Hey Tom - I've just gone through a renovation and did research some of this stuff, though I did not end up putting my listening room in the basement as I thought I might. Anyway, the best approach if you have a ceiling that low, and this is a second-hand suggestion from an authority on such things so take it with the usual grain of salt you may with any advice you receive here, is to leave the joist bays open and do not use any drywall or panel covering. Stuff the bays with the (uncovered) insulation of your choice. There is a more expensive, very dense almost wool-like insulation that we used upstairs in our home that is the best solid insulation for sound dampening (better still is blown-in but that may not be a good idea if you are leaving it uncovered). So you leave the insulation exposed and hang some kind of fabric beneath it to cover the ceiling and keep it sealed up. The combination fabric and insulation will be much better at deadening that low reflective surface than just hanging fabric over hard drywall. If you must do drywall I'd consider blown-in insulation and a more agressive acoustic treatment attached to the ceiling such as those sold by RPG.
Suggest you forget the drywall ceiling, and use acoustical tiles, which are not called acoustical for nothing. I used Roxul bats, and Celotex tiles that are 2x4' but made with a groove to look like 2x2'. One three inch Roxul bat is plenty. Use lengths of steel wire cut an eighth of an inch longer than the distance between joists to hold the Roxul up against the floor. Leave an airspace between the Roxul and Celotex. Avoid flourescent (sp?) lights; use recessed lights instead. There's a rule or formula for spacing recessed lights to prevent shadows on the walls. I used this approach. It has many benefits. e.g., sound doesn't travel to the main floor; ceiling is practically transparent acoustically for good vertical soundstaging; combination of bats, airspace, tiles, grid, joists, and lighting make for good absorption and diffusion; and it's easy to remove tiles if needed for pipe, electrical, heating, etc., repairs.
I wouldn't go with a drop ceiling: Too much shaking around. If burlap is OK with you, I would go with Marco's suggestion: Use sound insulation (like what you were thinking about) between the joists up against the ceiling and leave an air space. An effectively taller ceiling will give you better acoustics and you can add half a foot of height with the burlap approach.
That's really interesting. My last house had dimensions very similar. The house was a split level with the down stairs having a bedroom, full bath, full utility kitchenette room and two large rooms measuring 16' x 24'. The ceiling was exactly like what you described 7'-7" finished. I loved the room with my Vandersteen 2c about 5 feet from the back wall and 3 feet from the sides. It threw a sound stage so big; it was incredible! I had popcorn ceiling removed and a 6" x 12" beam to cover in the stereo room. When the popcorn was removed, the removal process used soap water that caused the existing dry wall ceiling to sag. So instead of fighting it, I had the contractor put another 1/2" dry wall over the top and secure it with 3" screws and mud. I used 6" crown molding which knocked some of the reflection. The room was lively and just loved jazz and blues music. Classical was good too. My brother-in-law and his sons were all in the orchestra. They could not believe the presentation of the sound stage! It was like beening the conductor at Boston! They would point to instuments in the sound field with their eyes closed and never once did they point to a speaker! They kept asking me how the two speaker could produce a soundstage that was 30-40 ft deep and 20 feet high! The album was Yo Yo Ma and Boston S..
So here is the spec for that room.
- Waterproof epoxy coating with heavy wool padding and burbur carpeting wall to wall.
Concrete 1/2 wall on three sides 3 ft high.
- Waterproof with epoxy coating
- 2x4 stud spacing away from concrete
- Heavy fiberglass remodel insulation R45 (These are bagged in plastic liners.)
- 3/4" drywall screwed into studs.
- Blow out part of the end wall for glass french doors (Very lively rear projection, need to have curtains to baffle sun and sound).
- Large triple pane picture window above opposite wall behind listener (When covered with heavy curtain hurt the sound field, covered with light shear curtains only.)
Side walls into kitchenette laudary room
- Studded with 2x6.
- packed with remodel heavy fiberglass (R45)
- 3/4" dry wall
- 4 separate 20 amp electrical lines pulled into the room with 4-6000 watt isolation transformers on all four the lines with the electronics.
Some excellent responses.
In my HT which I built, soundproofing was of ultimate concern, as well as the sound quality. I had just under 8' of height.
To sound proof, I put prodigious amounts of insulation inbetween joists. However, I understand that if it's packed too tightly, it will actually work worse. I did pack it in around ducts, etc. which could carry noise.
I attatched "hat channel" or resilient channel (same thing) across the joists, then put up sheets of Homasote, which is a paper product good for noise barrier. I put the channel and homasote (you can check it out; it's at Home Despot), on the interior walls of the HT as well. It's excellent at sound blocking!
Then, put dropped ceiling in over the homasote and channel. This is one QUIET room! Very little noise transmission in or out of room. I can have system cranked pretty good and virtually no noise upstairs above.
Be forewarned; any "holes" or spaces in your ceiling will transmit noise. To allow for can lighting as well as a perfectly sound proof ceiling, I built individual sound-proof boxes recessed into the joists for the cans to sit in. They could be moved about within the boxes later for placement on the dropped ceiling grid. Worked perfect!
You'll have to caulk and foam all spaces! Even electrical outlets. Well worth the extra time.
I have zero noise from the dropped ceiling (it's a 3" drop; I had a professional install - very glad I did!)
Oh, and yes, if this room will double as a HT, DEFINITELY go witht he black ceiling tiles and channel! Very worth it! Really gives a classy appearance to the HT!
Get a subscription to Home Theater Builder Magazine and buy the past issues. There are some on sound proofing and every other aspect of room. Extremely valuable insights! don't begin building without first checking them out!
Resilient channels with one layer of gyproc, filled and taped. A second layer of gyproc installed going the other way so that that it covers the joints of the first one, filled and taped. Cover that with a rough stucco finish. Avoid suspended ceilings is my recommendation. You need both mass and resilience.
Unfortunately you can't have those nice coffered ceilings in a low basement, I don't know how good they are for acoustics, but they sure look nice.
Thanks for the responses folks, it gives me much food for thought.
Oh, forgot, fill the space between the joists with fiberglass batts!
My old listening room was in a condo and my primary concern was isolation so as not to bother the neighbors. Now that I'm trying to make an existing home theater room in our new house sound good, I realize how good my old room was. Here's what I did:
The listening room was in a concrete basement with about 7'6" from floor to ceiling. I ran felt strips across all of the floor joists and put R13 insulation between them. Then I used 5/8" MDF panels cut in 4' x 4' sections. In each of the panels, I drilled five 5/16" holes - one near each corner and one near the center. These holes were large enough that the mounting screw would not touch the MDF. Then for each hole, I used a self drilling screw, a large metal washer and two large rubber washers. The panels were put up so that the felt isolated it from the floor joists and the rubber washers isolated them from the mounting screws. After they were all up, I sealed the whole thing with silicon RTV. Then I ran furring strips and put up acoustic tiles. I used track lighting to avoid leakage from recessed lights.
Off the subject a little, the rest of the room was standard room within a room studs and sheetrock with staggered studs on the one set of support beams. In the upper corners where the walls were shared with adjacent condo units, I put in some rubberized sound deadening material that is normally used to sound insulate ducts in large buildings.
The room might be considered somewhat dead to many people but it stepped right out of the way of my system and I wish I could reproduce it's qualities in my new home.
I plan to use 3" batts of rock wool insulation in the joists. I am not sure if I should fill the whole 9" space with them or maybe use two batts for 6" and leave a little dead air space or have some space between each layer of batting.
has anybody done a drywall ceiling with a slope from front to back and if so how did this work out?