What are the characteristics of a better material for enclosure?

[DrDyna]

Originally Posted by madisonears

I think any PB, after sitting in a garage for 20 years, is probably compromised by moisture and/or heat. If you still want to use it, make the subs out of a combination of new material laminated over the old stuff. No need to use anything exotic; a layer of good ply would probably suffice.

I am beginning to think that many "problems" associated with material choice are effectively overcome by using two layers of different materials. Neither has to be perfect by itself (if there is such a thing), so there are many possible combinations.

Pics of my 12" sealed sub, which includes panels made of PB and panels made of MDF, all covered with ply. The plate amp is in its own enclosure, isolated from the driver's space. The black things on the sides are the kind of handles used on road gear, and they're a great feature on a box this big. This 6 cu ft enclosure weighs well over 100 pounds, probably over 150.

Note that the back is not a flat panel. I think that might be the single most important factor in determining good acoustic properties of any enclosure. Again, I cannot cite a study or provide hard data, but I'd be willing to learn from anyone who can. I don't mean that speakers with flat backs can't sound good, but all the speakers I've built with a non-flat back seem to sound better. Even with lots of absorbent material, I imagine those soundwaves just banging off a flat panel, straight back through the cone.

Peace,
Tom E

Those are almost made with the same idea that these ones are. I don't use them much anymore, but I still appreciate the design. (3/4 MDF for discussions sake)

[cradeldorf]

Originally Posted by Cal Weldon

The particle board is probably adding a colouration to the sound that you find pleasing. The stiff cabinet is not lively enough for your tastes perhaps.

I could hear the cabinets when they were rigid, now I just hear the sound.

[bcmbob]

I'll see if I can find the picture and post it later, but years ago someone built the ideal solution for eliminating enclosure problems. It was a sixteen foot long horn that started with a 12"x12" box to mount the driver and terminated at an 8ftx8ft opening built into the wall of the listening room. The walls of the horn were six to eight inch reenforced concrete. Of course two are required for stereo. So if you have the room in your back yard, a strong back and the uncontrollable need for perfection - Have at it.

[pietschu]

Originally Posted by Baldin

Been thinking about what is actually the best material for a speaker enclosure.
I would think the most important attributes would be stiffness and damping.

A little late to contribute but I found the following simplified but useful explanation at :

12.21 What is the best material to make speaker boxes out of? Why?


12.21 What is the best material to make speaker boxes out of? Why?
An ideal speaker cabinet material would be very stiff, so that
it would not tend to move with variations in box air pressure.
It would also be very well damped, so that if it ever does
deflect from air pressure, it will come back to the original
position without resonating. It would also have a very high
resonant frequency (supersonic), so that low frequency box air
pressure would not cause it to resonate. An attractive material
is preferred, and additional credit is given for a material
which is easy to cut, glue, and finish. A great material would
be cheap, too. Finally, it would be nice if the material were
light, because we all have to move our speakers sometimes,
and it's hard to appreciate good speakers with a sore back.

With all of those attributes, it would seem that no
material is perfect. However, there are many materials that
have enough of the above good attributes to make excellent
speaker cabinets. Yet each has advantages and disadvantages.

In the list of good speaker box materials below, letters are
used to indicate which attributes the material possesses.

S = Stiff
D = Damped
H = High Resonance
A = Attractive
M = Machinable
C = Cheap
L = Light


So how about Gator Board sandwiched between aircraft plywood?

[cradeldorf]

I'm saying Balsa wood, just because I can.. the stiffer something is the more it Rings.

[bcmbob]

Just want to make a quick comment on "overbuilding". Keep in mind, in a bass reflex design the port and the air in it will most likely respond to pressure changes long before the walls of a cabinet start fluctuating. A simple wooden dowel anchored to the center of opposing sides divides the area of possible movement by at least 4. That alone raises the resonant frequency of each quarter panel to a point that a bass driver probably will not have a physical effect. The larger the box the more braces are needed, In my experience two evenly spaced dowels in a three foot tall cabinet is plenty. I always physically tie the horizontal and vertical.braces together where they intersect with a screw and a good amount of construction adhesive or epoxy..Adding at least one front to back intersecting brace ,also tied to the H and V braces gives superb results. If you are going to cover the cabinet, use a properly sized wood screw thru the side into the center of the dowel in addition to glue or epoxy between the end of the dowel and the inside of the box. If the cabinet has a final finish I try to make all the braces a hair over sized to apply a slight outward pressure to the walls
This method is great for ported cabinets and in my experience is even quite effective in a sealed box, if one doesn't want to mess with a matrix.

I like wooden dowels from .5 to .75" and even 1" because they are harder wood with little chance of vibrating if tied together.

I have never used anything thinner than .75" no mater the size of the speaker. I did a few with 1" MDF (weighs a ton) but .75' MDF is my standard now. On a couple subs I used .75" laminated to .5" show wood for top/bottom/sides/back. The front baffle was double MDf for rigidity and secure driver mounting.

[DualTriode]

Originally Posted by cradeldorf

I'm saying Balsa wood, just because I can.. the stiffer something is the more it Rings.

Originally Posted by cradeldorf

Is there a list that describes all terminology somewhere? I'm trying to read the thread on tapped horns but there is so much terminology I don't have a clue what is being said.

[Brisso57]

I friend of mine is using this material as external cladding for his new house.
For a thin section it is incredibly stiff, whilst being readily workable with "domestic" tools.

ALUCOBOND® - Alucobond Architectural

The above site has links to technical specifications and fabrication techniques.

cheers

Doug

[mycity33]

Manufacturers of speakers that "ring" quite a bit use piece of thin foam around woofer for damping at source. Look at those large towers manufactured using synthetic marble and imagine how sound would travel up and down that square tube. On positive side no bracing required here

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