Studio build in London UK - currently underway

Hello all I'm a long term reader and had a previous account many years ago but can no longer access it. I'm currently past the mid stages of building a new studio. It is located in the middle of a coffee shop/arts venue on the ground floor of a 3 story building with residential accommodation above (where my wife and I live) and a shop to the south side. Budgetwise I have already invested every penny into the development and we are both continuing to put our income into it to produce an ongoing business so realistically there is no current limit set on it. I am looking to achieve 80-85dB in isolation with this room. It will be used solely for recording/editing and mixing so will never have any live instrumentation to contend with. Low frequency attenuation is the primary goal here. The internal block walls were completed early last year. You will notice a 100mm gap between the new walls and the existing ones. In the gap I have created a trench that decouples the slab where the internal walls sit from the original walls. In addition to the internal concrete slab there is a timber floating floor made from 18mm ply on 18mm T&G chipboard, on 2x4 floating on Auralex U-Boats at 60mm centres. This floor is insulated with 100mm RW45 insulation. The ceiling (though not completely finished) is made from a beam and block system. Once this is completed I can start to look at the internal modifications to what should hopefully be a well isolated room. At this point I would like to ask a couple of questions and would be most grateful if anyone can offer some advice 1. Adhering to the principle of having a 12 degree splay - would it be best to offset by internal walls both by 6 degrees: Or both by 12 degrees (given the impact on space) 2. Should these angled additions be solid (i.e. plasterboard on RC on timber studs - infilled with RW45) or should they be made from a porous surface (burlap/hessian) and filled with RW45. I had always planned to do that latter, however I wonder if that has any effect whatsoever on probable room modes/standing waves. That said - would the former, hard option, provide an issue in effectively being 3 leaf system? 3. The existing 100mm air gap around the internal wall has no insulation. I remember reading before that this is preferable to any insulation in the cavity - I just need to be sure that this is the correct way to go before I seal the cavity up. Any advice would be most appreciated and please feel free to ask any questions if I am not clearly explaining something or more details are required Thanks in advance Andy

Having had more time to reassess the layout and look through a lot more posts i have made the following corrections. The speakers are now at 0.28% in from the sides and the listening position is now 0.38% from front to back. I have kept the splay at 6 degrees on each side - giving a total yield of 12 degrees. I think this provides a much better environment, though I'm a little worried about reflections from the front stub of wall in between the speakers (where the flat screen is) The speakers are flush mounted at a height of 1.2m and angled at 30 degrees to the listening position. My biggest question really is whether the stud work (that provides the soffits and angled framework) should use plaster board on RC and then be filled with rock wool or use a burlap covering? i.e. - should these angles walls be solid or permeable?

had a previous account many years ago but can no longer access it.

Hey Andy! If you let me know what your previous user-name was, then I can reset your password for you, so you can access your old account again. PM me. - Stuart -