[JoshK]

I was dinking around brainstorming as usual and I thought up (likely not the first) a idea on how to make a relatively cheap (I think) TT stand, which could also be applied to speaker stands, that would be super heavy, rigid and vibration absorbing.  

Simple and easy I believe.  Build an box out of MDF (maybe subs with plywood?) paying particular attention to the joints to make them rigid and tight (no seepage).  You could use mortising jointer or other if you wish.  Fill the box with concrete 100%.  Stain, paint, veneer or otherwise finish to your liking.  Viola!

Anyone see any issues with this design?  First thing I thought of was you would probably have to first coat the inside of the box with some sort of sealant so the MDF wouldn't soak up the water from the concrete and warp.  Don't know if this would be hard or expensive but seems easy enough.  

I am envisioning speaker stands made to the same dimensions (w & d) as the bottom of your speaker, creating the perfect "skirt" for the bass to travel from your monitor to the floor.  The mass of these stands would be unmatched by anything commercially available that I can think of.  

Concrete itself is ugly, imo, and not suited for indoor decor applications.  However, with the concrete merely on the inside and MDF which can be finished to liking on the outside this seems in my mind to be a pretty good solution.  

Anyone want to take a stab at how much concrete it would take to fill a 9" x 15" x 24" stand?  Might be a lot.

[MediaSeth]

What would you put under them? Spikes might puncture the floor!   They might call for extra strong casters, otherwise I hope you don't have to move them after.    
How about bricks inside this thing?  You can make a panel on the back swing open, coating the back of the panel (or the whole inside) with sounnd proofing type stuff, and remove the bricks to be lighten the weight for moving them - or try different materials inside.  The wood/mdf joints would be more critical, and perhaps the top should be thick acrylic/marble/thick&heavy whatever to make up for the fact that it won't be solidly braced by concrete, which may not brace the top of the stand well anyway.  Or, have the top be the panel that swings open so you can pour in sand, hot molten lead, or whatever
I do think your idea is good in theory, and perhaps my lack of carpentry skills makes me think it would be difficult when it's actually possible...

[Rob Babcock]

I think you'd have to be awfully diligent about sealing the inside against moisture or else the MDF probably would eventually rot out.  Otherwise, aside from being very heavy and hard to move, the idea seems pretty sound.

[bubba966]

It would be pretty easy to P-Lam the interior sides of the box first. The after you've built the box seal the joints with a good roof/gutter silicone sealant. Then you'd have no problems with the moisture getting to the MDF.

One problem is this though. You'd pretty much have to let it cure for 60-90 days before you could put the lid on. You'd have to get all of the moisture out of the concrete before closing it up as you can't easily seal up a box from the inside...

It'd be quicker to do it with molten lead. You'd be able to finish it much quicker as there'd be no moisture problems.

[bubba966]

Anyone want to take a stab at how much concrete it would take to fill a 9" x 15" x 24" stand?  Might be a lot.

That'd be 22 cubic feet of concrete per stand. So it'd take 1.63 yards of concrete for a pair of stands.

[Brad]

.75 x 2 x 1.25 = 1.875 cu. ft

How did you come up with 22 cu. ft?

[bob82274]

He got it this way:

9" * 15" + 24" = 3240
3240/144 = 22.5

A small miscalculation there bubba.  Should be 12^3 instead of 12^2.

[bubba966]

He got it this way:

9" * 15" + 24" = 3240
3240/144 = 22.5

A small miscalculation there bubba.  Should be 12^3 instead of 12^2.

  Thanks for showing me how I wasn't thinking . Too many years of board ft, not enough concrete work, and way too much chemical exposure apparently leads one to such dumbass mistakes...

Goes to show you, don't use solvents without proper chemical gear. Or else you'll end up like me.

[JoshK]

not to sound like a smart ass but I understand how to calculate volumes, what I didn't/still don't know if how they quote concrete.  When it is quoted in yards is that square or cubic yards?  

If its cubic then
1.875 cu. ft / 27 cu. ft per cu. yd = .0694 cu. yd

That doesn't sound like a lot.  How much concrete is in a bag usually?

[JoshK]

Also,

I had envisioned that the last side to be put on after the mud had dried was the back side.  I would want a really tight fit with the top and bottom to prevent any vibrations.

[bubba966]

It's cubic yards when buying it mixed.

But by the bag it's by the pound. And there's many different options when picking it up by the bag. I don't recall if they list on the bag how many cubic yards that particular size bag will yeild as most of my concrete work has been done with pre-mix.

[Rob Babcock]

Of course, building the box and filling it with sand or lead shot would work pretty well, too, I think.  Certainly it'd be a lot less mess and bother.  Dunno if you've mixed cement before, but it can be PITA.

[Brad]

Sorry Bubba,

Wasn't trying to bust your chops.
Just really wanting to make sure MY calculation was right.  

Agreed that mixing the stuff manually is a messy p.i.t.a. if you don't do it very often.

[bubba966]

Also,

I had envisioned that the last side to be put on after the mud had dried was the back side.  I would want a really tight fit with the top and bottom to prevent any vibrations.

That'd be fine, but you'd still have to wait 60-90+ days to put the last side on. There's a hell of a lot of moisture in concrete. And it takes a while to cure enough so that you won't have a moisture problem when covering it with moisture sensitive materials.

The last house I worked on had in floor heating throughout. And after having the heat on in the floor at 65 degrees for 60 days there was still too much moisture in the concrete to lay the flooring down. And the pour was only 1.5" thick.

[bubba966]

Sorry Bubba,

Wasn't trying to bust your chops.
Just really wanting to make sure MY calculation was right.  

Agreed that mixing the stuff manually is a messy p.i.t.a. if you don't do it very often.

No problem. Actually appreciate that you pointed out I screwed the pooch. I thought 1.63 yards for 2 speaker stands seemed like way too much...

And yes, mixing it yourself IS a royal pain. I've only mixed it myself once, and I don't ever want to do it that way again.

If you wanted to do it quicker, easier, cleaner and even heavier use slag or sandblast iron. I've worked with both at the cement plant I used to work at. They're both exremely heavy. As well as being small in size so they'd fill a space better.

[JoshK]

Well I don't know how you would fill with molten iron but sand sounds like a good alternative then.

[bubba966]

I was referring to slag after it's cooled down. It looks a lot like sand. But is abrasive & very heavy.

[Thump553]

Note to self-never volunteer to help JoshK move.

[bob82274]

I've never done anything like this before but may I suggest building it so that it has interchangeable feet?  This way you could put casters on it to move it and put your favorite isolation device on it while it is in the system.