I'm about to finish my riser, and I was shocked to see how much insulation costs. Unless I'm doing something wrong or looking at the wrong stuff, it would cost several hundred dollars if I packed my 4' x 8' riser full of insulation.

That being said, what is the downside of not doing it? I don't be having buttkickers or anything in the seats. Just a regular old 2 seater black leather couch. I thought about using my leftover linacoustic instead. I don't have enough to pack it full, but enough to line it and then some.

You could get some pillows, newspaper, or whatever works. It would be better than not being full. It really depends on your room, riser size, and location. My guess based on my own expereince would be that not filling it, there will be more sound trapped, less sound damped, or filled there will be less sound trapped, more sound damped.

Here's a roll with 50 sqft at 9.5" high. Even two bundles would be less than $100.

http://www.acehardware.com/product/index.jsp?productId=1390343

If you leave it empty, it will act like a drum and sound will resonant inside.

Don't pack it full. Just get something in there.

would lining it with a layer or two not be effectve? I may try the pillows if not.

Is blown insulation, like you'd put in an attic, acceptable? It seems to cost less.

Can't say this didn't cross my mind too! My riser is 17.5x16' !!! cha-ching.

I went ahead did it. If I noticed any issues after the room was done, it would be a real pain to go back and do it later.

That being said, I had a smaller riser in my last room that was not filled and I never noticed an issue.

Don't pack it full. Just get something in there.

A little goes a long way. Don't worry about filling the cavity

I advise against pillows it is really no less expensive and begs the opportunity for mold and vermin. which fiberglass does not. I have a 7 x 12 foot 15" high riser and I think it cost me about $100 for the batting to fill it.
and as wor the consequences you asked about in your title. I big hollow DRUM.

I advise against pillows it is really no less expensive and begs the opportunity for mold and vermin.

That's a really good point, and like Ted said, a little goes a long way. It shouldn't break the bank...the consequences for not doing it can be pretty unpleasant.

Frank

Cost me close to $400 to do mine. Not a light decision for some.

To "pack" by defintion means to fill a cavity but also can mean to compress tightly. I thought since by the title of the thread to pack it meant to put something in an area, versus nothing at all.

In my contruction I was forced to use very little amount of insulation intially and the middle of riser was left empty, but this is between areas that are packed on the left and right sides so should not be any consequence? Wrong. What we had as a result is that sounds as high as 150Hz or more could be felt durring movies for prolonged moments after the sound had reached our ears, and could be localized to the area that was left empty. Since I have stuffed insulation in there (not compressed) where the area was left empty because I left an opening to do so. Now the riser has an even amount of insulation with areas that are not damped more than others, and the result is that one area does not draw attention to itself, or act as a drum.

Areas should have an even and uniform sound, and if this means something such as your riser is going to be making a sound that isn't supposed to exsist, and other areas are not... well thats distortion.

Lining an area will damp sounds as the enter or exit the area, somtimes conducting sound into it or out of it sooner, laying it in the center of the area will dampen the sound as it inside.

Bellow you can see what the effect of compressing insulation does, not that I would advise it. This is the difference between having compressed insulation in corners in my room (green) or not (orange). They are averaged responses of four seats in my front row. That is why I said depends where it is, your room, etc. Have the area full, at least effective to the primary frequencies of human speech IMO. Notice how adding more insulation in my corners where there was none or very little, and putting a very little amount of insulation in my riser makes those frequencies change. I do not want that to happen in what is near the center of my room.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=120370&stc=1&d=1222116901

I don't know if you noticed, but prices on insulation have actually gone down the past few weeks at Home Depot and Lowes.

Thanks everyone for clarifying that I don't need to compress and pack it in there. I was able to get what I needed for $45 instead of $200-$250 that I thought it would be.

I have a question about what to fill the riser with if I know I am going to put the sub on it. Because of my room, I am going to be forced to put the sub on the riser. Originally I was going to put it on the stage and purchased sand for that. I imagine since the left/right front speakers will be on the stage that I should still fill it with sand. The riser that I am in the process of building for the back will be two 14'W x 3'6"L and 9"H. I built it in two sections so that I can take it out of the room when I sheet rock and put the dricore in then easily put it back. Does this whole riser need to be filled with sand? Does just one of the 14'x3'6" sections have to be filled? Or just the area where the sub goes? If not the whole riser then I would imagine fill the rest with insulation. I am hoping the whole thing doesn't have to be filled as that is alot of sand to bring down the basement :)

I didn't fill mine and I don't notice a difference. It is covered with 3/4" plywood, 1/2" backerboard and tiled on top with a layer of mastic in between each coat. My ears may not be as sensitive as other's though and my riser is not very big. Just big enough for a sofa and a couple feet of foot room in front. In future home theater's I'll probably insulate it though. Might as well while you're building it. I've learned some since I began construction by being on this site!

Brian

Additionally, what do you guys typically put on top of your riser? I put 2 layers of 1/4" OSB. it seems strong enough - it doesn't bend and I can jump up and down on it no problem. I'm concerned though that the weight of 2 people and a loveseat may be too much.

Since I was replacing the carpet in the room, I cut the existing carpet into strips (1'X5') and placed them in the riser between the 2X10's.

Sounds fine.

If you do not insulate your riser, people will die. So many have fallen because this has been overlooked.

Any advice on my issue above or should I start a seperate thread? Thanks in advance.

mike, I do not know what "has" to be done, but I can tell you what I did for my theater. I put sand in the riser underneath that area that would have the sub:

http://i103.photobucket.com/albums/m157/kwadswor/Basement%20Finishing/Riserfilledwithinsulationandsandind.jpg

I'm happy with the results.

Kevin,

Thanks for the help. I was hoping that would be the answer. So unless anyone says different I will just fill with sand in the areas where I think I may put the sub. It looks like you also put it under your seating, correct?

Mike

That's the most cost effective solution. Just block the areas off and fill them with a liner to keep the sand out of the other chambers. Also, you'll want to leave it uncovered until it is completely dry, which can take a couple of days sometimes.

Jason,

Thanks for the tip on letting it dry. I probably would have just sealed it up not knowing.

Mike