Home Theatre Sound damping?

[Lord Nikon]

I live in a house that has a basement, first floor, and a second floor. My subwoofer and all are on the first floor. My concern is that since the floor is sort of carpet cushion and plywood that I am losing sound to the basement. The basement isn't finished, so you can see the wood material if you are in the basement. Is there some sort of material I can put on the bottom of that floor to keep some of the subwoofer frequencies in that room and not escape through the floor?

[Lensman]

I live in a house that has a basement, first floor, and a second floor. My subwoofer and all are on the first floor. My concern is that since the floor is sort of carpet cushion and plywood that I am losing sound to the basement. The basement isn't finished, so you can see the wood material if you are in the basement. Is there some sort of material I can put on the bottom of that floor to keep some of the subwoofer frequencies in that room and not escape through the floor?

You can either reflect sound or absorb it. It appears you wish to reflect it back into the room. This is extremely difficult to with bass do as it requires lots of mass. Doubtless more so than you have physical room for or can comfortably afford to install.

But loss of bass to your basement is actually much less of a problem than bass that stays in your listening room. This is because the bass waves that reflect off the walls, floor and ceiling create interference as they hit each other, potentially canceling out much of your subs output. By reducing the amount of sound that gets canceled, you can increase your bass and smooth out your sub's response. The way to do this is to not to reflect the waves, but to absorb them.

If you feel your sub is "losing" bass, you should turn your attention to bass traps. A good article on what they do can be found here:

http://www.audioholics.com/techtips/setup/acoustics/BassTraps.html

If late you become concerned that you may have unwanted sound in the basement when you finish it, the best thing to do is make sure you place insulation (the thicker the better) under the floor before you finish the basement ceiling. For superior sound isolation, though at more expense), you can install acoustic insulation batting. Here's a link to a brochure from Owens Corning:

http://www.owenscorning.com/worldwide/admin/tempupload/pdf.3-74495-165%20_QuietZoneBro_E.pdf

[Sir Terrence the Terrible]

You can either reflect sound or absorb it. It appears you wish to reflect it back into the room. This is extremely difficult to with bass do as it requires lots of mass. Doubtless more so than you have physical room for or can comfortably afford to install.

But loss of bass to your basement is actually much less of a problem than bass that stays in your listening room. This is because the bass waves that reflect off the walls, floor and ceiling create interference as they hit each other, potentially canceling out much of your subs output. By reducing the amount of sound that gets canceled, you can increase your bass and smooth out your sub's response. The way to do this is to not to reflect the waves, but to absorb them.

If you feel your sub is "losing" bass, you should turn your attention to bass traps. A good article on what they do can be found here:

http://www.audioholics.com/techtips/setup/acoustics/BassTraps.html

If late you become concerned that you may have unwanted sound in the basement when you finish it, the best thing to do is make sure you place insulation (the thicker the better) under the floor before you finish the basement ceiling. For superior sound isolation, though at more expense), you can install acoustic insulation batting. Here's a link to a brochure from Owens Corning:

http://www.owenscorning.com/worldwide/admin/tempupload/pdf.3-74495-165%20_QuietZoneBro_E.pdf

Unfortunately bass traps are usless with his problem. Acoustic batting will only give limited success. If he is trying to keep bass in his room, and isolate the basement in the process, he will have to build a false flooring that raises the sub up off the floor. Only then will batting, very thick acoustical material be helpful. You must isolate the sub from from the floor to avoid any losses through it.

[Lensman]

Unfortunately bass traps are usless with his problem. Acoustic batting will only give limited success. If he is trying to keep bass in his room, and isolate the basement in the process, he will have to build a false flooring that raises the sub up off the floor. Only then will batting, very thick acoustical material be helpful. You must isolate the sub from from the floor to avoid any losses through it.

I'm not sure I quite follow. If I may beg your indulgence, could you please clarify a couple of points?

Are you saying most of his bass loss is actually occuring from resonations of his sub's cabinet being transmitted to the floor, which then easily passes through to be lost?

Are you suggesting by "false floor" that he build a small wood platform little larger than his sub perhaps stuffed with insulation, place the sub on it, then insulate under his entire floor? Would the platform be separated from the floor with feet of spikes?