[Rob Babcock]

I'm a little curious- all room treatment packs from 8th Nerve to Auralex to Foam by mail all seem to treat the trihedral corners formed by the walls & ceilings.  But they all ignore the corners formed by the walls & floor.  Why is this?  Is there a different force at work here or is it simply for aethetic purposes.

The laymen acoustician in me thinks those corners would load the sound just as badly.

[zybar]

I am no expert, but I posed that exact same question to Ethan at www.realtraps.com.  Etahn told me there isn't a difference and that you can treat at those boundaries as well as the usual corner ones.

Not only did Ethan tell me this, but I was able to test his theory in my room.  

Out of the six MiniTraps I have in my room, three are placed at the usual corner boundaries, two are placed at the floor/wall boundary, and one is placed at the wall/ceiling boundary.  The only reason I don't have three at the wall/ceiling boundary is that I haven't had time to mount the other two.

George

[Ethan Winer]

Rob,

> Why is this? <

As George said, all corners are valid. If you think about it, there's no concept of up, down, left, or right in a room. It's like a 3D object floating around in space. The main reason you don't usually see treatment in the wall/floor corners is because it looks strange and would be in the way of foot traffic. But it's a great place for treatment behind a fabric wall or TV projector screen, or anywhere else you don't have to worry about kicking or stepping on them.

--Ethan

[John Casler]

I have seen several rooms with many of the "interesecting boundaries" treated including the floor/wall intersecting boundaries.



Also well placed furniture "can" offer some small benefits in this regard.

For example, placing OS fabric covered chairs or sofas in a rooms rear corners, and along back walls can offer some very good benefits.

[8thnerve]

I'm a little curious- all room treatment packs from 8th Nerve to Auralex to Foam by mail all seem to treat the trihedral corners formed by the walls & ceilings.  But they all ignore the corners formed by the walls & floor.  Why is this?  Is there a different force at work here or is it simply for aethetic purposes.

The laymen acoustician in me thinks those corners would load the sound just as badly.

There are a few reasons we don't usually treat the floor corners.  As Ethan said, it's mostly due to ease and aesthetics.  However, we think they are a bit less important for a few reasons.  First, the floor area is usually broken up by furniture, speakers, etc. while a ceiling is generally open space, and the sound will couple more effectively there.  Second, many of us have wall-to-wall carpet, which is already providing us some absorption for half of the treatable area.  But it certainly is still effective.  In many dedicated listening rooms, especially ones with rugs instead of carpets, we suggest placing Corners on the floor in the corners of the room to very positive effect.

[Rob Babcock]

Yeah, I figured it was greatly due to aethestic reasons, but I also got to thinking that lots of rooms already have things in the corners & room boundries that would help acoustics (ie furnature, etc).

[Ethan Winer]

Rob,

> a lot of rooms already have things in the corners & room boundries that would help acoustics (ie furnature, etc) <

I don't think furniture will do much. Jeff Szymanski, head acoustician at Auralex, posted some before/after plots a few months ago in another forum showing the low frequency response with and without two large stuffed couches. The difference was not very significant. However, those couches were in the middle of the room. Had they been near the edges, closer to the corners, the large amount of stuffing would probably have had more affect.

8th (what's your name?), I've been doing a lot of measuring lately, and I'm coming to the conclusion that the front and rear wall surfaces and corners of a room are more important to trap than the side walls and corners. This makes sense, since the main wavefront from the speakers travels the length of the room, assuming the speakers face that way.

--Ethan

[zybar]

Ethan,

With your new findings, should I try my MiniTraps in different locations?

Right now I have them in the three room corners, at the midpoint of the room on the side walls, and the midpoint of the rear wall.

George

[8thnerve]

8th (what's your name?), I've been doing a lot of measuring lately, and I'm coming to the conclusion that the front and rear wall surfaces and corners of a room are more important to trap than the side walls and corners. This makes sense, since the main wavefront from the speakers travels the length of the room, assuming the speakers face that way.

It's Nathan.  Pleasure to meet you.  Strangely enough, I spent quite a bit of time in New Milford.  One of our original partners was the Director of Choirs at the Canterbury School.  Small world, eh?

Those are my findings as well, but I tend to focus on the corners since in addition to the increased pressure levels, the corners contribute to distortion while the wall surfaces are generally benign in these areas.  SPL readings of course don't tell the whole story.  I think SII readings will become the de-facto standard, unless of course someone comes up with something better...

[John Casler]

Rob,

> a lot of rooms already have things in the corners & room boundries that would help acoustics (ie furnature, etc) <

I don't think furniture will do much. Jeff Szymanski, head acoustician at Auralex, posted some before/after plots a few months ago in another forum showing the low frequency response with and without two large stuffed couches. The difference was not very significant. However, those couches were in the middle of the room. Had they been near the edges, closer to the corners .the large amount of stuffing would probably have had more affect.

Hi Ethan,

I think your right, if the OS chairs and couches are not in the intersections or corners, they will probably have little effect on LF.  I would also guess that a large cloth upholstered couch up against the back wall, or a similar chair placed in a corner, would have "measurable effect".

And a "corner sectional" piece in a corner, might be even better

 8th (what's your name?), I've been doing a lot of measuring lately, and I'm coming to the conclusion that the front and rear wall surfaces and corners of a room are more important to trap than the side walls and corners. This makes sense, since the main wavefront from the speakers travels the length of the room, assuming the speakers face that way.

I think I agree, with the front wall and rear wall being important but at this point we might want to "define" what they are important to, and what is meant by "corners".

Typically in a normal room with four walls, you have four corners where the vertical walls intersect, but many might call the intersection of the ceiling (or floor) and the wall (= 2 vertical walls and the ceiling, or two vertical walls and the floor), in which case there are 8 corners.

Do any of you, (Ethan, Eighth Nerve, etc) have  special "terms" that denote what intersecting boundary is being discussed.

For example if we were talking about the rear of the right wall's "upper" intersection with the ceiling?  What is that called??? Right upper rear corner?

I see that in the "marketing" and technical explanations to the lay person (like me) that having assignable and prioritized locations would make "acoustical set up" of a room more fruitful and result producing.

And I would say that "priority" of treatment would fundamentally be determined by the degree of problems and personal listening preferences.  That is, if we are farfeild listeners in a system set up on the short wall then the priortity of surfaces and intersections changes than if we were listening to nearfeild on the long wall.

I think we can see that in the farfield/short wall, versus nearfield/long wall set ups, that the side walls are either more or less important to specific frequency ranges.

And I can see that we all agree on some "treatment goals" and disagree on others.  Exploring those areas and where those differences are is probably as interesting as the different "listening preferences" we all have.

It is obvious too, that aesthetics can play a huge role and in some case either allow or dis-allow the use of certain treatments, based on a happy domestic (as opposed to sonic) environment.

The room I posted above, is from one of my speaker clients (hope he doesn't mind me linking to his gallery - thanks X-trum) it is in my opinion very clean looking and probably very effective for many of the sound grungies we face.

Some might think it looks fine,   others might find that they could not get it past the "design committee".

[Rob Babcock]

Lots of guys I've known do have their listening couch backed right up next to the rear wall.  While this might allow the couch to work as a room treatment, that's a lousy spot to choose to do your critical listening!

[John Casler]

Lots of guys I've known do have their listening couch backed right up next to the rear wall.  While this might allow the couch to work as a room treatment, that's a lousy spot to choose to do your critical listening!

Excellent point and I hope no one thought my mention of OS fabric furniture in those positions, thought I meant for them to be also used for primary listening, when placed there

[Ethan Winer]

George,

> With your new findings, should I try my MiniTraps in different locations? <

Note that I said "front and rear wall surfaces and corners" with the corners still being most important. So my basic advice has not changed. But when the room is large, and the rear wall is large too, a few extra traps flat on the rear wall (but spaced away a few inches using the supplied spacers) can only help even more. As opposed to putting them flat on the side walls.

--Ethan

[Ethan Winer]

Hi Nathan,

> Pleasure to meet you <

Yes, same here. And Nathan is not unlike Ethan!

> but I tend to focus on the corners <

Of course, and so do I. See my clarification above.

> SII readings <

What's SII?

--Ethan

[Ethan Winer]

John,

> have special "terms" that denote what intersecting boundary is being discussed. <

I call them "regular corners" and "ceiling corners." Sometimes I talk about "floor corners" because in recording studio control rooms there's often a space in front of the console where a few traps can lay on the floor and be out of the way.

--Ethan

[nathanm]

Lots of guys I've known do have their listening couch backed right up next to the rear wall.  While this might allow the couch to work as a room treatment, that's a lousy spot to choose to do your critical listening!

Well, if you've got a small room it's the most sensible choice.  I quite like the rear wall seating location myself.  If your space is cavernous then sure, you can move out in the middle, otherwise it feels weird IMO. Getting a decent spread between the speakers almost forces this position in a small room anyway.  This is also why I think home theater rear channels are almost totally impractical in most spaces.

[JoshK]

Well, if you've got a small room it's the most sensible choice.  I quite like the rear wall seating location myself.  If your space is cavernous then sure, you can move out in the middle, otherwise it feels weird IMO. Getting a decent spread between the speakers almost forces this position in a small room anyway.  This is also why I think home theater rear channels are almost totally impractical in most spaces.

Couldn't agree more!

[Rob Babcock]

This is almost a topic for another thread, but I really don't like listening very close to a rear wall- close proximity to room boundaries can wreak havok with the sound.  Although there are a lot of modes that can trash the sound in the dead center of a room, too.

In my system the rear wall is roughly 10-12 feet from my listening position (the front wall is very roughly 15 feet away).  When I arrived at this spot I noticed that moving the seat a foot or two front to back made drastic and unwelcome changes to the sound.

If I was forced to put my listening seating at the back of a room at the boundary, at the very least I'd want some potent absorber on the wall right behind my head to mitigate strong reflections from the wall surface.

[nathanm]

At the very least I'd want some potent absorber on the wall right behind my head to mitigate strong reflections from the wall surface.

Yep, I've got that.  I have a 2x4' sheet 'o 2" foam back there.  Of course I'd rather have the whole wall covered, but it does the trick in a pinch. The other thing is that you have to aim the speakers right at your head in this small room scenario.  Forward-facing speakers never sounded right in my room, as I assume more sound is being reflected off the side walls.  Plus it made the speakers look anti-social.

[Rob Babcock]

Geez, NathanM, I'd assumed your speakers were probably specially modified to look extra antisocial!   A couple more of your pentagram stickers on them would help in that regard!