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Plasterboard or panels ? Bright or flat ?

Discussion in 'Home Cinema Buying & Building' started by Ray, Mar 6, 2005.

  1. Ray

    Ray
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    Hi Guys,

    Oribinally posted the folloeing in the DIY forum but Pemberto brought this forum to my attention.

    My plan is to build a room within my double garage as many of you already done. Usual stuff i.e stud wall, plaster board and soundproofing of some sort. Only one wall will be against the garage wall so for three of them I will have to plasterboard both the inner and outer skin of the partition (probably doubled on the outer wall).My concern is that once it's finished and the kit is installed I'll find it horribly bright with sound bouncing around all over the place and then I'll have to resort to sticking bits of carpet on the wall, hanging cutains I don't want and generally messing about with acoustic whatnots (a technical term :) ).

    I was thinking that perhaps a better idea is rather than plasterboard the inner walls I should construct a number of frames covered with some decent fabric and use these to cover the inside wall. My theory is that it is probably better to let the sound through the inner wall to be absorbed as much as possible by the soundproofing material inside. The sound would then travel through the material and hit the out double skinned plasterboard and bounce back then having to passthrough the sound absorber for a second time before coming back into the room.

    Ok big question. From your experience guys do you think this may make the acoustics a bit flat ? Is it better to have some reflected sound and then deal with it rather than trying to get rid of it in the first place as I am suggesting ?
    Am I imagining a problem that is unlikley to occur so should just get on a plasterboard the inner wall as well ? Will I knacker the bass response ?

    LIke to know your thoughts

    Thanks

    Ray :thumbsup:
     
  2. Gary Lightfoot

    Gary Lightfoot
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    Soundproofing needs the mass of the plasterboard to be effective. In order to absorb sound, you need to make it change direction. Every time it hits a surface it changes direction as it pases through it, and loses some energy in the form of heat. The more effective barriers in it's way the more sound will be absorbed. Some sound will bounce off of course. Mass and isolation are the best methods to reduce bass transfer.

    The insulation you place inside helps to attenuate some frequencies and reduce internal resonance, it's not a great soundproofer by itself as far as I know.

    You only need to fit the 4" x 2" stud wall an inch from the existing walls, fill with 4" insulation then fit 2 layers of plasterboard for a reasonably good method of soundproofing. Did you plan on fitting some plasterboard between the old wall and new wall?

    Don't forget to use silicon sealant or similar at all edges. Where air can go, so can sound, so make sure there are no gaps. An inch square gap will allow 15dbs or sound to pass through it, and that will negate most of the soundproofing.

    There are two schools of thought for multi-channel AV rooms, and they are:

    1. Screen wall and lower side walls should be absorptive (dead) and the upper walls and ceiling reflective (live). The floor should be carpeted too.

    2. All walls and floor made dead with the ceiling reflective. The idea behind this method is that in real life you aren't surrounded by reflective surfaces.

    I use method 1 and it works fine for my room.

    HTH

    Gary.
     
  3. Ray

    Ray
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    Gary,

    Thanks for the in-depth reply. Your posts always make good reading :smashin:

    Looks like I'll be going down the plasterboard route (which is easier anyway I think) but I still have a couple of questions (as ever):

    On the dead/live wall issue - it does seem a bit strange that the llive wall is the upper half which is at ear level. This works ok for you though does it ? Or do you have a few acoustic panels dotted around ?

    On the issue of carpeting the wall - did you use glue ? Does it stay up ? If it's anything like my wallpaper it'll fall down after half an hour :eek: !

    In terms of overall soundproofing I don't mind if some sounds leaks out - I'll be in a room within a detached garage - so it's more sound absorption and the lack of reflected sound that concerns me.

    Thanks for you advice.

    Ray :thumbsup:
     
  4. Gary Lightfoot

    Gary Lightfoot
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    Hi Ray,

    It does seem to work fine, allowing some reflections, but how it would compare to an all dead room I couldn't really say. The front speakers are below the carpeted area, so the reflections from those are minimal I would think. Other than the carpet, I have no other accoustic treatments. It could probably be better, but I'm happy with how it sounds so I haven't looked into it further. I don't think I'm as bothered about my accoustics as some, especialy as my loft room is very much a compromise, so I don't expect too much.

    Idea 1 is from Dennis Erskine who builds custom theaters for people, and is very knowledgable in scoustice etc, and idea 2 is from Terry Montlich (sp?). Both post(ed) frequently over on avsforum, so it might be worth doing a search and see why Dennis favours his approach over Terry's. It's something I will have to have a look at my self at some time I think. :)

    You OK with how you're going to build the new internal walls? If not, I'll try and post some links with images if that will help. You mention being in a room within a room so it sounds like you know what to do already..

    I used a very thickly mixed wallpaper paste. It worked well and everything is still stuck to the walls! Yopu may need some small nails to help it stay in place, but I didn't need to. The idea is that if you need to remove the carpet, it should come off with a steamer without damaging the plasterboard underneath. The guy I got the idea from carpeted his room from floor to ceiling without any problems.

    Gary.
     
  5. Ray

    Ray
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    Gary,

    Thanks for the info - I'll check out the AVs forum.

    Funnily enough an Allied Carpets sale leaflet came thru the door tonight with lots of cheap carpets in it - an omen I suspect :D

    I'm ok with building partition walls - done a few before - just wasn't too clued up on the soundproofing bit.

    Cheers

    Ray
     
  6. avanzato

    avanzato
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    I'm using 'Wide band' treatment. Which is Corner absorbers + panels around the room (mine are 10cm thick). The 'method 1' Gary posted would be quiet easy to do aesthetically with a wainscot around the room filled with absorbers/diffusors and covered with fabric. In the US they tend to have a Stage and Proscenium/Screen wall infront of the 'real wall', the 'real wall' being the one that gets the absorbant treatment.

    I don't actually have any carpet in my room just the furniture and 'treatments'.
     
  7. Gary Lightfoot

    Gary Lightfoot
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    I think I'll start having to learn more about treatments and placment etc. It's a bit more exact by the sounds of things. :)

    Gary.
     

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