Exterior wall concept

Stuart, i found a very helpful post you made on this thread... viewtopic.php?f=1&t=15658&p=110594&hilit=distance+from+the+speaker#p110594 A "soffit" (more correctly called "flush mount") is just a large flat rigid massive panel around your speaker, which acts like an extension of the front panel. Technically, it is an infinite baffle. In other words, take the very largest piece of plywood or MDF that you can fit across the front corner of your room, cut a hole in the middle of it just big enough for the front of the speaker to poke through from behind, fill the gap behind it with insulation, and you have a soffit. (OK, its a bit more complex than that, but that's the basic idea.) It's just a really BIG front panel for your speaker, that covers the entire room corner, floor to ceiling, and as wide as you can make it." Given that i have roughed in my front corners better(for now) The angles going down the sides could be soffits or what ever is needed there, they could extend further no problem. Again, my goal right now is to get the outer dimensions for the control room feeling right and to be technically un-impeding to a good interior design. Anything look off in that regard? Here is an updated sketch with dimensions, hopefully i have the mix position right. One question, How far is too far for a distance from the speakers? I plan to flush mount my Adam S2a's.

xSpace wrote:

That isn't what is happening here. The poster actually attempted to re-create the path lines using the tools included in Sketchup. What might be in question is the angle of incident of all the angles.

I just took the angle of incidence and mirrored it for the exit, seemed to make sense.

seaweed wrote:

xSpace wrote:

That isn't what is happening here. The poster actually attempted to re-create the path lines using the tools included in Sketchup. What might be in question is the angle of incident of all the angles.

I just took the angle of incidence and mirrored it for the exit, seemed to make sense.

I do not know of a mirror of incident feature within sketchup. When a ray comes out of a 30 degree angled wall and hits a barrier that is @ a 22 degree across the room, the angle of incident is still whatever the ray is traveling, but the plus side is the barrier it hits which will modify the ray. So it might seem that if the ray came out oft this speaker at a 33 degree, traveled across the room and hit a 22 degree boundary, that the incident angle would be 30 degrees. In a rectangular room it would, but under these conditions the 22 degree boundary modifies the deflection which changes the direction to an even more acute angle. Like I said, it was a smart move on your part...but needs more...thinking.

xSpace wrote:

seaweed wrote:

xSpace wrote:

under these conditions the 22 degree boundary modifies the deflection which changes the direction to an even more acute angle.

I was accommodating that. (see below) So are you saying that given the surface doesn't interfere with the direction of the ray it still does not follow this path? Please explain more if you can.

You still seem to be missing the point about ray tracing: The speaker does not produce just a single ray! It produces a cone full of millions of rays, all going in different directions, normal to the surface of the wave front, which is hemispherical. One ray tells you nothing useful at all: a the very least you need to trace a bunch of rays around the edge of the cone, at the limits. Also, you are tracing the rays that end up in the diffuse sound field, where they aren't really rays any more, so the entire exercise just seems a bit pointless. Tracing rays for your first reflection points is a totally different things, and is very useful, but that's not what you are doing. - Stuart -

Soundman2020 wrote:

You still seem to be missing the point about ray tracing: The speaker does not produce just a single ray! It produces a cone full of millions of rays, all going in different directions, normal to the surface of the wave front, which is hemispherical. One ray tells you nothing useful at all: a the very least you need to trace a bunch of rays around the edge of the cone, at the limits. Also, you are tracing the rays that end up in the diffuse sound field, where they aren't really rays any more, so the entire exercise just seems a bit pointless. Tracing rays for your first reflection points is a totally different things, and is very useful, but that's not what you are doing. - Stuart -

I did get your point initially, i just followed this conversation for the sake of interest alone, thanks for the reminder though. Any other comments from my questions in the previous post?

Seaweed wrote:

I am aware of the mirror trick, since it cannot be done yet, as the room is not built...

I don't think you understood the method I was referring to. It requires no physical mirror and can be done completely in Sketchup.

BriHar wrote:

copying a mirror image of your room to either side of the actual room diagram, then drawing a line from the actual listening position to the centre of the reflected images of your monitors - where it crosses the actual room boundary is your primary reflection point for that wall. You can do the same for the ceiling and even the floor using the side-view of course (including the desk if you've got it scaled in the drawing). Using this method can also help you work out the required angles for walls, hardback-clouds etc. for RFZ as well as treament.

I've found this method to be very helpful during the design phase, i.e. before the room is even finished. Remember that if you splay a wall then you'll have to additionally rotate the mirror image by the same angle as the splay (with the splay being the border or mirror line). Basically you're doing essentially the same thing as with the mirror in a physical room so always keep that in mind as a visual aid.

Thanks for clarifying that, i did miss it. Link bookmarked.

Down and dirty, sound follows the path of least resistance. The path that it takes in this pursuit and the boundaries it will encounter establish the incident angle, where it begins from and what it intersects. I made a quick graph to show one little ray, just one...and imagine there are thousands in a conical shape resembling a balloon...there's the rub:) Not as easily done as might have been imagined.

:shock: That hurts my head! I know it is often said here that acoustics seem to sometimes follow a logic of their own, but this seems to go against everything learned in basic physics, not to mention billiards :lol: Highschool physics tells us that a ray will bounce off a (flat) boundary at an equal but opposite angle to that at which it strikes said boundary, and not always 90°. In your example the first trajectory hits the 45° wall at an angle of let's say (just an estimation judging from the 3D graphic) 75°. It will then be reflected off of that wall at an angle of 105° (all relative to the plane of the wall in question). ...or do I err? :? Please explain the principles at work here.

...or do I err? :?

Nope! You don't err.... You are correct... :) - Stuart -

BriHar wrote:

Please explain the principles at work here.

Yes please Brien, it does seem like the main ray is lost after the first reflection, what's the deal leo?

If i have a 2x6 outer wall strapped with 2x3(on end)(all filled with pink insulation) and then an interior 2x4 wall (with pink FG insulation)with a total of a 3.5 inch airspace plus one inch between the 2(no insulation) i then have a total of a 12.5" air space in my wall. Is it of any benefit to increase the space more still than that if i can? It's easy now, like i could without blinking add 6 inches, thoughts? I should note what may be the obvious factor in a big "NO" is that i cannot do this to the ceiling, sooo, maybe forget i mentioned it. :oops:

BriHar wrote:

:shock: That hurts my head! I know it is often said here that acoustics seem to sometimes follow a logic of their own, but this seems to go against everything learned in basic physics, not to mention billiards :lol: Highschool physics tells us that a ray will bounce off a (flat) boundary at an equal but opposite angle to that at which it strikes said boundary, and not always 90°. In your example the first trajectory hits the 45° wall at an angle of let's say (just an estimation judging from the 3D graphic) 75°. It will then be reflected off of that wall at an angle of 105° (all relative to the plane of the wall in question). ...or do I err? :? Please explain the principles at work here.

No principles at work and by the way, AGAIN, this is not acoustics we are talking about. The ray started from a 30 degree angle wall and hit the 45 degree wall. I mentioned up front "down and dirty. The goal was not to try to establish what the entire spectrum would do, or even that one little ray except to show the poster that it isn't doing what you think it is doing...and how hard would that be for me, I wanted to represent how the angle changes, the path changes...and it is only one simple ray. Pretty big difference, errors included, between my interpretation and the original thought. Yes, a ray coming in at 90 degree that hits a hard boundary that is canted @ 45 degree will produce a 105 degree angle from the point of incident. A 90 degree intersection hitting a 45 degree angle will produce a 75 degree angle between the two, the difference between 90 and 75 is 15, that added to 90 gives 105 degree. Seaweed said "Yes please Brien, it does seem like the main ray is lost after the first reflection, what's the deal leo?" The ray in this picture is a simple representation...and it travels around the room and makes no less than 8 impacts. In reality, depending on the frequency, the sound that travels across this room will lose sound pressure level as it strikes the boundary and as time passes, so may not make even 8 iterations.

xSpace wrote:

BriHar wrote:

:shock: That hurts my head! I know it is often said here that acoustics seem to sometimes follow a logic of their own, but this seems to go against everything learned in basic physics, not to mention billiards :lol: Highschool physics tells us that a ray will bounce off a (flat) boundary at an equal but opposite angle to that at which it strikes said boundary, and not always 90°. In your example the first trajectory hits the 45° wall at an angle of let's say (just an estimation judging from the 3D graphic) 75°. It will then be reflected off of that wall at an angle of 105° (all relative to the plane of the wall in question). ...or do I err? :? Please explain the principles at work here.

No principles at work and by the way, AGAIN, this is not acoustics we are talking about. The ray started from a 30 degree angle wall and hit the 45 degree wall. I mentioned up front "down and dirty. The goal was not to try to establish what the entire spectrum would do, or even that one little ray except to show the poster that it isn't doing what you think it is doing...and how hard would that be for me, I wanted to represent how the angle changes, the path changes...and it is only one simple ray. Pretty big difference, errors included, between my interpretation and the original thought. Yes, a ray coming in at 90 degree that hits a hard boundary that is canted @ 45 degree will produce a 105 degree angle from the point of incident. A 90 degree intersection hitting a 45 degree angle will produce a 75 degree angle between the two, the difference between 90 and 75 is 15, that added to 90 gives 105 degree. Seaweed said "Yes please Brien, it does seem like the main ray is lost after the first reflection, what's the deal leo?" The ray in this picture is a simple representation...and it travels around the room and makes no less than 8 impacts. In reality, depending on the frequency, the sound that travels across this room will lose sound pressure level as it strikes the boundary and as time passes, so may not make even 8 iterations.

So essentially the logical path of ray travel, though some rays may take that route, is of no use at all, is that your point? Because rays travel in a cone or some similar shape, respond differently to the surface on reflection depending on the frequency, and the type of surface, and depending on frequency the ray may expire to a non critical volume(12db or less than departure) long before it ever makes the later reflections anyway. Does that sum it up mostly?

Anyone.... How far is too far for a distance from the speakers? I plan to flush mount my Adam S2a's.

I don't agree: in any elastic collision, angle of reflection is always = angle of incidence, even for waves. A wavefront can be viewed as a group of particles (because that's basically exactly what it is!), with each particle moving on a slightly different path, and each will react to whatever hard boundary it encounters in the normal manner, where once again the angle of reflection will be the same as the angle of incidence. And those angles should be measured with respect to the surface normal at the point of collision. So if a ray strikes a surface at an angle of (for example) 20° from the normal, it will bounce off at an angle of 20° from the normal towards the same direction it was originally traveling. In other words, if it was traveling from the top left of the computer screen toward the bottom center, basically it is going "left to right". When it hits the bottom edge of the screen and bounces back up, it will STILL be going "left to right", and will continue up towards the right hand side and top of the screen. That is and always has been, and always will be the way that elastic collisions work: conservation of momentum, and angle of incidence = angle of reflection. It works for pool balls on a pool table, light rays on mirrors, tennis balls on walls, and sound waves on hard room boundaries. - Stuart -

How far is too far for a distance from the speakers? I plan to flush mount my Adam S2a's.

As long as you are well within the critical distance for the room, you are fine. - Stuart -

Soundman2020 wrote:

How far is too far for a distance from the speakers? I plan to flush mount my Adam S2a's.

As long as you are well within the critical distance for the room, you are fine. - Stuart -

What about a consideration for speaker power. I have read that the speakers are more efficient when soffit mounted, but at 10 feet away, might i be getting a little past the power of self powered monitor?

With S2a'a? You'd be fine at 10' as far as power is concerned, but I personally I wouldn't like to be that far back. Not only that, to get 10' away from the speakers in your room, you'd have to be about half way between the front and back wall! Why would you want to listen there anyway? :shock: - Stuart -

Soundman2020 wrote:

With S2a'a? You'd be fine at 10' as far as power is concerned, but I personally I wouldn't like to be that far back. Not only that, to get 10' away from the speakers in your room, you'd have to be about half way between the front and back wall! Why would you want to listen there anyway? :shock: - Stuart -

I'm 9'7"and 1/16 at the 38% line from the speaker. The room is 24' 2", the speakers i put about a 1' 8 inches off the front wall(space behind for trapping). What am i missing?

Here are some updated pics of the actual build. The exterior wall-1/2 osb, 5/8th ext DryWall and cement board over top. Some slab prep which should be done by the end of the week end.

Soundman2020 wrote:

I don't agree: in any elastic collision, angle of reflection is always = angle of incidence, even for waves. A wavefront can be viewed as a group of particles (because that's basically exactly what it is!), with each particle moving on a slightly different path, and each will react to whatever hard boundary it encounters in the normal manner, where once again the angle of reflection will be the same as the angle of incidence. And those angles should be measured with respect to the surface normal at the point of collision. So if a ray strikes a surface at an angle of (for example) 20° from the normal, it will bounce off at an angle of 20° from the normal towards the same direction it was originally traveling. In other words, if it was traveling from the top left of the computer screen toward the bottom center, basically it is going "left to right". When it hits the bottom edge of the screen and bounces back up, it will STILL be going "left to right", and will continue up towards the right hand side and top of the screen. That is and always has been, and always will be the way that elastic collisions work: conservation of momentum, and angle of incidence = angle of reflection. It works for pool balls on a pool table, light rays on mirrors, tennis balls on walls, and sound waves on hard room boundaries. - Stuart -

I'll stick with the important stuff, as mentioned the first reflections and mirror stuff. Not a huge priority at the moment though.

I'll stick with the important stuff, as mentioned the first reflections and mirror stuff.

It looks like you are doing an RFZ design, so my crystal ball shows me that you have some ray tracing in your future! :) (But just to clarify what I said before: you have the "bounce angle" thing correct. I was agreeing with you there! I read over what I wrote, and realized it wasn't very clear, so I thought I should clarify that...) - Stuart -

Ok so then if i wanted to keep the soffit mounted speaker design on the front wall, the 60 degree angle, and i also want to be at the 38% line, but i don't want to be 10 feet back from the speaker, which do i change? If i move the speakers forward(towards listening position) with more trapping behind them, does that then change the position of the 38% line given the front wall comes forward?