Setting Up
Loudspeakers
Author: Shane Mattson
January/1999
Loudspeaker placement can be a
difficult as well as frustrating task. Owning a pair Apogee Acoustics Stage ribbon
loudspeakers; I have spent a countless number of hours tweaking the positioning, searching
for that magical –or should I say "right"- sound. I would like to
share with you some of my experiences with loudspeaker positioning with hopes that you
might benefit from some of the successes as well as failures throughout the process.
First,
take a good look at your listening room. What are the dimensions? Where is the
furniture placed? How about the windows? Where are they located in conjunction
with your loudspeakers? Do you have hard wood floors or wall to wall carpet?
How high are the ceilings in the room? How high is your listening position?
There are so many factors effecting the
acoustic environment that it is nearly impossible to address all of the commonly found
issues. Unless you have a dedicated listening room, turning your living room or
other public area into an acoustically-sound room is quite a challenge.
Where do you start? Measure your room length wise, and then
divide it into thirds. Place your speakers one-third the distance from the rear wall
and then place your listening position one-third distance from the wall behind you.
The distance from the front wall to the loudspeakers, loudspeakers to the listening
position and listening position to the back wall should be one-third distance apart.
Can’t do this in your listening room? Try dividing into fifths instead.
If you divide into fifths, make sure your listening position is one fifth distance
from the loudspeakers and NOT from the wall behind you. The ideal distance between
the loudspeakers should be at least 6 feet, anything closer condenses the sound stage thus
closing in –or boxing in- the imaging. The distance from the side wall should
be at least 1-1/2 to 2 feet (center of woofer to side wall measurement). For
now, do not toe-in the speakers. The measurements we are going to take should be
with the loudspeakers pointed straight ahead with no toe-in. I assume that you have
some sort of test CD. Make sure you have at least one test CD with test tones along
with reference recordings. Stereophile has a few that you can order which work very
well. I use Stereophile’s Test CD 2 along with disks from Denon and Chesky.
Now it's time to use a sound
pressure level (SPL) meter to create a frequency response graph. If you don’t
have an SPL meter, a great one for the money is made by Radio Shack, the digital
SPL. Radio Shack also carries an analog meter, but the digital meter is better
suited for the type of measurements we are going to take. Digital readout is the key
feature for precise measurements. I use the digital SPL on a tripod which works very
well and allows quite a bit of flexibility when making measurements (See picture).
Place the meter at the listening position with the height being the same in
reference to where your ears are when sitting down. You want to make sure that the
location where the measurements are taken, correspond to the precise listening position.
Make a simple graph with the dB spec on the Y axis, and the frequency spec on the X
axis. The Freq. spec should correspond with the test tone frequencies on your test
CD.
You
are now ready to take some measurements. On your test CD there should be a white
noise track. The white noise track is used to set a reference dB level prior to each
measurement session. Adjust the volume of your system so that the meter reads 75 dB of
SPL. If you do this prior to each test session your results will be more accurate
when comparing against previously taken measurements. Next, play each test tone and
mark the dB level each frequency is measured at on the graph. When complete, connect
the dots on the graph and the result will be the frequency response of the system.
Now
let's take some measurements with the loudspeakers configured differently. Place
each speaker 3 feet from the front wall, 2 feet from the side wall (remember, measure from
center of woofer to wall), 6-7 feet apart with listening position the same distance from
the speakers as they are apart. A triangular formation is now created. Still,
do not toe-in the loudspeakers for the next series of measurements, article 2 will cover
toe-in procedure. Follow the previous steps for taking measurements then plot out
your frequency response graph.
This
concludes article 1 of 3. You now have a good way of testing the overall balance of
your systems frequency spectrum. In the next section I will discuss how to fix some
of the problem areas discovered after taking the measurements, and how to use the ear as
the final judge when positioning loudspeakers. Also, I will be talking about
different ways of setting up your loudspeakers in various room configurations. The
whole idea here is to combine the test results with what you hear to find the best speaker
location in your listening room. The outcome will be a much more balanced and neutral
overall sound, resulting in tighter bass, wider soundstage, precise imaging and a smoother
midrange to upper end transition. See you in the next article!
Happy Listening!
Shane Mattson
Founder, SoundReproduction.com
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