Open baffle in a small room

How big does your room need to be for open baffle speakers? My room is 4.7m wide x 3.9m deep and works quite well. I wouldn't want to go much smaller than that, but a little bigger would be better. Here is a room which is about 4.7m in both directions. The following diagram shows a starting point for placing open baffle speakers in a room:

Firstly you'll notice the speakers are toed in so that they point at the listening. Normally this will work best, although in some cases you might toe them in so that their axes cross in front of the listener. It's not likely that it would ever be a good idea to point them straight into the room without any toe in. They should not be parallel to the front wall (behind the speakers).

They should be placed in from the front and side walls, ideally 1m being the minimum at least from the centre if not from the closest edges. More is better as long as they don't sit too close together.

It's no accident that the two dimensions shown on the left side are the same. This results in the first reflection from the front and rear walls being cancelled. The sound wave from the rear and that from the front of the speaker are out of phase but have the same path length to the listener. The result is cancellation.

The dimensions of this room are not ideal, and I would not aim for a room where the length and width are equal - this is shown for the purposes of illustration, to indicate minimum dimensions to allow for. In a very small room it's best to place the speakers so they fire into the room along the longest dimension. This is because open baffle speakers reduce side wall reflections while emphasizing the front and rear radiation.

Room treatment

Room treatment for an open baffle speaker should be moderate, especially in a small room. It's best to aim for an overall sound that is similar to what you would find in a typical living room with carpet, modern window treatments (not heavy curtains) and a moderate amount of decoration (pictures on walls, shelving, etc). A very formal living room full of furniture, heavy curtains, deep pile carpet and a dead sound will take the life out of the music. A very live room with tiled floor and large open spaces with little to absorb or diffuse the sound, not even blinds on large areas of glass, concrete, tiles - this will create too much of it's own sound.

A little diffusion behind the speakers can be an enhancement, but it's important not to place diffusion too close to the listener. A diffusor placed too close does more harm than good.

On the rear wall behind the listener some absorption may be used. Experiment with how much.

Please note that the areas shown indicate where the different types of treatment may be appropriate, but don't show the extent. It's probably best not to cover the entire areas shown.