S E T U P D E T A I L S
35
Here’s the procedure:
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Set one speaker into a corner of the room. If your main speakers are too hard to
move around, this could be any speaker, as long as its woofer(s) are about the
same height as the one(s) in your main speakers.
•
Set the RTA display to update fairly quickly, e.g., with not too heavy averaging.
•
Set the RTA’s signal generator to make pink noise and turn it on. The volume
doesn’t have to be loud, but loud enough to be a few dB above the ambient
noise.
•
Use the microphone to sniff around the perimeter of the room while keeping an
eye on the RTA display. Keep the microphone either at a height that is the same
as your ear height when seated and listening to music, or the same as the
speaker’s woofer height, or if the speaker has two woofers, the average height of
the woofers.
•
Sweep the mic back and forth at varying distances from the walls, say from one
to three feet away [30 - 100 cm].
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You’ll notice a couple of bass frequencies that have large humps, probably below
100 Hz, and certainly below 120 Hz. Take note of these frequencies.
•
Now set the RTA’s signal generator to make a sine wave at the frequency with
the tallest hump, or if there are two humps closely spaced, the average of the two
frequencies.
•
Carry some items with you that can drop to mark the positions of the anti-nodes.
•
Walk around the room with your head at about the same height as if you were
seated and listening.
•
You’ll find spots where the hum of that bass tone is very strong, and others
where it is relatively weak. The strong spots are the nodes, and the weak spots the
anti-nodes.
•
Wherever you hear an anti-node, drop a marker on the floor. Those will be your
candidate speaker positions.
•
Hopefully, there are two of those positions that can be used for speaker
placement. In our experience, a pair of good ones are likely to appear on the
longer wall, near to one end of the room, but not necessarily.
•
Finally, listen for a spot or area where you can place your seat, where the hump is
also minimal.
By this means, you should be able to knock the effect of the worst mode or pair of
adjacent modes down by 10 dB, for instance reducing a monstrous 15 dB hump to a
much less noticeable 5 dB.
