How does one know where to put specific treatment for sound?

I am new here...read through about 80-100 posts...but since I am not "building", "designing", "contructing" a studio--the most basic answer is kinda hard to find. Everyone seems to be way advanced in their questions for me :( I see posts, pictures but what I cant understand is when folks are putting up materials, diffusers, absorbers etc etc all over their walls, ceilings etc---how do they know that exact spot is where it needs to go? I get the bass traps around corners, edges of the rooms etc---but everything else doesnt make any sense to me! Sorry if I didnt follow specific enough instructions :)

kktk wrote:

how do they know that exact spot is where it needs to go?

Live rooms are unique and each needs different treatment. The general goal is to absorb bass ringing and excess reverb, and absorb or diffuse flutter echo and reflections from nearby surfaces. For a control room: * Broadband (not tuned) bass traps straddling as many corners as you can manage, including the wall-ceiling corners. More bass traps on the rear wall behind helps even further. You simply cannot have too much bass trapping. Real bass trapping, that is - thin foam and thin fiberglass don't work to a low enough frequency. * Mid/high frequency absorption at the first reflection points on the side walls and ceiling. * Some additional amount of mid/high absorption and/or diffusion on any large areas of bare parallel surfaces, such as opposing walls or the ceiling if the floor is reflective. Diffusion on the rear wall behind you is also useful in larger rooms. --Ethan

Hey Ethan, I've been reading through your acoustics section on your website and I understand that you are treating different frequencies in a specific way, bass with bass traps, mid/high etc etc differently.. But what I dont get is where exactly are those first reflection points? and how do you measure them? How would I know that I need to put something on the side wall 4 ft from the corner instead of 6? That I would need to put up 3 panels instead of 2?

kktk wrote:

But what I dont get is where exactly are those first reflection points? and how do you measure them?

Here ya go: How to set up a room Early Reflections --Ethan

I guess, It's also my problems.... Ethan, I read many post that acoustic treatment will be done well if make measurement in freq response etc before. But, I saw in design forum, people can determine in the design phase where the soffit speakers will be, the listening position etc. How to determine all of this in the design phase? I read about the 38%, and all agree it's only starting point. I also read splaying wall, ceiling and equilateral triangle 60deg and 90deg. But that all only starting point? So when it become the fix point? after build the soffit frame and all the hanger bass stuff, absorption and make a test? what if the test fail? I have to change all? :shock: Regards, Joseph

audio wrote:

So when it become the fix point?

After you measure the LF response in the room at high resolution. So you build everything, and install the speakers, then measure to decide how far back to put the listening position. 38 percent should be pretty close. --Ethan

Ethan, Hopefully, you still willing to answer... :) Can you gave direction/step by step how to measuring/analyzing LF in hi resolution. The only software I have right now is wavelab... I can have my friend's SMAART soft. The Microphone I have Behringer ECM8000. AD/DA Digi003. I plan to use free stand speaker, not to soofit the speakers. I really took hard study about modes and playing arround with room mode calculator from different resources, but I really don't understand. My room (acording to bobgold site-if I was no mistake inputing the numbers) have no coincident modes. It's (H)2.93mx(W)3.18mx(L)3.94m (The room already isolated with double 12mm gypsum (these the only common) on steel-hollow frame and have 10cm cavity behind it. Fill it with fiberglass 60kg density. the outer wall is solid brick with cement-finsihed. ) Is it mean I'm free for problem in LF? and can mode calc determine where I should positioning the speakers? Thanks alot

audio wrote:

Can you gave direction/step by step how to measuring/analyzing LF in hi resolution.

This article explains how I use ETF, and the principles apply to all such programs.

can mode calc determine where I should positioning the speakers?

No, ModeCalc is for picking room dimensions. The only way to know the best places for things is to measure the response as you experiment. --Ethan

Thanks Ethan, I'll check the link... I'll back again if I'm pleased to ask :D ...