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Discussion Starter · #1 ·
Hi all,


I have just finished the plans for my new home, and on the weekend, took a look at the block of land that we have decided upon (Australia).


As it turns out, our new home will need to be on bearers and joists, and not a cement slab.


I am wondering wether this will negatively affect my home theater room.


Im guessing I can do an extra thick flooring with particle board layers and thick carpet?


In your experience, does a cement slab allow for better, or worse acoustics. I would have thought that a cement slab would actually reflect a lot of frequencies, including bass, adding to standing waves and room modes?


My room is going to be 5.36m x 4.21m (that's 17.59 x 13.81 feet). I have run my dimensions through a spreadsheet to calculate room modes. It should be okay. Though no matter what I did, I always had a NULL in the central seating position down between 38 - 42Hz which is a bit annoying.


The room isn't going to be too full on - ie it won't LOOK like a cinema like some home theaters, but it WILL be a dedicated theater room with projector and screen, 7.1 surround (yamaha RXV3800). I guess it will be a cross between a big loungeroom and home cinema.


After reading up some white papers, and after having many years of playing around with subwoofer placement and standing waves, I really want to get the best full bass response that I can - so, I am going for 4 subwoofers, one placed on each wall, in the centre. From what I have read this negates standing waves and room modes as best as possible.


CSR is the company here in Australia that builders use for gyp rock walls. They offer a special 'acoustic' package for home theaters... which I am guessing is thicker more suited material for the walls and insulation in the roof.


Not sure on screen size. Anyone with any suggestions would be greatly appreciated. It will be a 16:9 screen. Unsure wether to go DLP or LCD projection at this stage. Still researching.


If anyone has any ideas, thoughts or comments on my ideas, please let me know. The intention here is that I don't want to add too much additional cost to my house. Im willing to spend a few $k extra on building the room properly... but nothing too crazy (our NEXT home will be the one with the crazy multi-tiered home theater!).


In the mean time I'll keep reading around here.


Thanks in advance,


Scott
 

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Perhaps you could get them to put twice as many joists in the floor for that room?


Also instead of using chipboard do some research into the heaviest, thickest, stiffest board you can get and use that instead (just for the room) - I would have thought formply but might be wrong.


Get the builder to put staggered studd walls in if you cant do room in room.


Use hat channel and clips for the ceiling, unless you can put a room in room ceiling in.


get the BGC fire rated 16mm thick board - its cheaper and denser i.e. better then the CSR or Boral ones. Forget CSR's rubbish on soundproofing - just read this forum, there are better and cheaper methods.


4 subs....what's your budget? any brand/model in mind? Have a look at VAF's new sub - its $5k? I think and worth every penny IMHO - actually its kinda like 3 subs in one...you'll need a very good installer to get 4 subs working right


projectorscreens.com.au has a good range of screens - I understand its the same as SMX fabric. 2.35 is really, really cool - if you want the wow factor and you have the space do it. Can get a 2.35 screen and the new panny projector or get a cheaper projector and an anamorphic lens.


Dont worry about projector until you've finished - there will be a better cheaper one around when you're buying.
 

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I'm guessing that the floating floor will sound better than the concrete slab. It will certainly help with the isolation for the rest of the house. Personally, I would not put in extra joists, it would work against the sound isolation.


As far as the null goes, where is your center seating postion? The exact center of the room always has nulls. The best seating is either further front or further back (I can't remember the exact distance, but if you look in my theater thread I have it listed there).


Gypsum is fine for the wall board. It is the same thing used in much of the world (including the US). If you are concerned about sound isolation, search for Green Glue. Also, the recommendations of staggered studs and isolation clips made by Elill are good ideas.


CJ
 

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Discussion Starter · #4 ·
Ahh thanks for the replies guys.


OK so NOT having a slab isn't such a bad thing for acoustics then.


As for my seating position. Well, It would be about 3/4th back. When I ran my stuff through the spreadsheet, no matter what distance I sat from the rear wall, I always had a NULL in my central seating position... caused by the reflections from the side walls - I'm assuming? It seems that the only way to change the null frequency, is to widen my room or make it narrower. My null sits at 40Hz - a pretty crucial frequency in my opinion.


My room will be 5.63m long x 4.21m wide and 2.25m high. I'd like to sit about 1.5m from the back wall, so I can set up 7 channels of sound nicely.


My idea is to run 4 decent subs. I'll probably build them myself (bit of a hobby) or I'll buy some. If I buy them, I'll have to do them 1 or 2 at a time. I wouldn't mind checking out velodynes or JL audio subs - money permitting - otherwise something a bit cheaper. With 4 subs, I can probably get away with less powerful, slightly smaller ones, as there's gonna be a lot of movement of air with 4 subs!


OK so gyprock is fine. Bearers and joists are fine. This is good to know.


Thanks guys!
 

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The floor will be better for acoustics... no doubt.


Have you looked into Infinite Baffle subs? Not sure how this would run on your spreadsheet, but you could use the crawlspace or attic to house an IB sub and save the space in your room while getting much better performance... something to look into. If you really want the best full bass response, then IB is the way to go.


Check out the Cult of the Infinitely Baffled... ThomasW is the single greatest resource on IB subs on the planet... Talk with him about your issues and the possibility of doing an IB sub in your room... Tons of information there as well... Check out the FAQs and the gallery... Here's the site:

http://ibsubwoofers.proboards51.com/
 
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