New Construction Acoustic Design & Consulting


I need a professional consultant to work with my architect to help build as perfect a listening room over my garage as possible. RIVES is one possibility but I don't want to spend 10K just for the consulting work. I would like to build in as much sound isolation and room treatment as possible like that done for this person:
http://www.positive-feedback.com/Issue16/lavigneroom.htm--

Could I use ASC as a primary consultant and RIVES for after the room is built to do the final touch ups and room treatment? They only charge $100 for the engineer to help render sketches and make suggestions for the contractor.

acousticsciences.com

I would need detailed plans so that the architect would know how to impliment the built-in bass traps etc. I would need help with the specifics of window and door selection (materials) and placement, room dimensions, ceiling slope, floating floor, isolation etc... Please also see the list of ideas below. RIVES charges a fortune to render drawings based on a computer modeling system. I am not sure all of that makes sense until after the room is built, furnished and then tested, but certainly it is advantageous to build in as much acoustic isolation and treatment as possible from an aesthetic and cost perspective. Please comment on some of the suggestions below:

Room sizes

13X21X8 Feet
14 X18X8 Feet

windows o.k.
According to Dave Wilson

1. pitch ceiling height lower over speakers, higher over listener
2. Build bass traps into the wall
3. Corner loaded bass traps
4. Bass trap all four vertical corners and the ceiling perimeter corner with a soffit bass trap
5. Room dimensions:
Must over-size room by minimum of 6 inches walls, floor, and ceiling to allow for buildouts for acoustic treatments and sound isolation
A. 13-15 feet wide by 15-23 feet long
B. Room height 7-9 feet
must account for additional height of "floating floor"
C. Wall/stud resonance treatment and constrained layer damping: 1. Sandwich two layers of sheetrock. ? Gyproc Soundbloc 1.5 soundproofing plasterboard 2. Suspend sheetrock off studs by screwing into resilient metal fir strips called "z-metal" or "RC-1" 2. Visco damping material {1/16 " thick double sided adhesive visco-elastic sheet} is applied between the z-metal and the first sheet rock layer and a second visco-elastic sheet between the first and second layers. In place
of double sided adhesive visco-elastic sheet, can 100% glue to both sides a layer of sound board {firtex or celotex}. ? Staggered studs. The ceiling must be treated the same way.
D. Locate entry door behind the listner but on a SIDE WALL {nowhere near the speakers since the door will raddle} NOT ON A BACK WALL AND not flush to the corner and at least 2 feet from the corner. Door cannot rattle? Heavy acoustic door/frame?
E. Windows are very tympanic and should be avoided. Tall narrow windows are best.
Must not use standard thermal type instead use 2 layers of thick laminated glass [like that used for glass shelving in stores] separated by at least 4 inches of air space. The air space must be vented into the wall cavity. Set the glass into a bed of visco-elastic damping material. The glass sheets should be of different thicknesses.
F. Lighting should be subdued, indirect, and dimmable. Do not use standard wall dimmers since they will often hum or buzz. Use a variable voltage transformer. Consider low voltage lighting. Do not use ceiling cans, they rattle. The best light has a ceiling bezel and lens of thick rounded glass. Consider creating a false ceiling to hide projector, cabling, HVAC
ventilation big problem if room needs to be airtight to insure adequate sound isolation and room damping from the rest of the house
G. Address side wall, rear wall, and ceiling reflections which are determined by speaker placement. Room dimensions must account for acoustic panels
dbk
Although all the discussion have been interesting, the original questions and limitations you put forward were that you couldn't afford to put out lots of money on a consultant and that you had restrictions on the room dimensions.

Rather than focusing on I'd specifics first I'd ask you to identify clearly, the limitations of the space (size, windows, doors), the actual usage of the room (just you, multi-channel), cosmetic restrictions and the construction costs. After those are clearly identified then work on the practical aspects of the design.

Q. Floating floor
A. Floating floors are most often used to isolate rather than improve the interior acoustics of the room. I prefer to seperate surfaces (walls, ceiling, floors) into two things, lossy or isolating. As Mikelavigne already said he has a concrete floor (concrete is not lossy but is generally isolating) with no floating floor and it sounds great. That probably means that the lossy part is in the construction of the walls, ceiling and acoustical materials (bass absorbers).

I prefer predictable spaces (flat ceiling, parallel walls, shoebox) for the basic structure constructed as a damped diaphramatic shell using sheetrock. There are several good ways to make a wall damped and lossy or damped and isolating (ASC Wall damp system as example). Low frequencies are predicitable. We know pretty close to where the speakers should be and where we should sit. You can always add bass absorbers that changes the shape of the room baised on the needs of the room.

Q. Ceiling Design?
A. As I stated above I like predictable lower frequency spaces but that doesn't mean we can't add more materials to the interior to change the shape and behavior of lower frequecies and up.

Clouds built into, on or suspended from the ceiling work great. The choice of materials is strictly dependent on the rest of the acoustical materials in the room. If you have adequate broad band absorption on the walss then the ceiling usually diffusive concentrated between you and the speakers and over your head. You can use RPG Skylines, Omni's or only the open finished cavities of the floor joists above. or, if you have now where else to put broad and absorption the ceiling is a great place to get it out of the way without usually doing much harm but much good.

Attic spaces with pitched ceilings are an excellect places to suspend a cloud over the pitch or directly attached to the ceiling.

Q. Diagonal rooms
A. Really hard to do well. You have the built in benifit of very low first reflections since the sidewalls fade away but now you have to figure where to sit. Most of the time they work well if you set up the room like a mixing room with the speakers as near field monitors with the rear walls a ways back. Those base modes want to react with the parallel walls even if you have the speakers outside a corner and the rear walls now have first reflections that wouldn't occur otherwise. So you are forever deciding which mode/reflection to treat and mode to avoid/not avoid. Have I seen any work, absolutely. Have I seen more fail, absolutely.

The room size is the room size. The axial modes take precident (LxWxH). The tangentials and oblique modes (longer wavelengths)are general down in strength 6-12dB and only could be benificial if there is a concurrance of a weak axial modes with strong "other" modes.

Please anyone chime in. I really like a discussion of the issues for a non-price no object individual. I'm always interested in technical reasonings and lesser so with anecdotal experiences but they still may be helpful.

Dbk, maybe you could clarify my ealier questions to help us (the forum) help you sharpen your focus.

Rather than focusing on I'd specifics first I'd ask you to identify clearly, the limitations of the space (size, windows, doors), the actual usage of the room (just you, multi-channel), cosmetic restrictions and the construction costs. After those are clearly identified then work on the practical aspects of the design.

Dimensions approximately 17 feet by 20 feet by 8 feet

Two medium sized windows at the front and one rear entry door

Usage essentially just myself and occasional movie viewing via no frills ceiling projector and drop down motorized screen over the windows.

Cosmetic issues...clean and uncluttered, modern space with most of the acoustic treatment built-in

Construction cost including framing, roof buildout and interior finishes (not furniture) no more than 95K
I've run the numbers several times in several ways and the room appears to be too wide to behave well at lower frequencies (<250Hz) If you reduce the width 18" a big potential hole goes away around 50Hz. I don't see any reason why you couldn't have an excellent room given the modest restrictions of the room. You also have the flexiblity of placing your seating and speakers where they will do well.

The cost of the complete build would be between you and your contractor.

I'm an industry insider when it comes to these subjects and need to avoid promoting anyone but if you're spending that kind of money you should have someone help you. I'd look up "acoustical design home theater consultants" in a google search and work your way through a few pages and call some people or just ask people on this forum to give you names. Anyone want to throw out some names? Try RPG's website and go through the residential dealer list. You can except/reject them quickly with a few well framed questions.

Also, you can limit the fee for the consultant's help by reducing his/her responsiblities for inspection and drawing details. If you allow the consultant to drop the complete detail package you should find one that you can afford (try 2-5% of the build out).

Good mid/high frequency acoustical materials are modest in cost with low frequency absorption significantly more. That's the easy part except you need to make it fit the decor. Fancy stretched fabric over acoustical materials (whole walls) costs more than exposed fabric wrapped materials.

Please keep in mind our earlier threads and try to avoid exotic solutions. I'll answer as many more specific questions I can but my available time is limited and I won't be able to follow for awhile.