John Sayers' Recording Studio Design Forum Archive

Hi everyone, this is only my second post, so please be easy on me if I'm not quite in key with etiquette...

I am aware that it is against the rules to say "my room is x by x by x, what should I do" ... However, I do have a newly constructed control room which is 13' by 10' with a ceiling height of 8', built with double stud walls with 2 layers of drywall on each side. The floor is wood laminate. The mixing desk (my monitoring position) is situated along one of the 13ft walls, which is the front of the control room, with a window running horizontally, the length of the desk (6' x 3'). There is a leather sofa at the back of the room. I monitor with Adam A8x's and KRK RP6's and work with sub bass-driven dance music quite regularly

Although technically rectangular, the room is not far from square... I'm afraid I had no option, and with space being an issue, I couldn't do any funky shapes.

So with this room, I am now looking to handle the acoustic treatment, but am not entirely sure how to tackle it, as I have seen so many conflicting opinions. Will corner bass traps on each corner be sufficient for the lower frequencies? Should I have a diffusor on the rear wall?

One thing I thought may be useful, is that I have 2 large pieces of foam, each the size of a single mattress, both 4 inch thick, completely flat profile, similar to what you'd find in a couch or something like that.

Any advice or ideas would be HUGELY appreciated,

Many thanks,

Will.

Hi Will.

Your dimensions actually aren't too bad! It could be better, sure, but it could also be an awful lot worse.

Your room passes all 3 of the basic BBC tests, and has a ratio that is pretty close to one of the known good ones. There are a couple of issues, but nothing too serious.

The mixing desk (my monitoring position) is situated along one of the 13ft walls,

Any chance you can change that? Normally you want the speakers firing down the log axis of the room, not across the short axis. Your room is only 10 feet wide, so I'm guessing that your listening position must be pretty close to the center of the room, about 5 feet from the front wall, correct? That's not a good position, for several reasons, but among them is the fact that your head is relay close to the rear wall, and therefore you are almost certainly getting first reflections off that wall well inside the 15/15 window, and even inside the 10/10 window.

If you can, rotate the room 90° so that the front of the room faces one of the 10 foot walls, and the two 13 foot walls are on your left and right. That would improve things a bit.

I monitor with Adam A8x's and KRK RP6's and work with sub bass-driven dance music quite regularly

Nice speakers! (I'm an Adam fan...) Have you set your crossover correctly, to be as flat as possible, and have you measured the room response? If so, the curves and waterfall plot would be very useful to see what's happening in your room, and where the problems lie.

Although technically rectangular, the room is not far from square... I'm afraid I had no option, and with space being an issue, I couldn't do any funky shapes.

It's fine like that! Some people love splayed walls, some love rectangular, but both can be treated to work just fine.

So with this room, I am now looking to handle the acoustic treatment, but am not entirely sure how to tackle it, as I have seen so many conflicting opinions. Hopefully, you haven't seen too much conflicting opinion on THIS forum! It's one of the few place on the internet where opinions on acoustics are secondary to the actual science of acoustics. Treatment works because of the physics of how sound travels and interacts, not because of what people happen to imagine! Opinions don't affect sound waves very much, but the laws of physics certainly do!

Will corner bass traps on each corner be sufficient for the lower frequencies?

Do you mean in all twelve corners? that would probably be enough, yes. Or do you mean just the 4 obvious corners? That probably wont.

It's a small room, so it will need a lot of bass trapping: all you can fit in, really. But the best way to figure this would be to measure the room response (using REW) without any treatment, then put four superchunk traps in the four vertical corners and measure again, to see what changed and by how much, and what still needs doing. Then you add some more treatment based on that, and test again. You can keep on with that "test/treat" cycle until you either get perfect acoustics in your room, or run out of money: Most likely the latter...

Should I have a diffusor on the rear wall?

Nope! If you are talking about a typical QRD based design of some sort, then those are not recommendable for small rooms, for a couple of reasons. One of those is lobing: QRDs create patterns of "lobes" of varying intensity: Those lobes need distance to even out again, and small rooms don't have enough "distance". So diffusion is fine in large rooms, but not such a good idea in small rooms. Of course, that doesn't stop some manufacturers from trying to sell their diffusers for small room!

One thing I thought may be useful, is that I have 2 large pieces of foam, each the size of a single mattress, both 4 inch thick, completely flat profile, similar to what you'd find in a couch or something like that.

What type of foam? If it is closed-cell, then it isn't much use, acoustically. Only open-cell foam works for acoustics. Most types of mattress and upholstery foam are closed-cell, which is no use. So try to find out if it is closed or open cell that you have. One simple test: Can you blow through that foam easily? In other words, can air move through it freely? if not, then it is no use.


- Stuart -

Thanks ever so much Stuart for your in-depth reply, It is much appreciated!

So it's not all bad after all!

I'll try to strike a deal with a foam supplier for the corner traps... I take it that by all 12 corners, you mean the 4 obvious corners, top to bottom, as well as the corners where the wall meets the ceiling, all the way round the room?

I think the 2 foam slabs I have must be closed cell, so I'll dump them! I was thinking to go with 9, 2 inch acoustic tiles on each side wall and the rear wall, in a 3x3 format in the centre of each wall? And as the condole is 230cm with a 190cm window behind it, I was thinking to cover the entire wall around the window in foam, to compensate for the huge reflective area created by the glass... with a big slab on the ceiling above the mixing position. How does that sound to you?


Also, I made a mistake in the post, the console does run along one of the 10ft walls! Sorry, I'm an idiot But it's great to know now that it's a good position as you say.

So I'll run those REW tests to really fine tune it... But as you say, I think the moneywell will dry before that happens!

Thanks again for your help,

Will.

I'll try to strike a deal with a foam supplier for the corner traps...

You don't really need foam for those: plain old ordinary mineral wool and fiberglass insulation works very effectively, and is way cheaper! The kind of stuff you can buy at any hardware store.

I take it that by all 12 corners, you mean the 4 obvious corners, top to bottom, as well as the corners where the wall meets the ceiling, all the way round the room?

And also the one where the walls meet the floor...

You most likely won't be able to do all of them, as there will be doors, windows and other things in the way, but start out with the four obvious verticals, see how that works, then if you do need more, figure which of the remaining 8 corners can be done.

I was thinking to go with 9, 2 inch acoustic tiles on each side wall and the rear wall, in a 3x3 format in the centre of each wall?

2" is rather thin: Go for 4". And 3x3 is also rather small area. You need more coverage than that.

One very common, very good product for this is Owens Corning 703 semi-rigid fiberglass (commonly referred to as "OC703" or even just "703"). Very good acoustic properties, and can be found at many building supply centers. It comes in large panels (8' x 4', and other sizes), and you can simply put them in a simple wooden frame, covered with cloth to hide the "ugly", and place them diagonally across the corners. Or you can but them into large triangles and stack those in the corner, floor to ceiling, in which case it is called a "superchunk" bass trap. There are many other ways of using 703.

And as the condole is 230cm with a 190cm window behind it, I was thinking to cover the entire wall around the window in foam, to compensate for the huge reflective area created by the glass... with a big slab on the ceiling above the mixing position. How does that sound to you?

It would be good if you could post some photos of the room, and also an accurate diagram of the room, done in SketchUp (which is free!).

So I'll run those REW tests to really fine tune it... But as you say, I think the moneywell will dry before that happens!

REW is also free! Ain't it nice to have free design software (SketchUp) ans free room analysis software (REW)? Now if only someone would start giving away OC703...


- Stuart -