# None Square room differences...



## Guest (Jan 2, 2008)

Hi folks - Happy New Year,


I'm a noobie and just about to dive into room acoustics for the first time!! My listening room is in the top floor of the house as a roof conversion. So 2 of the walls are sloping – see .jpg. Actually I use the room for films as much as for 2 channel music not sure how that changes things? none of the walls have a solid base except for end wall (see "screen" end) which is brick with plaster (rock) board covering. 

The listening room is about 13Feet by 12 Feet – see bedroom 1 above. 

Most of the rooms I see on the web are square, mine isn’t and so my question is what is the best way to determine what I need to remove first reflection points (what effect will the sloping walls have?) and corner base traps.

Thanks for your help!


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## bpape (Sep 14, 2006)

Welcome to the forum.

The slanted wall/ceiling will tend to reflect more sound at the listening position than a vertical wall and should be dealt with accordingly. 

To find your reflections, get another person and a mirror. Sit in a seat and have them move the mirror until you see a speaker - mark that point in both dimensions. Repeat until you've seen all 3 speakers and marked their spots. Repeat for the next seat.

If the room is symmetric left to right to the seating, then the points on the other wall will be the same.

Bass control - go from the floor up to the slant. You may also want to straddle the front wall/ceiling intersection for some additional control. Also, the rear wall of the room behind the seatin is a good place for some additional bass control as it can cause a lot of abberations at frequencies based on the distance from seating to wall.

Bryan


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## Guest (Jan 3, 2008)

Hey Bryan,

Thanks man! OK understand the mirror trick, I guess the good news is the slope will reflect the sound into the floor carpet and furniture so could work to my advantage. 

What kind of base control do you think I need on the rear wall, there are 3 doorways along this wall, I guess I need intersections controlled, anything else? 

I've read here on this forum that most folks say the front wall should be "dead" would you reconmend this and if so what options do I have? 

thanks again

Chris


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## DrWho (Sep 27, 2006)

The slanted ceiling is actually a good thing because it breaks up a lot of the flutter echo.

You might also look into diffusion too instead of just absorption. Getting rid of the early reflections is important but you don't necessarily want to get rid of the late reflections...having no late reflections would be like listening in an anechoic chamber (not good). Diffusion can help redirect the early reflections around the room so that they arrive later and then they get perceived as part of the reverberation of the room. Diffusion also breaks them up so that they're not specular either. When done right, it will make your room sound larger and at the same time make the music more intimate and upfront sounding.


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## bpape (Sep 14, 2006)

Middle of the rear wall is usually a good place to help minimize nulls off the back - not to mention having some absorbtion opposite the live screen.

Don't be fooled - some of your reflections will absolutely be on the slanted ceiling.

Bryan


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## Guest (Jan 4, 2008)

Thanks guys

Question for DrWho? how can I determine if I need Absorption or Diffusion? or a bit of both.. I get the point about why - dead room is scary odd, masses of reflections and echo annoying, other than a listening test is there a rule of thumb I can apply to get 80% there?

Chris


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## Ethan Winer (Jul 21, 2006)

CharlieSpoons said:


> how can I determine if I need Absorption or Diffusion?


In a room that size you'll do best with absorption. If you're made of money some diffusion might be of benefit. The issue is that good diffusion costs a lot more than good absorption.

--Ethan


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