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Cylindrical vs. box shaped subwoofers
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Barkingspyder
Jul 15, 2012, 11:09:10 AM7/15/12
to
Are there any advantages other than a smaller foot print for
cylindrical subwoofers? Do they require damping material in the
same way a box would?
I'm considering a DIY project and would be curious as to the science
on this topic. Are there the same problems with vibrations inside
the enclosure, or does the cylinder reduce or make them a non-issue?
I see a lot of the sonotube desgins have the driver at one end and he
port at the other. Does it make any difference if they are are at
the same end of the tube assuming a large enough diameter?
I am considering a 143 L EBS alignment with both the port and the
driver at the bottom. The tube would be 20" in diameter and a 4"
port. I am not married to these dimensions but I thought there
would be a higher WAF if the thing looked less like a water heater.
Comments please.
cylindrical subwoofers? Do they require damping material in the
same way a box would?
I'm considering a DIY project and would be curious as to the science
on this topic. Are there the same problems with vibrations inside
the enclosure, or does the cylinder reduce or make them a non-issue?
I see a lot of the sonotube desgins have the driver at one end and he
port at the other. Does it make any difference if they are are at
the same end of the tube assuming a large enough diameter?
I am considering a 143 L EBS alignment with both the port and the
driver at the bottom. The tube would be 20" in diameter and a 4"
port. I am not married to these dimensions but I thought there
would be a higher WAF if the thing looked less like a water heater.
Comments please.
Gary Eickmeier
Jul 16, 2012, 9:59:04 AM7/16/12
to
"Barkingspyder" <kmck...@roadrunner.com> wrote in message
news:a6g4om...@mid.individual.net...
Hi Barking -
Some comments from a friend:
"Well, in theory a box-shaped sub enclosure will try to flex its wall inward
or outward as the cone moves in and out, with the idea being that the
pressure is trying to turn the box into a sphere.
A cylinder-enclosure shape, even with the cylinder walls only 3/8 inch
thick, cannot flex inward or outward (assuming the Sonotube fiber material
is decently strong in terms of stretch resistance, and believe me, Sonotube
is strong), because the surface is already curved to a circle. Yes, it is
not a sphere, but the top plate cannot flex outward or inward, because it is
mostly filled with the driver, and the bottom plate cannot flex much,
because it has the port tube in there reinforcing it and the thing is
usually too thick to flex much, anyway. My bottom plates are each 2.25
inches thick, for example, with the bottom plate itself standing on 3-inch
pegs that themselves are screwed to still another bottom plate. (There is a
similar standoff plate on the top that is there simply for cosmetic purposes
and to protect the driver cone.) The inside of the Sonotube should be
layered with a couple of inches of fiberglass (mine is held in place with 3M
spray adhesive, and the fiberglass is actually furnace pipe wrap with the
foil removed), and the idea there is for the heating and cooling of the
fiberglass under pressure (which can occur at any frequency above the port
resonance) to help the driver to "see" a larger interior space than is
actually there. (Acoustic-suspension woofers and subwoofers also have
something like that in their cabinet interiors for the same reason.) The
effect is actually minimal, but in any case the fiberglass is not there to
control resonances or absorb noise. Resonances are minimal with a cylinder
enclosure, actually, due to the lack of glued-together speaker-wall joints.
In any case, in practical terms, a Sonotube enclosure should be the most
resonant-free enclosure possible for a subwoofer, although the light weight
is a theoretical problem - that I have not encountered.
It really does not matter where the port is, although it can if the
woofer/port interface is not quite right.and the driver and port are side by
side The first successful commercial sub Poh Ser Hsu made was a pretty fat
cylinder and both the driver and the port were on the bottom. Later Hsu
models like the TN1220 had the driver at one end and the port at the other,
as did (and do) the SVS cylinder models. Ditto for the units I made for my
main audio system. If the port and driver are on the bottom, the designer
can have an attractive top on the cabinet that will allow it to function as
an end table, or the like. However, the light weight of a sonotube enclosure
will allow the entire unit to vibrate up and down, which might make that
table lamp dance around a bit.
There obviously is an advantage to a smaller footprint with a tall, skinny
design, if floor space is critical, but of course what you gain in in terms
of left-over floor space you lose in terms of space above the unit. No free
lunch there, particularly if the wife does not like to see cylinder-sub
towers rising towards the ceiling. (Fortunately, my wife may actually like
the looks of my units.)
What can matter when it comes to how low the sub can go, in additon to
port-tube length and diameter (and of course driver design), is the interior
space of the enclosure. There are web-sites out there that help the user to
calculate both interior cabinet space with a cylinder (square inches of
circular area can be calculated with one site; times length of Sonotube) as
well as the required tube length and diameter with a given enclosure space
and desired tuning frequency. The calculating can be done in less than a
minute, actually. Once that math work is done, all one need do is order the
parts (the driver, the Sonotube, which comes in 12-foot lengths and
obviously has to be cut down, mdf to make end plugs, port-tube materials,
screws, glue, and grill fabric). You need the grill fabric to wrap around
the finished product to keep it from looking, as the poster noted, like a
black-painted water heater, tall or short. Heck, grill cloth comes in a
variety of colors and one can even go to a fabric store and look through all
sorts of nifty designs. A bright red cylinder sub would look really cool.
Mine are both black, however, in keeping with tradition.
Note that the pair in my main room are now using 12-inch, Dayton Reference
Series drivers instead of the 12-inch, DaytonTitanic drivers I first tried.
They go down to the bottom end a bit smoother than the Titanics (although
theoretically they cannot play as loud, but can play plenty loud enough) and
have less cone-flex noise. The full systems are 68 inches tall and 14 inches
in diameter, although the Sonotubes themselves are only 56 inches tall (the
additonal 12 inches involve end plugs and standoff bottom and top plates),
giving they an interior volume of 5 cubic feet. This allows tuning to 19 Hz,
and to keep things really smooth I equalize the bottom seven 1/3-octave
points with an ART EQ-351 equalizer. The result is the best sub-extension
measurements I have encountered in that room. Power for the two subs, as I
may have noted before, is via a Crown XLS1000 digital D class, 700-watt
power amp. This is not a super-low distortion amp, but it is more than
adequate for sub driving, and has RCA jacks for an easy interface with a
consumer-grade receiver sub-out hookup. Seven hundred watts is way, way more
power than I need (the room is 3400 cubic feet, and the amp/sub pair combo
can give me 115 dB at 30 Hz with ease, and almost as much at 20 Hz), but I
got the amp cheap from Parts Express. The damned amp weighs less than 9
pounds (each cylinder sub weighs in at about 50 pounds, including driver, by
the way, making them featherweights in the super-sub sweepstakes), and it
has a cooling fan that is so silent that you have to put your ear against
the front panel to hear it running.
I plan on building two more for my AV system in the back area, using the now
spare Titanic drivers (which are better for home theater, anyway, than the
Reference units), mounted in same diameter enclosures as what I have in the
main room, but with a height of 58 inches. They will be tuned to about 24
Hz - proper enough for home-theater use. A second Crown XLS1000 will do the
powering work, and I will use an existing Rane THX-44 and outboard Hsu
"Optimizer" equalizer to fine-tune the response smoothness and extension."
End quote.
Gary Eickmeier
news:a6g4om...@mid.individual.net...
Some comments from a friend:
"Well, in theory a box-shaped sub enclosure will try to flex its wall inward
or outward as the cone moves in and out, with the idea being that the
pressure is trying to turn the box into a sphere.
A cylinder-enclosure shape, even with the cylinder walls only 3/8 inch
thick, cannot flex inward or outward (assuming the Sonotube fiber material
is decently strong in terms of stretch resistance, and believe me, Sonotube
is strong), because the surface is already curved to a circle. Yes, it is
not a sphere, but the top plate cannot flex outward or inward, because it is
mostly filled with the driver, and the bottom plate cannot flex much,
because it has the port tube in there reinforcing it and the thing is
usually too thick to flex much, anyway. My bottom plates are each 2.25
inches thick, for example, with the bottom plate itself standing on 3-inch
pegs that themselves are screwed to still another bottom plate. (There is a
similar standoff plate on the top that is there simply for cosmetic purposes
and to protect the driver cone.) The inside of the Sonotube should be
layered with a couple of inches of fiberglass (mine is held in place with 3M
spray adhesive, and the fiberglass is actually furnace pipe wrap with the
foil removed), and the idea there is for the heating and cooling of the
fiberglass under pressure (which can occur at any frequency above the port
resonance) to help the driver to "see" a larger interior space than is
actually there. (Acoustic-suspension woofers and subwoofers also have
something like that in their cabinet interiors for the same reason.) The
effect is actually minimal, but in any case the fiberglass is not there to
control resonances or absorb noise. Resonances are minimal with a cylinder
enclosure, actually, due to the lack of glued-together speaker-wall joints.
In any case, in practical terms, a Sonotube enclosure should be the most
resonant-free enclosure possible for a subwoofer, although the light weight
is a theoretical problem - that I have not encountered.
It really does not matter where the port is, although it can if the
woofer/port interface is not quite right.and the driver and port are side by
side The first successful commercial sub Poh Ser Hsu made was a pretty fat
cylinder and both the driver and the port were on the bottom. Later Hsu
models like the TN1220 had the driver at one end and the port at the other,
as did (and do) the SVS cylinder models. Ditto for the units I made for my
main audio system. If the port and driver are on the bottom, the designer
can have an attractive top on the cabinet that will allow it to function as
an end table, or the like. However, the light weight of a sonotube enclosure
will allow the entire unit to vibrate up and down, which might make that
table lamp dance around a bit.
There obviously is an advantage to a smaller footprint with a tall, skinny
design, if floor space is critical, but of course what you gain in in terms
of left-over floor space you lose in terms of space above the unit. No free
lunch there, particularly if the wife does not like to see cylinder-sub
towers rising towards the ceiling. (Fortunately, my wife may actually like
the looks of my units.)
What can matter when it comes to how low the sub can go, in additon to
port-tube length and diameter (and of course driver design), is the interior
space of the enclosure. There are web-sites out there that help the user to
calculate both interior cabinet space with a cylinder (square inches of
circular area can be calculated with one site; times length of Sonotube) as
well as the required tube length and diameter with a given enclosure space
and desired tuning frequency. The calculating can be done in less than a
minute, actually. Once that math work is done, all one need do is order the
parts (the driver, the Sonotube, which comes in 12-foot lengths and
obviously has to be cut down, mdf to make end plugs, port-tube materials,
screws, glue, and grill fabric). You need the grill fabric to wrap around
the finished product to keep it from looking, as the poster noted, like a
black-painted water heater, tall or short. Heck, grill cloth comes in a
variety of colors and one can even go to a fabric store and look through all
sorts of nifty designs. A bright red cylinder sub would look really cool.
Mine are both black, however, in keeping with tradition.
Note that the pair in my main room are now using 12-inch, Dayton Reference
Series drivers instead of the 12-inch, DaytonTitanic drivers I first tried.
They go down to the bottom end a bit smoother than the Titanics (although
theoretically they cannot play as loud, but can play plenty loud enough) and
have less cone-flex noise. The full systems are 68 inches tall and 14 inches
in diameter, although the Sonotubes themselves are only 56 inches tall (the
additonal 12 inches involve end plugs and standoff bottom and top plates),
giving they an interior volume of 5 cubic feet. This allows tuning to 19 Hz,
and to keep things really smooth I equalize the bottom seven 1/3-octave
points with an ART EQ-351 equalizer. The result is the best sub-extension
measurements I have encountered in that room. Power for the two subs, as I
may have noted before, is via a Crown XLS1000 digital D class, 700-watt
power amp. This is not a super-low distortion amp, but it is more than
adequate for sub driving, and has RCA jacks for an easy interface with a
consumer-grade receiver sub-out hookup. Seven hundred watts is way, way more
power than I need (the room is 3400 cubic feet, and the amp/sub pair combo
can give me 115 dB at 30 Hz with ease, and almost as much at 20 Hz), but I
got the amp cheap from Parts Express. The damned amp weighs less than 9
pounds (each cylinder sub weighs in at about 50 pounds, including driver, by
the way, making them featherweights in the super-sub sweepstakes), and it
has a cooling fan that is so silent that you have to put your ear against
the front panel to hear it running.
I plan on building two more for my AV system in the back area, using the now
spare Titanic drivers (which are better for home theater, anyway, than the
Reference units), mounted in same diameter enclosures as what I have in the
main room, but with a height of 58 inches. They will be tuned to about 24
Hz - proper enough for home-theater use. A second Crown XLS1000 will do the
powering work, and I will use an existing Rane THX-44 and outboard Hsu
"Optimizer" equalizer to fine-tune the response smoothness and extension."
End quote.
Gary Eickmeier
Barkingspyder
Jul 16, 2012, 5:07:25 PM7/16/12
to
On Monday, July 16, 2012 6:59:04 AM UTC-7, Gary Eickmeier wrote:
> "Barkingspyder" & wrote in message
> news:a6g4om...@mid.individual.net...
> > Are there any advantages other than a smaller foot print for
> > cylindrical subwoofers? Do they require damping material in the
> > same way a box would?
> >
> > I'm considering a DIY project and would be curious as to the science
> > on this topic. Are there the same problems with vibrations inside
> > the enclosure, or does the cylinder reduce or make them a non-issue?
> >
> > I see a lot of the sonotube desgins have the driver at one end and he
> > port at the other. Does it make any difference if they are are at
> > the same end of the tube assuming a large enough diameter?
> >
> > I am considering a 143 L EBS alignment with both the port and the
> > driver at the bottom. The tube would be 20" in diameter and a 4"
> > port. I am not married to these dimensions but I thought there
> > would be a higher WAF if the thing looked less like a water heater.
> >
> > Comments please.
>
> End quote.
>
> Gary Eickmeier
Thanks friend.
If you have the advantages of the curved shape and you have the right internal volume to begin with, ( I'll be using 143 liters with a Shiva MKII 12" woofer)
what actual need if any for the the fiberglass? As to fiberglass I would be hesitant about using it in a ported enclosure since the notion of fiberglass being pumped into the air from the port does not appeal to me. I t just seems to me that in 5 cu ft there is little chance of much heat developing, so little need for cooling. If it's necessary fine, but if not then why bother. I thought the main reason for damping material was to help absorb vibration and keep resonance down.
> "Barkingspyder" & wrote in message
> news:a6g4om...@mid.individual.net...
> > Are there any advantages other than a smaller foot print for
> > cylindrical subwoofers? Do they require damping material in the
> > same way a box would?
> >
> > I'm considering a DIY project and would be curious as to the science
> > on this topic. Are there the same problems with vibrations inside
> > the enclosure, or does the cylinder reduce or make them a non-issue?
> >
> > I see a lot of the sonotube desgins have the driver at one end and he
> > port at the other. Does it make any difference if they are are at
> > the same end of the tube assuming a large enough diameter?
> >
> > I am considering a 143 L EBS alignment with both the port and the
> > driver at the bottom. The tube would be 20" in diameter and a 4"
> > port. I am not married to these dimensions but I thought there
> > would be a higher WAF if the thing looked less like a water heater.
> >
> > Comments please.
>
> Hi Barking -
>
> Some comments from a friend:
>
>
>
> "Well, in theory a box-shaped sub enclosure will try to flex its wall inward
> Hi Barking -
>
> Some comments from a friend:
>
>
>
> or outward as the cone moves in and out, with the idea being that the
> pressure is trying to turn the box into a sphere.
>
> A cylinder-enclosure shape, even with the cylinder walls only 3/8 inch
> thick, cannot flex inward or outward (assuming the Sonotube fiber material
> is decently strong in terms of stretch resistance, and believe me, Sonotube
> is strong), because the surface is already curved to a circle. Yes, it is
> not a sphere, but the top plate cannot flex outward or inward, because it is
> mostly filled with the driver, and the bottom plate cannot flex much,
> because it has the port tube in there reinforcing it and the thing is
> usually too thick to flex much, anyway. My bottom plates are each 2.25
> inches thick, for example, with the bottom plate itself standing on 3-inch
> pegs that themselves are screwed to still another bottom plate. (There is a
> similar standoff plate on the top that is there simply for cosmetic purposes
> and to protect the driver cone.) The inside of the Sonotube should be
> layered with a couple of inches of fiberglass (mine is held in place with 3M
> spray adhesive, and the fiberglass is actually furnace pipe wrap with the
> foil removed), and the idea there is for the heating and cooling of the
> fiberglass under pressure (which can occur at any frequency above the port
> resonance) to help the driver to "see" a larger interior space than is
> pressure is trying to turn the box into a sphere.
>
> A cylinder-enclosure shape, even with the cylinder walls only 3/8 inch
> thick, cannot flex inward or outward (assuming the Sonotube fiber material
> is decently strong in terms of stretch resistance, and believe me, Sonotube
> is strong), because the surface is already curved to a circle. Yes, it is
> not a sphere, but the top plate cannot flex outward or inward, because it is
> mostly filled with the driver, and the bottom plate cannot flex much,
> because it has the port tube in there reinforcing it and the thing is
> usually too thick to flex much, anyway. My bottom plates are each 2.25
> inches thick, for example, with the bottom plate itself standing on 3-inch
> pegs that themselves are screwed to still another bottom plate. (There is a
> similar standoff plate on the top that is there simply for cosmetic purposes
> and to protect the driver cone.) The inside of the Sonotube should be
> layered with a couple of inches of fiberglass (mine is held in place with 3M
> spray adhesive, and the fiberglass is actually furnace pipe wrap with the
> foil removed), and the idea there is for the heating and cooling of the
> fiberglass under pressure (which can occur at any frequency above the port
> actually there. (Acoustic-suspension woofers and subwoofers also have
> something like that in their cabinet interiors for the same reason.) The
extension."
> something like that in their cabinet interiors for the same reason.) The
>
> End quote.
>
> Gary Eickmeier
Thanks friend.
If you have the advantages of the curved shape and you have the right internal volume to begin with, ( I'll be using 143 liters with a Shiva MKII 12" woofer)
what actual need if any for the the fiberglass? As to fiberglass I would be hesitant about using it in a ported enclosure since the notion of fiberglass being pumped into the air from the port does not appeal to me. I t just seems to me that in 5 cu ft there is little chance of much heat developing, so little need for cooling. If it's necessary fine, but if not then why bother. I thought the main reason for damping material was to help absorb vibration and keep resonance down.
Dick Pierce
Jul 16, 2012, 8:22:43 PM7/16/12
to
Gary Eickmeier wrote:
>
> "Well, in theory a box-shaped sub enclosure will try to flex its wall inward
> or outward as the cone moves in and out, with the idea being that the
> pressure is trying to turn the box into a sphere.
Several things poop into my head when I read this:
>
> "Well, in theory a box-shaped sub enclosure will try to flex its wall inward
> or outward as the cone moves in and out, with the idea being that the
> pressure is trying to turn the box into a sphere.
"What's the difference between theory and practice?
In theory, theory and practice are the same. In
practice, theory and practice are different."
It's on the Internet, so it must be true.
> A cylinder-enclosure shape, even with the cylinder walls only 3/8 inch
> thick, cannot flex inward or outward (assuming the Sonotube fiber material
> is decently strong in terms of stretch resistance, and believe me, Sonotube
> is strong), because the surface is already curved to a circle.
happily does. The assertion that it cannot is based on the
following assumptions:
1. That the wall material is infinitely rigid, has infinite
tensile strength, i.e., it can neither be stretched, compressed
or flexed. The 3/8" cardboard walls of a Sonotube are VERY
VERY far from that ideal,
2. That the internal forces on the walls are the same at every
point along the walls surface. With ANY musical material,
this is simply not the case.
3. That the cylinder is infinitely long, i.e., it has no
boundary conditions to deal with. Again, not the case
"in practice."
Consider two cyclinders of MUCH greater strength than that of a
20" Sonotube: the walls of the SRMs on a shuttle were 1/2" steel.
The ignition transient was predicted and was measured to cause the
walls halfway between the field joints to expand nearly a foot.
But because the field joints used a much heavier, thicker steel
ring, they did not bulge anywhere near that much. The result was
phenomenon called "joint rotation" and was crucial to causing
the failure of the field joints in the Challenger explosion.
Be that as it may, while "in theory" it seems like Sonotube is
an "ideal" way of building a subwoofer, "in practice"m most
of those teoretical advantages simply aren't there.
I had, for a former client, done quite a bit of measurements on
cardboard tube enclosure, most of which were MUCH more substantial
than Sontotube (minimum 3/4" wall thickness, higher density wrap).
Using acceelerometer measurements, wall flexing was NO better and
most of the time WORSE than a rectangular enclosure of the same
corss-sectional are. The unsuported walls of the rectangular
enclosure did no worse under the same conditions, and at the
corners, they behaved MUCH better.
At freuqencies where the wavelengths were smaller than either the
length or cricumerance of the tube, cyclinders tid MUCH worse
in almost every respect. We would see nodal vibration patterns
on the wall that had very high Q'. This is directly attributable
to the very dimensional symmetry of the shape. Siply because the
unsupported area of the "soundboard" was now the length of the
enclosure times its circumference: nodal patterns could be easily
set up and well established at MUCH lower frequencies than in a
similarly dimensioned rectangula enclosure: the largest unsupported
surface in a box is substantially smaller than that of the cylinder.
And the argument that
"A cylinder-enclosure shape ... cannot flex inward or outward"
Makes the simplifying and quite incorrect assumption that there's
a single, in phase constant force on every square cm of its curface,
annd thus the wall MUST be compelled to move uniformly radially.
Sorry, but that just doesn't happen in loudspeaker enclosures. TO
get the walls to fles very nicely, all you have to do is get it
going outward at one point atv the same time it's going inward
womehere else along its circumference. And, as far as local
stiffness is concerned, Sonotube ain't so hot, especially 3/8"
Sonotube.
If you want to deal with this issue, consider getting TWO sonotubes,
on loerger in diameter (by maybe 1-2"): place them concentrically
and then fill in the space between the two with something heavy and
mechancially lossy, like dry sand (or, uhm, concrete!).
> Yes, it is
> not a sphere, but the top plate cannot flex outward or inward, because it is
> mostly filled with the driver, and the bottom plate cannot flex much,
> because it has the port tube in there reinforcing it and the thing is
> usually too thick to flex much, anyway.
weakens it.
> My bottom plates are each 2.25
> inches thick,
because they have a driver, or becasue they have a port, they
don't flex merely because they are 2 1/4" thick.
> The inside of the Sonotube should be
> layered with a couple of inches of fiberglass (mine is held in place with 3M
> spray adhesive, and the fiberglass is actually furnace pipe wrap with the
> foil removed), and the idea there is for the heating and cooling of the
> fiberglass under pressure (which can occur at any frequency above the port
> resonance) to help the driver to "see" a larger interior space than is
> actually there. (Acoustic-suspension woofers and subwoofers also have
> something like that in their cabinet interiors for the same reason.) The
> effect is actually minimal, but in any case the fiberglass is not there to
> control resonances or absorb noise. Resonances are minimal with a cylinder
> enclosure, actually, due to the lack of glued-together speaker-wall joints.
the ability to suport quite nasty, highQ resonance. Take a
glass pie plate, fill it with water, and put a speaker near
it, driven by an oscillator: you'll find any enclosure with
a circular cross section support standing wave VERY nicely.
Or, for a dramatic acoustical demonstration of the effect,
toss a fire cracker into a cylinfrical storm drain: it
doesn't go bang! it goes Bonnnnnnnggggggg! for a VERY
long time. And, surprise, you find that the pitch of
the bong! it inversely proportional to its diameter.
And a cylinder also supports end-to-end standing waves quite
nicely as well. That's why flute, organ pipes and such are
made, largely, of cylinders.
> In any case, in practical terms, a Sonotube enclosure should be the most
> resonant-free enclosure possible for a subwoofer, although the light weight
> is a theoretical problem - that I have not encountered.
> If the port and driver are on the bottom, the designer
> can have an attractive top on the cabinet that will allow it to function as
> an end table, or the like.
impedance seen by both the port and the driver are: rest assured,
if you assume that it has no effect, you'll get it wrong.
> However, the light weight of a sonotube enclosure will allow
> the entire unit to vibrate up and down, which might make that
> table lamp dance around a bit.
smiley)?
Assume the mass of the driver cone is, oh 200 grams. Assume
also that the driver, enclosure and lamp together weigh 30
kilograms. By conservation of momentum calculate what the
worst case "bouncing" of the lamp will be. Show your work.
Get back to us when you have an answer.
--
+--------------------------------+
+ Dick Pierce |
+ Professional Audio Development |
+--------------------------------+
Audio Empire
Jul 16, 2012, 9:37:36 PM7/16/12
to
On Mon, 16 Jul 2012 06:59:04 -0700, Gary Eickmeier wrote
(in article <a6il17...@mid.individual.net>):
I don't think the subwoofer cares about the shape of the enclosure as long as
it's as inert as possible and the volume is sufficient and you do the port
maths correctly. You don't want the subwoofer enclosure to flex no matter
what shape it is. I once built a subwoofer from a piece of oval ceramic
fireplace chimney flue-liner pipe. I cut two 3/4" pieces of plywood to fit
on each end of the 3 ft flue-liner section. I cut an oval hole in one end to
take the odd-looking British KEF low frequency driver that was popular in
those days, and after measuring the inside dimensions of the "enclosure",
figured the bass reflex port size after Hoge and Bullock, and used four long,
threaded rods to clamp the end pieces onto the pipe after lining the pipe
with fiberglass insulation. The threaded rods extended about three inches
beyond the end with the driver attached and these served as legs to keep the
driver off the floor. I painted the flue liner pipe and the end baffles
black. It worked fine and I used it for many years with good results. I was
getting good bass down into the low thirties from that KEF driver.
(in article <a6il17...@mid.individual.net>):
it's as inert as possible and the volume is sufficient and you do the port
maths correctly. You don't want the subwoofer enclosure to flex no matter
what shape it is. I once built a subwoofer from a piece of oval ceramic
fireplace chimney flue-liner pipe. I cut two 3/4" pieces of plywood to fit
on each end of the 3 ft flue-liner section. I cut an oval hole in one end to
take the odd-looking British KEF low frequency driver that was popular in
those days, and after measuring the inside dimensions of the "enclosure",
figured the bass reflex port size after Hoge and Bullock, and used four long,
threaded rods to clamp the end pieces onto the pipe after lining the pipe
with fiberglass insulation. The threaded rods extended about three inches
beyond the end with the driver attached and these served as legs to keep the
driver off the floor. I painted the flue liner pipe and the end baffles
black. It worked fine and I used it for many years with good results. I was
getting good bass down into the low thirties from that KEF driver.
Dick Pierce
Jul 16, 2012, 9:40:07 PM7/16/12
to
Barkingspyder wrote:
that, well, falls a wee bit short of the mark,
> If you have the advantages of the curved shape and you have the
> right internal volume to begin with, ( I'll be using 143 liters
> with a Shiva MKII 12" woofer) what actual need if any for the
> the fiberglass? As to fiberglass I would be hesitant about
> using it in a ported enclosure since the notion of fiberglass
> being pumped into the air from the port does not appeal to me.
> It just seems to me that in 5 cu ft there is little chance of
Sound, as it turns out when you follow it down to its physical
underpinnings, is simply a thermodynamic phenomenon. ALL sound must,
at its very root, involve changes in temperature. Take the simple
case of a moving diaphragm in air: When it moves out, it not only
compresses the air it, it also raises its temperature. And the raise
in temperature and pressure results in the energy moving outward
as the air attempts top reach thermodynamic equilibrium with the
surrounding air. And when the diaphragm, conversely, moves inward,
not only does the pressure drop, but so does the temperature.
Now, it's not that the inside of your enclosure is going to heat
up to the point of causing serious thermal problems, it's that
the pressure AND the temperature in the box is constantly going
up and down, (both by quite small amounts, to be sure).
Now, if you're box was PERFECTLY sealed, and the walls were PERFECT
thermal insulators AND PERFECTLY rigid (such that 100% the acoustic
energy generated by your driver went into increasing and decreasing
the internal air pressure (and, at the same time, the temperature),
the box would follow perfectly the ideal gas relation, which looks like
PV = nRT
where P is pressure, V is volume, n is the total amount of gas in
the box (in conventional speak, that'd be in mols), R is a nice
constant (Boltsmann's in this case) and T is temperature. Any
chink in that "perfect" enclosure (a leak, the walls are thermally
conductive or can move), and the equation starts to work differently
(R, in this case, starts changing).
The idea to the fiberglass (or ANY fibrous tangle of the
appropriate properties) is not to insulate, but to change the
operating conditions of the system. Our "perfect" enclosure
would operating under "adiabatic" conditions (constant energy).
Pick the right kind of fibrous tangle (and fiberglas, for the
restricted purposes of this explanation, is not the ideal stuff),
and what happens is that it shifts the oepration to "isothermal"
(constant temperature).
Behind the big words is a pretty simple principle: with a fibrous
tangle in place, when the pressure in the system increases, so
does the temeprature, but a portion of that heat is transfered to
the tangle. The resulting loss of temeprature results in a reduction
in pressure. By the same token, when the pressure is reduced, so
is the temeprature, but now the tangle, being every so slightly
warmer than the auir, gives up some of its heat, which raises the
air temeprature and pressure slightly.
Now, the result is that because the presence of the tangle is
modifying the thermal and thus the pressure conditions: when
you compress it, the pressure doesn go so high, for example,
the entire system behaves as if the enclosed volume was slightly
larger. Assuming a "perfect" fibrous tangle" (with an appropriate
heat capacity and surface area, neither of which fiberglas has),
it's theoretically possible to make the enclosure appear about
1.4 times bigger than it really is.
Now, put a thermometer inside your enclosure BEFORE you put
the stuffing in. Play it REALLY loud for, oh, a day. Come back
and look at the temperature.
Now, put whatever stuffing you want inside the enclosure and
put the thermometer in again, and play the SAME music just
as loud for the same time. Then look at the thermometer.
(and, to be simple, assume a sealed enclosure in both cases).
Can you guess what the difference is going to be (assuming
room temperature is the same)?
(hint: there will be little if any difference at all).
> If it's necessary fine, but if not then why bother.
> I thought the main reason for damping material was to help
> absorb vibration and keep resonance down.
Yes, that's another good reason to have it.
The reason why it may NOT be appropriate for a reflex enclosure
is because it DOES change the effective volume.
Now, assuming your numbers are reasonably accurate, a 143 L
enclosure with an inside diameter of 19.25" will have to have
an internal length of 30", exclusive of the volume taken up by
the woofer and the port. Assuming a perfect absorber, the actual
physical length could be about 1.4 times smaller than this, or
only 12 inches.
Now, whether or not you actually use any absorbtive material is
dependent upon a number of things, most of which have to do
with the target alignment of system. A so-called Extended
Bass Shelf alignment (what I assume you mean by EBS) while it
has some bandwidth advantages, but the actual response can
be sensitive to tuning parameters (not that you or anyone might
case). The actual amount of internal stuffing really depends
upon the exact parameters of the woofer usedm the desired response
and the acceptable tolerance to misalignment. Certainly, systems
such as B4 alignments would really like to have minimal enclosure
losses: that not only includes absorbtive losses, but leakage losses
as well.
At very low frequencies, a small ampount of stuffing is unlikely
to make a large difference. But you're not only building a subwoofer
with that tube, you're building an organ pipe. And, at 30" long, it's
going to support some NASTY 1/2 wave resonances, like a big one at
justr above 200 Hz. And don't believe for a moment that your crossover
is going to help unless you have yourself a nice, sharp high-order
low-pass. Assume you cutoff is 80 Hz and 2nd order: by 200 Hz, your
drive to the woofer is down a measely 18 dB at the point where you're
near the peak in typical music energy spectrum.
Cylindrical enclosure may look neat and be easy to build and may
make you feel like it has all sorts of advantages because of its
symmetry: but that symmetry makes for very high-Q, sharp line
resonances: the worst, by the way, is a spherical enclosure. One
might argue that it is or is not mechanically the best, but
acoustically, it's a "perfect" disaster.
Lot/s of absorbtive ,aterial at one end will help. And I'd line
at least half the circumference to try and tame the higher
frequency cylinder-mode resonances, if possible.
> Gary Eickmeier wrote:
>> The inside of the Sonotube should be layered with a couple
>> of inches of fiberglass (mine is held in place with 3M
>> spray adhesive, and the fiberglass is actually furnace
>> pipe wrap with the foil removed), and the idea there is for
>> the heating and cooling of the fiberglass under pressure
>> (which can occur at any frequency above the port resonance)
>> to help the driver to "see" a larger interior
>> space than is actually there.
While all the words are sorta right, they're assembled in a way
>> The inside of the Sonotube should be layered with a couple
>> of inches of fiberglass (mine is held in place with 3M
>> spray adhesive, and the fiberglass is actually furnace
>> pipe wrap with the foil removed), and the idea there is for
>> the heating and cooling of the fiberglass under pressure
>> (which can occur at any frequency above the port resonance)
>> to help the driver to "see" a larger interior
>> space than is actually there.
that, well, falls a wee bit short of the mark,
> If you have the advantages of the curved shape and you have the
> right internal volume to begin with, ( I'll be using 143 liters
> with a Shiva MKII 12" woofer) what actual need if any for the
> the fiberglass? As to fiberglass I would be hesitant about
> using it in a ported enclosure since the notion of fiberglass
> being pumped into the air from the port does not appeal to me.
> much heat developing, so little need for cooling.
Actually, it's not about "insulating" to keep the heat down.
Sound, as it turns out when you follow it down to its physical
underpinnings, is simply a thermodynamic phenomenon. ALL sound must,
at its very root, involve changes in temperature. Take the simple
case of a moving diaphragm in air: When it moves out, it not only
compresses the air it, it also raises its temperature. And the raise
in temperature and pressure results in the energy moving outward
as the air attempts top reach thermodynamic equilibrium with the
surrounding air. And when the diaphragm, conversely, moves inward,
not only does the pressure drop, but so does the temperature.
Now, it's not that the inside of your enclosure is going to heat
up to the point of causing serious thermal problems, it's that
the pressure AND the temperature in the box is constantly going
up and down, (both by quite small amounts, to be sure).
Now, if you're box was PERFECTLY sealed, and the walls were PERFECT
thermal insulators AND PERFECTLY rigid (such that 100% the acoustic
energy generated by your driver went into increasing and decreasing
the internal air pressure (and, at the same time, the temperature),
the box would follow perfectly the ideal gas relation, which looks like
PV = nRT
where P is pressure, V is volume, n is the total amount of gas in
the box (in conventional speak, that'd be in mols), R is a nice
constant (Boltsmann's in this case) and T is temperature. Any
chink in that "perfect" enclosure (a leak, the walls are thermally
conductive or can move), and the equation starts to work differently
(R, in this case, starts changing).
The idea to the fiberglass (or ANY fibrous tangle of the
appropriate properties) is not to insulate, but to change the
operating conditions of the system. Our "perfect" enclosure
would operating under "adiabatic" conditions (constant energy).
Pick the right kind of fibrous tangle (and fiberglas, for the
restricted purposes of this explanation, is not the ideal stuff),
and what happens is that it shifts the oepration to "isothermal"
(constant temperature).
Behind the big words is a pretty simple principle: with a fibrous
tangle in place, when the pressure in the system increases, so
does the temeprature, but a portion of that heat is transfered to
the tangle. The resulting loss of temeprature results in a reduction
in pressure. By the same token, when the pressure is reduced, so
is the temeprature, but now the tangle, being every so slightly
warmer than the auir, gives up some of its heat, which raises the
air temeprature and pressure slightly.
Now, the result is that because the presence of the tangle is
modifying the thermal and thus the pressure conditions: when
you compress it, the pressure doesn go so high, for example,
the entire system behaves as if the enclosed volume was slightly
larger. Assuming a "perfect" fibrous tangle" (with an appropriate
heat capacity and surface area, neither of which fiberglas has),
it's theoretically possible to make the enclosure appear about
1.4 times bigger than it really is.
Now, put a thermometer inside your enclosure BEFORE you put
the stuffing in. Play it REALLY loud for, oh, a day. Come back
and look at the temperature.
Now, put whatever stuffing you want inside the enclosure and
put the thermometer in again, and play the SAME music just
as loud for the same time. Then look at the thermometer.
(and, to be simple, assume a sealed enclosure in both cases).
Can you guess what the difference is going to be (assuming
room temperature is the same)?
(hint: there will be little if any difference at all).
> If it's necessary fine, but if not then why bother.
> I thought the main reason for damping material was to help
> absorb vibration and keep resonance down.
The reason why it may NOT be appropriate for a reflex enclosure
is because it DOES change the effective volume.
Now, assuming your numbers are reasonably accurate, a 143 L
enclosure with an inside diameter of 19.25" will have to have
an internal length of 30", exclusive of the volume taken up by
the woofer and the port. Assuming a perfect absorber, the actual
physical length could be about 1.4 times smaller than this, or
only 12 inches.
Now, whether or not you actually use any absorbtive material is
dependent upon a number of things, most of which have to do
with the target alignment of system. A so-called Extended
Bass Shelf alignment (what I assume you mean by EBS) while it
has some bandwidth advantages, but the actual response can
be sensitive to tuning parameters (not that you or anyone might
case). The actual amount of internal stuffing really depends
upon the exact parameters of the woofer usedm the desired response
and the acceptable tolerance to misalignment. Certainly, systems
such as B4 alignments would really like to have minimal enclosure
losses: that not only includes absorbtive losses, but leakage losses
as well.
At very low frequencies, a small ampount of stuffing is unlikely
to make a large difference. But you're not only building a subwoofer
with that tube, you're building an organ pipe. And, at 30" long, it's
going to support some NASTY 1/2 wave resonances, like a big one at
justr above 200 Hz. And don't believe for a moment that your crossover
is going to help unless you have yourself a nice, sharp high-order
low-pass. Assume you cutoff is 80 Hz and 2nd order: by 200 Hz, your
drive to the woofer is down a measely 18 dB at the point where you're
near the peak in typical music energy spectrum.
Cylindrical enclosure may look neat and be easy to build and may
make you feel like it has all sorts of advantages because of its
symmetry: but that symmetry makes for very high-Q, sharp line
resonances: the worst, by the way, is a spherical enclosure. One
might argue that it is or is not mechanically the best, but
acoustically, it's a "perfect" disaster.
Lot/s of absorbtive ,aterial at one end will help. And I'd line
at least half the circumference to try and tame the higher
frequency cylinder-mode resonances, if possible.
Arny Krueger
Jul 17, 2012, 6:31:27 PM7/17/12
to
> Are there any advantages other than a smaller foot print for
> cylindrical subwoofers?
Potentially low cost and easier assembly, particularly if the cylinder is
> cylindrical subwoofers?
based on Sonotube.
> Do they require damping material in the
> same way a box would?
> I'm considering a DIY project and would be curious as to the science
> on this topic. Are there the same problems with vibrations inside
> the enclosure, or does the cylinder reduce or make them a non-issue?
(1) Vibrations of the air
(2) Vibrations of the enclosure
(1) Is based on enclosure volume, driver characteristics, stuffing, and are
the same given the same volume, driver, etc.
(2) Is based on the stiffness of the enclosure.
> I see a lot of the sonotube desgins have the driver at one end and he
> port at the other. Does it make any difference if they are are at
> the same end of the tube assuming a large enough diameter?
at the port tuning frequency.
> I am considering a 143 L EBS alignment with both the port and the
> driver at the bottom. The tube would be 20" in diameter and a 4"
> port. I am not married to these dimensions but I thought there
> would be a higher WAF if the thing looked less like a water heater.
I've never heard of a 143 L EBS alignement and can find no online references
to it.
Barkingspyder
Jul 17, 2012, 7:10:55 PM7/17/12
to
On Tuesday, July 17, 2012 3:31:27 PM UTC-7, Arny Krueger wrote:
> "Barkingspyder" ; wrote in message
> news:a6g4om...@mid.individual.net...
>
> > Are there any advantages other than a smaller foot print for
> > cylindrical subwoofers?
> > same way a box would?
>
> Yes.
>
> > I'm considering a DIY project and would be curious as to the science
> > on this topic. Are there the same problems with vibrations inside
> > the enclosure, or does the cylinder reduce or make them a non-issue?
> > port at the other. Does it make any difference if they are are at
> > the same end of the tube assuming a large enough diameter?
> > would be a higher WAF if the thing looked less like a water heater.
>
> What driver?
>
> I've never heard of a 143 L EBS alignement and can find no online references
> to it.
The Adire Audio Shiva MkII. The figures for the internal volume come from their own design of an EBS system only in the original design it was in a typical box.
My intention is to use the sonotube to free up some floor space and give me something that I can move around without killing my spine.
If you search for Shiva vented applications you will find it. If not I can e-mail it to you.
In re-reading the diagram it does in fact specify NO POLYFILL.
The following is a bit from the PDF.
The 142.5 liter PR Shiva box is the EBS alignment. The vent is our FP-4 flared vent kit, with a full-length
12” center tube, for a final tuning of 18.1 Hz. This box, while physically the largest of the three designs
shown in this paper, yields the lowest frequency extension, as well as the widest and flattest in-room
response. If the size of the cabinet (5 cubic foot net) can be tolerated, the EBS will reward you with
maximum SPL and bass extension. The EBS is the ideal subwoofer for organ and very demanding home
theater applications.
They also give plans for an 85L box they call an Adire alignment and a 95L box SBB4 alignment.
Based on what I have read here if I'm going to use Sonotube, it would be very wise to find some way to brace it internally. Possibly, there is some other brand of tubing that would be thicker and possibly more rigid.
> "Barkingspyder" ; wrote in message
> news:a6g4om...@mid.individual.net...
>
> > Are there any advantages other than a smaller foot print for
> > cylindrical subwoofers?
>
> Potentially low cost and easier assembly, particularly if the cylinder is
> based on Sonotube.
>
> > Do they require damping material in the
> Potentially low cost and easier assembly, particularly if the cylinder is
> based on Sonotube.
>
> > same way a box would?
>
> Yes.
>
> > I'm considering a DIY project and would be curious as to the science
> > on this topic. Are there the same problems with vibrations inside
> > the enclosure, or does the cylinder reduce or make them a non-issue?
>
> Two types of vibrations
>
> (1) Vibrations of the air
> (2) Vibrations of the enclosure
>
> (1) Is based on enclosure volume, driver characteristics, stuffing, and are
> the same given the same volume, driver, etc.
> (2) Is based on the stiffness of the enclosure.
>
> > I see a lot of the sonotube desgins have the driver at one end and he
> Two types of vibrations
>
> (1) Vibrations of the air
> (2) Vibrations of the enclosure
>
> (1) Is based on enclosure volume, driver characteristics, stuffing, and are
> the same given the same volume, driver, etc.
> (2) Is based on the stiffness of the enclosure.
>
> > port at the other. Does it make any difference if they are are at
> > the same end of the tube assuming a large enough diameter?
>
> Not unless the enclosure is itself a signficiant portion of a 1/4 wavelength
> at the port tuning frequency.
>
> Not unless the enclosure is itself a signficiant portion of a 1/4 wavelength
> at the port tuning frequency.
>
> > I am considering a 143 L EBS alignment with both the port and the
> > driver at the bottom. The tube would be 20" in diameter and a 4"
> > port. I am not married to these dimensions but I thought there
> > driver at the bottom. The tube would be 20" in diameter and a 4"
> > would be a higher WAF if the thing looked less like a water heater.
>
> What driver?
>
> I've never heard of a 143 L EBS alignement and can find no online references
> to it.
The Adire Audio Shiva MkII. The figures for the internal volume come from their own design of an EBS system only in the original design it was in a typical box.
My intention is to use the sonotube to free up some floor space and give me something that I can move around without killing my spine.
If you search for Shiva vented applications you will find it. If not I can e-mail it to you.
In re-reading the diagram it does in fact specify NO POLYFILL.
The following is a bit from the PDF.
The 142.5 liter PR Shiva box is the EBS alignment. The vent is our FP-4 flared vent kit, with a full-length
12” center tube, for a final tuning of 18.1 Hz. This box, while physically the largest of the three designs
shown in this paper, yields the lowest frequency extension, as well as the widest and flattest in-room
response. If the size of the cabinet (5 cubic foot net) can be tolerated, the EBS will reward you with
maximum SPL and bass extension. The EBS is the ideal subwoofer for organ and very demanding home
theater applications.
They also give plans for an 85L box they call an Adire alignment and a 95L box SBB4 alignment.
Based on what I have read here if I'm going to use Sonotube, it would be very wise to find some way to brace it internally. Possibly, there is some other brand of tubing that would be thicker and possibly more rigid.
Arny Krueger
Jul 18, 2012, 8:45:18 AM7/18/12
to
"Barkingspyder" <kmck...@roadrunner.com> wrote in message
news:a6m9nv...@mid.individual.net...
> Based on what I have read here if I'm going to use Sonotube, it would be
> very wise to find some way to brace it internally.
wall screws, a 1/8" drill, and some construction adhesive.
Your knuckles and ears are probably your best tools.
> Possibly, there is some other brand of tubing that would be thicker and
> possibly more rigid.
it is entirely adequate if not overbuilt for that purpose.
Audio Empire
Jul 18, 2012, 7:44:01 PM7/18/12
to
On Wed, 18 Jul 2012 05:45:18 -0700, Arny Krueger wrote
(in article <ju6b4...@news3.newsguy.com>):
What's wrong with ceramic (or concrete) pipe or chimney flue liners? They're
cheap, unbelievably stiff and easy to find.
(in article <ju6b4...@news3.newsguy.com>):
cheap, unbelievably stiff and easy to find.
Dick Pierce
Jul 19, 2012, 7:04:21 AM7/19/12
to
they're probably okay. One problem is that their internal
losses are low, which means any mechanical resonances that
might get started are goign to hang around for a while.
They're also not the easiest material to work with.
Dick Pierce
Jul 19, 2012, 7:04:43 AM7/19/12
to
Arny Krueger wrote:
> "Barkingspyder" <kmck...@roadrunner.com> wrote in message
> news:a6m9nv...@mid.individual.net...
>>Based on what I have read here if I'm going to use Sonotube, it would be
>>very wise to find some way to brace it internally.
>
> Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2" dry
> wall screws, a 1/8" drill, and some construction adhesive.
Onw of the real big problems with these concrete forms
> "Barkingspyder" <kmck...@roadrunner.com> wrote in message
> news:a6m9nv...@mid.individual.net...
>>Based on what I have read here if I'm going to use Sonotube, it would be
>>very wise to find some way to brace it internally.
>
> Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2" dry
> wall screws, a 1/8" drill, and some construction adhesive.
is that they are wax-coated (first to prevent water
from soaking in to them when they're filled with
concrete, secondly to make it easy to strip them off
once they're done.
The wax coating makes the use of any adhesive-based
solution a real challenge.
>> Possibly, there is some other brand of tubing that would be thicker and
>> possibly more rigid.
wrong with the idea of taking two forms of somewhat different
diameter and filling the space between them with sand?
Barkingspyder
Jul 19, 2012, 7:05:00 AM7/19/12
to
On Wednesday, July 18, 2012 5:45:18 AM UTC-7, Arny Krueger wrote:
> "Barkingspyder"wrote in message
> news:a6m9nv...@mid.individual.net...
>
>
> > Based on what I have read here if I'm going to use Sonotube, it would be
> > very wise to find some way to brace it internally.
>
> Not exactly rocket science.
You never know, get a nose cone and some fins................ :-)
> "Barkingspyder"wrote in message
> news:a6m9nv...@mid.individual.net...
>
>
> > Based on what I have read here if I'm going to use Sonotube, it would be
> > very wise to find some way to brace it internally.
>
> Not exactly rocket science.
You never know, get a nose cone and some fins................ :-)
Barkingspyder
Jul 19, 2012, 3:03:55 PM7/19/12
to
On Thursday, July 19, 2012 4:04:43 AM UTC-7, Dick Pierce wrote:
> Arny Krueger wrote:
> > "Barkingspyder" wrote in message
> > news:a6m9nv...@mid.individual.net...
> >>Based on what I have read here if I'm going to use Sonotube, it would be
> >>very wise to find some way to brace it internally.
> >
> > Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2" dry
> > wall screws, a 1/8" drill, and some construction adhesive.
> >> possibly more rigid.
>
> If you're so committed to marrying these things, what's
> Arny Krueger wrote:
> > "Barkingspyder" wrote in message
> > news:a6m9nv...@mid.individual.net...
> >>Based on what I have read here if I'm going to use Sonotube, it would be
> >>very wise to find some way to brace it internally.
> >
> > Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2" dry
> > wall screws, a 1/8" drill, and some construction adhesive.
>
> Onw of the real big problems with these concrete forms
> is that they are wax-coated (first to prevent water
> from soaking in to them when they're filled with
> Onw of the real big problems with these concrete forms
> is that they are wax-coated (first to prevent water
> concrete, secondly to make it easy to strip them off
> once they're done.
>
> The wax coating makes the use of any adhesive-based
> solution a real challenge.
>
> >> Possibly, there is some other brand of tubing that would be thicker and
> The wax coating makes the use of any adhesive-based
> solution a real challenge.
>
> >> possibly more rigid.
>
> If you're so committed to marrying these things, what's
> wrong with the idea of taking two forms of somewhat different
> diameter and filling the space between them with sand?
>
> --
> +--------------------------------+
> + Dick Pierce |
> + Professional Audio Development |
> +--------------------------------+
Nothing I suppose. I was hoping to keep the whole thing as small as possible and as light as possible, but since this is likely to be the last sub I ever construct it's entirely doable.
> diameter and filling the space between them with sand?
>
> --
> +--------------------------------+
> + Dick Pierce |
> + Professional Audio Development |
> +--------------------------------+
Audio Empire
Jul 19, 2012, 7:58:01 PM7/19/12
to
On Thu, 19 Jul 2012 04:04:21 -0700, Dick Pierce wrote
(in article <a6q7tl...@mid.individual.net>):
I found just the opposite to be true. You need to make a couple of endcaps
out of 3/4" plywood and affix them to the pipe using threaded rods (makes a
sandwich. Wooden end-caps (one with woofer, one with port) and the pipe
essentially squeezed between them by the threaded rods). Paint the pipe (or
leave it natural clay color) and you have it made.
(in article <a6q7tl...@mid.individual.net>):
out of 3/4" plywood and affix them to the pipe using threaded rods (makes a
sandwich. Wooden end-caps (one with woofer, one with port) and the pipe
essentially squeezed between them by the threaded rods). Paint the pipe (or
leave it natural clay color) and you have it made.
Dick Pierce
Jul 19, 2012, 7:58:43 PM7/19/12
to
simulating a rocket on a 36" diameter, 40 foot long sonotube
loaded with about 3/4 ton ammonium perchlorate/polyurethane
solid fuel. With an optimized thrust profile, optimum cone,
glass-smooth finish, etc., I figured I had about a 20% chance
of putting the carcass into on unstable earth orbit.
Now, the issue of the illegality of launching such a contrivance
from one's back yard came up, but I figured that when the town
police showed up in my driveway to investigate, the fact that
I was sitting at the bottom of a pretty substantial column of
smoke 30 miles high might raise the though that, indeed, I
was a force to be reckoned with. The first question they should
probably entertain is: did I have another one at hand.
Ironically, I did this work about a month before the Oklahoma
Federal Building bombing: right after that, getting a half a
tone of ammonium perchlorate on the open market got a bit more
difficult :-)
Dick Pierce
Jul 19, 2012, 8:43:14 PM7/19/12
to
On 7/19/2012 3:03 PM, Barkingspyder wrote:
> On Thursday, July 19, 2012 4:04:43 AM UTC-7, Dick Pierce wrote:
>> One of the real big problems with these concrete forms
> On Thursday, July 19, 2012 4:04:43 AM UTC-7, Dick Pierce wrote:
>> is that they are wax-coated (first to prevent water
>> from soaking in to them when they're filled with
>> concrete, secondly to make it easy to strip them off
>> once they're done.
>> from soaking in to them when they're filled with
>> concrete, secondly to make it easy to strip them off
>>
>> The wax coating makes the use of any adhesive-based
>> solution a real challenge.
>>
>> The wax coating makes the use of any adhesive-based
>> solution a real challenge.
>>
>> Possibly, there is some other brand of tubing that would be thicker and
>> possibly more rigid.
>>
>> If you're so committed to marrying these things, what's
>> wrong with the idea of taking two forms of somewhat different
>> diameter and filling the space between them with sand?
>
>> diameter and filling the space between them with sand?
>
> Nothing I suppose. I was hoping to keep the whole thing as small
> as possible and as light as possible, but since this is likely
> to be the last sub I ever construct it's entirely doable.
swell, unfortunately, the mechanical properties that best suit
> as possible and as light as possible, but since this is likely
> to be the last sub I ever construct it's entirely doable.
the design and construction of subwoofers don't include "as
light as possible" as viable choices. "Light as possible"
means flexible (claims about the superior rigidity of cylinders
notwithstanding), acoustically transparent, and a bunch of
other things: all are poor choices for a subwoofer enclosure.
Consider a piano: the soundboard is deliberately made "as
light as possible." Is that what you REALLY want?
Gary Eickmeier
Jul 19, 2012, 8:43:55 PM7/19/12
to
"Dick Pierce" <dpi...@cartchunk.org> wrote in message
news:a6q7ub...@mid.individual.net...
> If you're so committed to marrying these things, what's
> wrong with the idea of taking two forms of somewhat different
> diameter and filling the space between them with sand?
Is that what you would do?
The reason such silliness is not necessary is that Sonotubes are audibly
plenty stiff enough. Refer to Hsu and SVS's use for their commercial subs.
If somebody is paranoid about what a Sonotube will do when trying to get
down to really low frequencies, they should just build a clone of the Hsu
TN1220 or one of the bigger SVS models. That way, they will be taking
advantage of research done by people who know what they are doing.
Gary Eickmeier
news:a6q7ub...@mid.individual.net...
> If you're so committed to marrying these things, what's
> wrong with the idea of taking two forms of somewhat different
> diameter and filling the space between them with sand?
The reason such silliness is not necessary is that Sonotubes are audibly
plenty stiff enough. Refer to Hsu and SVS's use for their commercial subs.
If somebody is paranoid about what a Sonotube will do when trying to get
down to really low frequencies, they should just build a clone of the Hsu
TN1220 or one of the bigger SVS models. That way, they will be taking
advantage of research done by people who know what they are doing.
Gary Eickmeier
Arny Krueger
Jul 20, 2012, 8:53:50 AM7/20/12
to
> Arny Krueger wrote:
>> "Barkingspyder" <kmck...@roadrunner.com> wrote in message
>> news:a6m9nv...@mid.individual.net...
>>>Based on what I have read here if I'm going to use Sonotube, it would be
>>>very wise to find some way to brace it internally.
>>
>> Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2"
>> dry wall screws, a 1/8" drill, and some construction adhesive.
> Onw of the real big problems with these concrete forms
> is that they are wax-coated (first to prevent water
> from soaking in to them when they're filled with
> concrete, secondly to make it easy to strip them off
> once they're done.
> The wax coating makes the use of any adhesive-based
> solution a real challenge.
Friends who have done projects with them tell me that scrubbing with
>> "Barkingspyder" <kmck...@roadrunner.com> wrote in message
>> news:a6m9nv...@mid.individual.net...
>>>Based on what I have read here if I'm going to use Sonotube, it would be
>>>very wise to find some way to brace it internally.
>>
>> Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2"
>> dry wall screws, a 1/8" drill, and some construction adhesive.
> Onw of the real big problems with these concrete forms
> is that they are wax-coated (first to prevent water
> from soaking in to them when they're filled with
> concrete, secondly to make it easy to strip them off
> once they're done.
> The wax coating makes the use of any adhesive-based
> solution a real challenge.
petroleum distillates solves that problem when it exists.
>>> Possibly, there is some other brand of tubing that would be thicker and
>>> possibly more rigid.
>
> If you're so committed to marrying these things, what's
> wrong with the idea of taking two forms of somewhat different
> diameter and filling the space between them with sand?
mention very heavy.
Barkingspyder
Jul 22, 2012, 10:23:25 AM7/22/12
to
put some casters on the bottom as I've seen some others do.
Barkingspyder
Jul 22, 2012, 10:19:53 PM7/22/12
to
On Sunday, July 22, 2012 7:23:25 AM UTC-7, Barkingspyder wrote:
> On Friday, July 20, 2012 5:53:50 AM UTC-7, Arny Krueger wrote:
> > "Dick Pierce" <dpi...@cartchunk.org> wrote in message
> On Friday, July 20, 2012 5:53:50 AM UTC-7, Arny Krueger wrote:
> > news:a6q7ub...@mid.individual.net...
> > > Arny Krueger wrote:
> > >> "Barkingspyder" &> wrote in message
> > >> news:a6m9nv...@mid.individual.net...
> > >>>Based on what I have read here if I'm going to use Sonotube, it would be
> > >>>very wise to find some way to brace it internally.
> > >>
> > >> Not exactly rocket science. Get a bunch of 2x2 clear pine, some 3 1/2"
> > >> dry wall screws, a 1/8" drill, and some construction adhesive.
> >
> > > Onw of the real big problems with these concrete forms
> > > is that they are wax-coated (first to prevent water
> > > from soaking in to them when they're filled with
> > > concrete, secondly to make it easy to strip them off
> > > once they're done.
> >
> > > The wax coating makes the use of any adhesive-based
> > > solution a real challenge.
> >
> > Friends who have done projects with them tell me that scrubbing with
> > petroleum distillates solves that problem when it exists.
> >
> > >>> Possibly, there is some other brand of tubing that would be thicker and
> > >>> possibly more rigid.
> > >
> > > If you're so committed to marrying these things, what's
> > > wrong with the idea of taking two forms of somewhat different
> > > diameter and filling the space between them with sand?
> >
> > Now that would be a robust and very acoustically dead solution, not to
> > mention very heavy.
>
> Oy, my back. Looks like I'll need my son to give me hand and maybe
> put some casters on the bottom as I've seen some others do.
One other question. INstead of Sonotube what about something like a cardboard core which is much thicker. Like the ones here http://www.spiralpaper.com/products/cores/ Dunno about how solid they are but they seem like they might possibly be a better choice.
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