Paul's Posts — 27 September 2011
By Paul McGowan
In our post about where the image should appear, behind the loudspeakers and not in front, we stirred a bit of controversy on the one hand and sparked a number of questions on the other.
Several of you have asked how you can manage depth in your sound system and asked what controls the depth of the soundstage?
Hint: it’s not just one thing, but a combination of many.
I will offer you two ideas to help: pulling the loudspeakers away from the rear wall and/or diffusing the rear wall reflections.
The simplest way of increasing the depth of the soundstage is to simply pull the loudspeaker pair away from the rear wall, sometimes just an inch or two if you’ve setup using the Rule of Thirds.
From a visual illusion standpoint, this helps create more empty space for the soundstage to exist, something you can overcome if you listen in the dark (try listening both ways to verify). More importantly, this helps diffuse and delay the rear wall bounce from reaching your ears directly. This is important to understand because just about anything you can do to get the first sound arrival uncluttered with wall and floor bounce, the better your depth and imaging will be.
Problem with moving further into the room is the family’s likely objection to you eating up their real estate.
If real estate in the living room is precious, try diffusing or scattering the sound behind the speakers to increase depth of soundstage. Diffusing is generally better than absorbing for spatial cues and what you’d like to do is randomly scatter the sound in many directions so it is not so direct.
Think of the rear wall like a big, flat, mirror. The sound from your loudspeakers bounces off this acoustic mirror largely intact and just slightly out of time with the primary sound from the front of the loudspeakers and this confuses the ear brain and the result is less than a 3D perfect image. But if the acoustic mirror is broken into multiple small strips, each pointing in a different direction and at a slightly different depth, then what we hear can’t be pinpointed and is ignored as noise – thus the ear/brain pays attention to the primary audio first and the three dimensional aspects intended by the recordist are preserved.
The net result is a better more accurate soundstage.
Forward to a friend and help us engage more readers
Related Articles
Share
About Author
(4) Readers Comments
Leave a Reply
You must be logged in to post a comment.
timequest
I get great depth and central imaging, but my soundstage is pretty much confined between the speakers. I read about people’s systems producing a wide soundstage well beyond the sides of their speakers. I have plenty of room between the sidewalls (four+ feet between each speaker and sidewall). I am using the “Rule of Thirds” with the speakers placed 8 feet tweeter to tweeter. I therefore get a soundstage that is very deep and precisely centered, but only 8 feet wide…???
Paul McGowan
This is one of the trickiest things to master and it’s usually room related. You’re going to have to do two things: make sure the speakers are toed in as little as possible (the more their toed in, the less likely you are to get an image outside the speakers) and start treating the room.
May favorite is the RPG diffusor panels – although they are not hard to build yourself – search the web. You’re going to need to diffuse the backwall by ear and then find the point on the sidewall where you get the first reflection and diffuse or absorb there. Are you familiar with the mirror trick to find the point of first reflection on the sideawall?
Bazza13
Paul, does having and electrostatic or planar speaker influence this rule of thirds and/or the diffusing vs absorbing sound on the rear wall?
Paul McGowan
With any kind of dipole (which an electrostat or Maggie is) the rule of thirds and the rear wall become even more critical. Dipole’s really appreciate diffusing in the back wall, perhaps more than anything I’ve ever tried to setup.
At shows, when I bring the Maggies, we have a set of 3 RPG wooden panels I use to diffuse and they work miracles. The added depth of placing the RPG panels behind the Maggies is amazing.