Starting HT in basement; need advivce!

Discussion in 'Home Theater Projects' started by jmk14, Jan 31, 2007.

  1. jmk14

    jmk14 Auditioning

    Dec 10, 2006
    Likes Received:
    I am starting to builld a HT in my basement. My question is when I fasten the walls to the floor joists should I use isolation clips or rubber padding when I fasten them or can I just nail them directly to the floor joists?
  2. BillSuneson

    BillSuneson Stunt Coordinator

    Sep 16, 2005
    Likes Received:

    You wouldn't necessarily have to use anything between the bottom plate and the subfloor. If you wanted one of the easiest things do use would be the insulation strips that are used on the sill of your house. And then make sure to nail the bottom plate right through that into the subfloor.

  3. BruceSpielbauer

    BruceSpielbauer Second Unit

    May 27, 2002
    Likes Received:

    It depends on what your goals are. IF you are trying to isolate the sound (block sound from escaping, or block sound from entering), then the answer is YES, and you should consider using some sort of isiolation hardware. I used RSIC clips (DC-04) to connect my 2 X 4 top plates to the joists above.

    Caveat -- if your goal is to try to treat the room for sound isolation, you must also consider the walls. And, all other potential access pathways. Otherwise, the sound will simply find another route, and you will find you have wasted the time and money you spent on treating the tops of the stud walls.

    As an example -- I used the RSIC clips to attach top plates. But, I also did the following:

    -The ceiling was drywall; I used two layers of 5/8 ", which was attached to hat channel, which was attached to some DC-01 RSIC clips, screwed into the ceiling joists; This was to partially decouple the ceiling drywall from the joists above.
    -the walls had two layers of 5/8 " drywall; This was to try to help block sound (more mass), especially the low bass (LFE subwoofer).
    -the stud walls were built as a room within a room; two sets of stud walls, with one inch separating them; This is effective for midrange and high frequency, especially.
    -Green Glue was applied in between all drywall sandwiches described above; This product is a visceoelastic sound treatment product, and it helps block the midrange, the highs, and also the low frequency LFE sound.
    -the floor was treated with Acoustik rubber flooring material, which stopped short of touching the walls; On top of that is thick carpet pad, and on top of this, sits my subwoofer.
    -the doors are exterior solid core, built as communicating doors (two doors are at the entrance, with offset handles); One enters by opening one door, and then is confronted with a second door. Both are heavy, and solid, and have the same sort of weather stripping you probably have on your outside front door.
    -all gaps and air pockets were sealed with acoustic caulk;
    -all electric boxes were sealed with putty;
    -All walls have standard fiberglass insulation (R-19), and so do the ceiling joists above. This does almost nothing for the LFE noise, but it does help a bit more on the midrange and the highs.
    -the HVAC ducting is flexible round ducting with a canvas liner covering the inner side, to aid in sound isolation.
    -even the projector mount was hung using isolation clips, and the mount itself has built in partial decoupling. This is not so much for sound isolation, as it protects the projector from the normal "bounces" produced when someone walks across the floor directly above it.

    The above list is pretty thorough -- sound isolation was a high priority for me. I went further than most (although I know of some who have gone further).

    However, the "caveat" I posted above is an important principle to keep in mind... do not waste time and money trying to isolate sound if you only treat the walls, but ignore the ceiling. And, vice-versa. Also, any doors or windows require equal attention.

    I do not know if you have heard the aquarium analogy (credit Dennis Erskine, on another forum): Here it is, in a nutshell: think of the entire room as an aquarium. You can have the best top on that aquarium, and three of the walls can be be the very best. Still, if there is a 5 inch hole in that fourth wall, the water is going to come pouring right out and quickly, just the same. In your home theater, sound will do the same thing. And, once outside the room, sound is free to travel up into the ceiling joists, and vibrate the structure of the house, rendering any partial effort you have expended as meaningless.


Share This Page