Diffusers distance from the wall

Thank you

I also see Real traps diffusers to be placed away from the wall - most likely for this reason

 ----cannot get rid of this icon- sorry 

they have fiberglass on the back and it works for  low frequencies absorption  also ...


So 

-my diffusers cannot be in the treatment but I could do the following :


On the rear wall -behind the engineer s back -
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One foot or less or more from the wall - bass traps
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2 inches air gap ?

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Diffuser almost same size as the bass traps - maybe the bass traps are slightly larger.  

All these centered vertically at ears height -
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This will be equally effective ?

Yes, RealTraps Diffusers are made of rigid fiberglass, so an air space behind increases the bass trapping.

--Ethan

So you want to relocate absorbers and diffusors in order to create a pedestrian passageway behind, between the diffusors and the grage door as back wall.

I don't know enough about Ethan's specific Q7D yet to be as much help as he would.  It looks like you're already pretty involved!  I'm still learning my way around.  Everything I have to add may be wrong if his diffusors are open-back and really absorb much...in which case the main room would benefit from the space behind and absorb any reverberations in that passageway too.

Most absorbers are likely to work better when moved farther from the wall, assuming the absorbers do not have sealed backs. If the backs are sealed the characteristics of that partition become involved.

The diffusors have two considerations:
- The properties of the bigger new "hallway" chamber behind them that this will create, and the dimensions of the openings from this new hallway to the main room. This can be addressed with additional absorption within that chamber, hopefully without interfering with pedestrian traffic. The difficult goal would be to turn this problem area into a tuned absorber. You might need to hang futons on the walls and walk on one in order to actually achieve that.
- The other problem is a side effect: making that area larger makes the main area smaller. Depending on the lowest frequency they intend to diffuse, there is a preferred minimum distance the listener or mic should be from a diffusor. So moving the diffusor nearer the listener is sub-optimal. But that's really a special case of something more fundamental: for mid & high frequencies, this is making the room acoustically smaller when the objective is the opposite. Making the main space smaller will not help you get rid of those early reflections <10ms and can raise the frequency of the lowest modes which are related to the length of the room. The diffusors are not going to work that low unless they are some hybrid 'diffsorbers' so you also have to consider the dimension of the step you are creating in the back wall of the main room, and whether the modes with and without the step will reinforce (frequencies of modes too close).

In general, I would recommend against making the main space smaller, especially not moving the diffusors closer to the listener. Assuming this is some sort of LEDE room, and you really need that passageway and have to make the main space smaller, maybe you could turn it around. Open-back absorbers will work to lower frequencies with the additional space behind, much more than the diffusors.  It sounds like you will be far enough from the diffusors, but more is always better IMHO.  You have one good dimension, why not keep it?  How do the main modes stack up now, are they a problem that might improve by moving the diffusors?  How difficult is it to do, and do you have any room measurement tools?

Look at it this way. Ideally, the area directly in front of diffusors is not really usable for much. It's an ideal location for an open passageway walking area IN FRONT of the diffusors. I hate fireplaces because you can't place furniture in front of them or they start on fire, so I design rooms with a fireplace to use that space for pedestrian traffic flow, just because it's not very useful for anything else. I'm starting to regard the space in a room in front of diffusors similarly: not useful for much else, so it might as well be the access pathway for foot traffic patterns. I think you're much better off putting the diffusors close to the garage door. And I'd probably install a garage door insulation kit since it's affordable and easy.