What are the characteristics of a better material for enclosure?

[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.

I have mostly worked with MDF, which is easy to work wit and gives good results. But what if you where to go the full mile?

Wilson uses X-material and M-material .... I would guess that it's some kind of Corian (also used for kitchen tables).

Some is talking about energy storage ..... any thoughts??

What about pure mass .... I would think it is desirable to have as much mass as possible, but I wuld also think what is even more desirable is high density (and therefore high mass)

Thinking about different materials:

Plywood
- Would think MDF is actuallt a lot better

Hard wood (e.g. Mesquite)
- Workable but quite hard
- probably good damping, and relative high resonance

Concrete
- High resonance, very stiff, probably not the best damping

Metal (Alu)
- Stiff, hight resonance, but not the best damping

Stone (Marble, Granite ...)
- Almost imposible to work
- super stiff, high density, high resonance .... would be great looking

Ceramics
- burned clay would be easy to work, if you had acces to an oven
- Very stiff, high density, high resonance, ....

Glass
Plexiglass
Acrylic
Fiberglass (epoxy based)

Do we have to use the same material for all enclosure parts.
Could we consentrate on the enclosure for mid and high??

What about sandwitch materials??

Any thoughts??
And even better experianece??

Best regards Baldin

http://www.thespeakerstore.com/glossary/enclosures.htm
http://diyaudioprojects.com/Speakers...nite-Speakers/
http://www.soundstagelive.com/factorytours/wilson/

[HK26147]

Do we have to use the same material for all enclosure parts.

Opinion: Since different designs have different approaches to the goal of moving air: The material should fit the design.
If goal is absorption then I would utilize the concept behind OM ( Opposite Moduli materials ) and sandwich layers.

Also there are the considerations: of what materials are readily available/cost/workability/use, etc. )

[rhapsodee]

There seems to be some consensus that high quality baltic birch plywood is the best material for building speakers, can't remember where i read it, might be this forum.

I thought this TNT Audio article was quite interesting, in that the midrange sounded best with medium thickness plywood. I would have though the plywood would add colouration to vocals and midrange, due to resonating from insufficient stiffness.

Interesting that MDF 'kills' the life of the music. Maybe the author had a personal preference for the 'sound' of plywood.

http://www.tnt-audio.com/clinica/spe..._energy_e.html

http://www.tnt-audio.com/clinica/cabinet_walls_e.html

[planet10]

Originally posted by rhapsodee
There seems to be some consensus that high quality baltic birch plywood is the best material for building speakers

Let's refine that definition... plywood with lots of plys and no voids (or well filled voids, is the best easily available material for building cabinets using standard wood-working tools.

It is also durable & long-lived (this last giving it a big edge over solid wood, where you have to have skill & take care to not have the cabinets explode or crack with changes in humidity)

It also fits well with a certain philosophy of cabinet design.

This may be the thread rhapsodee regers to...

Discussion on what materials to build speakers out of

I was a major participant in that thread (outlining and defending the specific building philosopy i follow) and butted heads with John alot... i got much satisfaction, when later on in another thread, it was like a ligt went on in John's head, he got it, and declared that it was a brillant way to approach the job.

More exotic materials have their benefits and if i felt it were practical, there are ways to take my technique even further.

dave

[Saturnus]

The question can be answered pretty simply by stating that the best enclosure material is the one that suits it's purpose the best.

[Baldin]

Very good response
.... seems this has been discussed before

Birch Ply seems a good choice.

Planet10 do you also use internal bracing for every 7,5 cm or less as Mark Wheeler? (this will push the resonance to over 2,2 kHz)

Do you use thin walls, e.g. 12 mm, or thicker e.g. 25 mm and up?
Of course if you have braces every 5 - 7 cm, 12 mm will probably be enough, but I would tend to go for a thicker front baffle.

Do you also use bitumen to dampen the walls (convert energy to heat)?

I'm still thinking about fiberglass. It prabably have higher inner damping, but I wuold guess it has some of the same benefits as plywood. For a mid high cabinet it would give som very nice sculpturing possibilities (like you se in car subs), making bending walls, reduceing difraction etc. a chields play
The mounting rings could still be made of ply.
http://www.youtube.com/watch?v=I9Snm3SRzeA
(Don't mind the music)
I would strengthen it with a lot more real fiberglass in stead og the filler.
http://www.geocities.com/fiberglasse...iberglass.html


Baldin

[planet10]

Originally posted by Baldin
Planet10 do you also use internal bracing for every 7,5 cm or less as Mark Wheeler? (this will push the resonance to over 2,2 kHz)

Not quite that much... the resonance not only depends on distance, but stiffness & mass as well... but we have other tricks

Do you use thin walls, e.g. 12 mm, or thicker e.g. 25 mm and up?
Of course if you have braces every 5 - 7 cm, 12 mm will probably be enough, but I would tend to go for a thicker front baffle.

We use 12 to 18mm BB and sometimes will double a panel (or as in many of the Fonkens, use an onken-style port which inherently doubles walls.

Do you also use bitumen to dampen the walls (convert energy to heat)?

No. It takes the panel the wrong direction. Plywood by its very nature has a high damping.

I'm still thinking about fiberglass.

If you laminate the plywood both sides with fiberglass that is definitely taking things in the right direction.

At some point in time i am also going to pour something like polyurethane/epoxt resin.or somesuch into the box and slosh it around to create an even stiffer 2st veneer layer as a budget variation on the fiberglass.

dave

[D OB G]

Colin Whatmough, a manufacturer of excellent speakers in Australia, used to use a laminate of ply? with lead sheet. He still uses lead in his top model, I believe.

[Geek]

You forgot one:

Oiled softwood (pine, spruce, hemlock, fir):
- Takes on some characteristics of hardwood
- Less resonance than hardwood
- Light weight
- Least wear on tools
- Good damping
- Used throughout the cab and not just the baffle, can become part of the LF driver system and increase LF output over hardwood/MDF (spruce is often used by luthiers for this)

Cons:
- Takes more router skills than hardwood
- Requires more bracing for a sonic-neutral cab

[HK26147]

Like mentioned: If a cab is going to be move and banged around, I would use the best ply I could find.
Unfortunately in some areas, the better grade BB is not easy to obtain ( and it's never cheap ). So I have to cherry pick from what is available locally or obtain the best stuff from the nearest source ( 200 miles ).
MDF being cheap and fairly easy to obtain is used a lot, but it has workability issues, must be sealed and finished. For PA use it's too heavy and not very durable.

I'm still thinking about fiberglass.

I have used it, but as the exterior layer.

I am aware of a couple of different approaches:
As much mass as possible ( several layers of MDF )
Use of layers of acoustically dissimilar mediums.
and constrained layers.

I have seen a lot of materials used and containers recycled or unusual items converted into enclosures.
The results seemed to be contingent on the implementation more than the material: A unbraced box of thin wood with no dampening, makes a good drum.
I have small speakers made with a metal exterior, KEF 207/2 uses aluminum in the HF spheroid. These are not simple metal cabs but have internal dampening and bracing.
I have heard a oil drum that someone stuck a speaker in: It had no bracing or dampening and it sounded dreadful ( after all they have steel drum bands ).