# Subwoofer placement ?'s



## chrapladm (Jun 17, 2009)

I am getting ready to build another subwoofer system that will be my last for atleast the next three years.

Now I have read that Bryan states to try and avoid placing the subs in the corners. Now I wasn't planning on doing that but figured I would place them either center right and center left or other.

Now I will have four subwoofers in whatever cabinets depending on best locations. I will eventually have a 4.5m x 5.5m x 2.8m HT room. Now with four subwoofers I thought of doing dual subs in each cabinet and placing one center right and the other center left position.

Now the other option would be to make four subwoofers and place them around the room for hopefully a better even room bass response.

I would have two rows of seats in the future HT if that helps.

I am going to start to build the cabinets as soon as I get the T/s specs and whether or not I am going to build four cabinets or two.

Thanks to anyone who can share any info.


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## bpape (Sep 14, 2006)

Generally, corners are not good when you only have 1 or 2 subs. With 4, the Harman research suggests that all 4 corner loaded can work very well. There are also 2 other options.

- Center L, R, Front, and Rear

- Randomly and deliberately non-symmetric placement

Bryan


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## chrapladm (Jun 17, 2009)

Thanks Bryan.

Instead of starting another thread I thought I might ask a one more question in regards to ceilings.

I thought of trying to do a cove ceiling but wondered is a flat ceiling better for acoustics?

I would do a normal flat ceiling with mutli layers of drywall and green glue and then thought of doing a cove ceiling like this.








I have always seen studios with ceiling treatments but never have seen home theaters with treatments on ceilings. I have seen star ceilings, dome ceilings and weird grid like ceilings but never understood how this was good for acoustics. Maybe I just dont understand but I figured I would ask here and learn.


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## bpape (Sep 14, 2006)

You're not misunderstanding anything. Any sort of concave curve anywhere in a room is a bad thing acoustically as it tends to act like a lens and focus reflections at specific points. Stick with a flat ceiling. If you want to do anything different, one thing that can help is to angle the ceiling (still flat) so it's lower in front rising to maximum height in the rear of the room. This helps to push reflections toward the rear of the room and if there is enough angle, it can help with height related modes.

Bryan


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## chrapladm (Jun 17, 2009)

Would 1ft be enough across an 17.5ft span?

In other words an 8ft ceiling on the viewing wall then ascending to a 9ft wall on the rear wall.


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## bpape (Sep 14, 2006)

That will help a little with reflections but not enough to help with bass modes. To do that, it's more like 1" per foot per side (or in the case of a ceiling, 2" per foot since the floor stays flat). It's not doable in most rooms with real ceilings but if you had the height, it works great.

Bryan


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## chrapladm (Jun 17, 2009)

Well last question for now then. I think I would build on the walls flat first. Then I could build another ceiling that is angled. That way I could return the ceiling back to normal if I ever sell the place. But if this helps with room modes would a single layer of drywall be enough for the angled ceiling?

I am starting to think that anything that helps with bass would need to be maybe atleast a double layer of DW and green glue or no?

AND with a 18ft room that would be about a 3ft drop which would be too much for me. I could probably work out a way to about 1" but thats about it. I could drop the ceiling two feet and I think I could still do everything else I want. But would this ceiling help enough or should I just stick with 1ft?

I will be building the room from scratch so acoustics are the main concern for me with in reason. Dont want a 9.5ft ceiling going to 6ft just for room modes. That being said I would rather start with a good foundation hence why I wouldn't mind doing a 2ft drop.


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## bpape (Sep 14, 2006)

That's what I'm saying. For no more slant than you can do, I wouldn't worry about it. Just get the most height you can. It will be of more benefit. 

You'll still want double drywall and green glue on all surfaces.

Bryan


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## chrapladm (Jun 17, 2009)

Instead of asking on another thread this whole Harman paper has me wondering if placement was only on 2 planes.

My subs are not small so they will be placed center left and center right. Now the third or forth, depending what is needed, is where I am getting confused. Would a sub center back wall and near the ceiling be a good placement?

Or would, same height, but left center and right center back wall be better?

I was thinking of placing the subs beneath the surround channels but that will not be ideal placement according to what others have told me. Now the rear subs will be much smaller than the main subs up front but will play at least down to 20hz if needed. Placement is just the main question.

And secondly will the rear subs need to go down to 20hz or is 30-35hz fine?

The extension is not hard to get its just a matter of understanding what I need to design for.

Thanks again to anyone and thanks again for your info so far Bpape.


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## bpape (Sep 14, 2006)

I'm pretty sure they were only looking in 2 dimensions and assuming all sub placements were on the floor.

When you start getting into an odd amount with non-centered type of placement, many times you're better off to be deliberately asymmetric.

Up at the ceiling - hard to say without trying it.


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## bpape (Sep 14, 2006)

I'm pretty sure they were only looking in 2 dimensions and assuming all sub placements were on the floor.

When you start getting into an odd amount with non-centered type of placement, many times you're better off to be deliberately asymmetric.

Up at the ceiling - hard to say without trying it.


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## chrapladm (Jun 17, 2009)

Well the subs was just going to be either centered L and centered right wall on the floor or placed high near the ceiling. They can lay horizontal also but if they did they would be more like a single sub placed center of the back wall.

I guess I will just stick with floor placement for now. Where would the best likely position for the rear subs to be placed if dealing with 2 more for the rear?

Four cornered subs is possible but I was thinking that it was best to stay out of the corners and utilize them for bass traps.

And when looking at the paper it would seem that the subs are fired in towards the opposite sub. I am not sure how this would work with a false wall. The front subs will be behind a false. But I would guess this would not be a problem with frequencies lower than 80hz.No?


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## bpape (Sep 14, 2006)

Hard to say. once you get the side ones set up, just bring the other 2 in one at a time and measure each to get them to blend.

Bryan


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