Not a joke...

I got to thinking about this because of a 'room' I'm dealing with that is actually part of an high-ceilinged loft-like 'open plan' living space. There's two 'traditional walls (behind the listener, and to the left). The front wall is a slab about 8 ft wide, flanked by floor-to-ceiling openings to the room behind it (no doors) . The right 'wall' is a complicated space that includes a wall and a hallway to the rest of the space.


Here's a simplified view. The green oval is the listening couch . The black
boxes are walls or walled-off areas.


http://www.m-ideas.com/sullivan/Room_EQ/room.bmp

When there is this much connection to other parts of a larger space, what constitutes the 'room', for purposes of acoustics calculations?

All of it. When I did a CARA simulation of my city space, it indicated a large bass node under the dining table in the adjacent room and I confirmed it with direct measurements. Of course, putting a large bass trap there is not acceptable but an experiment confirmed that it really would help.

I have a post saved somewhere, by Dick Pierce, that explained why CARA is fundamentally flawed, but I can't find it right now :D


Another way to phrase my question (as Tom Nousaine phrased it once) at what point does an adjacent space go from being a 'coupled space' to an 'absorber' (like the space outside an open window)?

I have a post saved somewhere, by Dick Pierce, that explained why CARA is fundamentally flawed, but I can't find it right now


Another way to phrase my question (as Tom Nousaine phrased it once) at what point does an adjacent space go from being a 'coupled space' to an 'absorber' (like the space outside an open window)?
It never really becomes an absorber, at least not for low frequencies. But low frequency modes get lowered, and this is often a good thing.

Regards,
Terry

You still have a room, it is just that your room is subdivided into areas without complete visual isolation from each other. Modes could be estimated by the giant room dimensions to a point (although depending on the setup, it may be very difficult to do by hand-calculator), although reflections and decay times may be harder to estimate by hand due to all the half-height walls you may have. I would think that for imaging, as long as you have left/right symmetry, you should be fine. I think understanding the problems in the bass are going to be a bit more difficult.

As for when a coupled space influences your reflections less, I would assume that condition to require the coupled space to be spacious enough so that returning reflected waves are attenuated to a much higher extent than if the space was decoupled. What that means quantitatively, I'll have to leave that to the pros. :)

I have a post saved somewhere, by Dick Pierce, that explained why CARA is fundamentally flawed, but I can't find it right now Mebbe but this prediction was accurate.

You still have a room, it is just that your room is subdivided into areas without complete visual isolation from each other. Modes could be estimated by the giant room dimensions to a point (although depending on the setup, it may be very difficult to do by hand-calculator), although reflections and decay times may be harder to estimate by hand due to all the half-height walls you may have. I would think that for imaging, as long as you have left/right symmetry, you should be fine. I think understanding the problems in the bass are going to be a bit more difficult.


Thanks. Btw...possibly misread or misunderstood...there are no half-height walls in this space. There are what might be called 'incomplete width' walls, though ;).


As for when a coupled space influences your reflections less, I would assume that condition to require the coupled space to be spacious enough so that returning reflected waves are attenuated to a much higher extent than if the space was decoupled. What that means quantitatively, I'll have to leave that to the pros. :)

The room layout means te front L/R are asymmetricallly positioned with reference to their nearest sidewalls....left speaker being much close to its nearest side reflection wall, than the right.

It never really becomes an absorber, at least not for low frequencies. But low frequency modes get lowered, and this is often a good thing.

Regards,
Terry

That's what I was guessing. I'm curious to see what the data are if I run Room EQ wizard on this room.

This might be a related question.

If you have an open door going into another room, in one of the corners of your listening room, does that effectively work as a bass trap?

Ah, yeah I misread. I am familiar with the open concept kitchen/dining room/living rooms where half-height walls separate the areas.

Thanks. Btw...possibly misread or misunderstood...there are no half-height walls in this space. There are what might be called 'incomplete width' walls, though ;).



That would cause an audible imaging problem. If you can address this, it would be in your "best" interest.


The room layout means te front L/R are asymmetricallly positioned with reference to their nearest sidewalls....left speaker being much close to its nearest side reflection wall, than the right.

Rutgar: I would think that it would just act to lower the modal frequencies. If the other room has enough attenuation/tortuosity for the returning reflected bass wave, it may act as a bass "trap" although I wouldn't know how to model its "effectiveness" compared to say, a resonator or fiberglass absorber.