absorbtion vs diffusion

organ

OK guys, I'm ready to work on sound treatment. I've been doing some research and it looks like some people prefer absorbtion only, some prefer diffusion only, and some say you need both.

I am in an L shaped room. Speakers are about10ft away. I've added some padding to the wall behind the couch because I sit right against the back wall. The rest of the back wall is bare and the front wall is also bare.

Should diffusion panels be on the rear and absorbtion on the front wall?

pearsall001

A combination of both along with bass traps will make a huge difference in your listening pleasure. Here's a great place to start learning about room treatments & how important the "room" really is in reproducing music at it's finest. Equipment & speakers will only get you so far...the room is the icing on the cake so to speak. http://www.realtraps.com/

Gaara

Think about how diffusion works. The wound waves hit the diffusor and spread out, whereas with absorption they are partially absorbed and slowed before bouncing back. Because of the way a diffusor works there is a minimum amount of space required to be effective.

If you are sitting against the back wall then you would not want diffusion, as there is not enough space to be effective.

How large is the room? It sounds like you would be best just using absorption, as diffusors on the front wall aren't as effective, as that isn't a first reflection point.

organ

Thanks guys. I think I'm going to use absorbtion panels.
I"ve attached a layout of the room. Do you think I should use them on the back wall only? Or do I need both the front and back?
The walls are quite thin. Ceiling is made of some softer materials and floor is carpeted.

Also, where should bass traps be placed?

Face

IMO, back wall and first reflection points are the most important.

treitz3

There is a lot of reading but this website should give you what you need to know. Including what to do with an L-shaped room.

http://www.michaelgreenaudio.com/forum/index.php

organ

Sorry, had problems posting the layout. It's up on my previous post now.

The side walls are quite far away, so should they be left untreated?

Thanks for the links. I'm going to do some serious reading.

Early B.

Organ -- all of those speakers lined up in the front is likely to be **** up your sound big time. Go into any audio shop where they have multiple setups in one room and the sound will always suck, partly because of too much gear in the same room. No amount of sound treatment will cure that problem.

organ

Hey Early,
That's what I thouht at first as well and then I tried doing some comparisons.
All the speakers along the front are horn loaded, so their dispersion is very well controled. They could even go right up against the wall or corner and still image like crazy. Imaging is excellent with great depth and soundstage width can be wall to wall on certain recordings. The La Scala are what I use the most for 2ch. The imaging is razor sharp. If I'm going to use the Cornwalls, I switch their position with the La Scala.

I guess I forgot to post why I decided to want to treat the room.
The hand clap test in some areas reveal a very quick high pitched ring which follows the clap. I can hear it when I snap my fingers as well. Hell, I can hear it when I sneeze. Now I'm able to hear it when listening to both HT or 2ch. It's most audible when there is a loud passage or part. The room seems to be exciting some high frequencies and also produce a short echo within those frequencies. My guess is that the sound is bouncing off the back wall which is 90% bare and then hitting the front wall. This annoying "ring" is what I'm trying to eliminate. I"m sure bass the other stuff will improve as well after treatment.

Gaara

Face wrote: »

IMO, back wall and first reflection points are the most important.

Very true, especially with the stated problem.

organ wrote: »

I guess I forgot to post why I decided to want to treat the room. The hand clap test in some areas reveal a very quick high pitched ring which follows the clap.....My guess is that the sound is bouncing off the back wall which is 90% bare and then hitting the front wall. This annoying "ring" is what I'm trying to eliminate. I"m sure bass the other stuff will improve as well after treatment.

This is where the 1st reflection points come into play. You want to absorb the sound so it is a lower level after it reflects, causing less of the ringing that you hear, as well as helping comb filtering. You don't want any untreated parallel walls, this is what allows the sound to bounce around like that. Treating the back wall will be a big improvement.

As for bass, this is not necessarily the case. Just because you get room treatments doesn't mean it will improve bass, many acoustic treatments do next to nothing in this regard. Look at the absorption coefficients below ~125hz, most foam does little to nothing below this point.

For example Auralex's 2in wedge foam only has a coefficient of .11 at 125hz, and isn't even measured below 100hz. Compare that to a real bass trap, like the GIK 244 bass trap. It is effective down to 50hz and has a coefficient of 1.64 at 125hz. DRASTICALLY better then your basic foam.

awe-d-o-file

organ wrote: »

Thanks guys. I think I'm going to use absorbtion panels.
I"ve attached a layout of the room. Do you think I should use them on the back wall only? Or do I need both the front and back?
The walls are quite thin. Ceiling is made of some softer materials and floor is carpeted.

Also, where should bass traps be placed?

It took time and trials to find the best spots. Luckily my opening is in the center so I don't have an L. Jon Risch's DIY is what I used. Cheap and effective.


Link: http://www.geocities.com/jonrisch/a1.htm

madmax

In my old house I had absortion material behind the couch which had to sit against the wall. It caused a noticable lack of sound behind me and made me feel very uneasy. In the end I found out all my problems were coming from ceiling reflections. I tested by having a couple of foam pads (about 2'x2') and putting them everywhere. As soon as I set them on top of the speakers, protruding out from the front so the sound couldn't go up it sounded much better. Just something to try. Of course if that turned out to be the problem you would want to figure out where to mount them on the ceiling.

organ

Thanks again for sharing your experiences and links.

I'm going to start looking for panels early this year. Once I've got the panels done I will start looking for bass traps.

Madmax,
I think my ceiling should be ok. Don't know exactly, but it is made of soft material.
Snapping my fingers close to the wall makes the high pitched echo easy to hear. If the panels don't work, I will try diffusion. Came across a youtube video that looked good which talked about using diffusion if you're sitting against the wall. I'm sure I can come across plans and have a carpenter build one.