Angles....

marello · Post by **marello** » Wed Dec 28, 2005 11:14 pm

I've researched online for quite a while now, including searching this site and I can't seem to find anything which definitively tells me how to go about calculating wall angles when you're designing a studio. I'm trying to find out how to eliminate flutter echos (6 degrees per side wall?), but I'd also be interested in the maths behind RFZ rooms.

I'm thinking about a space which is 4.3x7x2.8m (14x23x9 feet)which is intended to be a control room.

If anyone knows of any links I'd be very very grateful for a link!

Thanks for reading

knightfly · Post by **knightfly** » Thu Dec 29, 2005 9:23 am

Try this

http://www.johnlsayers.com/phpBB2/viewt ... c&start=60

About 3/4 of the way down there is a drawing of the basic geometry for RFZ using angles instead of absorption. Keep in mind that for surround, it's all different... Steve

marello · Post by **marello** » Fri Dec 30, 2005 5:49 am

Thanks Knightfly, that diagram was quite helpful. I also found the diagram you made on ray tracing which looks like a really useful way of deciding which walls need to be absorbant.

Ive just had a play with that, and I don't really understand the section stating that "if the total path length starting with the point where the sound first reaches your head, then bounces off the wall and returns to your head.... " I'm not really sure which bit I'm measuring. I assume I measure along the line from the speaker to the test wall, then the reflection to the mixing point, but I wanted to check!

knightfly · Post by **knightfly** » Wed Jan 04, 2006 5:46 am

Assume a sound originates at the speaker; it then (among other paths) travels directly to your ears. From your ears, it continues on to whatever boundary is behind you, reflects off that, and (depending on the angle of reflection) returns to your ear or to another wall and THEN to your ear - if the measured distance the sound travels from the moment it passes your ear, until it RETURNS to your ear, is less than about 22 feet, the sound will return to your ears in less than 20 milliseconds.

When this happens, the brain "mixes" the two sounds and you get phasing problems (cancellations, or reinforcements, of different frequencies) - This is why any hard surfaces in the room that can cause early reflections need to be absorbed; if you get the level of these reflections low enough compared to the direct sound, the brain no longer considers them and you get much cleaner imaging.

Much longer than 20 milliseconds, and the reflections become a distinct slap echo (think early Elvis Presley vocals)

HTH... Steve