Sub Enclosure made out of concrete

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi All,

I'm planning to build a HIFI sub (still not sure which design to go with (Maybe Rythmic or PE Dayton Titanic 10"))
I have an idea of making the enclousure out of poured fiber concrete. This would make it easier to make curved walls and the box would be very solid and "dead" sounding (I hope). has anyone done something like this? Are there any resources you can point me to or comment on the idea in general?

Thanks,

Rafal
 
Concrete is my life

I've worked in construction for 28 years. Placed many, many cubic yards of concrete. Your intro leaves much to speculation. Please describe the enclosure you have in mind and we'll go from there.

We can discuss the merits of "fiber" reinforcement if your wish. Concrete alone has a tensile strength of 5-600 psi (or more). Fibers (steel or poly) add little to this unless used in ridiculously high doses.

You will need a model of your driver (at least the opening) to cast into the mold.

Normal concrete weighs ~150 pounds/ cubic foot. It will be heavy!

The mold will need to be constructed with a removable interior. Wood forms can be frustrating for the novice. And you have to be able to think in reverse. Foam may be a better option. A combination of foam and wood could be made to work. A "staged" construction may be necessary to stabilize the interior form. That is, place up to the lower third of the mold, let it set, then place the remainder. Care will be required to ensure a bond at the construction joint.

We are talking monolythic here. An option would be to pre-cast the sides with provisions for joining them together as cast-in details.

Be careful with the assumption of "dead" sounding. A section of concrete pipe, when struck with a hammer, rings like a bell.

Care to go on? I'll entertain the notion.:cool:

PS: I never, ever thought I'd get to talk about concrete on THIS forum
 
How about building a small box inside of a larger box and pouring concrete in between them? Ties could be used to equally space the gap which the concrete is supposed to fill just like the ties used in concrete forms for basement walls. The smaller box would not have to be removed.

On the other hand... If you are looking for a solid enclosure, concrete is not the way to go. Bracing could do a much more effective job. If you want a super heavy enclosure or some crazy round edges maybe concrete would be worth considering
 
Thanks everyone for your replies.

Peter, That floor horn sub is crazy. I'd like to hear that.

bg40403, Thanks for all your valuable input. you shed a lot of light on the concrete topic. This idea is still very much in conceptual stage. If I go for it, I would love to pick your brain further.

Does anyone have other ideas for non conventional enclosure building materials?
 
Concrete enclosure
 

Attachments

  • imag0017.jpg
    imag0017.jpg
    43.5 KB · Views: 1,255
On the left in this picture is the mold that was designed to be destroyed to remove the concrete enclosure.

This is a 12 litre enclosure with 1 1/4" wall thickness and it weighs about 35lb. Concrete rings. As it cures (which takes years) it becomes harder and harder. The resonant frequency gets higher and higher. They are no longer in use.

Concrete might be okay for a sub, but with a larger volume and thicker walls it will be heavy. I'd stick with mdf. It's a lot more practicle, and the results aren't bad either.

Regards,
Music Machine
 

Attachments

  • imag0016.jpg
    imag0016.jpg
    50.1 KB · Views: 1,253
Hi

What about using a driver with a low Q that likes a small enclosure, eg Peerless XLS 12, Q = (I think) only 0.20 – so the enclosure is cheaper and lighter, though may need a Linkwitz transform for good extension.

Buy concrete sewer pipes of say 12 inch internal diameter, cut them into appropriate length slices with an angle grinder, and do square (easier, and avoids rolling) MDF timber ends to seal and mount the driver in a normal way.
:up:
 
you can make a concrete enclosure by using 2 sono tubes.one smaller than the other and with the ends capped for the inside.and the larger tube for the outside.i would suggest using hight strength non srink grout,cut with 20% pea gravel.this mix comes in around 10,000 psi.much stronger than normal concrete.
i use this mix for concrete counter tops with much success!
 
Hi

While concrete is cheap but the specific gravity is high

you might find something like this cemlite lightweight (SG 1.2)

concrete that is easier to manage. Many years ago

a friend made a bass reflex cabinet with bricks. He said it

sounded great but his cat got stuck in it and he had to take

a pickaxe to get the animal out !


Good luck

regards

AnthonyPT

http://www.abilityproducts.com.au/hot_cemlite.html
 
You can lighten concrete considerably by using a lightweight aggregate that includes perlite or volcanic rock. Strength will be somewhat less, but I expect the acoustical properties as far as resonance to be better than conventional concrete. I plan to use a perlite aggregate for my next concrete midrange horn project - weight might be as little as half compared to a gravel aggregate mix.
 
Rafal,

If the walls are gong to be really thick like 3 - 4 inches then concrete should work well but as concrete has poor tensile strength I would not use it for an enclosure with walls that are less then two inches thick.

A better method is to make your own pourable synthetic marble like some of the high end speakers are made out of. Try mixing cheap economy grade epoxy with crushed rocks. The secret is to have mostly rock and only a small amount of epoxy to bind everything together.

There are pourable casting plastics used for casting bathroom sinks and stuff like that. This stuff mixed with a heavy filled material would work also.

Hezz
 
I am still dreaming of a sandwich design.
MDF / sand / MDF
Did anybody here already try that?

If we are talking a subwoofer (ie, playing <100hz), then this would not help much. Below 100hz the principle concern should be stiffness, not resonance control. The most important thing is to keep the walls from 'breathing', bowing in and out with pressure. This is most practically achieved with a high stiffness plywood like baltic birch or marine grade, and extensive bracing. The MDF/sand/MDF thing may work well for >100hz frequencies, but below 100hz I can't see it giving much benefit over a single layer of MDF.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.