Riser will only be 3.5" high (2x4 framing) plus double 3/4 ply on top.

Do I really need sand?

All speakers and several subs will be on top of the riser.

db

I would still use it. Consider the low riser a bonus that you won't need much sand. The difference in my stage with and without sand was astounding. Despite the 1750 pounds I had to lug down the basement...

I think I'll need about 1200 lbs; about 24 bags. Not too bad.

Has anyone left the sand in the bags it arrives in?

Otherwise, I need to line the framing with plastic sheeting to keep the sand off the bare concrete basement floor.

db

Hey db,

I had the same thought about perhaps leaving the sand in the bag it came in but my stage is made from 2X6's so I would have needed to line with plastic becaue I would have needed to add sand around it to top things off.

They recently just changed the bag style so if were to do this, it is a better option now. Before the bag was sealed, but with folds at the top and bottom. This still allowed for some sand to seep out. I needed one more bag of sand to top things off and got from the Lowes in WB. The play sand now comes in a bag that is sealed straight across the top and bottom and wont let any sand out so long as it's not damaged.

edit: I thought I needed about 24 bags of sand only used about 14. My stage is 11'5' x28" x6"

Forget the sand. With 1.5" of plywood or OSB, the tiny amount of air inside the framing won't matter. If it makes you feel better, fill the spaces will fiberglass insulation. The importance of sand is way overblown on these boards IMO.

Are you talking stage? or riser? you said riser but it sounds more like your stage. the most often heard advice is sand in stage unless contraindicated and fiberglass insulation in riser.
Those who have not wanted the weight of the sand say on a second floor have used Insulation instead with ok results.
My stage was pre-existing and so filled with insulation already. I used a SubDude for the sub on it and the other front speakers are on MDF shelves behind the screen.

Long time reader first time poster.

As I finally put a bid on a house I am getting closer to my very own HT build but I am left with some questions, one of which was brought to mind by this thread.

I assume that the sand is placed within the stage for audio reasons, is this correct?

Sorry for being unclear.

We are talking about my stage.

I also have a second row riser that will be 9.5'x6'x5.5" (cavity) topped with double 3/4 ply. I have committed to only fiberglass for same. It will also have sub columns on it.

I have a 3.5" plus double ply stage that I just filled with sand as there will be a sub sitting on it. It didn't take all that much compared to most of the other projects here (about 500 pounds) but even with the minimal air volume underneath, there's a world of difference in terms of vibration and resonance of the stage itself.

6 mil plastic sheeting is the easiest thing in the world to use. I just took a big sheet of vapor barrier and laid it across all the joists, dumped the sand in, and then trimmed the excess around the top.

I have a 3.5" plus double ply stage that I just filled with sand as there will be a sub sitting on it. It didn't take all that much compared to most of the other projects here (about 500 pounds) but even with the minimal air volume underneath, there's a world of difference in terms of vibration and resonance of the stage itself.

How do you know that? Did you complete your stage without sand, do extensive listening, and then open up the stage and fill it with sand?

Anyone care to do some mass calculations?

From
http://www.engineersedge.com/commercial_lumber_sizes.htm

2x4s are 1.25lb per foot and my stage will use approx 100 linear ft=125 lbs of lumber
plus 4 sheets of plywood - say 50 lbs each =200lbs

Total stage weight =325lbs of lumber

Subs+speakers - each sub =100lbs*2=200lbs.
LCRs weigh about 75lbs each * 3 = 225lbs
Total spk = 425lbs

Total stage + speakers = 750lbs - not insignificant.

Anticipated sand =1200 lbs - essentially tripling the total stage mass

For Riser, lumber about 400lbs+seating=800lbs+ a few people=400lbs=1600lbs

About 2200lbs in sand to fill, just more than doubles the mass.

Nonetheless, each of the stage and riser are fairly massive without the sand - key is to damp resonance rather than to add mass (essentially to also damp resonanace).

Hard to imagine a native 2x lumber contruction 12 or 16" o.c. topped (and made rigid by) with double layer of 3/4" ply has significant resonance. Especially with some cross bracing. I'm thinking fiberglass may be enough.

How do you know that? Did you complete your stage without sand, do extensive listening, and then open up the stage and fill it with sand?

I said there was a difference in the basic vibration of the stage itself; there was no mention whatsoever about ANY audio material. I simply stated that the stage vibrated more when empty as opposed to filled. I capped the stage, gave it a good whack, and walked on it - it echoed audibly. I removed the ply, filled it with sand and repeated - it did not. To me, this indicates a substantial difference in how the stage vibrates. It was not a subtle effect.

Will this ultimately impact the quality of music and movies? I don't know. I never said I did know. I haven't even unpacked my speakers yet.

I have seen allot of posts lately about "do I need to do this or that".

Maybe the 80/20 rule has been forgotten? In this case, 80% of the effort will net you the last 20% of improvement.

I plan on putting sand in the stage for a few reasons:

1) It's based on sound engineering principles, and at the very least it won't hurt anything
2) I have a couple kilowatts of sub power
3) easy and cheap
4) not easy and cheap to do later

Thinking about all this more, I have two thoughts:

1. I think my real problem is not the stage - easy to treat with sand, etc, but my riser with my sub columns sitting on it and also screwed to the wall. I am now concerned that the wall will vibrate/rattle. Not as concerned with the stage as it is a massive structure. I am not sure there is really any easy way to secure the column to the wall but also isolate it from same. Worst case I can take the two subs from the column and move then to new cabinets also on the stage. Will mess with my room mode calculations, but I'll deal.

2. for the stage, instead of sand, how about instead of 2x4 with double ply to total 5" high, I use 2x4 flat (1.5") + 5 layers of ply. Actually will cost less than the sand and I can't image any resonance.

One thing that dbbarron's calculations point out, is that a thin stage won't have mass if not sand filled. Snowcarver's small stage won't have mass if not for sand filling, whereas a large stage might.

My stage has heavy rubber matting underneath, plywood on top, 2x4" stud construction with two layers of 3/4" ply green glued, then a 2x6" section behind that, where the subs will reside. Despite being a small room, it did consume a surprising amount of time, material, and money. None of it will be seen, as the whole structure will be behind an AT front wall.

dbbarron, your calculations are very interesting, but it appears you are filling your riser with sand?? Risers get completely filled with insulation batt (non-backed) to avoid becoming a resonant cavity, and they can also be put to work to tame room nodes. 12" center construction and double plywood top with felt paper in between, to avoid wood on wood squeeks.

I can't imagine not filling the stage with at least insulation, but I wouldn't kid myself that a sand filled stage is the superior construction method. If you build the stage, then the cost difference is the price of sand/plastic sheeting versus insulation plus the additional time/labour involved with using sand.

Normally risers are not fastened to the wall, there is a small gap,and are often also placed on isolators underneath, [hockey pucks or real isolators] in my case my riser is not fastened to the wall. I have speaker columns on the riser but they are fastented to the wall not the riser so they float actually. One of my Subs IS on my riser but that is for tactlie response as much as sound response.

I'm afraid the rear sub columns must weigh about 150-200 lbs with drivers and all, and thus it will be hard to float them off just the steel studs in the wall. I am most concerned that they will vibrate the wall and everything else because they are secured to the wall.

However, wall constructions is 2x4 20 gauge steel studs (heavier than 'drywall studs' which are 25 gauge. loaded with fiberglass batt insualtion and covered in double 5/8+1/8 of plaster; a fairly heavy and sturdy assembly. I guess I'll just have to see if I get any wall/room rattles from the subs. Can always relocate to behind screen wall.

Regarding the stage, perhaps I only build it up to the screen wall and place my speakers directly on the concrete slab behind the screen wall.

I'm afraid the rear sub columns must weigh about 150-200 lbs with drivers and all, and thus it will be hard to float them off just the steel studs in the wall. I am most concerned that they will vibrate the wall and everything else because they are secured to the wall.

However, wall constructions is 2x4 20 gauge steel studs (heavier than 'drywall studs' which are 25 gauge. loaded with fiberglass batt insualtion and covered in double 5/8+1/8 of plaster; a fairly heavy and sturdy assembly. I guess I'll just have to see if I get any wall/room rattles from the subs. Can always relocate to behind screen wall.

Regarding the stage, perhaps I only build it up to the screen wall and place my speakers directly on the concrete slab behind the screen wall.

As I said I have one of my subs on the riser for tactile response, [have butt kickers too mounted IN the riser but the Sub adds a lot] Have you considered using your subs for that purpose? it is a really cool effect.Of course this assumes that that location for sub[s] works sonically for you.

The riser should be decoupled from the walls and mounted on isolators. that way the vibrations are not transferred to the walls or the floor.

The riser will be decoupled from the wall, but the column on the riser (the sub column) will have a few screws into a cleat in the wall so that it does not wall over. Not sure how to decouple it from the wall??

Do you need to put sand in the stage if you are putting the sub/mains on the stage? What if the stage was just for the looks?

I would definitely put the sand in the stage. In my build I needed 2800lbs of sand and it made a big difference. My subs are really big and I am sure they would have made the stage a big drum.

If you are not using a sub maybe you can get away without.

Itai

A couple thoughts:
1) Dennis and the rest of the gurus recommend sand in the stage. That was good enough for me
2) Sand has a unique dampening factor that is independent of the mass it adds to the structure. If I understand it correctly, energy is lost as one little grain tries to wiggle the grain next to it, and so on, and so on.
3) If no speakers or subs are on the stage, then filling it with insulation should be adequate. Basically treating it the same way that a riser is treated (ie, preventing it from being a resonating cavity).

In my last house I put sand inside a few hollow core doors - they needed hinge and jam reinforcement so this is not for the faint of heart.

It did an amazing job reducing sound transmission...you could knock on the door and hear nothing but a light thud with NO resonance.

Sand will go in may stage, additionally I may make custom doors for my HT in progress to incorporate sand in them :)

In my last house I put sand inside a few hollow core doors - they needed hinge and jam reinforcement so this is not for the faint of heart.

It did an amazing job reducing sound transmission...you could knock on the door and hear nothing but a light thud with NO resonance.

Sand will go in may stage, additionally I may make custom doors for my HT in progress to incorporate sand in them :)

Hey that's one thing we all have PLENTY of on the Cape! LOL
notice how many of us there are on the forum?

A couple thoughts:
1) Dennis and the rest of the gurus recommend sand in the stage. That was good enough for me

2) Sand has a unique dampening factor that is independent of the mass it adds to the structure. If I understand it correctly, energy is lost as one little grain tries to wiggle the grain next to it, and so on, and so on.

So yes, put sand in stage if putting sub or speakers on top of the stage.


3) If no speakers or subs are on the stage, then filling it with insulation should be adequate. Basically treating it the same way that a riser is treated (ie, preventing it from being a resonating cavity).

This actually helped me a lot. :)

Thanks.

Less and less sand on the cape everyday - at some point every property will be beachfront - - - for a while.

db

I have not seen any discussions of using acoustic caulk or silicon (assuming construction adhesive is too rigid) between 2x sleepers and concrete floor and between 2x sleepers and first layer of floor sheathing.


(for further anti squeek - in addition to sand, etc.)

Any input on this?

db

Forget the sand. With 1.5" of plywood or OSB, the tiny amount of air inside the framing won't matter. If it makes you feel better, fill the spaces will fiberglass insulation. The importance of sand is way overblown on these boards IMO.

+1

Just build your stage extra sturdy. 2 layers of 3/4" plus closely spaced framing members (~10") with some construction adhesive will give you an awfully sturdy hunk of wood. Resonance shouldn't be an issue.

I've got an extra 256 sq. ft. of 3 1/2" insulation waiting for a good use. Will stuff everything...db

A few Q's:

Between the 2x sleepers and the first layer of ply should I use GG or const. adhesive.

Between the 2 layers of 3/4 ply should I use GG, felt paper or both?

db

> If it makes you feel better, fill the spaces will fiberglass insulation.

That is what I did.