concrete form, if it was square it would bulge under the pressure of the concrete inside. If you really have a problem with the sonotube then go get some thick walled pvc sewer pipe. It works very well and can be cut and glued easily.
I'm sure he is planning to coat the tanks inside with some sort of tarlike substance. Ever bang two tanks together with a bitumin layer on the inside of them? Well, probably not, but I don't think there is going to be much ringing.... Also using them as enclosures isn't really the same thing as banging them together.
They will have a great advantage on lower notes in that the walls practically won't flex at all.
The high end Krell speakers are made from very thick welded aluminum plate. While they wouldn't ever ring as well a single piece shape the would certainly ring if not damped and banged together. I guess they ARE damped because they are reputed to sound very good.
They will have a great advantage on lower notes in that the walls practically won't flex at all.
The high end Krell speakers are made from very thick welded aluminum plate. While they wouldn't ever ring as well a single piece shape the would certainly ring if not damped and banged together. I guess they ARE damped because they are reputed to sound very good.
I built a pair of MK-style port loaded TL's from 8" x 4" x 1/4" wall steel rectuangular tube using TB W4-657B's. Unless you're prepared to go to extraordinary lengths to damp structural resonances, I wouldn't recommend steel. Though so far glueing homemade constrained layer damping panels (1/8" aluminum bonded to linoleum tile) to all interior surfaces, replacing the steel mounting hardware with nylon and standing the driver on a 3/16" rubber o-ring have done wonders to reduce cabinet talk, it's not yet gone. The only thing I can think left to try is wrapping the exterior with leather - for that Euro look - or vinyl/rubber to suppress cabinet radiation.
The frustrating part is the potential screams out every time the needle drops. The sound is quick, lively, and the bass is obviously as tight as your design, but there's always an underlay of nasality that wears after extended listening. That and an accidental drop can break your foot. No joke, these things tip the scales at close to 40 lbs a side and cut through floor tile like butter. Not at all kid safe.
The frustrating part is the potential screams out every time the needle drops. The sound is quick, lively, and the bass is obviously as tight as your design, but there's always an underlay of nasality that wears after extended listening. That and an accidental drop can break your foot. No joke, these things tip the scales at close to 40 lbs a side and cut through floor tile like butter. Not at all kid safe.
Isuppose it's conceivable that
I could be wrong....
It looks like the steel enclosures are on separate stands.
It would be a lot safer and prob sound better if you welded a column to the bottom of the enclosure and a plate on the bottom of that to have integrated stands..
Oh yeah- you have all the stuff glued to the inside which would prob catch fire..
They sure are beautiful though...
I guess aluminum generally would ring less and the thicker plates per given weight would be helpful.. I trhink the Krell are half inch plate
I could be wrong....
It looks like the steel enclosures are on separate stands.
It would be a lot safer and prob sound better if you welded a column to the bottom of the enclosure and a plate on the bottom of that to have integrated stands..
Oh yeah- you have all the stuff glued to the inside which would prob catch fire..
They sure are beautiful though...I guess aluminum generally would ring less and the thicker plates per given weight would be helpful.. I trhink the Krell are half inch plate
water jet cutting
perhaps it would be even safer if you live near a water jet cutting facility. Of course, they'd probably be wary of cutting the tank if ownership/legality is in question.
Rdf, those steel speakers look great! I'd love to see what they look like if you cover them in leather. Or maybe carpet or faux fur?
perhaps it would be even safer if you live near a water jet cutting facility. Of course, they'd probably be wary of cutting the tank if ownership/legality is in question.
Rdf, those steel speakers look great! I'd love to see what they look like if you cover them in leather. Or maybe carpet or faux fur?
Thanks Variac! You're right, those stands are rock bottom. $99 Future Shop specials, I was tired of looking at T-lines on chairs. The stands will sub for wind chimes or bells in a pinch.
Steel has a couple additional unique consequences I forgot to mention. Internal crossovers, for example, are a no-no. Can't put inductors near than much magnetic metal. Also internal wall damping becomes mandatory. Wood has at least some absorption at higher frequencies. There's a reason plate reverbs used metal.
Aluminum, especially sandwiched with linoleum, shows far more promise.
Steel has a couple additional unique consequences I forgot to mention. Internal crossovers, for example, are a no-no. Can't put inductors near than much magnetic metal. Also internal wall damping becomes mandatory. Wood has at least some absorption at higher frequencies. There's a reason plate reverbs used metal.
Aluminum, especially sandwiched with linoleum, shows far more promise.
Propane tanks etc..
I've built a couple of cylndrical models.
See one of them attached. Carbon fiber wrapped sonotube. Its a bass guitar cab I'm experimenting with.
It's true - a cylinder is a great cab - virtually no wall vibrations while still lightweight - although I do think steel would ring, untreated.
What I might do if I had a propane cylinder is use it as a form to wrap Kevlar or carbon fiber. You'd need a lot of layers. I'd grease the steel so the fiber will slip off when its cured.
Cutting and gluing baffles is tricky. The slot needs to be perfect.
You could leave the propane tank in there as additional structure and the carbon fiber would damp it. I'd damp the inside with spray foam. sticks to anything. Another thing I'd do is ground the chasis so to speak. The steel and the carbon fiber are both conductors so this might make a great rf sheild as a fringe benefit.
For design, Bass Box Pro has a built in cylinder design option - which saves a lot of number crunching. I'd probably try a sealed design if I could find a woofer that liked a sealed cab with the volume represented by the tank. That would challenge the structural advantages of the cylinder (in a good way). ted.
I've built a couple of cylndrical models.
See one of them attached. Carbon fiber wrapped sonotube. Its a bass guitar cab I'm experimenting with.
It's true - a cylinder is a great cab - virtually no wall vibrations while still lightweight - although I do think steel would ring, untreated.
What I might do if I had a propane cylinder is use it as a form to wrap Kevlar or carbon fiber. You'd need a lot of layers. I'd grease the steel so the fiber will slip off when its cured.
Cutting and gluing baffles is tricky. The slot needs to be perfect.
You could leave the propane tank in there as additional structure and the carbon fiber would damp it. I'd damp the inside with spray foam. sticks to anything. Another thing I'd do is ground the chasis so to speak. The steel and the carbon fiber are both conductors so this might make a great rf sheild as a fringe benefit.
For design, Bass Box Pro has a built in cylinder design option - which saves a lot of number crunching. I'd probably try a sealed design if I could find a woofer that liked a sealed cab with the volume represented by the tank. That would challenge the structural advantages of the cylinder (in a good way). ted.
Attachments
OK then, safety issues aside, I was thinking that if you didn't drive such a system with greater than 100Hz or so and wrapped it with carpet then ringing wouldn't be much of a problem. If it did turn out to be so then maybe you could build an outer box around it from say 12mm MDF and fill the space between the cylinder and the box with sand or rags or whatever. At least it would then look a bit more conventional, with the added benefit of enabling wifey-type loungeroom objects to be placed on it.
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