Simple Acoustic Treatment for Critical Listening and Vocals

Hi Everyone! I've been reading about acoustic treatment for a while now both here and on SOS forums and I've decided I'd like to dip my toes into the water with a small project. I am a synth player and singer and I write and produce my own music (dark electro industrial) using Ableton Live. I live on the Central Coast of New South Wales, Australia. I am only at the hobbyist level at present. All of my music is entirely electronic (therefore not recorded acoustically) except for vocals. I tend to do a lot of my own synth sound design so critical listening in my studio is important. In my house (which I own) I have a studio / office / workshop room all to myself where I can do whatever I like. (See picture below) This room is regular gyprock on stud wall all around except for one wall which has a large sliding glass door and two windows which look onto the driveway. The small door in the opposite wall is an internal cavity sliding door that leads into the house. The floor is laminated MDF floorboards on top of a concrete slab. The wall along the bottom edge of the picture is gyprock on the inside but an external brick wall on the otherside, I don't know what's in-between, I presume it's bricks-stud-gyprock. The picture also shows a bounding box of my desk with my monitor speakers on top. These are drawn to scale and placed in their current position. I usually sit right in front of this desk in a regular office chair. Late last year I bought my first ever studio monitors in the form of a pair of Tannoy Precision 8D (the old model on a run-out sale). I'd like to maximise my investment in these monitors by improving the acoustics and positioning in the room so I can get the most from them. So my goals are: 1) A critical listening room for synth sound design and mixing my own tracks. 2) A vocal recording room Remember these goals are just to the hobbyist level. I only have a small budget ~$500 so I am looking for advice on the most effective way to spend that money. I don't expect a lot, I am posting this thread to make sure that I am not totally wasting my money. Note that I am only wanting acoustic treatment, not sound proofing. Soundproofing would be nice but I understand it is way beyond my budget and probably also beyond my DIY abilities. From what I've been reading it seems that the way to go is some DIY bass trapping and broadband absorbers. I have read with interest numerous threads on this forum (and others) showing how to build these cheaply using rockwool, simple timber frames and covering material. I would like to do the same. I have looked around for local suppliers of rockwool and have found that Bunnings sell a product called Soundscreen by Bradford. The product brochure claims this is made of rockwool, so I am presuming it is roughly equivalent to what others are using. The Soundscreen batts at Bunnings are the "R2" variety with a density of 32.5kg/m^3 and you get a pack of 1350x580x75mm x6 batts for $50. My current pan is to put bass traps in all four corners first using a double layer of batts (150mm or 6 inches thick), and then some broadband absorbers made of single layer batts at the first reflection points to the left, right, in front and behind the mix position and perhaps another on the ceiling. I am thinking that the left/right/front/back wall absorbers will be made as Gobos so I can pull them into the middle of the room to form a booth for vocal recording, then push them back against the walls for critical listening. My questions are as follows: 1) Is this a cost effective and worthwhile plan for improving my critical listening and vocal recording environment? 2) Are Bradford Soundscreen batts a good choice for the filling? (spec sheets are available from the linked page) 3) How tall should I make my bass traps? The batts are 1350mm tall and the ceiling is 2400mm high. Do taller bass traps (covering more and more of the corner) give a linear return in bass trapping, a diminishing return or an increasing return? My options here are to make them as high as 1 batt (1350mm simplest construction) or 1.5 batts (2025mm cover most of the corner with minimal wastage) or cover the whole corner floor to ceiling (2400mm with batt wastage and construction hassle of cutouts for cornices and skirting boards). 4) Do you like my plan of dual purpose gobos for first reflection absorbers and vocal booth? 5) Do you have any advice for placement of my desk and speakers in the room? Thanks in advance for your time and any advice you can give. Cheers, Sam

Sam, Welcome. You have the right idea. I'm sure that soundscreen rock wool will work, however, you would be better off with a density of around 60kg/m3 for most panels. Check pricing on RW3 type rock wool & just get the best deal. I would recommend trapping corners as much as possible from floor to ceiling. Next will be your early reflection points on the walls - left and right - and don't forget the ceiling above. Trapping behind the speakers will help with SBIR effects. You can go here http://www.jhbrandt.net/pubs.html to get my First Reflection Calc to help you with positioning of the panels for your RFZ. Try to get away from the front wall as much as possible but not in the middle of the room. You will probably end up with panels on stands in front of the sliding doors. Cheers, John

Thanks for your reply John! So that's one vote for full height corner traps. I guess my next task is to try to find some of that 60Kg rockwool from a local (NSW Central Coast or North/West Sydney) supplier. Cheers, Sam

After doing some research on the Internet, and ringing around for some prices I've decided to get the Tontine Acoustisorb 3 which is 48Kg/m^3. A couple of things decided me on this. Firstly, I have a 3 year old who is mildly asthmatic and also an 8 month old baby. So the "no breathable fibres" selling point really works on me. Even after they are built, it will be impossible for me to keep them from playing with them and potentially puffing out more fibres. Secondly, they are available from my local Bunnings store (by special order) for $157 per bag (2400x1200x50x3pieces) with no minimum quantity. Thirdly the length of one piece is exactly the height of my ceiling. :)

Here's another question, does it matter much if the panel, when pushed into the corner, does not seal against the side walls? Reason I ask is because if I build a full floor to ceiling trap, then it will be running into the skirting at the floor and cornice at the ceiling. Should I bother to make cutouts in the timber frame to accomodate the skirting and cornice?

Sam, Actually an air gap behind the absorber increases the it's effectiveness. So, gap it out. ;) Cheers, John