theatre in basement with concrete floor

well I have 2 f133 subs and wasn't getting the bass I wanted, in my old HT with wood floors so I added butt kickers 2 of the big ones, one in each couch. They are awesomd when diled in right they just blend and it feels natural, people say the base is awesome and have no idea they are there. The sound is there with the f113 but I had to get more powerful subs withthe concreat but the vibration wasn't.

Some people build a wood platform and put them on the platform then put the coutches on that.

I highly recomend them.

Are you putting carpet over the concrete?

Do you have any issues with dampness or with the concrete feeling cold? If so, I recommend DriCore or similar subfloor products.

I also have a concrete floor, and didn't realize there would be an issue. I will have two subs and carpet. Though perhaps with concrete, bass trapping wouldn't be necessary? Please explain how big of an issue this is.

I'm in the same boat. I have a poured concrete basement. Wasn't planning on adding a subfloor although I see many here have. I have no problems with dampness. The basment is already pretty cool in summer and warm in winter. It is an energy star certified home. I realize that cutting the basement up into sections (rooms) will change things but we are adding the proper heating/cooling vents and returns throughout the basement. Is there someone knowledgeable in this area that could speak on the topic?

If it is a basement carpet can be tricky I recomend something else waterproof with big area rug. However if you are doing carpet use a indoor outdoor that can get wet and a low weeve so it doesn't hold moisture and put a layer of 6m or thicker plastic down under the carpet padding. You can get it at any BORG/home srore. I did this in my old house and it turned out ok for years. Sealing the concreat with a sealer also helps and is cheap if you do carpet. The sealer really helped just pour it on and spread it.

This really depends on how much soft matter is throughout the rest of the basement.

Empty with a concrete floor would sound horrible. With a lot of furniture etc, it would not be bad.

My theater is in the basement with just a regular carpet on the concrete. They laid a pad underneath that is just a regular pad made for concrete floors. I have never had any problems with moisture, however our home is new, tiled and has a sump pump installed. Plus I do run a dehumidifier in the basement during the summer.

Wondering how your carpet feels underfoot for warmth? I'm struggling with cost of Dricore (upwards of $1700 for close to 900 sq ft) vs. not using at all and doing good pad/carpet for slab install.

Putting carpet of basement concrete slab is a bad idea. You risk moisture on the backside and then mold!

I'm pricing it out now myself.

2" foam board (R10) + 1/2" plywood would be about 2/3rd the cost of drycore (but you will need help installing it)

OR

6 mil plastic sheet then 2x4 pressure treated #3 grade lumber then add 3/4" plywood/osb sheething would be a little cheaper.

The foamboard would be simpler to put down and provide good sound isolation. It also provides an R value of 10.

What's your definition of "moisture" on the backside? Is it in the form of actual water from a leak/crack, or moisture in the form of humidity that naturally emits from concrete? I think there are construction techniques that help mitigate both conditions and the opinion of just "never put carpet on a slab" is debatable. For instance, if your builder used a vapor barrier as part of the basement pour, that helps with moisture intrusion through the slab. I still have to test mine to see where it falls. Even with a vapor barrier like that, I don't believe it won't help much with insulating it.

For my build, it will be either Dricore or nothing. I'm not willing to lose any more headroom than the 7/8" that Dricore has. I'd certainly consider the alternate subfloor methods you describe if I was only smart enough to pay the the $1K-2K extra the builder wanted for another course of block and had the additional headroom

Not good isolation. Foam rarely has a place when soundproofing, I'm afraid.

If your basement has been dry for an extended period of time even during heavy rain and the humidity level is fairly decent, then carpet on concrete is fine.

Do this simple test: get some clear plastic/tarp, and duct tape it down to the concrete (2x2 or so) and leave it in place for 48 hours. If there is no moisture trapped, then you are probably ok (basement flooding nonwithstanding).

I used special moisture resistant high quality padding and then carpet.

You are correct Ted. There are a lot better products.

But would you agree that a solid floor is better than a false floor on 2x4s? There's a lot of hollow empty chamber space in there for reflection of sound. I thought the former (solid floor) is better than the later.

You are the expert, so I will yield to your opinion.

I was referring to humidity which most basements are notorious for in summer months.

Anytime you have something cold (slab) touch warm humid air, you'll get condensation. A carpet will soak that up and hold onto it.

More annoying is French drains that a lot builders put around the interior parameter walls now. (Open gap along base of parameter walls, designed to let water out.) They go all the way to the stone/ground so water can drain beneath the slab. Unfortunately they let a good bit of water vapor up, and worse radon. I'm not sure why they even place them there unless they are worried about basement flooding.

Ted agree with the foam board . I believe I have read somewhere in a previous post about someone who used Stall Mats that are sold by Tractor Supply . They are rubber mats 4 x 6 x 1" thick . Then install a 3/4 " plywood over that . Not the cheapest way out but a good alternative to concrete?

In your opinion do you think this is a possible solution to a good acoustical fix for concrete floors ? Anyone?

Acoustically, a concrete floor under good pad and carpet is not going to affect your overall sound to the point of concern. Remember, there are 5 other walls in which to absorb low frequency sound (depending on how much flexure you give these walls). Concrete floors combined with rigid walls (double dry wall, green glue adhered to closely spaced studs) will increase bass reflection due to the reduced flexure of the walls. More importantly than the concrete floor, and this is where most people make mistakes, is positioning of seats and subs, poor riser design, integrating the subs improperly into the system, and not using correction. These factors will be far more harmful than any concrete floor.

My basement theater has 2 concrete walls and concrete floor. I did use carpet on the floor, but I have not had moisture problems, I also use a dehumidifier and monitor the humidity, and have a radon system which should allow for some airflow under the slab.

I was very surprised and dissapointed with the lack of bass when I placed the subwoofer on the concrete floor. At first, I thought the sub was not plugged in. I had to turn the volume way up. I then moved it to the back riser and it provides much better bass, but mostly for the back row of seats. The front row of seats has much less bass. I'm currently looking at installing bass traps, or possibly a second subwoofer.

A cheaper option similar to Dricore is Platon. It's essentially the Dricore plastic liner in bulk. You unroll it, then put down standard plywood and carpet on top. I'll be picking some up this weekend for my own construction, so if there's anything about it I should be aware of, someone please fill me in!

If one were to take the insulation/heat loss issue out of the equation, and just address the moisture vapor issue, why couldn't you use something like this:
http://www.radonseal.com/radonseal-mitigation.htm or http://www.concretesealers.com/ and then just do carpet/pad over it?

There appears to be several mfg's of similar product, where it penetrates the concrete (up to 4") and seals the small pores. Looks like you could do upwards of 1000 sq ft of slab for less than $150.

Anyone have any comments or experience with this approach?

If I were to put anything under the carpet, it would be Dri-Core. Installed within the 4 walls, after they are sealed and drywalled.

Regarding the walls and flex, some frequencies absorbed are interestingly related to the LF resonance point. Perhaps not surprisingly, if a partition has a LF resonance point of say, 75Hz, you'll likely have a less than desired measurement at that frequency. The partition is much more transmissive at the resonance frequencies.

So another reason to drive the LF resonance point down as low as we can.

Dricore has two problems in my book:
1) 33% price premium. For a 1000 sq ft basement, that's a look of $$$.
2) Dricore claims a 6->7F difference. Add in padding and carpet you'll get a 11F difference at best. On a typical 55F degree slab that's 66F. Still a little chilly

I've read six basement remodel books and watched I dozens of DIY shows. They either use false floor over 2x4 studs, or foamboard + 1/2" plywood.

If you removed dricore and bare slab how would you do it? If there isn't any other alternatives, I'll go with dricore.

Most don't want to add much to the floor height. Height loss is a constant battle.

Personally, I wouldn't see a problem with foam under ply. My comment regarding the foam was with respect to acoustic performance. So many want to use it within cavities for absorption.

In the floor application you described (thermal) it seems like a fine idea, actually.

To get back to your original question:

Basement slabs will reflect sound, and carry (transmit) very low low frequency sound. The latter (Transmission) isn't really an issue as so much the former (reflections)

A number of people here suggested just slapping down carpet. A few recommended a type of subfloor/false floor.

My main concern with just slapping down carpet is humidity. Carpet backings act a like a sponge when it comes to moisture. Most people don't realize that basements can reach 70% relative humidity or more during the SUMMER months. Mine reached 80% one summer day.

These kinds of levels lead to rust and mold. It will absorb into wood work and may affect your speakers. A lot of moisture forms on walls and slabs where the moist air hits it. (Slabs more than 40" underground are typically 55F->60F.) And carpet on slabs will wick that up. (Dehumidifier or not)

The recommended humidity level is about 40->50%. Anything over 50% encourages mold growth.

So before you make any decisions about sticking your equipment in the basement and throwing down a carpet, get a humidistat ($5 at walmart) and measure the humidity levels in your basement during the summer months. You may be surprised.

I also have the best padding available laid directly over a very dry basement concrete floor. Floor was painted with Dryloc first. No coldness so far, but it's not winter yet either. I think we will be fine because last year I spent a lot of time down there with just socks on and it wasn't an issue at all. I also looked at dricore, but just couldn't bring myself to paying that price for such a small return, if any, on the comfort scale.

Mine's on a slab... No problems if you buy enough sub!

IF your basement does not have problems with outside moisture getting in (low water table, drainage issues, landscaping issues, etc.) AND you have adequate air circulation/recycling, then a basement should not have moisture issues.

Do you get water in your basement?

I have never really noticed as I usually have socks on. it has never been "oh that's cold on my feet" As far as moistureis concerned. As I stated previously, I do run a dehumidifier during the summer. Normally, without it running it stays about 60%, with it running it drops it down into the low 50% range and sometimes in the 40% range. Running one is just a good idea, even if the basement is not finished. We have new house and i have never noticed any smell of mustyness (sp) and dampness). As far as subs are concerned my Paradigm PW2200 will shake my berklines, which are sitting on the floor.
Someone also mentioned about the carpets being big wicks. If you turn over any sort of looped carpet you will notice that the back is mostly plastic glue, which is used during the manufacturing process, and which makes it stiff to work with. Plastic, to my knowledge, will not wick moisture. I'm sure they are different carpets that maybe don't have that sort of back. But that is what I have always seen on stuff I have worked with.

Sorry if this takes the tread off track, but this raised a question for me. (this question is based on a room in a room build) I was under the impression that it was best to build your floor and then frame the walls on top of the floor. Is it is your opinion that it is best to frame the walls down to the concrete and then add the floor inside the walls?