John Sayers' Recording Studio Design Forum Archive

Hi Everyone,

I joined today. I'm hoping I get this right and don't annoy anyone.

I'm an experienced Audio guy, but I'm very new to the realm of acoustic treatment, so please be patient with me.

Basically - I finally have a house which has a spare room that I can use to do tracking and mixing at home. As you will see - its not a big room - and doing some tracking in here already I can tell that it doesn't sound all that great, and needs some treatment badly. Ive been doing as much reading as I can to try and get my head around everything, but im still a bit lost at where to start. I was starting to get the idea that I should be able to build a bunch of Fibreglass absorber panels to hang on the wall using this product - http://www.insulation.com.au/products-1 ... insulation, although - im not sure exactly if its the best thing I can get locally (Sydney Australia), and which thickness would be best to use. I'm also wondering if it would be good to build corner traps with also.

So really - im unsure about how much of the walls, roof, and corners I should be covering with the panels - and if there is such thing as too much? If I make the room too dead is it bad for tracking? or is trying to capture reverb in such a small room pointless and im better off deadening the room and adding reverb later in mixing?

I know it would be a bit rude to expect for anyone to design my acoustic treatment for free. But as much (or as little) advice and help would be appreciated greatly as I don't have the money to hire in a professional to do it for me.

Room Dimensions:
3110mm wide
4285mm deep
2695mm high

As you will see in the pics below - there is a chunk missing from the rear of the room which is 800mm wide, and 970mm deep

The floor is polished timber floorboards (no carpet) and the walls appear to be the regular kind of plaster walls.

I rent the premises so I cant do any sort of major construction, but im pretty sure ill be fine to hang panels on the walls / ceilings.
- Tim Robinson

Hi there Tim, and welcome to the forum!

I'm hoping I get this right and don't annoy anyone.

so far you are doing great (very nice first post, by the way), and it takes a lot to annoy me, so everything is good!

Basically - I finally have a house which has a spare room that I can use to do tracking and mixing at home. As you will see - its not a big room - and doing some tracking in here already I can tell that it doesn't sound all that great, and needs some treatment badly.

Based on what you are saying, it seems that you are not concerned with sound getting in or out of your room, and all that you need right now is to improve the interior acoustics, so that you can mix more accurately? Is that about right?

Ive been doing as much reading as I can to try and get my head around everything, but im still a bit lost at where to start.

That makes you fully qualified to build a home studio!

I was starting to get the idea that I should be able to build a bunch of Fibreglass absorber panels to hang on the wall

That will be a big part of it, yes. But not all...

using this product -

Well, it MIGHT work, ... but they don't have any acoustic information at all on their web site for that product! There are a lot of claims, and pretty graphics in their brochures, but not a single table of coefficients of absorption, nor any laboratory test results... So unless you can get that information from them, then I'd say to forget that manufacturer and instead look for one that does believe in their own products enough to publish the acoustic details. Without those numbers, it's impossible to say if that stuff will work well for what you need.

im unsure about how much of the walls, roof, and corners I should be covering with the panels -

I guess you are wanting to get the room as close to a professional control room as possible? Based on your room dimensions, theoretically you need a total of about 352 sabins of absorption to get the decay times within ITU specs for such a room. In real-world terms, that equates to about 32 square meters of perfect absorber. There is no such thing as a perfect acoustic absorber (except for an open window!), but you can get close with good fibrous insulation... if you know what the characteristics are! so figure on roughly 30 to 35 m2 of fiberglass or mineral wool panels. The total surface area of your entire room is about 64 m2, so you need to cover roughly 50% of the surface. However! 13m2 of that is floor, and it's pretty impractical to have mineral wool absorbers all over your floor (as well as being a really bad idea, psycho-acoustically), so that leaves you with the walls and ceiling. You'll need to cover about 60% of your walls and ceiling.

But you can't just do it any-old-how! It needs to be spread around correctly.

And before you even get to that, if you want your room to be as good as it can be, then first of all you need to lay it out correctly, which means getting your speaker and listening position geometry right.

Item number 1: get your speakers off the desk! Putting speakers on the desk or console is a bad idea in many, many ways. Your speakers should go on stands behind the desk, and the stands should be very massive (heavy). Some people use hollow metal or PVC stands and fill them with sand. Others stack up bricks to make their stands. You are in Australia, so your cheapest, simplest, fastest option is to run down to your local building supplies store, pick up some Besser bricks, and stack them at the front of your room. Wrap them in black cloth so they don't' look so ugly.

For your room each speaker should be about 86 cm from the side wall, which means they will be about 138 cm apart (all measurements here are referenced to the center of the front panel of the speaker). Push them up almost tight against the front wall, leaving only a 10cm gap for the acoustic panels that will go in there (more on that below).

Next, set up your chair so that your head is about 165 cm from the front wall, exactly on the room center line, set up a mic stand about 30 to 40cm behind your head (also on the room center line), and aim your speakers so they are both pointing at the same spot on the mic stand. The speakers must be set up such that the height of the acoustic axis is 1.2m above the floor. (NOTE! "acoustic axis"!!! not the top, bottom or middle of the speaker. Check the manual for your speakers to find out where that point is).

That takes care of the speaker geometry. If you do that right, your speakers will be toed-in somewhere around 30°.

Now for room treatment, which is applicable to the above layout.

First, this is a small room so it will need a LOT of bass trapping. I'd suggest building "superchunk" style bass traps in all four vertical corners of the room. You do that by cutting suitable insulation into large triangles and stacking them up in the room corners, floor to ceiling, then putting up a simply wood frame with cloth over it to hide them. The front face of the bass trap should measure about 90cm. You might also need to partially cover the front face of those with plastic (before you put the cloth on) to prevent them from sucking up too much of the high frequencies, but that can be done later if you want to fine-tune your room.

Next, is first reflection points. You need a large, thick absorption panel on the side walls of the room, and on the ceiling, at the points where the sound waves from the speaker will hit the surface and bounce straight off towards your head. Put a full height panel on the side walls at each of those points, and hang a cloud from the ceiling above your desk. Make them BIG. For maximum effect, do the cloud as a "hard backed" frame with insulation on both sides, and angle it (tilt it a it) so the front edge (over the speakers) is lower down and the back edge (over your head) is higher up. Tilt it at least 9°, and much more if you can: 15° would be good.

Next is the panels that go between the speakers and the front wall: 10cm thick, floor to ceiling, and each one about twice as wide as the speakers, or more if you can.

Finally, the rear wall: cover it completely with about 15cm thickness of insulation.

That's the basic treatment, and should get you well on the right track to making your room sound usable.

After you have all that in place, try tweaking the location of your speakers and chair a bit, to see if you can find a better spot: what I gave is the theoretically "best" position, but for most rooms there's a better spot close by. So move your head backwards and forwards a bit to see if you get an improvement, and also try moving the speakers closer together or further apart by a few cm to see if that makes a difference. Once you have found the best possible spot, move your desk so that you can sit comfortable at it while your head remains in that position.

If you want to do this right, then BEFORE you install any treatment, but AFTER you have the geometry set up correctly, run an acoustic test on your room with the REW software package (it's free!), and post the results here on the forum, so we can analyze them. Then start installing your treatment, and do a few couple REW tests while you are doing that, as you complete each stage outlined above, so you can see how the treatment is affecting the room, and what still needs to be done.

Hope that helps!


- Stuart -

Thankyou so much for the reply, this is so much more than I expected.

I'm going to start with the Bass traps soon, does this product look like it would be suitable? (Brochure includes absorption spec @ various frequencies) - http://fletcherinsulation.eprospect.com ... and_Sheets. And if so - Is it best to use the thickest? (100mm).

I'm also going to add all of your suggestions to my sketch up model - and then post them images here along with some REW results.

Actually - How does this look? - http://www.polymaxinsulation.com.au/dow ... _Sheet.pdf

That Polymax stuff looks interesting. I'd suggest using the MD-50 or HD-50 stuff for your bass traps. Looks like it should work well.


- Stuart -