Wall angles, is it worth it in this case.

bitdump · Post by **bitdump** » Tue Sep 30, 2003 6:30 pm

Hello all,

I am slowly reading though all the info here and I have a question about the room I will build in a month or so.

It is my home studio and I have a space limitation to work with in.

5 m by 4.80 meters with a height of 3 meters.
current walls are concrete and with the exception of 1/2 a metter at the top, 3 walls are surrounded by earth.

My biggest sound proofing issue is the ceiling. The two gig pluses are all new room in room and fresh leg of power.

Thing is I was wondering if it is worth it to angle the walls some what and if so by how much as I already have decided to store half the gear out of this room. (got too much stuff to make it all fit and have a decent comfort factor so many of the electronic stuff will be brought in when needed.

Another point to mention is my monitors are KRK V6's which will remain the only monitoring option. I would like to help them as much as possible so learning them in this room might be a bit easier.

The only gear nesseities are a 8 person table the three PCs (DAW, dedicated Kurzweil PC, and eventual Csound PC) a three tier stand with K2000, K26R, KSP8 and space for the other synth of choice. Soundtracs Solo 16, and home made patchbay . The table, bay and mixer come in at a tad over three meters. Idea is to add some comfy seating and still have space to track a clean enough vocal, and the other stuff which will be stored out of the room, guitars, drums ect.

So anyway back to the walls, is it worth angling them even a bit, and by how much.

thank you very much if anyone has any ideas.

barefoot · Post by **barefoot** » Wed Oct 01, 2003 5:22 am

The main purpose of angling the walls isn't sound isolation (though, running the inner and outer walls non-parallel does help with sound isolation). The main purpose is to break up standing waves. This is particularly a concern in your room, since it is almost square. The two similar dimensions will tend to reinforce the same frequency modes. John usually recommends splaying opposing walls by about 24 degrees relative to one another. I think this is a very good idea.

I know it's difficult to loose all that floor space, but think of it this way. If the acoustics are bad, then really none of the space is useful as a studio.

Thomas

bitdump · Post by **bitdump** » Wed Oct 01, 2003 7:29 pm

Thanks for the answer.

Sorry for the babble, writting at work at too many things going on at once.

I wasn't wondering about angles for isolation. I was as you are thinking about them pesky standing waves and options for handling them.

In this case, I deal with the bass managment once my cube is up enough to start listening.

In the current location (dining area of the open living/dining room area of my house, half of the studio takes up about half that space, I am screwed by the fact once I have kids and they are old enough to want a Vespa, I need somewhere to put it. Two kids two Vespas.

I will be happy in my cube considering what the other space will be used for.

Thanks ciao all,

subatom · Post by **subatom** » Thu Oct 02, 2003 1:37 am

John usually recommends splaying opposing walls by about 24 degrees relative to one another

just curious, but why 24? trial and error? and how do other angles vary?

barefoot · Post by **barefoot** » Thu Oct 02, 2003 2:43 am

That's 12 degrees per side, which is simply a convenient fraction of 360 degrees. Nothing magical about it. It just turns out to be a reasonable compromise between room dimensions and a good step away from parallel walls.

Increasing the angle tends to reduce the intensity of the standing waves - as well as making their frequency distribution more complex (less harmonic).

Thomas

knightfly · Post by **knightfly** » Thu Oct 02, 2003 4:40 am

Actually, I was confused by John's comments on this and asked him to clarify a few weeks ago - he said that he meant 6 degrees per side, for a total of 12. However, that was just to get rid of flutter echo, you would need more of an angle to set up a decent Reflection Free Zone.

None of the affordable CAD programs I've seen will do any sort of ray tracing, so the only way I've been able to do this is by changing ortho angles within a basic cad program so I can draw multiple rays from speakers to walls at different angles, then compute angle of incidence/reflection, and continue each ray until it's at least 22-25 feet long - if it doesn't come back to the mix position by then, it's long enough not to be an "early" reflection and I then attack the next ray; this is, as it sounds, very time consuming and if I ever find a drawing program that does ray tracing without giving up the other "goodies" I use, I'll let you all know.

I just recently loaded CARA into my machine, and havent even gotten through all the tutorials - it has a CAD module, and I thought I "smelled" the possibility of ray tracing, but haven't had time to get back to it. The cool thing is that the SW is less than $100 including a test tone CD - the UN-cool thing is, their "controller" that hooks up to the 'puter for live testing, only works on serial ports. Hello; any new machines out there that even HAVE a serial port any more?

I'll keep you posted on the drawing part, it'll be probably a week or so before I get the chance... Steve

Post by **John Sayers** » Thu Oct 02, 2003 6:23 am

Guys - ideally the angle should be 30 degrees each side so the whole front splays fully - the 12/6 degrees are minimum compromises for small rooms where you can't afford that much splay.

cheers
john

jsshop · Post by **jsshop** » Sat Oct 04, 2003 12:22 am

I am glad this question was asked since I have some similar questions. What is the pros/cons of the angled walls as opposed to putting up diffusers? If I do my next room myself it might be a heck of a lot easier to make diffusers and if I ever sell the house it is in it will be a lot easier to remove them than it will be to redo the walls.

barefoot · Post by **barefoot** » Sat Oct 04, 2003 2:29 am

All diffusors, regardless of their type, have a low frequency limit. Their diffusive characterizes start to decrease when the sound wavelengths get larger than twice the depth of the surface variations. In the case of a quadratic residue diffusor the deepest cavity is 1/2 wavelength of the lower cutoff frequency. So, if you wanted to use diffusors to break up standing wave modes, you would literally need to double the room dimensions - or fill 3/4 of the space up with diffusors!

Diffusion is only practical for midband and high frequency treatment.

Thomas

PS - I imagine it's possible to break the 1/2 wavelength rule by using an "active diffusion" method. This would mean covering the walls with loudspeakers!..... Pretty cool, but hardly practical.

jsshop · Post by **jsshop** » Sat Oct 04, 2003 2:46 am

Very helpful reply. Next question - what if instead of angling the walls for a long part of their length I build a normal room and then add a zig zag set of extra walls - this would be easy to remove and would take up less room space - or at least the room would not be as narrow.

barefoot · Post by **barefoot** » Sat Oct 04, 2003 3:24 am

Once again, the angle's effectiveness at breaking up standing waves depends on the variation in depth it creates. Two zigzag walls create only half the depth variation of a single full-length wall with the same angle. You can image a zigzag pattern with very steep angles, but with many zigs and zags. As the number of zigs and zags gets larger and larger, d gets smaller and smaller. Eventually d gets so small that you're just left with flat parallel walls. So it's really not the angle that matters per say, it's the depth variation.

Thomas

matucha · Post by **matucha** » Mon Oct 06, 2003 4:17 am

what about the mirror trick? it saves you the computation, but it is still pretty time comsuming... and any change in the plan is pain, because you have to redo a lot of raytracing