Absorption or Diffusion?

[ejspain]

Are you absorbing or diffusing behind you ML?
Are you absorbing or diffusing your first reflection points?
Are you absorbing or diffusing your rear walls?

 

[Rich]

I have diffusion about 5 feet behind the speakers (no longer ML, but still an electrostatic panel speaker). I have absorption on the side walls and in the corners. I have absorption and diffusion on the rear wall. Makes for a detailed and spacious sound with incredible imaging and sound staging.

 

[ejspain]

I have diffusion about 5 feet behind the speakers (no longer ML, but still an electrostatic panel speaker). I have absorption on the side walls and in the corners. I have absorption and diffusion on the rear wall. Makes for a detailed and spacious sound with incredible imaging and sound staging.

Do you think adding some diffusion behind your electrostatics would open your sound stage even more or make it sound cathedral? Unless you're absorbing the ceiling also. (Oh crap my bad...you said you have diffusion behind the electrostatics).

 

[Robert D]

Ceilings is a good question. If building a new home theater, are you best off putting in a drop ceiling with special sound absorption panels or just do regular drywall? Ceiling tiles would be nice too if you have to do work on wiring. I think I prefer the look of drywall more, but I have very little experience with drop ceilings. I'm also not one to place form over function.

 

[ejspain]

Ceilings is a good question. If building a new home theater, are you best off putting in a drop ceiling with special sound absorption panels or just do regular drywall? Ceiling tiles would be nice too if you have to do work on wiring. I think I prefer the look of drywall more, but I have very little experience with drop ceilings. I'm also not one to place form over function.

My HT ceilings are 10' so I put some absorption just over the seating and it works perfect to eliminate the Cathedral factor.

 

[Brad225]

When I built my room I chose to use absorption on all walls floor to ceiling. As time went by I added diffusion panels to the front wall and side walls back to where first reflections would be. The rest of the room remains absorption only.

The ceiling in the room is slopped up on all 4 sides to a flat center that is parallel with the floor. When I first finished the room there were no absorption panels on the ceiling.
My listening chair is located under on of the sloped sections. When I started playing music even though ELS panels don't throw sound waves up, the music was also coming from overhead straight down on me.
The next day I was back in my shop building absorption panels for the ceiling. The issue was then solved.

I am able to move the diffusion panels anywhere along the walls as they are hung on the top of the absorption panels. It is very interesting how you can alter the sound stage and image. I have gotten to a very small diffusion panel on the wall in the center between the speakers. I found a larger one would make the center vocals or instruments way to intense.

 

[Robert D]

When I built my room I chose to use absorption on all walls floor to ceiling. As time went by I added diffusion panels to the front wall and side walls back to where first reflections would be. The rest of the room remains absorption only.

The ceiling in the room is slopped up on all 4 sides to a flat center that is parallel with the floor. When I first finished the room there were no absorption panels on the ceiling.
My listening chair is located under on of the sloped sections. When I started playing music even though ELS panels don't throw sound waves up, the music was also coming from overhead straight down on me.
The next day I was back in my shop building absorption panels for the ceiling. The issue was then solved.

I am able to move the diffusion panels anywhere along the walls as they are hung on the top of the absorption panels. It is very interesting how you can alter the sound stage and image. I have gotten to a very small diffusion panel on the wall in the center between the speakers. I found a larger one would make the center vocals or instruments way to intense.

Thats probably a lot of fun being able to do that, and then see how dsp deals with it. I'd love to do that.

 

[ejspain]

Would love to hear you guys/gals take on this guys suggestion of NOT using any room treatments with the ML?

Soundex

 

[Rich]

Do you think adding some diffusion behind your electrostatics would open your sound stage even more or make it sound cathedral? Unless you're absorbing the ceiling also. (Oh crap my bad...you said you have diffusion behind the electrostatics).

Yes, I have diffusion behind my panels. I tested both absorption and diffusion. Imaging and soundstage are excellent with both. But I found absorption deadened the sound too much. Diffusion provided a lot more of the ambiance and spaciousness that electrostats are known for and a threw a wider, deeper soundstage. You can get used to either sound, but I preferred diffusion. But in order for diffusion to work properly, you need about five feet between your speaker panels and the diffusors. If you have much less than that, you might be better going with absorption.

Ceiling treatments don’t really make a difference with electrostats because they don’t have any vertical dispersion, being a line source speaker.

 

[Album56]

Look at the Haas effect, reflections from the wall behind the speakers can enhance the imaging & size / depth of the stereo.
Needs trial & error to get the distance from the wall to your liking tho.

 

[Robert D]

Yes, I have diffusion behind my panels. I tested both absorption and diffusion. Imaging and soundstage are excellent with both. But I found absorption deadened the sound too much. Diffusion provided a lot more of the ambiance and spaciousness that electrostats are known for and a threw a wider, deeper soundstage. You can get used to either sound, but I preferred diffusion. But in order for diffusion to work properly, you need about five feet between your speaker panels and the diffusors. If you have much less than that, you might be better going with absorption.

Ceiling treatments don’t really make a difference with electrostats because they don’t have any vertical dispersion, being a line source speaker.

How about some of the Martin Logan speakers that are raked upward?

 

[ejspain]

the Masterpiece series have a natural 5 degree tilt with the spikes set to leveled. Unless your listening position is substantially higher, the 44" x 11" Xstat panel with the 5 degree tilt should be fine.

 

[Robert D]

the Masterpiece series have a natural 5 degree tilt with the spikes set to leveled. Unless your listening position is substantially higher, the 44" x 11" Xstat panel with the 5 degree tilt should be fine.

Yeah, I'm just thinking that at some point the sound waves are going to strike the ceiling toward the rear of the room? With the panels not being parallel with the ceiling.

 

[Rich]

Yeah, I'm just thinking that at some point the sound waves are going to strike the ceiling toward the rear of the room? With the panels not being parallel with the ceiling.

You mean perpendicular to the ceiling. And it’s a non-issue. The reflections would strike the ceiling, if at all, so far back that they would have to reflect off the rear wall before they made it to the listener’s ears. And by that time, they would be weakened and time-delayed enough not to interfere with the perception of the front wave off the speaker. Imaging would not be affected.

 

[Robert D]

You mean perpendicular to the ceiling. And it’s a non-issue. The reflections would strike the ceiling, if at all, so far back that they would have to reflect off the rear wall before they made it to the listener’s ears. And by that time, they would be weakened and time-delayed enough not to interfere with the perception of the front wave off the speaker. Imaging would not be affected.

What I meant to say is that the sound wave wouldnt be traveling parallel to the ceiling. Thats what I figured, about it being far back. So just having a regular drywall ceiling wont matter, sound will be just as good as when using special tiles for the ceiling.

 

[Fidji99]

Would love to hear you guys/gals take on this guys suggestion of NOT using any room treatments with the ML?

Soundex

His front wall actually IS treated with all the books. And as it seems he has some distance to side walls. And we do not see how far is his listening position from the rear wall, if he has enough space, it is also beneficial for overall acoustics. There are rooms that are naturally very acoustics friendly.

You can not judge from the pictures, but it looks quite lively and he has them placed relatively near to each other in a big room. I wonder what reverb time he might be having, and whether he is not sacrificing a lot of spatial cues in the music.

 

[ejspain]

Yeah, I'm just thinking that at some point the sound waves are going to strike the ceiling toward the rear of the room? With the panels not being parallel with the ceiling.

Yea I was kinda thinking the same but I guess that would depend on the depth of your room because I kinda agree with @Rich the xstat just aren't designed that way but a sound wave is a sound wave is a sound wave and given enough distance it will eventually rise. I have a small amount of absorption in my ceiling and it hasn't seemed to hurt any of the transformations in my room.

 

[ejspain]

His front wall actually IS treated with all the books. And as it seems he has some distance to side walls. And we do not see how far is his listening position from the rear wall, if he has enough space, it is also beneficial for overall acoustics. There are rooms that are naturally very acoustics friendly.

You can not judge from the pictures, but it looks quite lively and he has them placed relatively near to each other in a big room. I wonder what reverb time he might be having, and whether he is not sacrificing a lot of spatial cues in the music.

Great points. You're right the books will definitely act as some absorption and diffusion.

 

[JonFo]

Are you absorbing or diffusing behind you ML?
Are you absorbing or diffusing your first reflection points?
Are you absorbing or diffusing your rear walls?

All of the above.

Absorption behind the front three speakers, abfusion behind the rear speakers, and 3D Diffusion between the rear speakers, which primarily impacts the front speakers reflections off the rear wall. Massive bass absorption in the rear corners and lighter stuff on most exposed areas of the rear wall.

First reflection point on ESL is at the wall behind them, but I think you mean the sidewalls, so I'll answer that. Yes, a combination of mostly absorption, but also use the used stators from my Monoliths as curved abfusion (the cavity behind the stator is absorptive, so <500Hz is absorbed).

Full details on the side and general room treatments, including a diagram in the last post of this thread: Room treatments – part 2

 

[JonFo]

Since 'first reflection points' was raised here and recently on one of the FB ML fans groups, I will post my thoughts here, so they persist longer than the nanosecond they last on FB.

Given the line-source radiating pattern of the ESL, coupled with the fact we toe-in the speakers, the sound coming off the front of the panel will not interact with the immediate, closest sidewall. So all the traditional advice regarding determining and treating those points is irrelevant (as it relates to the front wave).
Rember, the 'traditional' advice is regarding monopole point-source speakers, and our ESLs are line-source dipoles, with radically different radiating patterns. And thus, radically different treatment needs.

On any dipole speaker, the first (meaning shortest path) reflection point is the wall directly behind the speaker, and the second reflection point derives from the first and will be the side wall to the outside of the speaker.
Since a dipole radiates 100% as much energy from the speaker's rear as it does from the front, it is critical to understand where that energy is directed and where it reflects back into the listening area.

Managing that path is the difference between a muddled mess and a satisfying soundstage.

I've written about this before, but the summary is that room size, placement, treatments (or lack thereof), and many variables make a single recommendation near-impossible to make.

While I set up my room with a ton (literally) of absorption and other treatments, I did so to achieve a very focused multichannel immersive sound field.

But one can set up a very satisfying system with minimal treatments IF the room and placement allow. So as long as the rear-wave paths are delayed enough and attenuated enough (by distance vs absorption), and the listener is well away from room boundaries and not in any major nulls. But from 18 years following ESL deployments, shared here and on the web, rooms like that are extremely rare.

That rarity in naturally good rooms for ESL is why many of us turn to various forms of acoustic treatments (and some room correction as well) to manage the soundfields to achieve results we can be pleased with.