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New Home Theatre - Help with sound insulation

derekhansen

Established Member
Hi everyone

I am at the planning stage of a dedicated Home theatre ( I will start a thread and post pics when I start building) in the spare bedroom of my Edwardian period end of terrace home.
Some more info:-
The floor area measures 3.6 x 3.8m (14m2) and above the ceiling is a loft. There is one entrance door and 1 double glazed window.
The audio gear will include a 5.1 or 7.2 speaker system and amp/receiver. I plan to do the majority of the building work myself.

The issue occupying my mind at the moment is what is the best way to insulate/sound proof the existing walls?
I am considering either:-

1. 2x layers of 12.5mm soundbloc plasterboard on resilient bar.
or
2. 50 x 50 battens with 50mm Rockwool infill all covered by stretch fabric.

Both methods are an attempt to keep as much floor space as possible.

Frankly, I favour the soundbloc/resilient bar method which I am confident can be done for £1000 including an allowance for a plasterer to do the final skim finish. But... would the battens/roockwool/fabric method be cheaper, simpler and give a better performance?

Any thoughts, advise or suggestions would be very much appreciated.
 

adam-burnley

Distinguished Member
I've started a similar project myself, and what I have discovered is that you need to soundproof all walls and ceiling (possibly the floor too) to avoid the 'flanking' effect - where sound will escape through the area that is not soundproofed effectively.

I'll probably be going with a similar method to your option 1, however, with the addition of Green Glue between the two layers of plasterboard. In my case, the resilient bar will be on studding to allow 50mm of Rockwool insulation as well.

My room is approx. 2.7m x 5.3m, and I have roughly calculated the cost of materials nearer £2k, so I'd like to know where you will be getting yours from?!

You also need to consider the door, which will always be the weak point of any room. I'm looking at a solid door with a soundproofing kit (all sides are sealed with an automatic drop down seal at the bottom). I'll also consider adding a second door on the hallway side if required.
 

derekhansen

Established Member
I've started a similar project myself, and what I have discovered is that you need to soundproof all walls and ceiling (possibly the floor too) to avoid the 'flanking' effect - where sound will escape through the area that is not soundproofed effectively.

I'll probably be going with a similar method to your option 1, however, with the addition of Green Glue between the two layers of plasterboard. In my case, the resilient bar will be on studding to allow 50mm of Rockwool insulation as well.

My room is approx. 2.7m x 5.3m, and I have roughly calculated the cost of materials nearer £2k, so I'd like to know where you will be getting yours from?!

You also need to consider the door, which will always be the weak point of any room. I'm looking at a solid door with a soundproofing kit (all sides are sealed with an automatic drop down seal at the bottom). I'll also consider adding a second door on the hallway side if required.

Thanks Adam. That's useful.
I didn't mention the floor and ceiling but I intend to fill them with Rockwool and yes I will take care at all the junctions to avoid flanking.
Regarding my costings the £1000 is just for the resilient bar and plasterboard materials for the walls. Prices were from the Wickes web site.
I hadn't taken into account the Green glue which I will want to use so that's an added cost.
The addition of the battens and rockwool as a sub-frame to the resilient bar is not something I had considered. Plainly it will provide more soundproofing but is this usually required in conjuction with the resilient bar and 2 layers of soundblock?. Perhaps I need to research that a bit more.

Good advice on the door. I hadnt really given that too much thought if I am honest.

Once again thanks for the help.
 

derekhansen

Established Member
I got my greenglue from affixit.co.uk, best price I could find.

Thank you I will take a look at their web site.

As an update I have decided to go with the battens/rockwool infill/stretched fabric option as this will work out considerably cheaper than the resilient bar and soundbloc plasterboard route.
 

adam-burnley

Distinguished Member
Thank you I will take a look at their web site.

As an update I have decided to go with the battens/rockwool infill/stretched fabric option as this will work out considerably cheaper than the resilient bar and soundbloc plasterboard route.
I have read other threads where this method has been used, but I wonder how effective this will be. Essentially you are adding absorption (rockwool), but you are not adding mass (plasterboard), nor are you adding any damping (green glue), so the joists (and walls?) are going to vibrate.

You will end up with one ginormous broadband absorber though!
 

derekhansen

Established Member
I have read other threads where this method has been used, but I wonder how effective this will be. Essentially you are adding absorption (rockwool), but you are not adding mass (plasterboard), nor are you adding any damping (green glue), so the joists (and walls?) are going to vibrate.

You will end up with one ginormous broadband absorber though!

Three of the walls are solid 9" inch brick so I will be fitting the battens on to surfaces with good mass to start with. The internal walls are 4" lath and plaster on timber stud (it's an Edwardian period house) but I intend to de-couple the battens on all walls to address the vibration issue by putting a rubber pad or grommet at the screw positions between the batten and the existing walls.
I am over boarding the existing ceiling with plasterboard and will sandwich Green glue or equivelant between the two surfaces. The floor will be similarly damped by fitting pads or grommets between the joist and boards. I will of course be laying acoustic insulation (Rockwool RWa45) inbetween the rafters and joists and I intend to use acoustic underlay beneath the carpet.
I know there are possible flaws and weaknesses like only having 50mm of acoustic insulation on the walls and a lack of mass on the one internal walls but it's a compromise between performance and cost to be honest.
Very good point about the broadband. I will need to think about hard wiring.
 
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