Ceiling first reflection points, absorption or diffusion?

LordCloud · « **on:** 1 Nov 2005, 03:20 pm »

I've treated my room and I am pleased wit the results, however, I am thinking of treating my ceiling at the first reflection points with 2 inch thick panels. Does anyone have any experience experimenting with both in the same system on the ceiling. My experience with the wall behind the speakers tells me that diffusion will increase soundstage height but take away some delicacy and sounstage cues. Anyone care to chime in?

Ethan Winer · « **Reply #1 on:** 1 Nov 2005, 04:54 pm »

Cloud,

> I am thinking of treating my ceiling at the first reflection points with 2 inch thick panels. <

That's a good plan, and I suggest absorption over diffusion. Diffusion is best applied farther away from your ears. So unless your room is very large, and you're 10 feet or more away from the reflection points, you'll do much better with absorption. One of the "problems" with diffusion is the good ones are very complex and expensive, and the cheap ones are, to my ears, worse than a plain bare wall.

--Ethan

ctviggen · « **Reply #2 on:** 1 Nov 2005, 05:07 pm »

I agree with Ethan -- take down the level of the first reflections using absorption. I also agree with Ethan that good diffusion products are unbelievably expensive. A market need perhaps?

zybar · « **Reply #3 on:** 1 Nov 2005, 05:20 pm »

Quote from: Ethan Winer

Cloud,

> I am thinking of treating my ceiling at the first reflection points with 2 inch thick panels. <

That's a good plan, and I suggest absorption over diffusion. Diffusion is best applied farther away from your ears. So unless your room is very large, and you're 10 feet or more away from the reflection points, you'll do much better with absorption. One of the "problems" with diffusion is the good ones are very complex and expensive, and the cheap ones are, to my ears, worse than a plain bare wall.

--Ethan

So far all of Ethan's advice and products has improved the sound of my system, so I wold highly suggest following his advice.

George

LordCloud · « **Reply #4 on:** 1 Nov 2005, 06:47 pm »

Thanks everyone for the advice, absorption is the way I was leaning. I do worry about the sound becoming too dead though. But we'll see.

dwk · « **Reply #5 on:** 1 Nov 2005, 07:03 pm »

Quote from: ctviggen

. I also agree with Ethan that good diffusion products are unbelievably expensive. A market need perhaps?

At RMAF I ran into some folks that I've known through the local audio scene for a while, and they had prototypes of their new diffusor there. These are pretty good and bright guys, so when they say they work I tend to believe them, although I'm looking forward to being able to try them out.. The pricing targets they indicated are well below what I expected.

So, there may be some hope on the hopefully not too distant horizon.

ctviggen · « **Reply #6 on:** 1 Nov 2005, 07:26 pm »

That would be good. After more absorption and more bass trapping, diffusion is my next item to get, but diffusive products are very expensive, particularly for the coverage you get with them.

michaelv · « **Reply #7 on:** 2 Nov 2005, 10:21 pm »

talking about reflection point on ceiling,i have tried with fiber glass and the panel is so heavy for ceiling application. I'm thinking of just wrapping fabric and hang it in the ceiling with some sort of brackets.

matix · « **Reply #8 on:** 3 Nov 2005, 01:46 am »

Sorry to hijack this thread... seems some experts lurking around here.

I have my speakers set up along the long wall of a 3m X 10 m room. The speakers are already half metre from the back wall, and I am forced to position my sofa touching the opposite wall. I guess this is less than ideal as my ears are only about 30cm from the wall behind me. Any suggestions, methods to treat this situation.

ooheadsoo · « **Reply #9 on:** 3 Nov 2005, 01:56 am »

Quote from: michaelv

talking about reflection point on ceiling,i have tried with fiber glass and the panel is so heavy for ceiling application. I'm thinking of just wrapping fabric and hang it in the ceiling with some sort of brackets.

Really? I have some 3lb.pcf hanging right above my head right now, and it doesn't seem that bad. I have it hanging from these small screw hooks I bought from a fabric store...You may not be able to hang big slabs of the stuff, but it's manageable in smaller pieces.

Ethan Winer · « **Reply #10 on:** 3 Nov 2005, 03:46 pm »

Matix,

> my ears are only about 30cm from the wall behind me <

This is a big probem. Ideally you'll set up so the loudspeakers fire the long way down the room. That improves the low end a lot, and also puts you farther from the wall behind you where peaks and nulls are always the worst. The drawing below shows what I consider the ideal setup in a rectangular room.

--Ethan

LordCloud · « **Reply #11 on:** 3 Nov 2005, 10:16 pm »

Quote from: matix

Sorry to hijack this thread... seems some experts lurking around here. I have my speakers set up along the long wall of a 3m X 10 m room. The speakers are already half metre from the back wall, and I am forced to position my sofa touching the opposite wall. I guess this is less than ideal as my ears are only about 30cm from the wall behind me. Any suggestions, methods to treat this situation.

My listening position is also right against the wall, and I honestly don't have any problems with it. There are some who advocate listening right against a wall, I'm not one of them, that's just how it ended up in my room. But I get incredible sound in my opinion.

ScottMayo · « **Reply #12 on:** 4 Nov 2005, 02:42 am »

Quote from: Ethan Winer

Um.. if the pink rectanges on the side walls are traps, I'm going to protest that that room is under-treated.... and while it's really noble for a trap manufacturer to understate the need for traps, I think that design is optimistic for 5 channel sound.

Red Dragon Audio · « **Reply #13 on:** 4 Nov 2005, 04:28 am »

Hi Scott,

That particular rendering from Ethan onlyaddresses first reflection points on the wall and ceiling. Reading further on Ethan's website shows he recommends using more panels for complete room treatment. Here are a few examples found on Ethan's website.

www.RealTraps.com

Ethan Winer · « **Reply #14 on:** 4 Nov 2005, 02:54 pm »

Cloud,

> There are some who aadvocate listening right against a wall <

Yes, as you get closer to the wall the response becomes riddled with peaks and deep nulls due to comb filtering. The drawing below shows the response measured 20 inches from a standard sheet rock wall.

--Ethan

ctviggen · « **Reply #15 on:** 4 Nov 2005, 03:19 pm »

And I thought my room response looked bad!

That's horrible.

LordCloud · « **Reply #16 on:** 6 Nov 2005, 05:16 am »

Quote from: Ethan Winer

Cloud,

> There are some who aadvocate listening right against a wall <

Yes, as you get closer to the wall the response becomes riddled with peaks and deep nulls due to comb filtering. The drawing below shows the response measured 20 inches from a standard sheet rock wall.

--Ethan

Ethan,

While I don't dispute the measurements, for me, they are ultimately just pictures that mean very little in comparison to actual listening. Any graph you show me won't be meaurements of my room. Please don't take this as any form of attack against you or measurements, as I said, I am not one who advocates listening while seated against a room boundary (even thugh people who's opinions as well as their products I respect, do) . But in my room, it sounds best to me.

matix · « **Reply #17 on:** 6 Nov 2005, 05:42 am »

Quote from: Ethan Winer

Matix,

> my ears are only about 30cm from the wall behind me <

This is a big probem. Ideally you'll set up so the loudspeakers fire the long way down the room. That improves the low end a lot, and also puts you farther from the wall behind you where peaks and nulls are always the worst. The drawing below shows what I consider the ideal setup in a rectangular room.

--Ethan

I would love to put the speakers this way. Unfortunatly, that is where the balconey is, where my wife's plants are. No way is she going to allow this.

And the dining table is at the other end of the room. And she won't have her guests staring at the back of speakers....

Anyway, that is my problem.... Back to my situation, any product available to "better" my situation? Diffuser, Absorption??

I was told that I am already in a nearfield listening situation, and no need to treat anything behind... I want to try though.

Ethan Winer · « **Reply #18 on:** 6 Nov 2005, 04:07 pm »

Cloud,

> Any graph you show me won't be meaurements of my room. <

If only!

Seriously, this is exactly what you get in any room at that distance from a wall behind you. The only saving grace is that you have two ears spaced apart, so the peak / null frequencies are different in each ear and the brain is able to average them out.

> in my room, it sounds best to me. <

I can't dispute that. And the skewed responce can often be pleasing. For example, if your distance adds a null in the boomy range around 200 to 300 Hz and a peak a little lower that adds fullness. But it's impossible to have anything even close to a flat response a few feet in front of a reflecting boundary.

--Ethan

ScottMayo · « **Reply #19 on:** 6 Nov 2005, 05:32 pm »

Quote from: Ethan Winer

Seriously, this is exactly what you get in any room at that distance from a wall behind you. The only saving grace is that you have two ears spaced apart, so the peak / null frequencies are different in each ear and the brain is able to average them out.

It's not always that simple. When the ears perceive different loudnesses, they try to establish where the source is, based partially on that. For low frequency stuff, the ear isn't good at pinning down a direction anyway, so it's not critical. At higher frequencies, combing will smear subtle imaging cues to no end, and if you move your head an inch, it messes it up differently. How pronounced this gets depends on a bunch of things, but if you want imaging to work really well, keep sources and ears off the walls, and treat reflection points.