Wednesday, May 15, 2013

Room Tuning - Part 1

Pretty much everyone knows that rooms affect the way a speaker or system sounds.  This means that if you were to put your system into a friend's home and listen to a familiar song, it will sound very different from that in your listening room.  This is because of the way a room interacts with primarily your speakers and this is what I starred fussing with in my listening room.

Several really good books have been written on the subject or room tuning, the most popular being Get Better Sound by Jim Smith.  In his wonderful book, Jim discusses many real-life issues and uses many precise measurement techniques that combined with his decades of experience will move any listening experience closer to its full potential.  But for those of us who want to play with your room much like you do by swapping interconnect cables on your gear, there is another way to do this and achieve some very interesting and rewarding results.  All you have to do is understand a few important issues about the behavior of sound.

Before I begin, here are my basic assumptions:
  1. Your speakers are in the position you know them to perform their best (you have moved them left/right, up/down, forward/backward to find their best physical location)
  2. Your listening position (sweet spot) is at its stable location (you do not plan to change where you listen to your system)
  3. You are not planning to change your speakers
  4. You are not planning to alter the content or shape of your listening room (most importantly you do not plan to move or change walls as in a major construction project)
In other words, your listening room is pretty stable and you are happy with your speakers.  If you have a subwoofer and surround sound system, we'll get to these later but for now we'll just look at the primary front two speakers (front left and front right) and address the other channels later (their treatment needs are a bit different).

First of all, echoes are great in places like churches and canyons where sound can bounce all over the place creating a mesmerizing experience of reverberation and time delay.  Echoes are possible because of the speed that sound travels through the air, rather slow compared to something like the speed of light.  So when a reflecting surface is a long way off from where you are standing (like the wall of a canyon or wall in a very large room), exactly the same sound bounces back to your ears but at a differently-perceived time and at a reduced level (i.e., it is delayed and less loud than before).

When sound bounces off of a surface, some of its energy is absorbed by that surface and the echo is less loud than the sound that originally struck that surface.  When a surface is very flat, the reflected sound is louder than say if it were to bounce off a curved or irregularly shaped surface.  And when the surface is softer (like a blanket or down comforter), a lot of the sound is absorbed and very little is reflected as opposed to a hard surface.  Within these three statements hide the keys to how you can control echoes (reflections) in your listening room.

So the trick in your listening room is to control these reflections and to do so you can either change the shape of the reflecting surface (flat to irregular), change the composition of the reflecting surface (hard to soft), or remove the reflecting surface (something that is a little harder to do).  But the big question is WHERE to do this in your listening room to get the results you desire?  Enter a simple everyday state-of-the-art ultra-high-technology device called a MIRROR.

Mirrors do for light what walls do for sound, that is, they are both flat and hard and they both absorb little of the energy that strikes its surface.  So the first tool you need to get is a mirror, about a 12" x 12" will do nicely.  The next tool you need is a friend to hold that mirror against the surfaces in your listening room.  The last tool you will need is some blue or green painter's tape to put on the surfaces without harming them.

What you want to do is to locate where in the room you can see the fronts and backs of your speakers from your sweet spot.  Your friend will slide the mirror along the walls, floor, windows, and ceiling to where you see one speaker and then the other from your sweet spot and then use the painter's tape to mark those areas.  Now do not forget to mark the areas along the wall behind the speakers where you see the backs of the speakers in the mirror AND the walls behind the sweet spot.  What you have done in this simple exercise is to identify what is called the FIRST REFLECTION surfaces in your listening room.  These are the surfaces that reflect the MOST high-energy echoes to your ears and what we now want to do is to somehow change them so less energy is reflected.

Blue Areas are First Reflection Locations

Pretty neat trick, right?  So what you should have is a couple of rectangular areas taped on each of these surfaces that mark where you can see your speakers in the mirror (one taped rectangular area for the left speaker and one for the right).

The next question is this: NOW WHAT DO I DO?  For the answer to that, you'll have to tune in next time.

Yours for higher fidelity,

Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:

Copyright © 2015 by Philip Rastocny. All rights reserved.

No comments:

Post a Comment

To comment on this blog, you must first be a member. All comments are moderated.

Note: Only a member of this blog may post a comment.